1169:
963:
566:
935:
947:
740:
171:
760:, which compensates for the loss of gain caused by negative feedback. Williamson optimized operating points of each stage for best linearity with sufficient overload reserve. The output stage is biased into pure class A; traditionally it used triode-connected beam tetrodes or pentodes. With American 807 or British KT66 valves (Williamson recommended the latter type) and specified power supply the amplifier delivered 15 watts of output power. Further increase in output, according to Williamson, required use of four output valves; his 1947 article mentions construction of a 70-watt prototype.
1059:
in each case at least three of four or five cutoff frequencies were dangerously close to each other, which was a certain sign of instability. Williamson, again, fixed the problem with an RC compensation network, but even then phase margin remained dangerously low. DIYers had to tackle oscillations themselves: some added shunting capacitors to the screen grids, others tweaked layout and wiring, or deliberately narrowed the amplifier's bandwidth, negating the benefits of the original circuit.
515:. Chief editor H. F. Smith knew Williamson for his earlier contributions; he contacted the author directly and requested a detailed article written specifically for the DIY readers. Williamson promptly responded, but for unknown reasons the publication, originally slotted for 1946, was delayed until April–May 1947. While the paper was waiting for print, the magazine had published the new version of Cocking's
1297:. Very soon the American public acquired taste to high-power amplification, and the industry launched the "race for Watts". By 1955 Hafler and Keroes, now working separately, were offering 60-Watt models employing pairs of 6550 tetrodes or quartets of KT66s. Thus in less than a decade, step by step, the industry abandoned the principles set by Williamson, but continued to use his name as a convenient free
1039:. The transformer's nonlinearity also improved stability: at high signal currents effective inductance of the primary increased, causing a decrease in cutoff frequency and a rise in phase margin. The simplest solution was to spread apart cutoff frequencies of the RC filters, provided that the output transformer conforms to the Williamson specification. For example, the 1952
984:. Astor and Langford-Smith, who gave the Williamson excellent ratings, reported that "for fairly large outputs at low frequencies a high frequency oscillation about 60 kC/s would commence and be accompanied by a pulsed output of some other frequency". The Australians, armed with first-class test equipment, suppressed the 60 kHz oscillation with small capacitors on
465:, the KT66 prototype delivered 20 Watts at no more than 0.1% distortion. A less costly +425V power supply enabled 15 Watt output power at no more than 0.1% distortion; this arrangement became standard for the Williamson amplifier and defined its physical layout. The complete prototype system, including the amplifier, the experimental magnetic pickup and a
1546:
1068:
768:. Cathode bypass capacitors are absent: Williamson, like Cocking before him, tried to linearize open-loop performance of each stage, and deliberately sacrificed gain for linearity; he was also concerned with potential low-frequency instability introduced by added capacitances. The circuit in either 1947 or 1949 variant contains no
993:
frequency response from 10 to 100,000 Hz, but were also prone to infrasonic "breathing". The worst transformers displayed prominent ultrasonic resonances that, however, did not cause sustained oscillations. Some "ringed" at relatively low frequencies of 30 to 50 kHz, others extended into 500...700 kHz range.
1379:. Advertisements claimed that these models performed as well as the original Williamson, with higher output power and with guaranteed stability. The customers could not verify these claims, and had to rely to listening tests, hearsay and expert advice. The problem was partially addressed by the concept of
542:
In August 1949 Williamson, responding to letters from the readers, published the "New
Version" of this amplifier. The article dealt extensively with construction, tuning and troubleshooting issues, however, its main objective was to address stability issues reported in letters from the readers. Apart
845:
predicted that an amplifier built to
Williamson's specifications could only be stable if the bandwidth of its output transformer was no less than 2.5...160000 Hz. This was impractically wide for an audio amplifier, requiring an exceptionally large, complex and expensive transformer. Williamson,
820:
components are located in the first and second stages of the circuit: their local smoothing RC filters subtly alter frequency response at infrasonic frequencies. An additional RC-filter in the first stage, introduced by
Williamson in the 1949 version, prevents oscillations at ultrasonic frequencies.
1597:
Transformer-coupled valve amplifiers do not choke, as long as the driver valve(s) can deliver required grid current(s). However, interstage transformers are incompatible with global negative feedback. A series combination of two transfromers (interstage and output) is inherently unstable; it cannot
1159:
Kiebert rated the design positively but warned the readers that following
Williamson's instructions is possible only in a laboratory environment. The amplifier reveals its potential only with expensive, properly matched components that were out of reach of an average amateur. Even a perfectly built
1058:
and nonlinearities of the output stage. Depending on the chosen analysis model, open-loop response can be roughly approximated with a combination of either four or five low-pass filters. Different authors used different approaches and estimated somewhat different cutoff points of these filters, but
834:
Williamson was confident that the output transformer is the most critical component in any valve amplifier. Even before applying global feedback, the transformer is liable for at least four types of distortion. Their causes cannot be addressed simultaneously, and the designer must make a compromise
460:
Valve complement of the original
Williamson amplifier was determined by scarce supply in wartime Britain. The two suitable and available output valves were either the PX25 triode, or a triode-connected KT66 beam tetrode. Williamson initially used the PX25, an already obsolete directly-heated triode
1393:
Objectively, many deep-feedback valve designs of the 1950s matched or exceeded the 0.1% distortion rating of the
Williamson amplifier, but none could significantly improve on this figure. Williamson had found that valve amplifier performance was limited mostly by the output transformer. Transistor
825:
is connected to the transformer secondary, thus feedback depth is dependent on loudspeaker impedance, and setting it at precisely 20 dB requires altering the divider ratio. The voltage divider is purely resistive, with no capacitive or inductive frequency compensation components. According to
451:
dB higher open loop gain to compensate the effect of feedback). Deep feedback inevitably causes sudden, harsh onset of distortion at overload but
Williamson was content with this flaw. He argued that it is a price worth paying for an improvement in linearity at medium and high power levels. On the
355:. In April 1944 Williamson transferred from production line to Applications Laboratory of the company, where he had enough free time for his own DIY projects. Management did not object, and by the end of 1944 Williamson had conceived, built and tested the amplifier that would soon be known as the
1079:
The
Williamson amplifier was very sensitive to the quality and parameters of passive components and valves. Carbon and composition-type resistors generated excessive noise and caused harmonic distortion; American valves used as substitutes for the British types specified by Williamson, could not
615:
amplifiers", "absolute tops for obtaining natural reproduction" and so on. America lagged behind by about two years: first reviews appeared in the second half of 1949, and were just as complimentary. American companies adapted the circuit to locally available components, and soon began importing
1280:
in the 1930s. An ultralinear stage delivered 50% to 100% more output power than the same stage in triode connection, at roughly the same distortion, and cost less than a pure pentode or tetrode stage (the latter required a separate screen grid supply, the ultralinear did not need it). The first
1144:
driver stage was often unable to properly swing the KT66 grids, causing excessive distortion. According to
Kiebert, the American 5687 dual triode was clearly superior. According to Talbot Wright, the 6SN7 was not at fault - distortion was caused by incorrectly set standing current, and could be
1101:
Articles by professional engineers dealing with analysis and fine tuning of the
Williamson amplifier were published relatively late, when the original DIY enthusiasm had already faded - in 1952, 1957, 1961. Martin Kiebert, who built professional-grade Williamson amplifiers for his laboratory at
992:
examined seven different commercially available Williamson amplifiers, and found that all of them oscillated at infrasonic frequencies of 2...3 Hz. Replacement of output transformers affected stability only at audio and ultrasonic frequencies. The best transformers displayed perfectly flat
626:
The spread of DIY construction and the abundance of publications addressed to the amateurs had a solid economic reason: factory-made electronics of the 1940s were too expensive. The industry has not yet reorganized for mass production of affordable consumer products. Home construction of valve
1011:
and presented the second version of the Williamson in 1949. Williamson could not fix the fundamental stability problem; the "New version" was just barely stable. Independent analysis published in December 1950 proved that the revised Williamson amplifier remained prone to both infrasonic and
552:
stages and brief "Replies to Queries" concerning assembly and testing. A collection of articles published by Williamson in 1947–1950 was printed as a standalone 36-page brochure in 1952, with a second edition in 1953. The Williamson amplifier itself, as described in the August 1949 issue of
538:
production model. Leak and Walker tried to commercialize their ideas on the meagre post-war British market; their achievements were practically unknown outside of the United Kingdom. Williamson did the opposite: he donated his design to worldwide DIY community, thus securing lasting popular
614:
adapted the Williamson circuit for American 6SN7 and 807 valves; a 6L6 variant followed soon. British and Australian press was unanimously enthusiastic: "by far the best we have ever tested ... extraordinary linearity and lack of harmonic and intermodulation distortion", "amplifier to end
1386:, advanced by Hafler and Keroes back in 1951: "Excellent measurements are a necessary but not a sufficient condition for the quality of sound. The listening test is one of most importance... the most stringent test of all". By the end of the 1960s subjectivist approach was adopted by the
161:
of the Williamson could not fix this fundamental flaw. For this reason, and due to high costs of required quality components, manufacturers soon abandoned the Williamson circuit in favour of inherently more stable, cheaper and efficient three-stage, ultralinear or pentode-output designs.
491:
system, the first true high fidelity medium in the United Kingdom. These records, which exceeded any preexisting media in sound quality, helped Williamson with fine-tuning his prototypes. He was certain that he was now firmly on the right track, but neither Marconi, nor its parent the
866:
had to be heavier, larger, more complex and more expensive than typical audio transformers, and yet they could only guarantee minimally acceptable stability. A wider phase margin, wrote Williamson, was highly desirable but required absolutely impractical values of primary inductance.
779:
Derivative designs of the 1950s often deviated from Williamson's recommendations while retaining his four-stage topology. According to Peter Stinson, this alone is not sufficient to be called a Williamson amplifier. A true Williamson amplifier must meet five criteria simultaneously:
59:
throughout the 1950s. The original circuit was copied by hundreds of thousands amateurs worldwide. It was an absolute favourite on the DIY scene of the 1950s, and in the beginning of the decade also dominated British and North American markets for factory-assembled amplifiers.
442:
Williamson reviewed contemporary amplifier configurations, and, just like Cocking, settled on a low distortion push-pull, class A, triode output stage. Unlike Cocking, Williamson believed that such a stage can deliver high fidelity sound only when the amplifier is governed by
1529:
Regular FM broadcasting in both the United States and the United Kingdom began in 1946. By April–May 1947 British FM transmissions were still limited in duration and area covertage; Williamson in his opening article anticipated "the possible extension of u.h.f. high-quality
603:. The high fidelity media that did not exist in the 1930s became a reality, and the public wanted playback equipment of matching quality. Off-the-shelf amplifiers available in 1947 were not fit for the task. At the same time, electronic components markets were flooded with
885:
when large signal swings intermittently attempt to bias the grids of the output valves above zero. Positively-biased grids begin conducting, but the coupling capacitors cannot delivered required current. Grid voltages do not reach target values, output waveform flattens.
