460:
645:
transformer primary at the frequencies in use is much higher than the DC resistance of the windings, often kilohms. High performance transformers are, however, severe engineering compromises, are expensive and, in operation, are far from ideal. Output transformers dramatically increase the cost of a valve amplifier circuit compared to a direct-coupled transistor alternative. However, in both tube and solid state amps, matching output transformers are required for public address applications where low-loss high impedance/high voltage lines are used to connect multiple distant loudspeakers.
828:" – the building blocks of much modern linear electronics. An op-amp typically has a differential input stage and a totem pole output, the circuit usually having a minimum of five active devices. A number of "packages" were produced that integrated such circuits (typically using two or more glass envelopes) into a single module that could be plugged into a larger circuit (such as an analog computer). Such valve op-amps were very far from ideal and quickly became obsolete, being replaced with solid-state types.
492:
521:
55:
483:. In a tube amplifier, the transition from linear amplification to limiting is less abrupt than in a solid state unit, resulting in a less grating form of distortion at the onset of clipping. For this reason, some guitarists prefer the sound of an all-tube amplifier; the aesthetic properties of tube versus solid state amps, though, are a topic of debate in the guitarist community.
152:
325:
776:
784:
850:
Broadband circuits require flat response over a wide range of frequencies. RF circuits by contrast are typically required to operate at high frequencies but often over a very narrow frequency range. For example, an RF device might be required to operate over the range 144 to 146 MHz (just 1.4%)
535:
Can be constructed on a scale that can dissipate large amounts of heat (some extreme devices even being water-cooled). For this reason valves remained the only viable technology for very high power applications such as radio and TV transmitters long into the age when transistors had displaced valves
475:
Many professional guitar players use 'tube amps' because of their renowned 'tone'. 'Tone' in this usage is referring to timbre, or pitch color, and can be a very subjective quality to quantify. Most audio technicians and scientists theorize that the 'even harmonic distortion' produced by valve tubes
846:
RF circuits are significantly different from broadband amplifier circuits. The antenna or following circuit stage typically contains one or more adjustable capacitive or inductive component allowing the resonance of the stage to be accurately matched with carrier frequency in use, to optimize power
842:
Historically, pre-WWII "transmitting tubes" were among the most powerful tubes available. These usually had directly heated thoriated filament cathodes that glowed like light bulbs. Some tubes were capable of being driven so hard that the anode itself would glow cherry red; the anodes were machined
499:
Power valves typically operate at higher voltages and lower currents than transistors - although solid state operating voltages have steadily increased with modern device technologies. High power radio transmitters in use today operate in the kilovolt range, where there is still no other comparable
467:
In audio applications, valves continue to be highly desired by most professional users, particularly in recording studios' equipment and guitar amplifiers. There is a subgroup of audio enthusiasts who advocate the use of tube amplifiers for home listening. They argue that tube amplifiers produce a
804:
itself takes a small current and thus loads the circuit to which it is attached. This can significantly alter the operating conditions in the circuit being measured. The vacuum tube voltmeter (VTVM) uses the high input impedance of a valve to buffer the circuit being measured from the load of the
511:
and many of the directly heated single-ended triode (DH-SET) audio amplifiers use radio transmitting tubes designed to operate in the megahertz range. In practice, however, tube amplifier designs typically "couple" stages either capacitively, limiting bandwidth at the low end, or inductively with
385:
was able to drive full frequency range loudspeakers (for the first time, often with multiple drivers for different frequency bands) to significant volume levels. This, combined with the spread of TV, produced a 'golden age' in valve (tube) development and also in the development of the design of
374:
stimulated dramatic technical progress and industrial scale production economies. Increasing affluence after the war led to a substantial and expanding consumer market. This enabled electronics manufacturers to build and market more advanced valve (tube) designs at affordable prices, with the
673:
single ended power stages using very large valves exist and dominate in radio transmitter applications. A sidebar is the observation that the niche "DH-SET" topology favored by some audiophiles are extremely simple and typically constructed using valve types originally designed for use in radio
812:
share this very high input impedance and thus can be used to measure voltages even in very high impedance circuits. There may typically be 3 or 4 stages of amplification per display channel. In later oscilloscopes, a type of amplifier using a series of tubes connected at equal distances along
644:
of valves (compared with transistors) usually requires matching transformers to drive low impedance loads such as loudspeakers or cutting lathe heads. The transformer is used as the load, in place of the resistor usually used in small-signal and driver stages. The reflected impedance of the
397:" transformer connection for tetrodes) rapidly became widespread. This family of designs remains the dominant high power amplifier topology to this day for music application. This period also saw continued growth in civilian radio, with valves being used for both transmitters and receivers.
