Tube Amps / Music Electronics
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|2/7/2000 6:16 AM|
|Bob Isaacson||Re: Crate Vintage Club 312 amp ?'s|
The standard preamp tube used in Crate tube amps is a Sovtek 12AX7WB, which perform well in this amp. The GT EL84's are probably well-matched Sovteks, which is what Crate uses. I've had microphonic and noise problems with these tubes in the past. I prefer to replace them with either EI or tesla brands for improved reliability.
True, the clean channel is noisier, and the volume control is more sensitive in this channel. By going to a 12ax7wa or wb in the first stage, it will reduce the sensitivity somewhat. The wxt that you have is and extremely high gain tube (u >100).
The symtoms that you are experiencing are not unique to the 3112 Class A amp, Since the 51xx class AB series behave the same way.
I've worked on many of these amps over the years as a Crate service tech and can tell you that many crate noise problems can be reduced by resoldering the tube socket pins on the pc board; tightening the bushing nuts on the pots; and tightening the ground screws on the pc board. Other problems show up in the input and effects loop jacks, which may need to be resoldered or replaced. The other area is loose solder connections or dirty pots.
Hope this helps