607:, including cheap American 6L6 and 807 power valves. For a while, DIY construction was the only way to obtain high fidelity amplification. Thousands of amateurs began copying the Williamson design; the required transformers and chassis were soon provided by industry.
743:
The 1949 version of the Williamson circuit. Power supply components omitted. AC voltages at 15 W output power, specified by Williamson in peak volts, shown recalculated to effective sine volts. Value of feedback resistor X depends on load impedance (two options
763:
The plate of the first stage and the grid of the phase splitter are connected directly. This configuration, known since 1940, was still uncommon in 1947; American designers considered it a novelty even in the early 1950s. Phase splitter, driver and output stage are
1000:
were imperfect, but general-purpose, off-the-shelf transformers used by amateurs were far worse. Their resonances could only be tamed by narrowing the amplifier's bandwidth. The extent of stability problem in the DIY community remains unknown: the editors of
496:
were willing to invest in mass production of amplifiers for the civilian market. The design was not interesting to company lawyers either, because it did not contain anything patentable. Williamson merely put together well-known circuits and solutions.
809:, "this is a severe test of design and is one of the outstanding features of the Williamson circuit." Williamson wrote that the depth of feedback can be easily increased from 20 to 30 dB, but the audible improvements of deeper feedback will be
1587:
The original Leak Point One design of 1945 also employed four stages and global negative feedback, and was even less stable than the Williamson. Harold Leak soon abandoned the idea and in 1947 released the successful three-stage Leak TL12.
1452:
in the early 1930s. He was a prolific content contributor, often addressing the how-to side of electronic projects. During World War II Cocking was drafted into classified military research. After the war, he served as the chief editor of
547:
network, a biasing potentiometer and a new, indirectly-heated rectifier valve that was not available in 1947, the circuit remained the same. In October 1949 – January 1950 and May 1952 Williamson published a series of articles on matching
1470:
The PX25 was a unique directly-heated power triode, with an unusually high voltage gain (μ=9). A PX25 amplifier would have more than twice open loop gain than an amplifier employing typical directly-heated triodes like 2A3 or AD1 (μ=4).
1260:
AR-425 (also 1953) use a tetrode-mode output stage in an otherwise familiar Williamson topology. Both Bell and Stromberg-Carson modifications further worsened stability, and required additional frequency compensation. Designers of the
627:
electronics was relatively simple and promised considerable savings. The number of home-made Williamson amplifiers is estimated at least in hundreds of thousands; they absolutely dominated the DIY scene in English-speaking countries.
635:. Each one differs in minor details, assembly quality is usually inferior to factory-made models. In the 21st century these monaural amplifiers are commonly sold at online auctions, but finding a matching pair is almost impossible.
1031:, formed by the valves' output impedances and the transformer's primary inductance. At zero input signal, the nonlinear RL filter has a cutoff frequency of 3 Hz. This combination of cutoff frequencies, wrapped inside a 20–30
290:
leaned to push-pull, class A, RC-coupled triode output stages. RC coupling, as opposed to transformer coupling, argued Cocking, extended the amplifier's bandwidth beyond the required minimum of 10 kHz and improved its
1179:. In addition to ultralinear 6L6 output, it deviates from the original in having cathode bypass and frequency compensation capacitors in the output stage, and an inexpensive CRC power supply filter instead of CLC.
1371:, which followed this topology, became the most produced valve amplifier in history. North American consumer market was flooded with millions of similar, almost identical amplifiers and receivers claiming 25 to 20
1137:
Frequency and harmonic distortion caused by asymmetry of passive components in two sides of a push-pull circuit. Typical components of the 1950s had 20% tolerances, which was unacceptably high for the Williamson;
1423:
Introduction of sound film coincided with the Great Depression. Although the entertainment industry fared much better than the society in general, cinema owners had to be very frugal with their investments in
509:. A few months later a senior Marconi salesman, who sought new means of promoting the KT66 to general public, noticed Williamson's 1944 report about his amplifier prototypes, and sent it for publication to
826:
Williamson, a capacitor shunting the upper leg of the divider is only necessary for inferior-quality transformers; if the transformer matches requirements set by Williamson, the capacitor is useless.
4221:
1007:
were flooded with readers' letters, but preferred to redirect them to Williamson. What is known is that the inventor was compelled to revise and improve the design; he took a leave from his job at
476:, has proven to Williamson that a low distortion, deep feedback amplifier, indeed, sounded superior to amplifiers without feedback. The difference was particularly audible with the best available
752:
built around a high quality, wideband output transformer. Its second (concertina-type phase splitter, V1B), third (driver, V2A and V2B) and fourth (output, V3 and V4) stages follow Cocking's
1437:
the war: "these experiments might have been carried through to products had it not been for the upsurge of interest and publicity for the new marvel, experimental television, from 1934."
850:
to a bare minimum; even then, the required bandwidth had to be no less than 3,3...60000 Hz. Such a transformer, driven by a pair of triode-connected KT66, had to have primary winding
1301:. In the 21st century it is even used for amplifiers without global negative feedback; the only thing they have in common with the true Williamson amplifier is the four-stage topology.
190:
can reach 5%, provided that distortion rises smoothly rather than abruptly, and that it generates only low-order harmonics. Kellogg's work became the de facto industry standard of the
1557:. However, Americans and Britons "discovered" the tape recorder only after the war. It is true, however, that the Germans perfected the technology throughout the war, and by 1945 new
65:
1114:
caused by noisy carbon or composition-type resistors and incorrect layout of the first stage. Replacement of resistors specified by Williamson with wirewound resistors could improve
642:, announced production in October 1948. In the early 1950s the Williamson amplifier dominated factory production in both the United Kingdom and the United States; John Frieborn of
303:
of the loudspeaker. Cocking wrote that Kellogg's 5% distortion limit was too high for quality amplification, and outlined a different set of requirements - the first definition of
1168:
311:(harmonic distortion), Cocking set three simultaneous targets - low frequency distortion, low harmonic distortion, and low phase distortion. In 1934 Cocking published his first
619:
British valves and transformers, thus launching the market for British hi-fi in the United States. By the end of 1949 the Williamson amplifier became a universally recognized
237:
of matching quality. Industry leaders of the 1930s agreed that the improvement of commercial amplifiers and loudspeakers would make sense only after the introduction of new
1344:) agreed that the ultralinear stage was, indeed, preferable in mass production. Williamson gradually stepped aside from audio engineering. He made his living by designing
261:
boomconsecutively delayed this goal. Development of commercial audio equipment came to a standstill; the few enthusiasts seeking higher level of fidelity had to literally
523:, certainly had precedence; according to Peter Stinson, he was sceptical about the Williamson amplifier, believing that his own design needed no further improvements.
1183:
After 1950 the industry produced numerous derivatives of the Williamson amplifier, often deviating significantly from the principles outlined by its creator. In 1950
940:
Williamson's 1949 design. Dashed lines: open loop response, solid lines: closed loop response. Resonant bumps at low and high extremes indicate narrow phase margins
364:
315:
design - a two-stage, RC-coupled triode class A amplifier that achieved no more than 2–3% maximum distortion without using feedback. Feedback appeared in his 1943
281:
274:
270:
70:
1324:, Britain's largest valve manufacturer and provider of reference designs to the European industry, publicly supported the novelty. Williamson's former employer,
1195:
which, according to Keroes, significantly reduced distortion at high output power. Contrary to recommendations by Cocking and Williamson, Keroes and his partner
483:
The prototypes impressed the Marconi management, who granted Williamson unlimited access to the company's test facilities and introduced him to the people from
1098:
MHz bandwidth. In the 1950s bandwidths of many commercial oscilloscopes were too narrow for the task, and even these models were too expensive for the DIYers.
806:
461:
introduced in 1932. In his second prototype, Williamson used the more efficient KT66, which became the valve of choice in post-war period. Powered from +500 V
21:
573:, Australia, March 1948. The sample shown here uses American 6SN7 and 807 valves and a surplus chassis of an Australian-made radio transmitter. However,
1484:
emphasized 0.1% distortion rating claimed by Leak. His aggressive marketing provoked public suspicion in the validity and necessity of such low ratings.
153:
frequencies. Enclosing four valve stages and an output transformer in a negative feedback loop was a severe test of design, resulting in a very narrow
1003:
1545:
itself was not new; in fact, broadcast-quality production models were built and presented to general public before the outbreak of World War II. In
1184:
1048:
531:
452:
contrary, wrote Williamson, slow but steady rise of distortion to 3–5%, as advocated by Kellogg, is distinctly unwanted in a high fidelity system.
862:
of no more than 33 mH. These were extremely demanding specifications for the period, far exceeding anything available on the consumer market. The
1394:
amplifiers did not have this limitation, and yet it took around 15 years to bring their performance to the level attained by Williamson in 1947.
1199:
used cathode shunt capacitors in most of their designs; by 1956 this approach became de facto industry standard. In the same 1956 Hafler used
1160:
and tested Williamson amplifier would sooner or later need valve replacement, which would very likely cause an unexpected rise in distortion.
796:
Global negative feedback loop must be connected from transformer secondary to the cathode of the input triode, and be exactly 20 dB deep.
534:
in September 1945; later in the same year Peter Walker published the first sketch of his distributed-load output stage that would become the
408:
which, in addition to above frequency and phase requirements, demands perfectly constant gain when handling complex waveforms and transients;
805:
The 20 dB (ten-to-one) feedback loop of the Williamson amplifier wraps around all four stages and the output transformer. According to
585:
The Williamson amplifier was an instant success. The publication coincided with the resumption of television broadcasting, the beginning of
4090:
1207:
Williamson. Later, fixed bias became a staple of Soviet and Russian Williamson-like designs that employed exotic output valves like the
889:
Feedback attempts to overcome choking by increasing driver voltage swing, but fails because coupling capacitors cannot physically pass
4253:
178:, 1946. Absence of cathode bypass capacitors was a "trademark" feature of Williamson's design inherited directly from Cocking's work
3749:
4115:
1080:
match their performance. Williamson warned that the KT66 has no direct substitutes, and should be preferred over any alternatives.
3906:
1367:
combined phase splitter and driver functions in one valve, and thus cost proportionally less than four-stage amplifiers. Hafler's
989:
969:
953:
3790:
1578:, Richard C. Hitchcock is now remembered as the creator of the 'Westinghouse Organ' (also called 'Electric Radio Organ', 1930).
