TUBES
Just like all other parts in the Convertible amps, the tubes were selected for providing
the most musical tones. Tubes can be temperamental, but there are things that can be
done to avoid problems.
Module Preamp Tubes The
1 2AX7
Tungsram tubes will give you the least amount of
noise and the sweetest tone. However, they develop a microphonic ringing when
subjected to a lot of bumps from traveling.
Typically, microphonics are most sensitive from the input module (the module that's
shared by both channels). Here are some ways to eliminate microphonics.
1. You can swap the tube from another preamp module with the input module.
2. If you are using two identical modules and one of them is the input module, just
switch the position of the two modules.
Classic ----- Hi Gain
For example: Classic
Normal
-----
Presence
Just take the two "Classic" modules and switch their positions. If the second "Classic"
module's tube does not have microphonics you've solved the problem.
3. Polish 1 2AX7 tubes are constructed differently than the Tungsrams. Although
Polish tubes are noisier and harder sounding, they are less subject to
microphonics. Radio Shack and other companies offer Polish tubes. "Made in
Poland" is stamped directly on those tubes so you can be sure where they come
from.
4.
Try using an FET or IC module in the input. Because neither of these are tube
designs, you'll get no microphonics. For a warmer tube sound, use an FET
module in the input stage. If you're after a harder solid-state sound, use an IC
module in the input stage.
If you're involved in a touring schedule and you want to avoid tube related problems,
bring some extra tubes with you for all YOUR equipment.
