Tube Amp Archive

I appreciate this, and I am in the US or I would talk more about your proposition. Sounds like I would need to upgrade to a real high-voltage power supply. The irony is that this project idea started because the amp sounds pretty harsh when you lean on it and lacks the distortion that I like. Assumi...

Ok all, here's the schematic that I cobbled together. I used a combination of the PicoValve schematic for the power section, a VHT Special 6 power amp, and Rob's SLO Nakid preamp. I measured the B+ voltage on the amp, and I'm getting 320v off the single B+ the PicoValve has. That seems low compared ...

Sounds good, thank you! I'll take a pass at a proposed schematic, including the transformer and choke specs, and post back.

With SE amps, especially high-gain ones, be sure to use an extra first filter stage, called Pi or CLC/CRC filter. This will cut the hum common to SE builds. The Pico has a 10H choke, so I planned on using that. I'll take a look at the caps it is using. I'm hoping to reuse the entire power section w...

Hello all, and thank you in advance for your guidance. I am finishing up my first build, a TW Express clone, and I'm hooked. Rather than another scratch build and the associated costs, I'm interested in using my PicoValve as a donor. I did some small mods to it a while back, but am ready to reimagin...

I made a bit of progress here and am feeling a bit foolish looking back. I looked at the schematic and saw all of the filter caps going to ground, so when I glued the stack together, I made a nice little grid with the leads and tied them all together and grounded to the chassis. I looked at the layo...

It looks like the chassis cover has solved that oscillation issue, so that's good news. After fiddling with the preamp tubes and following Rob Robinette's guidance ( https://robrobinette.com/Tube_Guitar_Amp_Troubleshooting.htm#Weird_Noises ) it seems the noise/buzz is eliminated when I pull the PI t...

Hey all, I am working on my first build, an Express (Kelly '90 schematic) with JJ 6V6 power tubes. I was able to get advice on solving a wiring mistake, and now I'm on to the task of troubleshooting some noise problems. I'm getting some oscillation, which comes and goes as I move, so I'm hoping that...

It sounds like the next step on the noise front is to chopstick a bit and remove tubes to locate the source.

I will give that negative feedback wire trick a try and see if that may fix the oscillation issue.

Thanks!

No worries, gktamps! That raised dash was convincing, for sure. Sluckey, you're amazing. I only had to unsolder a single ground wire and was able to remove the under the board jumpers. I corrected it from the top, and I'm happy to say things look much better. I plugged a guitar in and got sound (cou...

Sluckey, you are impressive. I was able to get the board turned enough to confirm that the jumpers are in fact as you described. I need a bit of focus time this evening to make the repair and will report back.

That would certainly explain it. I wouldn't be surprised if in my decisioning between the top of the board and bottom, I followed the shape of the jumpers from the top, but on the bottom. I'll get it torn apart and report back. gktamps, the datasheet on those caps is not incredibly specific. it talk...

Yep, I missed the RESISTANCE keyword there. Pin V3 pin 8 to chassis = 15.03k

Yep, I missed the RESISTANCE keyword there. Pin V3 pin 8 to chassis = 15.03k

sluckey wrote: ↑Mon Apr 10, 2023 4:35 pm MEASURE THE VOLTAGE ON V3 PINS 1 AND 6. WHAT HAVE YOU? I WANT NUMBERS.

MEASURE RESISTANCE FROM PIN 8 TO CHASSIS. WHAT HAVE YOU? I WANT NUMBERS.

check out that picture above. i measured all those voltages (except heaters) from pin to chassis ground.