KCA NOS Tubes. Audio tubes for guitar amplifiers and audiophile equipment. 12AX7, 6L6GC, 12ay7, el34, el84, Fender amplifier,5AR4, 5U4GB, cv4004, 6SN7, 8417, 7027, gz34, Mullard, EF86, 6ca7, 6bq5, 7025, 12at7

Fender Amp Preamp Tube Layout and recommendations

Fender 2 channel reverb amp preamp tube layout (as seen from the back of the amp)
Tube Designation	V6	V5	V4	V3	V2	V1
Type-->	12AT7	12AX7	7025/12AX7/A	12AT7	7025/12AX7A	7025/12AX7A
Specified Function-->	Phase Inverter	Tremolo	2^nd gain stage for channel 2 and reverb return amplifier	Reverb driver	First gain stage for channel 2	First gain stage for channel 1

Typical examples: Deluxe Reverb, Vibrolux Reverb, Super Reverb, Twin Reverb, Showman Reverb, Pro Reverb and Dual Showman Reverb.

If you don't use channel 1, don't worry too much about this tube, any 12AX7 or 7025 will work though noisey or microphonic tubes in this postion can be a problem even if you're not using that channel. You can also opt to remove this tube entirely. Doing so will give you increased/earlier overdrive in channel 2.

If you do use channel one, this tube is the most critical to tone for that channel. Pick the highest quality 12AX7A or 7025 (7025s are nearly impossible to find). Highly recommended: NOS Tesla E83CC, Tungsram 12AX7, Brimar CV4004, RCA 12AX7A or JAN GE 12AX7WA, RFT 12AX7. Excellent: Raytheon 12AX7.
Best new production tubes for this socket are Tung Sol Reissue 12AX7 (Full and Fat sounding), JJ ECC803S, EH 12AX7 (brighter sounding), Sovtek 12AX7LPS or the Ruby STR 7025.

This tube is critical for the best tone for channel 2 (your reverb/tremolo channel). Experiment with different types to find your tone. Get the best tube you can afford. This position is particularly sensitive to microphonic tubes due the high gain of channel 2. Highly recommended: NOS Tesla E83CC, Tungsram 12AX7, Brimar CV4004, RCA 12AX7A or JAN GE 12AX7WA, RFT 12AX7. Excellent: Raytheon 12AX7.
Best new production tubes for this socket are Tung Sol Reissue 12AX7, JJ ECC803S, EH 12AX7, Sovtek 12AX7LPS or the Ruby STR 7025.

12AY7/6072s (as used in the front end of many Fender tweed amps) or 5751s (a lower gain 12AX7 great for smoothing out any harshness sometimes caused by humbucker pickups in Fender amps) are often substituted in the V1 and V2 sockets. Each will give reduced gain and a different tone. Often, one of these substitutes is used to reduce harshness in the first stage of an amp. Highly recommended: JAN GE 5751, RCA 5751, JAN GE 6072 (12AY7) or any other NOS 12AY7.

Because of the high demands placed on this tube by the Fender reverb driver design, it's important to get a good quality 12AT7 for this slot. Some 12AT7s that will work just fine as phase inverters (V6) will crackle and hiss in this position. Better 12AT7s (notably, the Mullard CV4024, Mullard ECC81 or RCA 12AT7s) will also improve the tone of your reverb. Some customers say that the CV4024s remove an overly "surfy" reverb tone which can result from using a low end 12AT7.

The 2^nd most important socket affecting the tone of channel 2. If you have a tube that's microphonic in the V2 position, try it here. This is a much lower gain stage and won't be as sensitive to a microphonic tube. Highly recommended: NOS Tesla E83CC, Tungsram 12AX7, Brimar CV4004, RCA 12AX7A or JAN GE 12AX7WA, RFT 12AX7. Excellent: Raytheon 12AX7.
Best new production tubes for this socket are Tung Sol Reissue 12AX7, JJ ECC803S, EH 12AX7, Sovtek 12AX7LPS or the Ruby STR 7025.

This is the least critical tube position in your amp. This is used as an oscillator for the tremolo circuit and has absolutely no effect on tone. This is a good place for microphonic or cheap 12AX7s.

V6: The phase inverter should always be replaced when replacing power tubes. Opinions on how the phase inverter affects tone vary. Some say it has little or no effect while others claim it's critical to have a high quality 12AT7 in this slot. I highly recommend the Mullard CV4024 or ECC81, or RCA 12AT7 for V6. Some players prefer a 12AX7/A in this postion as it allows an amp to "break up" or distort at lower volumes due to being "mis biased" in the 12AT7 circuit. This is a perfectly safe substitution to make. Try it, you may like it!