midwayfair
Well-known member
I've had this amp for a long time, but it's been a while since I plugged it in (I tend to use a 5W that I built to be a tiny version of it). I loaned it to my dad since he decided to buy some electrics recently, and I noticed that the reverb hiss is much louder than I remember. I always remembered it being noticeably hissy but I think it's quite loud now.
I've replaced the reverb driver and receiver tubes; the driver is specced as 12AT7 IIRC, but I've tried some 12AY7 and 12AX7 that I know are quiet in the other positions in the amp. The hiss sounds sounds the same except for the total output, so I don't think it's the tube. However, it does lead me to believe that the problem exists before the reverb out amplification stage.
Here's the schematic (this is the 20th anniversary but everything except the tremolo is identical I believe):
http://schems.com/bmampscom/tone_king/20th_Imperial_SC200HB_pg1.pdf
The power supply for the reverb is shared with the preamp, so if it was a PSU issue it would be in the whole amp. I'm not sure what else I can check or what would cause hissing.
Any ideas?
I've replaced the reverb driver and receiver tubes; the driver is specced as 12AT7 IIRC, but I've tried some 12AY7 and 12AX7 that I know are quiet in the other positions in the amp. The hiss sounds sounds the same except for the total output, so I don't think it's the tube. However, it does lead me to believe that the problem exists before the reverb out amplification stage.
Here's the schematic (this is the 20th anniversary but everything except the tremolo is identical I believe):
http://schems.com/bmampscom/tone_king/20th_Imperial_SC200HB_pg1.pdf
The power supply for the reverb is shared with the preamp, so if it was a PSU issue it would be in the whole amp. I'm not sure what else I can check or what would cause hissing.
Any ideas?