Fulltone Tube Tape Echo - Manual (Page 15)

Page 13
Tubes!
Refer to Page 9, Main Chassis Diagram
Warning! There are 3 Tubes in your TTE, two (V1 and V2) you can change if need be, and
another one (V3) that you shouldn’t mess with!
V2 is a 12AX7, which is powering the Guitar Preamp section, and V1 is a 12AX7/ECC83
powering the Echo “reproduction” stage of the circuit. You can experiment with other 12AX7’s but
always test for noise and Microphonics. You can tailor the sound with V1 and V2.
V3 is actually the most CRUCIAL tube choice and
must be a JJ branded 12AU7/ECC82. No other
tube should be used, otherwise you will get Hiss, a weak echo sound, and the unit won’t erase
properly!
It is used for the Bias Oscillator/Erase function of the TTE. Do not confuse the term
“Bias” with the Bias you set on the output tubes of an amplifier, this Bias Section is a complex
circuit specifically dedicated for the Erase Function of the TTE.
Warning! Changing this tube to anything other than an JJ12AU7 may require an adjustment to the
Bias Oscillator Trimmer (no diagram available), and you should contact us before attempting this
procedure. The stock V3 tube should function trouble free for many years to come.
You’ll notice that V3 does not have a tube shield on it….since it is not an audio tube, there is no
need to have a shield to shield out noise, and not having a shield allows it to run much cooler, thus
allowing it to last for a very very long time.