Fender Brown, Blonde, Blackface and Silverface Tube Amps

Replacement Tube Packages are available for Fender tube amps.

By Eric Barbour - Former Vacuum Tube Valley senior editor

What the tubes do in most Fender tube amps:

The first preamp tube (or the first 2 tubes, in 2 channel amps) provide the first gain of the guitar signal. It usually drives the tone control "stack", depending on the model. A low noise, low microphony tube is recommended here.

If the amp has reverb, there will usually be a 12AT7 to drive the reverb spring. This is severe duty and will use up the tube's cathode quickly. This tube need not be low-noise or nonmicrophonic. Some early models used 12AX7s or 7025s for this job, however we still recommend using a 12AT7 here. Reverb amps will also have an additional 12AX7 to reamplify the output from the spring. Because this tube amplifies the signal from a reverb spring (which is inherently microphonic), a really quiet tube is not really needed. However, it should be a 12AX7 with plenty of gain.

Fender had tremolo or vibrato on some amps. Both terms mean the same thing--an oscillator makes a low-speed signal that varies the gain of the guitar signal. If the amp has tremolo or vibrato, it will have at least one extra tube, usually a 12AX7. This tube need NOT be quiet--any inexpensive 12AX7 type (with adequate gain to oscillate) will work. 12AT7s might also work.

The last preamp tube before the power tubes is the "phase inverter", seen only in push-pull amps (those having 2 or 4 output tubes). It makes the "see-saw" drive voltages that properly drive the output tubes. It was usually a 12AT7, for the same reasons as the reverb driver above. Fender phase inverters in later amps used a very crude circuit which also provided some voltage gain. This tube need not be especially quiet, but its heater-cathode insulation must be very good. If the heater shorts to a cathode in this tube, the amp will not work properly. Some earlier Fender models used a 12AX7 or 12AX7 for the phase inverter--recommend a good-quality tube for such amps (12AT7s will usually work as well).

The power tubes in almost all Fender tube amps were either 6V6s or 6L6s. They drive the output transformer, then the speakers. Small amps like the Champ had one power tube and no bias adjustment. Larger amps had two or four power tubes in push-pull, which work like a see-saw -- when one tube is decreasing in voltage, the other is increasing. Most push-pull Fender tube amps have a tube bias adjustment inside, which varies the idling current in the power tubes (all at once). Bias should be adjusted when tubes are replaced. Matched pairs are recommended to keep the amplifier balanced from side to side -- if you amp uses 4 or more output tubes, you can use groups of matched pairs, and you do not necessarily need to buy a matched quartet, sextet or octet. So long as one tube from each pair is on one side of the transformer, and the other is on the other side, the amp will balance. If your amp was intended for 6L6s, do NOT try 6V6s, you might damage the tubes. If your amp was meant for 6V6s, do NOT try 6L6s, as this will overload the power transformer. It is VERY dangerous to blindly plug different tubes into a guitar amp. If you have a later silver-face or blackface Deluxe amp, the plate voltage will be very high--plugging low-cost Russian or Chinese 6V6s into such an amp is risky. Suggest NOS 6V6GTs or 7408s for such amps.
Note: Since this article was written Tung-Sol, Electro Harmonix and JJ Electronics have released 6V6 tubes suitable for high plate voltages making them a great option for these amps.

Many earlier Fender tube amps used rectifier tubes. These were almost always at the extreme left of the chassis, when looking at the rear of the amp. 5Y3s were seen in small tube amps, while large ones used 5AR4/GZ34s or 5U4s. DO NOT blindly swap different rectifiers, some consume more heater power than others and might damage the amp. After 1968, most Fender tube amps switched to solid-state rectifiers, until recent Custom Shop models reintroduced tube rectifiers. Solid -state rectifiers do not wear out as tubes do, nor can they be replaced by the user. The solid-state diodes used in older Fender amps are rather primitive compared to modern devices--if you wish slightly better performance, suggest speaking to a service technician about replacing the diodes with modern fast-recovery epitaxial (FRED) diodes.

By the way, in the past there were all kinds of suffixes on tubes--6L6, 6L6G, 6L6GA, 6L6GB, 6L6GC, etc. Some early Fender 6L6 tube amps can use any of these types. Later Fender blackface and silverface tube amps should NOT have 6L6, 6L6G, 6L6GA or 6L6GB installed, due to higher operating voltages and currents. If you wish to use modern tubes in such amps, stick to a true 6L6GC or KT66. Finally, 5881 meant a special high-quality tube in the past--it no longer means much today. True NOS 5881s are scarce and costly. If you really want to know the differences, we recommend you consult past issues of Vacuum Tube Valley magazine.