1083:
Amateurs who copied the Williamson amplifier were unable to identify and fix its critical weak points. An amateur armed with an
1208:
901:, is "of the desirable type", i.e. with abrupt onset of distortion at the extremes of otherwise highly linear response curves.
4297:
3709:
3693:
3677:
3887:
4415:
4353:Романюк, Ю. (1965). "Стереофонический усилитель с акустическим агрегатом" [Stereo Amplifier with Acoustic Unit].
1155:
Distortion was clearly influenced by the choice of output valves, however, Kiebert could not identify any specific rules.
835:
between conflicting requirements. Global feedback partially suppresses distortion, but also tightens requirements to the
323:
beam tetrodes; however, both the input stage and the output transformer were placed outside the feedback loop. Cocking's
186:
published the first comprehensive theory of audio power amplifier design. Kellogg proposed that the permissible level of
141:
The Williamson amplifier was sensitive to selection and matching of passive components and valves, and prone to unwanted
3998:
1608:
1054:
Precise analysis at ultrasonic frequencies is impossible due to the asymmetry of the phase splitter stage, and unknown
4079:
3984:
1650:
1571:
1506:
881:
in the same manner as transistor amplifiers (e.g. clamping output voltage to one of the supply rails). Instead, they
4172:
1090:
could "see" infrasonic oscillations by watching the instrument needle, but fixing high-frequency issues required an
327:
family became the foundation of post-war British and Australian audio industry, including the Williamson amplifier.
4156:
1328:, followed suit and published a reference "30-Watt Williamson" design built around a pair of ultralinear-connected
488:
40:
4276:
Williamson, D. T. N. (1947). "Design for a High Quality Amplifier.Details of Chosen Circuit and Its Performance".
4375:
4060:
4041:
3868:
1414:. The amplifier was designed well before the advent of stereo, and was never intended for multi-channel sound.
1341:
1035:
dB frequency loop, is unstable. Williamson tried to suppress it with a compensation network, also serving as a
962:
1349:
836:
487:. The latter provided Williamson with precious, exclusive test material - sample records of the experimental
473:
90:
74:
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and marketing people, who eagerly forgot about the objective principles devised by Williamson in the 1940s.
4207:
3647:
1111:
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The first attempts to build the Williamson amplifier revealed its tendency to oscillate due to very narrow
3777:
3663:
229:
improved performance of their experimental audio equipment to a level approaching modern understanding of
4405:
934:
914:
565:
211:
29:
3441:
1015:
According to the analysis, infrasonic open-loop response of the Williamson amplifier is shaped by three
988:, but could not identify and suppress the cause of "some other" oscillations. Later, technicians of the
4313:
946:
375:
Following Cocking's ideas, Williamson devised a different, much stricter set of fidelity requirements:
1716:
per channel mark. Transistor amplifiers easily surpassed it, and the race culminated in 1971 with the
170:
4400:
1253:
2200 amplifier (1953) replaced direct coupling of the first two stages with capacitive coupling; the
773:
684:
638:
Small-scale factory production in the United Kingdom began in February 1948; first big manufacturer,
131:
2800:
739:
3925:
2351:
1670:
1496:
1325:
1276:- a method of distributing load between anode and screen grid of a pentode or tetrode, invented by
1072:
493:
419:. At the very least, output impedance of an amplifier must be lower than the loudspeaker impedance;
3631:
1106:, identified five sources of distortion caused by inferior components other than the transformer:
3830:
784:
All four stages must use triodes; the output stage may use triode-connected tetrodes or pentodes;
344:
1036:
1653:, and various consultancies based in Washington, D.C. During the war he was stationed with the
1192:
1075:. Experience has proved that American substitutes were not an even match for the original KT66.
918:
875:
Valve amplifiers with capacitive coupling between the driver stage and the output stage do not
817:
769:
544:
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with two 8 μF paper capacitors, with a further LC filter feeding the first three stages.
387:
products) up to the maximum rated output, at all audible frequencies from 10 to 20000 Hz;
4395:
3190:
1654:
1333:
1226:
decreased, designers steadily increased their values. The original Williamson amplifier used
1115:
535:
142:
96:
all contributed to the performance of the Williamson. It had a modest output power rating of
86:
1340:. In September 1952 Williamson and Walker (then business partners in the development of the
668:), 2x KT66, 1x U52 directly-heated rectifier. The 1949 version also provided for the use of
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DB20 (1953) went even further, and combined global and local negative feedback loops with
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By 1947 British industry had already released two amplifiers of comparable sound quality.
206:
requirements were low, and customers were content with crude but efficient and affordable
8:
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4267:
Williamson, D. T. N. (1947). "Design for a High Quality Amplifier. Basic Requirements".
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Frankland, S. (2002). "The Contest for High Fidelity: Western Electric vs RCA, Part I".
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Hitchcock, R. (1959). "Chapter 15. Audio Frequency Amplifiers". In Keith Henney (ed.).
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High-quality output transformer must conform to the original Williamson specification;
295:. Tetrodes and pentodes were undesirable due to higher harmonic distortion and higher
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2801:"The 'Westinghouse Organ' or 'Electric Radio Organ' Richard C. Hitchcock. USA, 1930"
1433:
Stinson wrote that the nascent television adversely affected audio electronics even
1332:. The original Williamson amplifier lost the race, just like alternative designs by
3736:
1364:
1238:
1024:
1016:
985:
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or B65 double triodes, and replaced rectifier with the 53KU indirectly-heated type;
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650:, other audio designers had two apparent choices, beating him or joining him."
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has not been commercialized yet; almost all surviving Williamson amplifiers are
3740:
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dB deep negative feedback loop (and thus the complete amplifier must have 20–30
416:
347:. Theo was not physically fit for military service, so instead the authorities
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4344:Баев, А. (1977). "Усилитель НЧ мощностью 130 Вт" [130W LF Amplifier].
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Keroes, H. (1955). "Adapting the Ultra-Linear Williamson to 6550 operation".
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template, but in the next few years it was retired, too. The new three-stage
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Firsts in High Fidelity: The Products and History of H.J. Leak & Co. Ltd
1320:
disposed with "obsolete" power triodes and switched to ultralinear designs.
646:
wrote in 1953 that "since Williamson published the first description of his
4187:
3952:
3940:
3921:
3902:
3883:
1717:
1661:
in 1945. After the war, according to Kiebert's publications, he worked for
1642:
1516:
1380:
1376:
1375:
W per channel, as well as clones of less powerful British designs like the
1273:
1245:
bypass capacitors; the 1961 budget amplifier by Wright employed a total of
1196:
1091:
1044:
981:
855:
847:
549:
462:
348:
336:
266:
254:
233:, but none of these systems could be commercialized yet. They lacked sound
222:
power triodes, far exceeded the average level but were expensive and rare.
154:
44:
3798:. Washington D.C.: United States Naval Research Laboratory. Archived from
2195:
1704:
4263:
A collection of articles from the late 1940s and early 1950s, including:
4191:
3826:
3615:
3534:
1737:
1687:
1553:
is installed in a Finnish broadcast studio in anticipation of the failed
1541:
1293:; their second model, built around more powerful 807 tetrodes, delivered
894:
893:. Resulting distortion pattern, as Williamson proved with photocopies of
599:
398:
124:
47:. The original circuit, published in 1947 and addressed to the worldwide
4285:
Williamson, D. T. N. (1949). "High Quality Amplifier: The New Version".
1304:
Following the success of Hafler and Keroes, American manufacturers like
927:
Frequency, phase and transient response of various Williamson amplifiers
730:
below maximum output, almost entirely consisting of mains frequency hum.
623:, and a starting point for all valve designs employing global feedback.
505:
In February 1946 Williamson left Marconi, moved to Edinburgh and joined
3765:
Crowhurst, N.; Cooper, G. F. (1956). "Chapter 2. Analysis and Design".
1725:
1575:
1387:
1200:
1087:
1028:
1020:
851:
693:: not specified (Williamson did not have the necessary test equipment);
258:
199:
150:
146:
1356:, and never considered audio design a serious occupation for himself.
3694:"The Quality Amplifier. Wartime Modifications to a Well-Known Design"
2905:
2903:
2516:
2514:
2477:
2475:
2473:
2471:
2458:
2456:
1646:
1383:
1298:
1223:
1152:. This critical function required low-distortion wirewound resistors;
594:
300:
127:
4130:
Kitteson, C. (1995). "The History and Future of Dynaco Tube Audio".
1812:
1810:
1808:
1806:
748:
The Williamson amplifier is a four-stage, push-pull, class A triode
719:
Hz: "never exceeds a few degrees" at the extremes of audio spectrum;
343:
Theo Williamson failed mathematics exam and was discharged from the
269:. Australians preferred traditional push-pull circuits built around
1691:
1008:
632:
589:, the release of the first high fidelity gramophone records (Decca
506:
2900:
2511:
2468:
2453:
2443:
2441:
1913:
1803:
1666:
1359:
In 1956 most production amplifiers in North America followed the
1321:
1317:
723:
3414:
2607:
2605:
480:, despite the physical limitations of this low-fidelity format.
3262:
2531:
2529:
2438:
1368:
32:
3431:
3429:
1712:
among valve amplifier manufacturers eventually stabilized at
3404:
3402:
3202:
3117:
3115:
3113:
3045:
3035:
3033:
2602:
2136:
2134:
1645:. Prior to World War II he worked as electronics engineer at
1229:
1212:
1175:
HF-20 integrated amplifier, one of many inexpensive American
1127:
3849:
Frankland, S. (1996). "Single-ended vs. Push-pull, part I".
3524:
3522:
3520:
3481:
2781:
2526:
2302:
2121:
2119:
1461:
and their successor magazines until his retirement in 1972.
134:
figure of the Williamson amplifier became the criterion for
3546:
3426:
3351:
3341:
3339:
3266:
3153:
3151:
2852:
2842:
2840:
2838:
2771:
2769:
2724:
2722:
2672:
2670:
2668:
2666:
2664:
2662:
2649:
2647:
2634:
2632:
2387:
2377:
2375:
2373:
2371:
2356:
2232:
2230:
2228:
2106:
2104:
2102:
2100:
2098:
2096:
2094:
2092:
1954:
1952:
1611:, the country's largest radio manufacturer and broadcaster.