843:
from solid material (rather than fabricated from thin sheet) to withstand heat without distorting. Notable tubes of this type are the 845 and 211. Later tetrodes and pentodes such as 817 and (direct heated) 813 were also used in large numbers in (especially military) radio transmitters
686:
The high output impedance of tube plate circuits is not well matched to low-impedance loads such as loudspeakers or antennas. A matching network is required for efficient power transfer; this may be a transformer at audio frequencies, or various tuned networks at radio frequencies.
665:
Modern high power output stages are usually push pull, often necessitating some form of phase splitter to derive a differential/balanced drive signal from a single ended input, typically followed by a further gain stage (the "driver") prior to the output tubes. For example, a
733:
Telephony was the original, and for many years was a driving application for audio amplification. A specific issue for the telecommunication industry was the technique of multiplexing many (up to a thousand) voice lines onto a single cable, at different frequencies.
625:
The grid (where the input signal is presented) needs to be biased substantially negative with respect to the cathode. This makes it extremely difficult to directly couple the output of one valve to the input of a following valve as is normally done in transistor
768:, although these applications have different requirements regarding distortion which result in different design compromises, although the same basic design techniques are generic and widely applicable to all broadband amplification applications, not only audio.
771:
Post World War II, the majority of valve power amplifiers are of the Class AB-1 "push pull" ultralinear topology, or lower cost single ended i.e. 6BQ5/EL84 power tubes, but niche products using the DH-SET and even OTL topologies still exist in small numbers.
302:. The relationship between current flow and plate and grid voltage is often represented as a series of "characteristic curves" on a diagram. Depending on the other components in the circuit this modulated current flow can be used to provide current or
362:
in 1947, which was extremely advanced in many respects including very successful use of NFB, was a turning point in audio power amplifier design, operating a push-pull output circuit in class AB1 to give performance surpassing its contemporaries.
417:(ECCnn, 12Ax7 series) plus the EF86 pentode, and power valves were mostly being beam tetrode and pentodes (EL84, EL34, KT88 / 6550, 6L6), in both cases with indirect heating. This reduced set of types remains the core of valve production today.
357:
in 1927, but initially little used since at that time gain was at a premium. This technique allows amplifiers to trade gain for reduced distortion levels (and also gave other benefits such as reduced output impedance). The introduction of the
629:
Valve stages are coupled with components rated to withstand several hundred volts, typically a capacitor, occasionally a coupling transformer. The phase shifts introduced by coupling networks can become problematic in circuits that have
648:
The open loop linearity of valves, especially triodes, makes it possible to use little or no negative feedback in circuits whilst retaining acceptable or even excellent distortion performance (especially for small-signal
476:
sounds more pleasing to the ear than transistors, regardless of style. It is the tonal characteristics of valve tubes that have sustained them as the industry standard for guitars and studio microphone pre-amplification.
698:
configuration, the output is taken from the cathode resistance. Because of negative feedback (the cathode-ground voltage cancels the grid-ground voltage) the voltage gain is close to unity and the output voltage
854:
Today, radio transmitters are overwhelmingly silicon based, even at microwave frequencies. However, an ever-decreasing minority of high power radio frequency amplifiers continue to have valve construction.
724:
amplifiers due to the perceived sound quality they produce. They are largely obsolete elsewhere because of higher power consumption, distortion, costs, reliability, and weight in comparison to transistors.