In all cases, if you are not certain which amplifier version you have, do not experiment! You might damage the amplifier and the tubes. See an experienced technician.

Click a Fender tube amp in this list to jump to its description below...

Champ AA764
Vibro Champ and Bronco AA764
Princeton AA964
Princeton AA1164 with reverb
Princeton 6G2
Harvard model 6G10
Deluxe AB763
Deluxe Reverb models AA763, AB763, and AB868
Deluxe 6G3
Vibrolux models AA763 and AB763; Tremolux AA763, AB763; Pro-Amp AA763, AB763
Vibrolux models 6G9A, 6G9B, 6G11, 6G11A; Tremolux 6G9A
Bandmaster AA763, AB763
Bassman AA864, AA165, AB165
Bassman 6G6
Bassman 6G6A, 6G6B
Concert AA763, AB763
Pro-Amp 6G5, 6G5A; Vibrasonic 5G13
Super 6G4
Super 6G4A
Pro Reverb AA165; Super Reverb AA763 and AB763; and Vibroverb AA763 and AB763
Showman AA763, AB763
Twin 6G8; Showman 6G14
Twin 6G8A; Showman 6G14A
Twin Reverb AA763, AB763
Vibroverb 6G16
Bandmaster 6G7, Concert 6G12
Bandmaster 6G7A; Concert 6G12A; Vibrasonic 6G13A

Champ AA764 - Tube Package

Preamp tube is a 12AX7. Any 12AX7 type will work here. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Power tube (middle socket) is 6V6. Recommend using glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Rectifier tube is 5Y3GT. Avoid using NOS metal 5Y3s, only glass. You may also use 5V4 types or 5R4 types (if they fit physically). DO NOT use 5AR4, GZ34 or 5U4. Inexpensive Russian 5Y3GTs are readily available and suitable.

Vibro Champ and Bronco AA764 - Tube Package

Second tube-- 12AX7 specified. This is the vibrato tube. ANY 12AX7 type is suitable here--it is NOT critical, because this tube is not in the signal path, it serves only as an oscillator. 12AT7s and 12AU7s are not recommended.

Power tube is 6V6. Recommend using glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Princeton AA964 - Tube Packge

First tube is preamp, 7025 is specified. A low-noise, low- microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Second tube is a 12AX7. This is the phase inverter and vibrato tube. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are suitable. Good NOS 12AT7s may also be used here. We understand that some technicians recommend Ei or Preferred Series 7025 for this duty.

Power tubes are a pair of 6V6. Recommend using matched pair of glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Princeton AA1164 with reverb - Tube Package

Second tube is the reverbdriver. 12AT7 is specified. 6201 also usable. This tube does not need to be low in noise, however it should have good quality cathodes in order to handle the load. 12AX7 and 5751 types not recommended. This tube tends to wear out faster than the other preamp tubes.

Third tube is the driver and reverb recovery amplifier. 12AX7 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fourth tube is a 12AX7. This is the phase inverter and vibrato tube. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are suitable. Good NOS 12AT7s may also be used here. We understand that some technicians recommend Ei or Preferred Series 7025 for this duty.

Power tubes are a pair of 6V6. Recommend using matched pair of glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Rectifier tube: Some came with 5U4GB and some came with 5AR4/GZ34. Use the tube type found in your amplifier.

Princeton 6G2

First tube is preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Power tubes are a pair of 6V6. Recommend using matched pair of glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Harvard model 6G10

Power tube (middle socket) is 6V6. Recommend using glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Deluxe AB763 - Tube Package

Second tube is the driver and tremolo modulator. 12AX7 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Third tube is the tremolo. Any 12AX7 or 7025 is usable here--it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Fourth tube is a 12AT7. This is the phase inverter and vibrato tube. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are suitable in a pinch.

Power tubes are a pair of 6V6. Recommend using matched pair of glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Deluxe Reverb models AA763, AB763, and AB868 - Tube Package

Second tube is the driver and vibrato (tremolo) modulator. 12AX7 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Third tube is the reverbdriver. 12AT7 is specified. 6201 also usable. This tube does not need to be low in noise, however it should have good quality cathodes in order to handle the load. 12AX7 and 5751 types not recommended. This tube tends to wear out faster than the other preamp tubes.