1329:
1305:
1204:
1172:
1141:
1123:
790:
Phase splitter must be directly coupled to the input stage;
669:
527:
219:
99:
82:
3399:
3290:
3288:
3214:
3110:
3030:
3018:
2404:
2402:
2213:
2159:
2157:
2155:
2153:
2151:
2149:
2131:
2079:
2077:
2075:
2073:
2071:
2069:
2056:
2054:
2052:
2050:
2048:
2046:
1964:
1872:
1870:
1868:
1866:
1864:
1862:
1860:
1858:
1856:
1854:
664:
Tube complement, 1947 version: 4x L63 (each equivalent to
103:
but surpassed all contemporary designs in having very low
4238:"The rise and fall of the thermionic valves or tubes - 2"
3587:
3517:
3245:
3243:
3241:
3226:
3168:
3166:
3138:
3136:
3134:
3132:
3130:
3100:
3098:
3096:
3094:
3081:
3079:
2739:
2737:
2314:
2116:
1891:
1889:
1887:
1885:
1733:
1637:
Martin Peter Vlamingh Kiebert Jr, born in 1908, attended
1286:
665:
320:
226:
3792:
Laboratory Tests of Some of the Popular Audio Amplifiers
3723:
3505:
3336:
3196:
3148:
2987:
2985:
2983:
2944:
2864:
2835:
2811:
2766:
2719:
2659:
2644:
2629:
2546:
2544:
2368:
2292:
2290:
2277:
2275:
2273:
2271:
2269:
2254:
2225:
2178:
2176:
2174:
2172:
2089:
2021:
2019:
2017:
2015:
1949:
1772:
1770:
1768:
1766:
1764:
1762:
1760:
1758:
1756:
3387:
3375:
3285:
3066:
3064:
3062:
3060:
3008:
3006:
3004:
3002:
3000:
2956:
2922:
2920:
2918:
2709:
2707:
2705:
2703:
2701:
2699:
2697:
2580:
2578:
2576:
2574:
2561:
2559:
2399:
2146:
2066:
2043:
1851:
1446:
Walter Tusting Cocking (1907–1984) joined the staff of
1272:
In December 1951 Hafler and Keroes began promoting the
1067:
157:
or, quite often, no margin at all. Attempts to improve
3943:(1955b). "High Power Williamson Amplifier for Hi-Fi".
3565:
3563:
3561:
3493:
3469:
3363:
3238:
3178:
3163:
3127:
3091:
3076:
2823:
2734:
2682:
2617:
2487:
2426:
2000:
1988:
1976:
1937:
1882:
952:
Commercial amplifier with a high quality transformer,
3809:
3648:"The Care and Treatment of Feedback Audio Amplifiers"
3575:
3273:
2980:
2932:
2756:
2754:
2752:
2590:
2541:
2499:
2481:
2462:
2414:
2326:
2287:
2266:
2169:
2012:
1919:
1816:
1753:
1607:
Astor and Langford-Smith were staff engineers at the
394:
and constant output power at all audible frequencies;
4364:Ламповый Hi-Fi усилитель своими руками (2-е издание)
3907:"Ultra-Linear Operation of the Williamson Amplifier"
3838:
Biographical Memoirs of Fellows of the Royal Society
3457:
3312:
3300:
3057:
2997:
2968:
2915:
2694:
2571:
2556:
2031:
1901:
1841:
1839:
1837:
1822:
1793:
1791:
1789:
1787:
1785:
756:
circuit. The added first stage (V1A) is a dedicated
138:
performance that remains valid in the 21st century.
3710:"Wireless World Quality Amplifier. Circuit Details"
3687:(May 4, May 11, May 18): 302–304, 330–323, 336–339.
3609:
3558:
2909:
2888:
2520:
1686:brand of domestic electronics was owned not by the
968:Commercial amplifier with an inferior transformer,
4116:"The Williamson Type Amplifier brought Up to Date"
2876:
2749:
2242:
214:amplifiers. The best theatre amplifiers, built by
4311:
4170:
4018:"The Evolution of Audio Amplifier Design, Part I"
3324:
2447:
1834:
1782:
1628:kOhm plate impedance, as specified by Williamson.
4387:
4295:
3540:
3420:
1051:had these frequencies set at 1.3 and 6 Hz.
225:By the middle of the 1930s Western Electric and
55:sound reproduction and served as a benchmark or
3955:(1956). "Modernize Your Williamson Amplifier".
3764:
1925:
581:credit Williamson as the author of the original
4186:
2535:
1145:improved by a simple increase in bias voltage;
610:In September 1947 Australians R. H. Astor and
597:), and the "discovery" of the captured German
426:W for reproduction of orchestral music via a
63:The Williamson circuit was based on the 1934
4296:Williamson, D. T. N.; Walker, P. J. (1952).
3901:
3882:
3435:
3039:
1732:per channel). In the 1990s power ratings of
846:seeking a working solution, had to decrease
4314:"Adventurers in Sound: D. T. N. Williamson"
3810:Electronics Australia, (editorial) (1990).
3263:"EICO HF-20 Integrated Amplifier schematic"
1493:For a detailed account of Leak's work, see
1163:
4370:] (in Russian). СПБ: Наука и техника.
4312:Wallace, E.; Williamson, D. T. N. (1953).
4284:
4275:
4266:
4251:
3784:(Interview). Interviewed by Harris, Steve.
3024:
2870:
2858:
2846:
2817:
2787:
2775:
2728:
2676:
2653:
2638:
2432:
2408:
2393:
2362:
2163:
2125:
2083:
2060:
265:. American DIYers experimented with novel
3963:
3857:
3848:
3616:"The Design of a High Fidelity Amplifier"
3528:
3357:
2611:
2308:
2140:
2110:
1958:
1895:
1876:
1352:, which later earned him election to the
1289:in a Williamson-like topology, delivered
379:Negligible non-linear distortion (sum of
363:, would be commercialized in 1948 as the
4361:
4255:The Williamson Amplifier. Second edition
4235:
4154:
4138:
4129:
3866:
3629:
3581:
3487:
3408:
3393:
3381:
3345:
3294:
3157:
2829:
2743:
2688:
2623:
2493:
1501:. Audioxpress magazine. pp. 61–67.
1167:
1066:
738:
564:
194:, when most amplifiers were employed in
169:
4352:
4205:
4171:Radio and Hobbies, (editorial) (1948).
4113:
3976:The Routledge Guide to Music Technology
3966:Radio Engineering Handbook, 5th edition
3939:
3920:
3825:
3707:
3691:
3675:
3645:
3632:"Williamson Type Amplifier using 6A5's"
3552:
3499:
3475:
3318:
3249:
3232:
3220:
3208:
3184:
3172:
3142:
3121:
3085:
3051:
2991:
2596:
2550:
2505:
2420:
2381:
2332:
2320:
2296:
2281:
2260:
2236:
2219:
2182:
2037:
2025:
2006:
1994:
1982:
1970:
1943:
1907:
1828:
1776:
1705:The Routledge Guide to Music Technology
1233:paper capacitors; by 1952 Kiebert uses
1187:shunted common cathode resistor of his
990:United States Naval Research Laboratory
675:Output power and maximum distortion: 15
455:
85:power tetrodes, conservative choice of
4388:
4368:DIY Tube Hi-Fi Amplifier (2nd Edition)
4327:
4104:
4088:
3972:
3951:
3775:
3747:
3661:
3463:
3447:
3369:
3306:
3279:
3104:
3070:
3012:
2974:
2962:
2565:
2347:
2343:
2341:
1494:
519:. Cocking, as the technical editor of
81:loop. Deep feedback, triode-connected
4069:
4050:
4034:Valve and Transistor Audio Amplifiers
3788:
3199:, p. 561, Martin V. Kiebert Jr..
2950:
2938:
2926:
2894:
2882:
2713:
2584:
1561:were far superior to the 1939 model.
870:
787:Output stage must operate in class A;
4343:
4330:"Improving the Williamson Amplifier"
4028:
4012:
3993:
3769:. Gernsback Library. pp. 31–40.
3593:
3569:
3511:
3330:
2760:
2248:
1845:
1797:
1062:
904:
359:. Another wartime projects, a novel
4222:"Walter Tusting Cocking (obituary)"
4219:
4091:"Building the Williamson Amplifier"
2338:
1931:
1570:A long-time research engineer with
1222:Throughout the 1950s, as prices of
1027:of 6 Hz, and the output stage
401:within the audible frequency range;
351:him for mandatory civilian work at
299:that failed to control fundamental
13:
3926:"A 60-Watt Ultra-Linear Amplifier"
3831:"David Theodore Nelson Williamson"
1609:Amalgamated Wireless (Australasia)
1249:. Designers of the commercial Bell
653:
174:The ultimate version of Cocking's
14:
4427:
4157:"A Wide-Range Feedback Amplifier"
3750:"Audio Feedback Design. Part III"
1740:amplifiers crept even further up.
1651:Federal Communications Commission
1572:Westinghouse Electric Corporation
1094:with bandwidth of at least 1 or 2
658:
370:
280:British school of thought led by
4209:The Williamson Amplifier of 1947
4173:"Triode-Connected 807 Amplifier"
4141:"High Fidelity Power Amplifiers"
4074:(2nd revised ed.). Newnes.
3255:
1696:
1676:
1631:
1598:be enclosed in a feedback loop.
961:
945:
933:
66:Wireless World Quality Amplifier
3269:. 1959 – via tranola.com.
2910:Astor & Langford-Smith 1947
2793:
2521:Astor & Langford-Smith 1947
2188:
1614:
1601:
1591:
1581:
1564:
1533:
1523:
1487:
1474:
1464:
1440:
1427:
1410:All ratings here and below are
1215:generator pentode or the 6P45S
569:"Amplifier to End Amplifiers".
51:community, set the standard of
4323:(July–August): 32–33, 108–110.
4180:Radio and Hobbies in Australia
3776:Crabbe, John (July 14, 2009).
1417:
1404:
1350:flexible manufacturing systems
1342:Quad Electrostatic Loudspeaker
1071:British KT66 beam tetrodes by
829:
500:
474:acoustical labyrinth enclosure
330:
307:. Instead of Kellogg's single
1:
4307:(September). London: 357–361.
4298:"Amplifiers and Superlatives"
4252:Williamson, D. T. N. (1953).
2805:120 Years of Electronic Music
1747:
165:
3767:High Fidelity Circuit Design
3678:"High Quality Amplification"
3665:Power Amplifiers with Valves
3541:Williamson & Walker 1952
3421:Williamson & Walker 1952
1211:directly-heated triode, the
1112:electromagnetic interference
648:High-Quality Audio Amplifier
560:
530:announced production of his
7:
3935:(February): 45–47, 100–102.
3888:"An Ultra-Linear Amplifier"
1148:Distortion in the feedback
915:Nyquist stability criterion
800:
734:
715:Phase shift within 10-20000
37:valve audio power amplifier
10:
4432:
4416:1947 in the United Kingdom
4166:(October): 67–68, 166–167.
