I've tried using the search function, without finding what I'm looking for...
My Liverpool clone (Ceriatone) has a high-frequency whistle, which remains present (although reduced) even with the bright switch off and the treble and mid controls at zero.
Has anyone else had this phenomenon? Any suggestions would be very welcome.
Thanks for replying I tried some other JJs - they're all about the same, it seems. I also tried a couple of old 12AU7s. Of course, the whine goes away, but so does the overdrive and the volume...
Maybe I should try other brands of 12AX7... If the fix is as simple as finding the right tube (V1? V2?) then I'm happy...
1. Is the chassis in a head box or shielded? Try moving your rig in a different part of the room and also do not set it on the speaker cab.
2. Move around the V1 pin 2 grid wire and see if that helps. Are they shielded? You could also solder in a small resister (right on the pin of v1 pin 2) to help quell any occilation.
1. Is the chassis in a head box or shielded? Try moving your rig in a different part of the room and also do not set it on the speaker cab.
2. Move around the V1 pin 2 grid wire and see if that helps. Are they shielded? You could also solder in a small resister (right on the pin of v1 pin 2) to help quell any occilation.
1. Is the chassis in a head box or shielded? Try moving your rig in a different part of the room and also do not set it on the speaker cab.
2. Move around the V1 pin 2 grid wire and see if that helps. Are they shielded? You could also solder in a small resister (right on the pin of v1 pin 2) to help quell any occilation.
Good luck. That build is next on my list!
The chassis is in a temporary head cab - pretty rudimentary, in fact. I'll try your ideas out when I get a free half-hour
Allynmey wrote:Cap'n, post a clear pic of the amp guts. Lead dress is very important on these amps.
Since it was Nik's team that built it (I didn't have the courage, I freely admit) I was assuming that lead dress wouldn't be a likely culprit, but I'll gladly take some pics and post them
Is it a whistle? Use shielded cable from the input jack to V1. Try some NOS tubes. Any that you know are good. I had some issues with JJ's doing that in high gain preamp circuits.
My original '89 Express had a problem with this. The fix was simple.
On my amp the 2 wires that led from the output tubes to the output transformer didn't want to stay flat against the chassis as they wandered up under the power supply board. I put a tiny piece of foam rubber right under the edge of the power supply board to hold the wires down against the bottom of the chassis. No problems ever since. I could have used a dab of super glue. Actually you would be surprised at how many wires in my amp are lightly and cleanly super glued down to the chassis so that they would not move ever.
Just a thought to check into. I know my amp isn't a Liverpool but they are similar in gain and layout. These amps ride the fence on the edge of stability that's for sure.
I'll incorporate that - great idea, thanks 