Fourth tube is the driver and reverb recovery amplifier. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum might not be required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fifth tube is the vibrato (tremolo) oscillator. Any 12AX7 or 7025 is usable here--it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Sixth tube is a 12AT7. This is the phase inverter and vibrato tube. 6201 also usable. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are usable in a pinch.

Power tubes are a pair of 6V6. Recommend using matched pair of glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3 or 5V4. The AB868 version uses a 5U4 type.

Deluxe 6G3

Second tube is a 12AX7. This is the tremolo (vibrato) oscillator and driver. Any 12AX7 or 7025 is usable here- -it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Third tube is a 12AX7. This is the phase inverter tube. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are suitable. Good NOS 12AT7s may also be used here. We understand that some technicians recommend Ei or Preferred Series 7025 for this duty.

Power tubes are a pair of 6V6. Recommend using matched pair of glass 6V6GTs. Current JJ 6V6S and Tung-Sol 6V6GT are very good. NOS metal 6V6s run too hot. DO NOT use other types.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Vibrolux models AA763 and AB763; Tremolux AA763, AB763; Pro-Amp AA763, AB763 - Tube Packages

First tube is first channel preamp, 7025 is specified. A low- noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Second tube is second channel preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Third tube is the driver and vibrato oscillator. 12AX7 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fourth tube is 12AT7. This is the phase inverter and vibrato tube. 6201 also usable. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are usable in a pinch.

Power tubes are a pair of 6L6GC. Recommend using matched pair of 6L6GCs or NOS 6L6Gs, GAs, GBs, or WGB, or 5881s. Current Preferred Series 6L6GC and Tung-Sol 5881 reissue are the best option in place of NOS tubes. Also acceptable are NOS JAN-Philips 6L6WGB, and NOS types 7581A, KT66 or 350B. NOS metal 6L6s run too hot. DO NOT use other types.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Vibrolux models 6G9A, 6G9B, 6G11, 6G11A; Tremolux 6G9A

Fourth tube is the phase inverter. 12AX7 specified. Suggest a 12AX7 of reasonable quality and with good heater insulation, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended. 12AT7s can be used in a pinch.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Bandmaster AA763, AB763 - Tube Package

These models are identical to the Vibroluxes of the same model number (above), except the Bandmaster uses solid-state rectifiers rather than tube rectifiers. Solid-state rectifiers do not wear out as tubes do, nor can they be replaced by the user. The solid-state diodes used in older Fender amps are rather primitive compared to modern devices--if you wish slightly better performance, suggest speaking to a service technician about replacing the diodes with modern fast-recovery epitaxial (FRED) diodes.

Bassman AA864, AA165, AB165 - Tube Package

First tube is Bass channel preamp, 7025 is specified. A low- noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Second tube is a driver stage for both channels of preamp, 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Third tube is the Normal channel preamp. 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Fourth tube is 12AT7. This is the phase inverter and vibrato tube. 6201 also usable. This tube need not be low- noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are usable in a pinch.

Power tubes are a pair of 6L6GC. Recommend using matched pair of 6L6GCs or 5881s. Current Preferred Series 6L6GC, and Svetlana 6L6GC are acceptable, as are NOS types 7581A, KT66 or 350B. NOS metal 6L6s run too hot. DO NOT use other types.

This model uses solid-state rectifiers rather than tube rectifiers. Solid-state rectifiers do not wear out as tubes do, nor can they be replaced by the user. The solid-state diodes used in older Fender amps are rather primitive compared to modern devices--if you wish slightly better performance, suggest speaking to a service technician about replacing the diodes with modern fast-recovery epitaxial (FRED) diodes.

Bassman 6G6

First tube is bass channel preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Third tube is the bass channel driver. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fourth tube is the phase inverter. 7025 specified. Suggest a 12AX7 of reasonable quality and with good heater insulation, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended. 12AT7s can be used in a pinch.

Power tubes are a pair of 6L6GC (5881s originally suggested). Recommend using matched pair of 6L6GCs or 5881s. Current Preferred Series 6L6GC, and Tung-Sol 5881 reissue are acceptable, as are NOS types 7581A, KT66 or 350B. NOS metal 6L6s run too hot. DO NOT use other types.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Bassman 6G6A, 6G6B

These models are identical to the Bassman 6G6, except they models use solid-state rectifiers rather than tube rectifiers. Solid-state rectifiers do not wear out as tubes do, nor can they be replaced by the user. The solid- state diodes used in older Fender amps are rather primitive compared to modern devices--if you wish slightly better performance, suggest speaking to a service technician about replacing the diodes with modern fast-recovery epitaxial (FRED) diodes.