3999:"Straight Wire With Gain?"
3812:"The Williamson Amplifier"
3741:10.1109/JRPROC.1945.230873
3602:
2536:Sarser & Sprinkle 1949
2482:Electronics Australia 1990
2463:Electronics Australia 1990
1920:Electronics Australia 1990
1817:Electronics Australia 1990
1624:H primary inductance and 2
908:
772:; its power supply uses a
335:In 1943, in the middle of
57:reference amplifier design
4357:(in Russian) (10): 47–49.
4348:(in Russian) (58): 32–42.
4190:; Sprinkle, M.C. (1949).
4164:Radio and Television News
4107:Radio and Television News
4098:Radio and Television News
4072:Building Valve Amplifiers
3933:Radio and Television News
1012:ultrasonic oscillations.
696:Frequency range: 10-20000
317:Wartime Quality Amplifier
4362:Торопкин, М. В. (2006).
4055:(3rd ed.). Newnes.
3867:Frieborn, J. R. (1953).
3778:"John Crabbe: Firebrand"
3735:(8): 560–562. Aug 1945.
3657:(January): 20–22, 65–69.
3630:Beaumont, J. H. (1950).
3543:, pp. 358, 360–361.
3436:Hafler & Keroes 1951
3040:Hafler & Keroes 1952
1397:
1326:General Electric Company
1241:by Keroes used at least
1237:electrolytics; the 1955
1164:Variants and derivatives
1073:General Electric Company
494:General Electric Company
319:, built around American
4206:Stinson, P. R. (2015).
4114:Kiebert, M. V. (1952).
3869:"High-Quality Circuits"
3708:Cocking, W. T. (1946).
3692:Cocking, W. T. (1943).
3676:Cocking, W. T. (1934).
3671:. Lundahl Transformers.
3646:Bernard, W. B. (1957).
1657:, reaching the rank of
1191:amplifier with a large
1177:Ultralinear Williamsons
998:Williamson transformers
864:Williamson transformers
770:electrolytic capacitors
345:University of Edinburgh
275:interstage transformers
273:and complex, expensive
271:directly-heated triodes
241:surpassing low-quality
117:audible frequency range
4346:В помощь радиолюбителю
4321:High Fidelity Magazine
4192:"Musician's Amplifier"
4100:(December): 52–53, 76.
3748:Cooper, G. F. (1950).
3729:Proceedings of the IRE
3054:, pp. 21, 65, 68.
2448:Radio and Hobbies 1948
1361:Ultralinear Williamson
1285:, employing a pair of
1283:Ultralinear Williamson
1193:electrolytic capacitor
1180:
1076:
1041:Ultralinear Williamson
919:frequency compensation
818:frequency compensation
745:
582:
557:, remained unchanged.
545:frequency compensation
365:Ferranti ribbon pickup
179:
4245:Electronics Australia
4236:Williams, N. (1990).
4155:Mitchell, R. (1950).
4139:Marshall, J. (1956).
4022:Electronics in Action
3973:Holmes, Thom (2006).
3905:; Keroes, H. (1952).
3886:; Keroes, H. (1951).
3819:Electronics Australia
3805:on February 12, 2018.
3789:Dixon, T. O. (1953).
3211:, pp. 18–19, 35.
1655:Bureau of Aeronautics
1269:in the output stage.
1217:horizontal deflection
1171:
1116:signal-to-noise ratio
1070:
909:Further information:
742:
683:at no more than 0.1%
568:
422:Output power of 15–20
415:and, inversely, high
173:
75:error amplifier stage
73:, with an additional
4125:(August): 18–19, 35.
3853:(December): 110–121.
3844:(November): 516–532.
3761:; also reprinted as
3703:(December): 355–358.
3596:, pp. 148, 163.
2614:, pp. 117, 119.
1659:Lieutenant commander
1555:1940 Summer Olympics
1110:Excessive noise and
839:of the transformer.
807:Richard C. Hitchcock
766:capacitively coupled
612:Fritz Langford-Smith
543:from the additional
456:Prototypes and tests
357:Williamson amplifier
18:Williamson amplifier
4328:Wright, T. (1961).
4089:Keroes, H. (1950).
3878:(September): 33–35.
3662:Byrith, C. (2000).
3555:, pp. 522–525.
3514:, pp. 107–108.
3490:, pp. 192–194.
3197:"Contributors" 1945
2953:, pp. 414–415.
2311:, pp. 115–116.
2222:, pp. 520–521.
1973:, pp. 302–303.
1639:University of Idaho
1495:Spicer, S. (2000).
1130:could gain another
428:dynamic loudspeaker
381:harmonic distortion
353:Marconi-Osram Valve
208:transformer-coupled
188:harmonic distortion
105:harmonic distortion
41:D. T. N. Williamson
4406:1947 in technology
4289:(August): 282–287.
4261:. London: Illiffe.
4201:(November): 33–36.
4132:Vacuum Tube Valley
4070:Jones, M. (2013).
4051:Jones, M. (2003).
4030:Hood, John Linsley
4024:(February): 22–26.
4014:Hood, John Linsley
3995:Hood, John Linsley
3947:(December): 42–44.
3916:(June): 26–27, 43.
3897:(November): 15–17.
3860:Vacuum Tube Valley
3759:(December): 42–44.
3612:Langford-Smith, F.
3223:, pp. 18, 35.
3124:, pp. 19, 35.
2807:. 10 January 2014.
2790:, pp. 11, 14.
2323:, pp. 22, 36.
1690:companies, but by
1181:
1104:Bendix Corporation
1077:
871:Overload behaviour
860:leakage inductance
746:
583:
470:full-range speaker
406:transient response
392:frequency response
361:magnetic cartridge
339:, twenty-year-old
293:transient response
180:
113:frequency response
94:output transformer
4337:Electronics World
4271:(April): 118–121.
4199:Audio Engineering
4148:Radio-Electronics
4123:Audio Engineering
3945:Radio-Electronics
3914:Audio Engineering
3895:Audio Engineering
3876:Radio-Electronics
3827:Feilden, G. B. R.
3757:Radio-Electronics
3641:(October): 19–21.
3639:Audio Engineering
3411:, pp. 34–35.
3235:, pp. 18–19.
2965:, pp. 42–44.
2861:, pp. 12–13.
2396:, pp. 14–15.
2384:, pp. 27–28.
2365:, pp. 15–18.
2263:, pp. 17–18.
2239:, pp. 16–17.
1455:Wireless Engineer
1274:ultralinear stage
1267:positive feedback
1255:Stromberg-Carlson
1122:. Replacement of
1063:Component problem
1019:: two interstage
1017:high-pass filters
905:Stability problem
811:diminishingly low
754:Quality Amplifier
644:Radio-Electronics
575:Radio and Hobbies
571:Radio and Hobbies
517:Quality amplifier
325:Quality Amplifier
313:Quality Amplifier
257:and the post-war
184:Edward W. Kellogg
176:Quality Amplifier
89:, and the use of
87:standing currents
79:negative feedback
4423:
4401:Valve amplifiers
4381:
4358:
4349:
4340:
4339:(June): 104–106.
4334:
4324:
4318:
4308:
4302:
4290:
4281:
4272:
4262:
4260:
4248:
4242:
4232:
4226:
4216:
4214:
4202:
4196:
4183:
4177:
4167:
4161:
4151:
4145:
4135:
4126:
4120:
4110:
4109:(November): 1–3.
4101:
4095:
4085:
4066:
4053:Valve Amplifiers
4047:
4025:
4009:
4003:
3990:
3969:
3960:
3948:
3936:
3930:
3917:
3911:
3898:
3892:
3879:
3873:
3863:
3854:
3845:
3835:
3822:
3816:
3806:
3804:
3797:
3785:
3770:
3760:
3754:
3744:
3720:
3714:
3704:
3698:
3688:
3682:
3672:
3670:
3658:
3652:
3642:
3636:
3626:
3620:
3597:
3591:
3585:
3579:
3573:
3567:
3556:
3550:
3544:
3538:
3532:
3526:
3515:
3509:
3503:
3497:
3491:
3485:
3479:
3473:
3467:
3461:
3455:
3445:
3439:
3433:
3424:
3418:
3412:
3406:
3397:
3391:
3385:
3379:
3373:
3367:
3361:
3360:, p. 15.22.
3355:
3349:
3343:
3334:
3328:
3322:
3316:
3310:
3304:
3298:
3292:
3283:
3277:
3271:
3270:
3259:
3253:
3247:
3236:
3230:
3224:
3218:
3212:
3206:
3200:
3194:
3188:
3182:
3176:
3170:
3161:
3155:
3146:
3140:
3125:
3119:
3108:
3102:
3089:
3083:
3074:
3068:
3055:
3049:
3043:
3037:
3028:
3027:, pp. 9–10.
3022:
3016:
3010:
2995:
2989:
2978:
2972:
2966:
2960:
2954:
2948:
2942:
2941:, pp. 9–13.
2936:
2930:
2924:
2913:
2907:
2898:
2892:
2886:
2880:
2874:
2868:
2862:
2856:
2850:
2844:
2833:
2827:
2821:
2815:
2809:
2808:
2797:
2791:
2785:
2779:
2773:
2764:
2758:
2747:
2741:
2732:
2726:
2717:
2711:
2692:
2686:
2680:
2674:
2657:
2651:
2642:
2636:
2627:
2621:
2615:
2609:
2600:
2594:
2588:
2582:
2569:
2563:
2554:
2548:
2539:
2533:
2524:
2518:
2509:
2503:
2497:
2491:
2485:
2479:
2466:
2460:
2451:
2445:
2436:
2430:
2424:
2418:
2412:
2406:
2397:
2391:
2385:
2379:
2366:
2360:
2354:
2345:
2336:
2330:
2324:
2318:
2312:
2306:
2300:
2294:
2285:
2279:
2264:
2258:
2252:
2246:
2240:
2234:
2223:
2217:
2211:
2210:
2208:
2207:
2200:The Valve Museum
2192:
2186:
2180:
2167:
2161:
2144:
2143:, p. 15.17.