737:
The advantage of this is that a single valve "repeater" amplifier can amplify many calls at once, this being very cost effective. The problem is that the amplifiers need to be extremely linear, otherwise
595:
Tubes are available in only a single polarity, whereas transistors are available in complementary polarities (e.g., NPN/PNP), making possible many circuit configurations that cannot be realized directly.
742:
distortion" (IMD) will result in "crosstalk" between the multiplexed channels. This stimulated development emphasis towards low distortion far beyond the nominal needs of a single voice channel.
347:, almost all valve amplifiers were of low gain and with linearity dependent entirely on the inherent linearity of the valve itself, typically 5% distortion at full power.
459:
633:
There is no valve analog of the complementary devices widely used in "totem pole" output stages of silicon circuits. Push-pull valve topologies therefore require a
555:
Softer clipping when overloading the circuit, which many audiophiles and musicians subjectively believe gives a more pleasant and more musically satisfying sound.
432:, for the majority of their communications and military amplification requirements, in part due to valves' ability to withstand instantaneous overloads (notably
39:
703:
the grid voltage. Although the cathode resistor can be many kilohms (depending on biasing requirements), the small-signal output impedance is very low (see
30:
This article is about valve (vacuum tube) amplifiers in general. For a more detailed discussion on the use of valve amplifiers in specific applications, see
343:
performance) despite extremely simple circuitry with very few components: important at a time when components were handmade and extremely expensive. Before
677:
more complex topologies (notably the use of active loads) can improve linearity and frequency response (by removing Miller capacitance effects).
977:
659:
Linear small signal circuits almost invariably use a triode in the single ended gain stage topology (in class A), including the output stage.
821:
was employed to amplify very high frequency vertical signals before application to the display tube. Valve oscilloscopes are now obsolete.
667:
1020:– Although oriented towards valve guitar amplifiers, AX84's free schematics and theory document apply well to any tube/valve project
940:
138:
72:
119:
932:
76:
581:
High impedance and low current output is unsuitable for the direct drive of many real-world loads, notably various forms of
447:
for mainstream products since the 1970s. Valves remained in certain applications such as high power RF transmitters and the
324:
91:
875:, copper oxide rectifier, or crystal detector diode were known before the transistor, but were unable to amplify a signal.
1008:– An almost complete list of manufacturers, DIY kits, materials and parts and 'how they work' sections on valve amplifiers
893:
451:, and audio amplification equipment, particularly for the electric guitar, recording studios, and high-end home stereos.
549:
Withstand very high transient peak voltages without damage, suiting them to certain military and industrial applications
98:
540:
180:
43:
375:
result that the 1960s saw the increasing spread of electronic gramophone players, and ultimately the beginnings of
479:
Tube amplifiers respond differently from transistor amplifiers when signal levels approach and reach the point of
65:
1039:
957:
872:
188:
105:
756:
Today, the main application for valves is audio amplifiers for high-end hi-fi and musical performance use with
552:
Generally operate at applied voltages well below their maximum capability, providing long life and reliability
618:
588:
Valves have a shorter working life than solid state parts due to various failure mechanisms (such as heat,
87:
751:
825:
818:
704:
575:
Tubes require higher voltages for the anodes compared to solid state amplifiers of similar power rating.
433:
31:
641:
409:
became increasingly pervasive. Valve production was sharply decreased, with the notable exception of
359:
354:
258:
168:
972:
880:
876:
491:
336:
329:
463:
A single-ended class 'A' guitar amplifier chassis, with additional GZ34 valve rectifier installed.
414:
987:
982:
837:
35:
413:(CRTs), and a reduced range of valves for amplifier applications. Popular low power tubes were
967:
936:
814:
350:
112:
952:
504:
480:
410:
246:
192:
507:. Signal amplifiers using tubes are capable of very high frequency response ranges – up to
472:. Companies in Asia and Eastern Europe continue to produce valves to cater to this market.
757:
739:
508:
262:
617:
All amplifier circuits are classified by "class of operation" as A, B, AB and C etc. See
191:
amplifiers in the 1960s and 1970s. Valve amplifiers can be used for applications such as
621:. Some significantly different circuit topologies exist compared to transistor designs.
