The Amp Garage

Did a lot of rewiring this evening and I'm still chasing something very odd in the preamp. Here are some updates: I deleted the 2nd Gen Deep Switch and converted it to a 4th/5th Gen Mid switch. This solved the issue of the preamp cutting out. OD and PAB switching works fine. Volume level is still ve...

Made some updates and still chasing gremlins in the preamp. Removed the 180k and 1Meg resistors from the OD output and ran it straight to the Ratio control Removed the FX loop completely. The wiper from the Master now goes directly to the PI input cap and the PI is now ground at the main preamp grou...

I worked on it some more last night but forgot to write the voltages down. From testing things earlier everything seemed ok, just a tad lower than what is on the layout and schematics since I had my variac running at ~115VAC to get the heaters right at 3.15VAC on both sides. I was thinking verify t...

I was about to say that to keep the 2nd gen's loading on the OD output, delete the 180k to ground and the 1Meg series resistor and go straight into a 250k pot for the added Ratio control. ...Should I pull the 180K and 1Meg resistor as the amp is now or is that for when it has been changed to the hy...

Hi Matt, Some of those solder joints on the jacks look a bit dry, but may just be the photograph. Have you tried inserting a patch cable in the fx loop jacks? -Dan I reflowed the solder joints, and tried a patch cable, no luck. The power amp still gets a signal if I plug directly into the FX send o...

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...