2138:
2129:
2123:
2114:
2108:
2087:
2081:
2064:
2058:
2041:
2035:
2029:
2023:
2010:
2004:
1998:
1992:
1986:
1980:
1974:
1968:
1962:
1956:
1947:
1941:
1935:
1929:
1923:
1917:
1911:
1905:
1899:
1893:
1880:
1874:
1849:
1843:
1832:
1826:
1820:
1814:
1801:
1795:
1780:
1774:
1741:
1731:
1724:700 designed by
1723:
1715:
1700:
1694:
1680:
1674:
1635:
1629:
1627:
1623:
1618:
1612:
1605:
1599:
1595:
1589:
1585:
1579:
1568:
1562:
1537:
1531:
1527:
1521:
1520:
1491:
1485:
1478:
1472:
1468:
1462:
1444:
1438:
1431:
1425:
1421:
1415:
1408:
1374:
1369:Dynaco Stereo 70
1365:reference design
1346:milling machines
1296:
1292:
1264:
1259:
1252:
1248:
1244:
1239:reference design
1236:
1232:
1133:
1121:
1097:
1037:smoothing filter
1034:
1025:cutoff frequency
965:
949:
937:
911:Stability theory
899:Lissajous curves
854:of at least 100
843:Stability theory
729:
718:
711:
707:
703:
699:
678:
621:reference design
605:military surplus
450:
446:
436:horn loudspeaker
433:
425:
413:output impedance
297:output impedance
263:do it themselves
251:Great Depression
216:Western Electric
119:, and effective
102:
4431:
4430:
4426:
4425:
4424:
4422:
4421:
4420:
4386:
4385:
4384:
4378:
4332:
4316:
4300:
4280:(May): 162–163.
4258:
4240:
4224:
4212:
4194:
4182:(March): 16–21.
4175:
4159:
4143:
4118:
4093:
4082:
4063:
4044:
4001:
3987:
3959:(January): 2–4.
3928:
3909:
3890:
3871:
3833:
3814:
3802:
3795:
3752:
3719:(January): 2–6.
3712:
3696:
3680:
3668:
3650:
3634:
3618:
3605:
3600:
3592:
3588:
3580:
3576:
3568:
3559:
3551:
3547:
3539:
3535:
3527:
3518:
3510:
3506:
3498:
3494:
3486:
3482:
3474:
3470:
3462:
3458:
3446:
3442:
3434:
3427:
3419:
3415:
3407:
3400:
3392:
3388:
3380:
3376:
3368:
3364:
3356:
3352:
3344:
3337:
3329:
3325:
3317:
3313:
3305:
3301:
3293:
3286:
3278:
3274:
3261:
3260:
3256:
3248:
3239:
3231:
3227:
3219:
3215:
3207:
3203:
3195:
3191:
3183:
3179:
3171:
3164:
3156:
3149:
3141:
3128:
3120:
3111:
3103:
3092:
3084:
3077:
3069:
3058:
3050:
3046:
3038:
3031:
3025:Williamson 1953
3023:
3019:
3011:
2998:
2990:
2981:
2973:
2969:
2961:
2957:
2949:
2945:
2937:
2933:
2929:, pp. 3–4.
2925:
2916:
2908:
2901:
2893:
2889:
2881:
2877:
2871:Williamson 1953
2869:
2865:
2859:Williamson 1953
2857:
2853:
2847:Williamson 1953
2845:
2836:
2828:
2824:
2818:Williamson 1953
2816:
2812:
2799:
2798:
2794:
2788:Williamson 1953
2786:
2782:
2776:Williamson 1953
2774:
2767:
2759:
2750:
2742:
2735:
2729:Williamson 1953
2727:
2720:
2712:
2695:
2687:
2683:
2677:Williamson 1953
2675:
2660:
2654:Williamson 1953
2652:
2645:
2639:Williamson 1953
2637:
2630:
2622:
2618:
2610:
2603:
2595:
2591:
2583:
2572:
2564:
2557:
2549:
2542:
2534:
2527:
2519:
2512:
2504:
2500:
2492:
2488:
2480:
2469:
2461:
2454:
2446:
2439:
2433:Williamson 1953
2431:
2427:
2419:
2415:
2409:Williamson 1953
2407:
2400:
2394:Williamson 1953
2392:
2388:
2380:
2369:
2363:Williamson 1953
2361:
2357:
2346:
2339:
2331:
2327:
2319:
2315:
2307:
2303:
2295:
2288:
2280:
2267:
2259:
2255:
2247:
2243:
2235:
2226:
2218:
2214:
2205:
2203:
2194:
2193:
2189:
2181:
2170:
2164:Williamson 1953
2162:
2147:
2139:
2132:
2128:, pp. 8–9.
2126:Williamson 1953
2124:
2117:
2109:
2090:
2084:Williamson 1953
2082:
2067:
2061:Williamson 1953
2059:
2044:
2036:
2032:
2024:
2013:
2005:
2001:
1993:
1989:
1981:
1977:
1969:
1965:
1957:
1950:
1942:
1938:
1930:
1926:
1918:
1914:
1906:
1902:
1894:
1883:
1875:
1852:
1844:
1835:
1827:
1823:
1815:
1804:
1796:
1783:
1775:
1754:
1750:
1745:
1744:
1729:
1721:
1713:
1701:
1697:
1681:
1677:
1636:
1632:
1625:
1621:
1619:
1615:
1606:
1602:
1596:
1592:
1586:
1582:
1569:
1565:
1547:this photograph
1538:
1534:
1530:transmissions".
1528:
1524:
1509:
1492:
1488:
1479:
1475:
1469:
1465:
1445:
1441:
1432:
1428:
1422:
1418:
1409:
1405:
1400:
1372:
1294:
1290:
1262:
1257:
1250:
1246:
1242:
1234:
1227:
1166:
1150:voltage divider
1131:
1126:with low-noise
1119:
1095:
1065:
1032:
1004:Wireless Worlds
978:
977:
976:
975:
974:
973:
966:
958:
957:
950:
942:
941:
938:
929:
928:
921:
907:
873:
832:
823:voltage divider
803:
758:error amplifier
750:valve amplifier
737:
727:
716:
709:
705:
701:
697:
691:Intermodulation
676:
661:
656:
654:Design features
587:FM broadcasting
563:
503:
478:shellac records
458:
448:
444:
431:
423:
385:intermodulation
373:
333:
309:figure of merit
247:shellac records
243:AM broadcasting
192:interwar period
168:
115:throughout the
109:intermodulation
97:
12:
11:
5:
4429:
4419:
4418:
4413:
4408:
4403:
4398:
4383:
4382:
4376:
4359:
4350:
4341:
4325:
4309:
4305:Wireless World
4293:
4292:
4291:
4287:Wireless World
4282:
4278:Wireless World
4273:
4269:Wireless World
4249:
4233:
4229:Wireless World
4217:
4203:
4184:
4168:
4152:
4136:
4127:
4111:
4102:
4086:
4080:
4067:
4061:
4048:
4042:
4026:
4010:
3991:
3985:
3970:
3968:. McGraw-Hill.
3961:
3949:
3937:
3918:
3899:
3880:
3864:
3855:
3846:
3823:
3807:
3786:
3773:
3772:
3771:
3745:
3725:"Contributors"
3721:
3717:Wireless World
3705:
3701:Wireless World
3689:
3685:Wireless World
3673:
3659:
3643:
3627:
3625:(128): 99–102.
3606:
3604:
3601:
3599:
3598:
3586:
3574:
3557:
3545:
3533:
3531:, p. 119.
3529:Frankland 1996
3516:
3504:
3492:
3480:
3468:
3456:
3440:
3425:
3423:, p. 360.
3413:
3398:
3386:
3374:
3372:, p. 105.
3362:
3358:Hitchcock 1959
3350:
3348:, p. 160.
3335:
3323:
3311:
3299:
3284:
3272:
3254:
3237:
3225:
3213:
3201:
3189:
3177:
3162:
3160:, p. 166.
3147:
3126:
3109:
3107:, p. 104.
3090:
3075:
3056:
3044:
3029:
3017:
2996:
2979:
2967:
2955:
2943:
2931:
2914:
2912:, p. 100.
2899:
2887:
2875:
2863:
2851:
2834:
2822:
2810:
2792:
2780:
2765:
2748:
2733:
2718:
2716:, p. 414.
2693:
2681:
2658:
2643:
2628:
2616:
2612:Frankland 1996
2601:
2589:
2587:, p. 425.
2570:
2555:
2540:
2525:
2523:, p. 101.
2510:
2498:
2486:
2467:
2452:
2437:
2425:
2413:
2398:
2386:
2367:
2355:
2337:
2325:
2313:
2309:Frankland 1996
2301:
2286:
2265:
2253:
2241:
2224:
2212:
2187:
2168:
2145:
2141:Hitchcock 1959
2130:
2115:
2113:, p. 115.
2111:Frankland 1996
2088:
2065:
2042:
2030:
2011:
2009:, p. 518.
1999:
1997:, p. 519.
1987:
1985:, p. 355.
1975:
1963:
1961:, p. 117.
1959:Frankland 1996
1948:
1946:, p. 304.
1936:
1924:
1912:
1900:
1896:Frankland 2002
1881:
1879:, p. 113.
1877:Frankland 1996
1850:
1833:
1821:
1802:
1781:
1779:, p. 520.
1751:
1749:
1746:
1743:
1742:
1695:
1675:
1630:
1613:
1600:
1590:
1580:
1563:
1532:
1522:
1507:
1486:
1473:
1463:
1459:Wireless World
1449:Wireless World
1439:
1426:
1416:
1402:
1401:
1399:
1396:
1338:Frank McIntosh
1185:Herbert Keroes
1165:
1162:
1157:
1156:
1153:
1146:
1138:
1135:
1064:
1061:
1049:Herbert Keroes
1023:, each with a
967:
960:
959:
951:
944:
943:
939:
932:
931:
930:
926:
925:
924:
923:
922:
906:
903:
891:direct current
872:
869:
831:
828:
802:
799:
798:
797:
794:
791:
788:
785:
736:
733:
732:
731:
720:
713:
694:
688:
673:
660:
659:Specifications
657:
655:
652:
562:
559:
555:Wireless World
532:Leak Point One
521:Wireless World
512:Wireless World
502:
499:
457:
454:
440:
439:
420:
417:damping factor
409:
402:
395:
388:
372:
371:Design targets
369:
332:
329:
287:Wireless World
282:Walter Cocking
239:physical media
204:public address
167:
164:
91:wide-bandwidth
71:Walter Cocking
49:do it yourself
9:
6:
4:
3:
2:
4428:
4417:
4414:
4412:
4409:
4407:
4404:
4402:
4399:
4397:
4394:
4393:
4391:
4379:
4373:
4369:
4365:
4360:
4356:
4351:
4347:
4342:
4338:
4331:
4326:
4322:
4315:
4310:
4306:
4299:
4294:
4288:
4283:
4279:
4274:
4270:
4265:
4264:
4257:
4256:
4250:
4246:
4239:
4234:
4230:
4223:
4218:
4211:
4210:
4204:
4200:
4193:
4189:
4188:Sarser, David
4185:
4181:
4174:
4169:
4165:
4158:
4153:
4150:(May): 59–62.
