The Amp Garage

So I have played around a little more and I think I have narrowed it down to an issue in the preamp, possibly in the wiring of the FX send/return jacks. I plugged into the return jack and got a nice clean signal, only affected by the Presence control. Plugging in to the input jack got nothing. I des...

The more I have thought over, the more I am leaning towards changing it to have the separate masters for OD and Clean. The design I have seen the most for this is in the attached PDF. I have two questions on this; 1. Why is the clean master not connected to the ground bus? The outer (brown in this ...

The more I have thought over, the more I am leaning towards changing it to have the separate masters for OD and Clean. The design I have seen the most for this is in the attached PDF. I have two questions on this; 1. Why is the clean master not connected to the ground bus? The outer (brown in this d...

dbharris wrote: ↑Wed May 08, 2024 12:36 pm Sorry I misunderstood! Good luck tracking it down.

No problem! I'm actually second guessing myself and wondering now if I should have gone with a hybrid design with the separate masters.

Matt J.

I've rolled several tubes but keep getting the same result, OD goes in and out, then out completely. I'm starting to suspect I have an error in the relay wiring. The PAB is working fine, but I would appreciate another set of eyes on the OD relay board I'm using from Taylor at AN. From left to right...

I've rolled several tubes but keep getting the same result, OD goes in and out, then out completely. I'm starting to suspect I have an error in the relay wiring. The PAB is working fine, but I would appreciate another set of eyes on the OD relay board I'm using from Taylor at AN. From left to right:...

I recommend adjusting the 3k9. Start by clipping or tacking another 3k9 across the one that's there and see where that gets you. Update: It's alive! Well, sort of.... Dropping the 3.9k down to 1k gave me enough negative voltage to bias the 6L6GCs at about ~38mA at 440 VDC plate voltage. I rewired s...

BTW - I'm cleaning up some wiring and double checking some of the connections. While I'm in there with my soldering iron I would like to address the issue of not getting enough negative bias voltage. Which resistor should I adjust first? The 3.9k on the board, or the 27k running from the bias pot lu...

What program do you use to draw your circuit board layouts? Corel Draw? Now, don't laugh... PowerPoint. I've done faceplates with it too, just need to save as .pdf. No judgment from me since I still use Microsoft Paint for most things! :lol: I do need to look at Powerpoint now. There are some facep...

I apologize for butchering one of your board designs in Microsoft Paint! No worries, but it's best to clearly mark the modifications. I was planning on using my phone as a signal generator later when setting the PI balance trim pot. Instead of running my phone directly into the amp, would it be bet...

Typically when I check voltages I have a dummy load connected to the output. Recently I had a speaker connected and when I checked plate voltages on the preamp I noticed a POP sound as I touched the probe to the point I was checking. Maybe you can use this as a method to narrow down where the signa...

Matt, do you have a scope? If not, a meter set to measure AC might help, black probe to bus bar bar and clip the red probe to trace the signal at input jack and then after the coupling cap for each stage in the preamp. You can use a phone or tablet as a signal generator to send a sine wave in. Good...

I'm not real familiar with 2nd Gen. Is it supposed to have an OD entrance trim pot? Unable to see under the board but something seems off to me in that area. Where does the green wire land? Reflowed the solder on V1's heater to make sure that's connected. No trim pot with the OD entrance on the 2nd...

What's the value of the resistor on your input jack? Check it with a meter. Best I can tell (small phone screen) color code is Brn-Blk-Red. Good eye! I put a 1K in there on accident. Replaced it with a 1Meg. Still not passing signal but it is certainly something in the preamp. Plugging into the FX ...

I'm going to take a look at it tomorrow with a fresh set of eyes. My suspect is that it is a missed/accidental ground issue.

Any feedback is always appreciated!
Matt J.