317:' market that began in the early thirties. In due course amplifiers for music and later
721:
634:
604:– valves may sometimes be sensitive to sound or vibration, inadvertently acting like a
582:
569:
539:
Electrically very robust, they can tolerate overloads for minutes, which would destroy
448:
443:
levels and above all cost of electronics products based on transistors has made valves
390:
500:
technology available. (, so high power requires high voltage, high current, or both)
339:
gain stage, operating in class A, which gave very good sound (and reasonable measured
309:
The first application of valve amplification was in the regeneration of long distance
1033:
765:
761:
524:
377:
277:
905:
809:
601:
520:
425:
421:
394:
371:
344:
303:
172:
1011:
916:
280:
added a third electrode and invented the first electronic amplifying device, the
999:
589:
544:
469:
266:
225:
199:
54:
1005:
17:
605:
440:
406:
340:
318:
242:
222:
184:
245:
in 1947, most practical high-frequency electronic amplifiers were made using
797:
310:
270:
254:
196:
176:
779:
A pre-amplifier design using all power tubes instead of small signal tubes
775:
962:
598:
Valve circuits must avoid introduction of noise from AC heater supplies.
444:
429:
314:
783:
335:
The overwhelmingly dominant circuit topology during this period was the
801:
295:
203:
1026:– Massive collection (7 GB+) of tube data sheets and information.
824:
In the closing years of the valve era, valves were even used to make "
151:
847:
transfer from and loading on the valve, a so-called "tuned circuit".
286:
281:
389:
A range of topologies with only minor variations (notably different
782:
774:
578:
Tubes are significantly larger than equivalent solid-state devices
519:
458:
323:
299:
250:
215:
211:
572:. Heater power represents a significant heat loss and energy use.
210:, high quality stereo amplifiers, military applications (such as
183:. Low to medium power valve amplifiers for frequencies below the
382:
1023:
495:
1960's Fender
Bandmaster Reverb tube guitar amplifier chassis.
219:
207:
48:
269:
in one direction only and was used as a radio detector and a
439:
The dramatic reduction in size, power consumption, reduced
662:
Broadband valve amplifiers typically use class A1 or AB1.
503:
Many power valves have good linearity but modest gain or
313:
signals. Later, valve amplification was applied to the '
565:
Bad linearity, especially with modest feedback factors.
1017:
906:
1014:– distortion factor to distortion attenuation and THD
787:
A 300B preamp/solid state output 70Wrms/ch hybrid amp
512:transformers, limiting the bandwidth at both ends.
79:. Unsourced material may be challenged and removed.
424:retained valves to a much greater extent than the
832:Narrow band and radio frequency tuned amplifiers
883:were not directly useful as electronic devices.
720:Valves remain in widespread use in guitar and
532:Inherently suitable for high voltage circuits.
716:Audio frequency (AF) and broadband amplifiers
40:Valve audio amplifier technical specification
8:
42:. For tube amps from the Valve company, see
527:MC240 from 1961 with exposed vacuum tubes
294:modulates the current that flows between
139:Learn how and when to remove this message
592:, breakage, or internal short-circuits).
490:
150:
1002:– Henry Pasternack's FAQ from rec.audio
931:Radio communication handbook (5th Ed),
864:
265:in London in 1904. The diode conducted
879:were limited to below roughly 200kHz.
917:Audio Power Amplifier Design Handbook
7:
77:adding citations to reliable sources
668:shunt regulated push-pull amplifier
436:) that would destroy a transistor.
25:
978:Valve audio amplifier – technical
871:Solid state devices such as the
53:
64:needs additional citations for
933:Radio Society of Great Britain
321:were also built using valves.
1:
894:Nuclear electromagnetic pulse
249:. The simplest valve (named
27:Type of electronic amplifier
536:in most other applications.
468:"warmer" or more "natural"
434:due to a nuclear detonation
405:From the 1970s the silicon
241:Until the invention of the
44:Valve Amplification Company
1056:
835:
792:Instrumentation amplifiers
749:
386:valve amplifier circuits.