4149:
4142:
4137:
4133:
4128:
4124:
4117:
4112:
4108:
4103:
4099:
4092:
4087:
4083:
4081:9780080966397
4077:
4073:
4068:
4064:
4058:
4054:
4049:
4045:
4039:
4035:
4031:
4027:
4023:
4019:
4015:
4011:
4007:
4000:
3996:
3992:
3988:
3986:0-415-97324-4
3982:
3979:. CRC Press.
3978:
3977:
3971:
3967:
3962:
3958:
3954:
3950:
3946:
3942:
3938:
3934:
3927:
3923:
3919:
3915:
3908:
3904:
3900:
3896:
3889:
3885:
3881:
3877:
3870:
3865:
3861:
3856:
3852:
3847:
3843:
3839:
3832:
3828:
3824:
3820:
3813:
3808:
3801:
3794:
3793:
3787:
3783:
3779:
3774:
3768:
3763:
3762:
3758:
3751:
3746:
3742:
3738:
3734:
3730:
3726:
3722:
3718:
3711:
3706:
3702:
3695:
3690:
3686:
3679:
3674:
3667:
3666:
3660:
3656:
3649:
3644:
3640:
3633:
3628:
3624:
3617:
3613:
3610:Astor, R.H.;
3608:
3607:
3595:
3590:
3583:
3582:Kitteson 1995
3578:
3572:, p. 22.
3571:
3566:
3564:
3562:
3554:
3549:
3542:
3537:
3530:
3525:
3523:
3521:
3513:
3508:
3502:, p. 35.
3501:
3496:
3489:
3488:Торопкин 2006
3484:
3478:, p. 45.
3477:
3472:
3465:
3460:
3453:
3449:
3444:
3438:, p. 16.
3437:
3432:
3430:
3422:
3417:
3410:
3409:Frieborn 1953
3405:
3403:
3396:, p. 35.
3395:
3394:Frieborn 1953
3390:
3384:, p. 34.
3383:
3382:Frieborn 1953
3378:
3371:
3366:
3359:
3354:
3347:
3346:Торопкин 2006
3342:
3340:
3332:
3327:
3320:
3315:
3308:
3303:
3297:, p. 60.
3296:
3295:Marshall 1956
3291:
3289:
3282:, p. 53.
3281:
3276:
3268:
3264:
3258:
3252:, p. 35.
3251:
3246:
3244:
3242:
3234:
3229:
3222:
3217:
3210:
3205:
3198:
3193:
3187:, p. 20.
3186:
3181:
3175:, p. 18.
3174:
3169:
3167:
3159:
3158:Mitchell 1950
3154:
3152:
3145:, p. 61.
3144:
3139:
3137:
3135:
3133:
3131:
3123:
3118:
3116:
3114:
3106:
3101:
3099:
3097:
3095:
3088:, p. 66.
3087:
3082:
3080:
3073:, p. 44.
3072:
3067:
3065:
3063:
3061:
3053:
3048:
3042:, p. 27.
3041:
3036:
3034:
3026:
3021:
3015:, p. 43.
3014:
3009:
3007:
3005:
3003:
3001:
2994:, p. 65.
2993:
2988:
2986:
2984:
2977:, p. 42.
2976:
2971:
2964:
2959:
2952:
2947:
2940:
2935:
2928:
2923:
2921:
2919:
2911:
2906:
2904:
2897:, p. 11.
2896:
2891:
2884:
2879:
2873:, p. 15.
2872:
2867:
2860:
2855:
2849:, p. 17.
2848:
2843:
2841:
2839:
2832:, p. 66.
2831:
2830:Mitchell 1950
2826:
2820:, p. 12.
2819:
2814:
2806:
2802:
2796:
2789:
2784:
2778:, p. 18.
2777:
2772:
2770:
2763:, p. 26.
2762:
2757:
2755:
2753:
2746:, p. 49.
2745:
2744:Beaumont 1950
2740:
2738:
2731:, p. 34.
2730:
2725:
2723:
2715:
2710:
2708:
2706:
2704:
2702:
2700:
2698:
2691:, p. 67.
2690:
2689:Mitchell 1950
2685:
2679:, p. 13.
2678:
2673:
2671:
2669:
2667:
2665:
2663:
2656:, p. 14.
2655:
2650:
2648:
2641:, p. 11.
2640:
2635:
2633:
2626:, p. 33.
2625:
2624:Frieborn 1953
2620:
2613:
2608:
2606:
2599:, p. 25.
2598:
2593:
2586:
2581:
2579:
2577:
2575:
2568:, p. 52.
2567:
2562:
2560:
2553:, p. 30.
2552:
2547:
2545:
2538:, p. 33.
2537:
2532:
2530:
2522:
2517:
2515:
2508:, p. 24.
2507:
2502:
2496:, p. 46.
2495:
2494:Williams 1990
2490:
2483:
2478:
2476:
2474:
2472:
2464:
2459:
2457:
2450:, p. 16.
2449:
2444:
2442:
2434:
2429:
2423:, p. 31.
2422:
2417:
2410:
2405:
2403:
2395:
2390:
2383:
2378:
2376:
2374:
2372:
2364:
2359:
2353:
2349:
2344:
2342:
2335:, p. 36.
2334:
2329:
2322:
2317:
2310:
2305:
2299:, p. 22.
2298:
2293:
2291:
2284:, p. 18.
2283:
2278:
2276:
2274:
2272:
2270:
2262:
2257:
2251:, p. 95.
2250:
2245:
2238:
2233:
2231:
2229:
2221:
2216:
2202:. Allan Wyatt
2201:
2197:
2191:
2185:, p. 16.
2184:
2179:
2177:
2175:
2173:
2165:
2160:
2158:
2156:
2154:
2152:
2150:
2142:
2137:
2135:
2127:
2122:
2120:
2112:
2107:
2105:
2103:
2101:
2099:
2097:
2095:
2093:
2085:
2080:
2078:
2076:
2074:
2072:
2070:
2062:
2057:
2055:
2053:
2051:
2049:
2047:
2039:
2034:
2028:, p. 17.
2027:
2022:
2020:
2018:
2016:
2008:
2003:
1996:
1991:
1984:
1979:
1972:
1967:
1960:
1955:
1953:
1945:
1940:
1933:
1928:
1921:
1916:
1909:
1904:
1898:, p. 12.
1897:
1892:
1890:
1888:
1886:
1878:
1873:
1871:
1869:
1867:
1865:
1863:
1861:
1859:
1857:
1855:
1848:, p. 97.
1847:
1842:
1840:
1838:
1831:, p. 37.
1830:
1825:
1818:
1813:
1811:
1809:
1807:
1800:, p. 25.
1799:
1794:
1792:
1790:
1788:
1786:
1778:
1773:
1771:
1769:
1767:
1765:
1763:
1761:
1759:
1757:
1752:
1739:
1735:
1727:
1719:
1711:
1707:
1706:
1702:According to
1699:
1693:
1689:
1685:
1679:
1672:
1668:
1664:
1660:
1656:
1652:
1648:
1644:
1640:
1634:
1617:
1610:
1604:
1594:
1584:
1577:
1573:
1567:
1560:
1556:
1552:
1548:
1544:
1543:
1536:
1526:
1518:
1514:
1510:
1508:9781882580316
1504:
1500:
1499:
1490:
1483:
1477:
1467:
1460:
1456:
1451:
1450:
1443:
1436:
1430:
1420:
1413:
1407:
1403:
1395:
1391:
1389:
1385:
1382:
1378:
1370:
1366:
1362:
1357:
1355:
1354:Royal Society
1351:
1347:
1343:
1339:
1335:
1331:
1327:
1323:
1319:
1315:
1314:Harman/Kardon
1311:
1307:
1302:
1300:
1288:
1284:
1279:
1278:Alan Blumlein
1275:
1270:
1268:
1256:
1240:
1231:
1225:
1220:
1218:
1214:
1210:
1206:
1202:
1198:
1194:
1190:
1186:
1178:
1174:
1170:
1161:
1154:
1151:
1147:
1143:
1139:
1136:
1129:
1125:
1117:
1113:
1109:
1108:
1107:
1105:
1099:
1093:
1089:
1086:
1081:
1074:
1069:
1060:
1057:
1052:
1050:
1046:
1042:
1038:
1030:
1026:
1022:
1018:
1013:
1010:
1006:
1005:
999:
996:Custom-built
994:
991:
987:
983:
971:
964:
955:
948:
936:
920:
916:
912:
902:
900:
896:
892:
887:
884:
880:
879:
868:
865:
861:
857:
853:
849:
844:
840:
838:
827:
824:
819:
814:
812:
808:
795:
792:
789:
786:
783:
782:
781:
777:
775:
771:
767:
761:
759:
755:
751:
741:
726:: -85 dB
725:
721:
714:
695:
692:
689:
686:
682:
674:
671:
667:
663:
662:
651:
649:
645:
641:
636:
634:
630:
624:
622:
618:
613:
608:
606:
602:
601:
596:
592:
588:
580:
576:
572:
567:
558:
556:
551:
546:
540:
537:
533:
529:
524:
522:
518:
514:
513:
508:
498:
495:
490:
486:
485:Decca Records
481:
479:
475:
471:
468:
464:
453:
437:
429:
421:
418:
414:
410:
407:
403:
400:
396:
393:
389:
386:
382:
378:
377:
376:
368:
366:
362:
358:
354:
350:
346:
342:
338:
328:
326:
322:
318:
314:
310:
306:
305:high fidelity
302:
298:
294:
289:
288:
283:
278:
276:
272:
268:
267:beam tetrodes
264:
260:
256:
252:
248:
244:
240:
236:
232:
231:high fidelity
228:
223:
221:
220:300A and 300B
218:around their
217:
213:
209:
205:
201:
197:
193:
189:
185:
177:
172:
163:
160:
156:
152:
148:
144:
139:
137:
136:high fidelity
133:
129:
126:
122:
118:
114:
110:
106:
101:
95:
92:
88:
84:
80:
77:and a global
76:
72:
68:
67:
61:
58:
54:
53:high fidelity
50:
46:
42:
38:
34:
31:
27:
23:
19:
4396:Vacuum tubes
4367:
4363:
4354:
4345:
4336:
4320:
4304:
4286:
4277:
4268:
4254:
4244:
4228:
4220:TJB (1984).
4208:
4198:
4179:
4163:
4147:
4131:
4122:
4106:
4097:
4071:
4052:
4033:
4021:
4006:Studio Sound
4005:
3975:
3965:
3956:
3944:
3932:
3913:
3894:
3875:
3859:
3850:
3841:
3837:
3821:(July): 1–4.