Concert AA763, AB763

These models are identical to the Deluxe AB763, except the Concert models use solid-state rectifiers rather than tube rectifiers. Solid-state rectifiers do not wear out as tubes do, nor can they be replaced by the user. The solid-state diodes used in older Fender amps are rather primitive compared to modern devices--if you wish slightly better performance, suggest speaking to a service technician about replacing the diodes with modern fast -recovery epitaxial (FRED) diodes.

Pro-Amp 6G5, 6G5A; Vibrasonic 5G13

Third tube is the vibrato oscillator. 7025 specified (12AX7 in 6G5A version). Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fourth tube is the driver. 7025 specified (12AX7 in 6G5A version). Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 might be usable.

Fifth tube is the phase inverter. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Power tubes are a pair of 6L6GC (5881s were originally suggested for the 6G5A). Recommend using matched pair of 6L6GCs or 5881s. Current Preferred Series 6L6GC, and Tung-Sol 5881 reissue are acceptable, as are NOS types 7581A, KT66 or 350B. NOS metal 6L6s run too hot. DO NOT use other types.

Super 6G4

First tube is first channel preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Third tube is the vibrato oscillator. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fourth tube is the driver. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 might be usable.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Super 6G4A

Third tube is the vibrato oscillator. 12AX7 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Fourth tube is the driver and vibrato modulator. 12AX7 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 might be usable.

Fifth tube is the pre-driver. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 might be usable.

Sixth tube is the phase inverter. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Pro Reverb AA165 and AB668; Super Reverb AA763 and AB763; and Vibroverb AA763 and AB763 - Tube Packages

First tube is preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Fifth tube is the vibrato (tremolo) oscillator. Any 12AX7 or 7025 is usable here--it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Showman AA763, AB763 - Tube Package

Third tube is the vibrato oscillator. Any 12AX7 or 7025 is usable here--it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Fourth tube is a 12AT7. This is the phase inverter. This tube need not be low-noise or low-hum, nor does it need to be tested for microphony. It must have good quality heater insulation. 12AX7s or 7025s are not recommended here.

Twin 6G8; Showman 6G14

Second tube is vibrato channel preamp, 7025 is specified. A low-noise, low- microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Fourth tube is the driver and vibrato modulator. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum is not required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 might be usable.

Twin 6G8A; Showman 6G14A

Power tubes are a quad of 6L6GC. Recommend using matched quad of 6L6GCs or 5881s. Current Preferred Series 6L6GC, and Svetlana 6L6GC are acceptable, as are NOS types 7581A, KT66 or 350B. NOS metal 6L6s run too hot. DO NOT use other types.

Twin Reverb AA763, AB763 - Tube Package

Fifth tube is the vibrato (tremolo) oscillator. Any 12AX7 or 7025 is usable here--it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Power tubes are four 6L6GCs. Recommend using matched quad of 6L6GCs or 5881s. Current Preferred Series 6L6GC, and Svetlana 6L6GC are acceptable, as are NOS types 7581A, KT66 or 350B. NOS metal 6L6s run too hot. DO NOT use other types.

Vibroverb 6G16

First tube is preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Second tube is preamp, 7025 is specified. A low-noise, low-microphony 12AX7 or 7025 is recommended. Recommend a type with a coiled heater, such as NOS 7025s or ECC83s. Preferred Series 7025 and Tung-Sol 12AX7 are suitable. NOS 5751s recommended if lower gain is desired.

Fifth tube is the vibrato (tremolo) oscillator. Any 12AX7 or 7025 is usable here--it need not be low-noise or low-hum, nor does it need to be tested for microphony.

Sixth tube is the phase inverter and vibrato tube. 7025 specified. Suggest a 12AX7 with high gain and reasonable quality, though very low noise or hum might not be required. Preferred Series 7025 and Tung-Sol 12AX7 are suitable, 5751 not recommended.

Power tubes are a pair of 6L6GCs. Matched pair recommended. Our customers have preferred Svetlana 6L6GC, Preferred Series 6L6GC, and Electro-Harmonix 6L6GC for this amp. NOS types should be restricted to 6L6GCs, 7581s, 5881s, KT66s or 350Bs. DO NOT use 6L6Gs, GAs or GBs here. DO NOT try to use 6V6s, 6550s, KT88s or EL34s.