29:
958:Vintage musical equipment
187:were largely replaced by
619:power amplifier classes
873:cat's-whisker detector
826:operational amplifiers
796:The basic moving coil
788:
780:
752:Valve audio amplifiers
528:
496:
464:
393:arrangements and the "
353:(NFB) was invented by
332:
261:while working for the
214:) and very high power
156:
1012:Conversion calculator
819:distributed amplifier
786:
778:
705:operational amplifier
640:The very high output
523:
494:
462:
367:Post-war developments
328:Circuit diagram of a
327:
284:, which he named the
154:
32:Valve audio amplifier
881:Hydraulic amplifiers
360:Williamson amplifier
355:Harold Stephen Black
259:John Ambrose Fleming
169:electronic amplifier
73:improve this article
1000:The Vacuum Tube FAQ
973:Traveling wave tube
877:Magnetic amplifiers
337:single-ended triode
330:single-ended triode
253:because it had two
988:Valve transmitters
983:Valve RF amplifier
838:Valve RF Amplifier
815:transmission lines
789:
781:
541:bipolar transistor
529:
497:
465:
333:
290:. This additional
257:) was invented by
157:
36:Valve RF amplifier
1024:Tube Data Archive
1006:The Audio Circuit
968:Robert von Lieben
590:cathode poisoning
411:cathode ray tubes
351:Negative feedback
247:thermionic valves
193:guitar amplifiers
175:to increase the
149:
148:
141:
123:
88:"Valve amplifier"
16:(Redirected from
1047:
1040:Valve amplifiers
953:Guitar amplifier
919:
914:
908:
903:
897:
890:
884:
869:
758:electric guitars
692:cathode follower
682:Output impedance
568:Tubes require a
505:transconductance
155:6N3C power tube.
144:
137:
133:
130:
124:
122:
81:
57:
49:
21:
1055:
1054:
1050:
1049:
1048:
1046:
1045:
1044:
1030:
1029:
996:
949:
928:
923:
922:
915:
911:
904:
900:
891:
887:
870:
866:
861:
840:
834:
794:
762:electric basses
754:
748:
740:intermodulation
731:
718:
713:
684:
656:
615:
583:electric motors
562:
518:
509:radio frequency
489:
487:Characteristics
457:
403:
369:
263:Marconi Company
239:
234:
161:valve amplifier
145:
134:
128:
125:
82:
80:
70:
58:
47:
28:
23:
22:
18:Tube amplifiers
15:
12:
11:
5:
1053:
1051:
1043:
1042:
1032:
1031:
1028:
1027:
1021:
1015:
1009:
1003:
995:
994:External links
992:
991:
990:
985:
980:
975:
970:
965:
960:
955:
948:
945:
944:
943:
927:
924:
921:
920:
909:
898:
885:
863:
862:
860:
857:
836:Main article:
833:
830:
793:
790:
766:Hammond organs
750:Main article:
747:
744:
730:
727:
722:high-end audio
717:
714:
712:
709:
683:
680:
679:
678:
675:
671:
663:
660:
655:
652:
651:
650:
646:
638:
635:phase splitter
631:
627:
614:
611:
610:
609:
599:
596:
593:
586:
579:
576:
573:
570:cathode heater
566:
561:
558:
557:
556:
553:
550:
547:
537:
533:
517:
514:
488:
485:
456:
453:
449:microwave oven
402:
399:
391:phase splitter
368:
365:
238:
235:
233:
230:
179:or power of a
165:tube amplifier
147:
146:
61:
59:
52:
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
1052:
1041:
1038:
1037:
1035:
1025:
1022:
1019:
1016:
1013:
1010:
1007:
1004:
1001:
998:
997:
993:
989:
986:
984:
981:
979:
976:
974:
971:
969:
966:
964:
961:
959:
956:
954:
951:
950:
946:
942:
941:0-900612-28-2
938:
934:
930:
929:
925:
918:
913:
910:
907:
902:
899:
895:
889:
886:
882:
878:
874:
868:
865:
858:
856:
852:
848:
844:
839:
831:
829:
827:
822:
820:
817:, known as a
816:
811:
810:oscilloscopes
806:
803:
799:
791:
785:
777:
773:
769:
767:
763:
759:
753:
745:
743:
741:
735:
728:
726:
723:
715:
710:
708:
706:
702:
697:
693:
688:
681:
676:
672:
669:
664:
661:
658:
657:
653:
647:
643:
639:
636:
632:
628:
624:
623:
622:
620:
612:
607:
603:
600:
597:
594:
591:
587:
584:
580:
577:
574:
571:
567:
564:
563:
560:Disadvantages
559:
554:
551:
548:
546:
542:
538:
534:
531:
530:
526:
522:
515:
513:
510:
506:
501:
493:
486:
484:
482:
477:
473:
471:
461:
454:
452:
450:
446:
442:
437:
435:
431:
427:
423:
418:
416:
412:
408:
400:
398:
396:
392:
387:
384:
380:
379:
378:high fidelity
373:
366:
364:
361:
356:
352:
348:
346:
342:
338:
331:
326:
322:
320:
316:
312:
307:
305:
301:
297:
293:
289:
288:
283:
279:
278:Lee De Forest
274:
272:
268:
264:
260:
256:
252:
248:
244:
236:
231:
229:
227:
224:
221:
217:
213:
209:
205:
201:
198:
194:
190:
186:
182:
178:
174:
170:
167:is a type of
166:
162:
153:
143:
140:
132:
121:
118:
114:
111:
107:
104:
100:
97:
93:
90: –
89:
85:
84:Find sources:
78:
74:
68:
67:
62:This article
60:
56:
51:
50:
45:
41:
37:
33:
19:
912:
901:
888:
867:
853:
849:
845:
841:
823:
807:
795:
770:
755:
736:
732:
719:
711:Applications
700:
696:common-plate
695:
691:
689:
685:
674:transmitters
616:
602:Microphonics
545:milliseconds
502:
498:
478:
474:
466:
438:
419:
415:dual triodes
404:
395:Ultra-Linear
388:
376:
372:World War II
370:
349:
345:World War II
334:
308:
304:voltage gain
292:control grid
291:
285:
275:
240:
226:transmitters
200:transponders
173:vacuum tubes
164:
160:
158:
135:
129:October 2011
126:
116:
109:
102:
95:
83:
71:Please help
66:verification
63:
543:systems in
470:valve sound
455:Audio usage
428:during the
267:electricity
189:solid state
926:References
654:Topologies
649:circuits).
606:microphone
516:Advantages
441:distortion
407:transistor
341:distortion
319:television
255:electrodes
243:transistor
223:television
185:microwaves
171:that uses
99:newspapers
805:ammeter.
798:voltmeter
729:Telephony
642:impedance
630:feedback.
613:Operation
311:telephony
271:rectifier
197:satellite
177:amplitude
1034:Category
1018:AX84.com
963:Klystron
947:See also
935:, 1976,
626:designs.
525:McIntosh
481:clipping
445:obsolete
430:Cold War
315:wireless
276:In 1906
202:such as
802:ammeter
701:follows
422:Soviets
401:Decline
296:cathode
237:Origins
232:History
204:DirecTV
113:scholar
939:
808:Valve
764:, and
287:Audion
282:triode
181:signal
115:
108:
101:
94:
86:
38:, and
859:Notes
746:Audio
690:In a
300:anode
251:diode
216:radio
212:radar
120:JSTOR
106:books
937:ISBN
892:See
800:and
426:West
420:The
383:Hifi
298:and
218:and
206:and
92:news
707:).
694:or
220:UHF
208:GPS
163:or
75:by
1036::
760:,
381:.
306:.
273:.
228:.
195:,
159:A
34:,
896:.
738:"
670:)
637:.
608:.
585:.
142:)
136:(
131:)
127:(
117:·
110:·
103:·
96:·
69:.
46:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