3818:
3800:the original
3791:
3781:
3766:
3756:
3732:
3728:
3716:
3700:
3684:
3664:
3654:
3638:
3623:Radiotronics
3622:
3589:
3577:
3553:Feilden 1995
3548:
3536:
3507:
3500:Stinson 2015
3495:
3483:
3476:Hafler 1955a
3471:
3466:, p. 2.
3459:
3443:
3416:
3389:
3377:
3365:
3353:
3326:
3319:Романюк 1965
3314:
3309:, p. 2.
3302:
3275:
3257:
3250:Kiebert 1952
3233:Kiebert 1952
3228:
3221:Kiebert 1952
3216:
3209:Kiebert 1952
3204:
3192:
3185:Bernard 1957
3180:
3173:Kiebert 1952
3143:Bernard 1957
3122:Kiebert 1952
3086:Bernard 1957
3052:Bernard 1957
3047:
3020:
2992:Bernard 1957
2970:
2958:
2946:
2934:
2890:
2885:, p. 9.
2878:
2866:
2854:
2825:
2813:
2804:
2795:
2783:
2684:
2619:
2597:Stinson 2015
2592:
2551:Stinson 2015
2506:Stinson 2015
2501:
2489:
2484:, p. 2.
2465:, p. 3.
2428:
2421:Stinson 2015
2416:
2411:, p. 3.
2389:
2382:Stinson 2015
2358:
2333:Stinson 2015
2328:
2321:Stinson 2015
2316:
2304:
2297:Stinson 2015
2282:Stinson 2015
2261:Stinson 2015
2256:
2244:
2237:Stinson 2015
2220:Feilden 1995
2215:
2204:. Retrieved
2199:
2190:
2183:Stinson 2015
2166:, p. 9.
2086:, p. 8.
2063:, p. 7.
2040:, p. 3.
2038:Stinson 2015
2033:
2026:Stinson 2015
2007:Feilden 1995
2002:
1995:Feilden 1995
1990:
1983:Cocking 1943
1978:
1971:Cocking 1934
1966:
1944:Cocking 1934
1939:
1927:
1922:, p. 1.
1915:
1910:, p. 7.
1908:Stinson 2015
1903:
1829:Stinson 2015
1824:
1819:, p. 4.
1777:Feilden 1995
1718:Phase Linear
1709:
1703:
1698:
1683:
1678:
1643:Reed College
1633:
1620:Assuming 100
1616:
1603:
1593:
1583:
1566:
1559:Magnetophons
1558:
1550:
1540:
1535:
1525:
1497:
1489:
1481:
1476:
1466:
1458:
1454:
1447:
1442:
1434:
1429:
1419:
1411:
1406:
1392:
1377:Mullard 5-10
1360:
1358:
1334:Peter Walker
1303:
1282:
1271:
1221:
1197:David Hafler
1182:
1176:
1158:
1100:
1092:oscilloscope
1082:
1078:
1053:
1045:David Hafler
1040:
1014:
1002:
997:
995:
986:screen grids
982:phase margin
979:
972:measurements
956:measurements
895:oscillograms
888:
882:
876:
874:
863:
848:phase margin
841:
833:
815:
804:
778:
774:CLC π-filter
762:
753:
747:
647:
637:
625:
609:
598:
590:
584:
578:
574:
570:
554:
550:preamplifier
541:
525:
520:
516:
511:
504:
482:
463:power supply
459:
441:
374:
356:
337:World War II
334:
324:
316:
312:
285:
279:
255:World War II
234:
224:
181:
175:
155:phase margin
143:oscillations
140:
64:
62:
45:World War II
39:designed by
17:
15:
4247:(6): 42–47.
4008:(4): 22–29.
3862:(18): 9–13.
3851:Stereophile
3782:Stereophile
3464:Keroes 1955
3448:Holmes 2006
3370:Wright 1961
3307:Hafler 1956
3280:Keroes 1950
3105:Wright 1961
3071:Cooper 1950
3013:Cooper 1950
2975:Cooper 1950
2963:Cooper 1950
2566:Keroes 1950
2348:Crabbe 2009
1738:home cinema
1736:-certified
1688:Bell System
1551:Magnetophon
1542:Magnetophon
1412:per channel
1388:audiophiles
1247:600 μF
1243:250 μF
830:Transformer
704:dB; 3-60000
600:Magnetophon
539:following.
528:Harold Leak
501:Publication
399:phase shift
397:Negligible
331:Development
130:. The 0.1%
125:loudspeaker
4411:1947 works
4390:Categories
4377:5943871772
4062:0750656948
4043:0750633565
4036:. Newnes.
3957:Audiocraft
3953:Hafler, D.
3941:Hafler, D.
3922:Hafler, D.
3903:Hafler, D.
3884:Hafler, D.
3450:, p.
2951:Jones 2003
2939:Dixon 1953
2927:Dixon 1953
2895:Dixon 1953
2883:Dixon 1953
2714:Jones 2003
2585:Jones 2013
2350:, p.
2206:2018-02-11
1748:References
1730:250 W
1726:Bob Carver
1710:power race
1576:Pittsburgh
1424:equipment.
1381:subjective
1310:The Fisher
1235:40 μF
1224:capacitors
1201:fixed bias
1132:12 dB
1120:12 dB
1088:multimeter
1056:parasitics
1021:RC filters
852:inductance
722:Noise and
700:Hz at ±0.2
489:Decca ffrr
259:television
200:sound film
166:Background
151:ultrasonic
147:infrasonic
132:distortion
128:resonances
22:four-stage
4231:(May): 8.
4134:(1): 5–7.
3924:(1955a).
3594:Hood 2006
3570:Hood 1975
3512:Hood 2006
3331:Баев 1977
2761:Hood 1994
2249:Hood 2006
1846:Hood 2006
1798:Hood 1994
1714:75 W
1647:KIRO (AM)
1549:, an AEG
1482:Point One
1480:The name
1384:listening
1299:trademark
1295:30 W
1291:20 W
1219:tetrode.
1029:RL filter
837:bandwidth
821:Feedback
617:"premium"
595:LP record
561:Reception
432:10 W
301:resonance
159:stability
26:push-pull
4032:(2006).
4016:(1994).
3997:(1975).
3829:(1995).
3614:(1947).
1932:TJB 1984
1692:TRW Inc.
1517:8683702M
1085:analogue
1009:Ferranti
801:Feedback
735:Topology
708:Hz at ±3
633:monaural
593:and the
507:Ferranti
467:Goodmans
341:Scotsman
198:. Early
182:In 1925
98:15
35:-output
3603:Sources
1671:Mallory
1667:Convair
1322:Mullard
1318:Marantz
1228:8
1203:in his
536:Quad II
390:Linear
349:drafted
235:sources
212:class B
196:cinemas
121:damping
111:, flat
43:during
30:Class A
4374:
4078:
4059:
4040:
3983:
2196:"PX25"
1722:
1708:, the
1663:Bendix
1649:, the
1626:
1622:
1515:
1505:
1435:before
1373:
1263:
1258:
1251:
1096:
1033:
970:US NRL
954:US NRL
917:, and
858:, and
744:shown)
728:
717:
710:
706:
702:
698:
677:
640:Rogers
629:Stereo
472:in an
449:
445:
434:for a
424:
249:. The
33:triode
4366:[
4355:Радио
4333:(PDF)
4317:(PDF)
4301:(PDF)
4259:(PDF)
4241:(PDF)
4225:(PDF)
4213:(PDF)
4195:(PDF)
4176:(PDF)
4160:(PDF)
4144:(PDF)
4119:(PDF)
4094:(PDF)
4002:(PDF)
3929:(PDF)
3910:(PDF)
3891:(PDF)
3872:(PDF)
3834:(PDF)
3815:(PDF)
3803:(PDF)
3796:(PDF)
3753:(PDF)
3713:(PDF)
3697:(PDF)
3681:(PDF)
3669:(PDF)
3655:Audio
3651:(PDF)
3635:(PDF)
3619:(PDF)
1720:Model
1398:Notes
1261:Bogen
1213:GU-50
1128:12AY7
883:choke
443:20–30
430:, or
404:Good
100:Watts
20:is a
4372:ISBN
4076:ISBN
4057:ISBN
4038:ISBN
3981:ISBN
3267:EICO
1684:Bell
1682:The
1669:and
1641:and
1539:The
1503:ISBN
1348:and
1336:and
1330:KT88
1316:and
1306:Eico
1209:6C4C
1205:EL34
1173:EICO
1142:6SN7
1140:The
1124:6SN7
1047:and
897:and
878:clip
816:All
670:6SN7
591:ffrr
577:did
411:Low
383:and
245:and
202:and
149:and
107:and
83:KT66
16:The
3737:doi
1734:THX
1574:in
1287:6L6
1189:807
1118:by
1043:by
724:hum
712:dB;
685:THD
681:RMS
666:6J5
579:not
321:6V6
284:of
227:RCA
145:at
123:of
69:by
4392::
4335:.
4319:.
4303:.
4243:.
4227:.
4197:.
4178:.
4162:.
4146:.
4121:.
4096:.
4020:.
4004:.
3931:.
3912:.
3893:.
3874:.
3842:41
3840:.
3836:.
3817:.
3780:.
3755:.
3733:33
3731:.
3727:.
3715:.
3699:.
3683:.
3653:.
3637:.
3621:.
3560:^
3519:^
3428:^
3401:^
3338:^
3287:^
3265:.
3240:^
3165:^
3150:^
3129:^
3112:^
3093:^
3078:^
3059:^
3032:^
2999:^
2982:^
2917:^
2902:^
2837:^
2803:.
2768:^
2751:^
2736:^
2721:^
2696:^
2661:^
2646:^
2631:^
2604:^
2573:^
2558:^
2543:^
2528:^
2513:^
2470:^
2455:^
2440:^
2401:^
2370:^
2340:^
2289:^
2268:^
2227:^
2198:.
2171:^
2148:^
2133:^
2118:^
2091:^
2068:^
2045:^
2014:^
1951:^
1884:^
1853:^
1836:^
1805:^
1784:^
1755:^
1665:,
1513:OL
1511:.
1457:,
1312:,
1308:,
1230:μF
913:,
813:.
679:W
367:.
277:.
253:,
210:,
28:,
24:,
4380:.
4215:.
4084:.
4065:.
4046:.
3989:.
3743:.
3739::
3584:.
3454:.
3452:8
3333:.
3321:.
2435:.
2352:4
2209:.
1934:.
1728:(
1673:.
1519:.
1134:;
856:H
687:;
438:.
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