Rectifier tube is 5AR4/GZ34. This tube should be of good quality. 5R4 types may also be used, although the amplifier will sound different. Do not attempt to use 5Y3, 5V4 or 5U4 types.

Bandmaster 6G7, Concert 6G12

V1--7025 specified. This is the channel 1 preamp. A low- microphony 12AX7 type is recommended for this space, preferably one with a coiled heater, such as NOS 7025 or ECC83. Some technicians recommend NOS GE 7025WAs, which are still available. Preferred Series 7025 and Tung-Sol 12AX7 are also suitable. If less gain is required, an NOS 5751 is suggested. 12AT7s and 12AU7s not recommended.

V2--7025 specified. This is the channel 2 preamp. A low-microphony 12AX7 type is recommended for this space, preferably one with a coiled heater, such as NOS 7025 or ECC83. Some technicians recommend NOS GE 7025WAs, which are still available. Preferred Series 7025 and Tung-Sol 12AX7 are also suitable. If less gain is required, an NOS 5751 is suggested. 12AT7s and 12AU7s not recommended. V3--7025 specified. This is the vibrato tube. ANY 12AX7 type is suitable here --it is NOT critical, becase this tube is not in the signal path, it serves only as an oscillator. 12AT7s and 12AU7s are not recommended.

V4--7025 specified. This is the driver stage and gain makeup stage. A reasonably low-microphony and low-hum 12AX7 type should be used here. Some technicians recommend NOS GE 7025WAs, which are still available. Preferred Series 7025 and Sovtek 12AX7LPSes are also suitable. 12AT7s and 12AU7s not recommended.

V5--7025 specified. This is the phase inverter tube. This tube need not be low -noise or low-hum, nor does it need to be tested for microphony. It does need to have good quality heater insulation. Good NOS 12AT7s may also be used here. We understand that some technicians recommend Ei or Preferred Series 7025 for this duty.

Power tubes--a pair of 6L6GCs. Matched pair recommended. Our customers have preferred Svetlana 6L6GC, Preferred Series 6L6GC, and Electro-Harmonix 6L6GC for this amp. NOS types should be restricted to 6L6GCs, 7581s, 5881s, KT66s or 350Bs. DO NOT use 6L6Gs, GAs or GBs here. DO NOT try to use 6V6s, 6550s, KT88s or EL34s.

Bandmaster 6G7A; Concert 6G12A; Vibrasonic 6G13A

V2--7025 specified. This is the channel 2 preamp. A low-microphony 12AX7 type is recommended for this space, preferably one with a coiled heater, such as NOS 7025 or ECC83. Some technicians recommend NOS GE 7025WAs, which are still available. Preferred Series 7025 and Tung-Sol 12AX7 are also suitable. If less gain is required, an NOS 5751 is suggested. 12AT7s and 12AU7s not recommended. V3--12AX7 specified. This is the FIRST vibrato tube. ANY 12AX7 type is suitable here--it is NOT critical, becase this tube is not in the signal path, it serves only as an oscillator. 12AT7s and 12AU7s are not recommended.

V4--12AX7 specified. This is the SECOND vibrato tube. ANY 12AX7 type is suitable here--it is NOT critical, becase this tube is not in the signal path, it serves only as a modulator. 12AT7s and 12AU7s are not recommended.

V5-- 7025 specified. This is the driver stage and gain makeup stage. A reasonably low-microphony and low-hum 12AX7 type should be used here. Some technicians recommend NOS GE 7025WAs, which are still available. Preferred Series 7025 and Sovtek 12AX7LPSes are also suitable. 12AT7s and 12AU7s not recommended.

V6--7025 specified. This is the phase inverter tube. This tube need not be low -noise or low-hum, nor does it need to be tested for microphony. It does need to have good quality heater insulation. Good NOS 12AT7s may also be used here. We understand that some technicians recommend Ei or Preferred Series 7025 for this duty.

Power tubes--a pair of 6L6GCs (5881s originally specified). Matched pair recommended. Our customers have preferred Svetlana 6L6GC, Preferred Series 6L6GC, and Electro-Harmonix 6L6GC for this amp. NOS types should be restricted to 6L6GCs, 7581s, 5881s, KT66s or 350Bs. DO NOT use 6L6Gs, GAs or GBs here. DO NOT try to use 6V6s, 6550s, KT88s or EL34s.

Fender Brown, Blonde, Blackface and Silverface Tube Amps

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