Pulling tubes to narrow down an issue.

[hesamadman]

I've just completed converting my 30 watt to a two channel, switchable via two DPDT relays. It actually seems to work fine (sort of). What I mean by work, is tone stack seems to function, MV seems to function. Gain knob seems to function. However the amp is VERY noisy and I am losing signal or something as there is not much gain at all. Volume seems good. But I can't get the distortion it should have or even close to it. I completely eliminated the second channel and have just the first hooked up (which is my original schematic that is proven) but problem still persists. I know people talk about removing preamp tubes to narrow issues down. I pulled tubes one by one and it seems that removing the PI eliminates the noise 100% so does that mean that the problem could be anywhere BEFORE the PI?

[sluckey]

Yes, most likely.

[hesamadman]

This is my schematic. Im hoping this is not an issue with the capacitance of relays. Im going to remove a few things related to channel two completely from relay and see if I can get higher gain channel working first and go from there.

[eleventeen]

Please describe your "noise" a little better.


AC-type Hum?
Local radio station pickup?
Ocean waves hiss?
Crackle?

[hesamadman]

AC-type Hum?

I re did the layout. Right now I have just a hum. Lower frequency. The way it is wired is just like the schematic in the photo. The red X's are not hooked up. I wanted to only hook up the main channel, get that one working, then hook up lower gain channel. Since the re-wire, here is my issue. Amp works. EQ works. Gain and MV works. But I have VERY low gain compared to before. I should note that I also had a PPIMV before but had to convert it to MV on TS for it to work right with channel switching. However, this is a HUGE gain loss and I have another amp like this with the PRE PI MV and it has the gain it should. This has plenty of volume when cranked.


Here is something I have been doing and I wonder if this is somehow playing a roll in it. When I do my ground buss, I just daisy chain. gain ground to MV ground to MID ground to preamp ground. I have a feeling this is part of the issue at hand OR just part of another issue I am having (completely separate and not a problem to me at the moment. But even with MV all way down, trebly signal still coming from speakers. This did not happen when it was PPIMV. And issue is on another one of these I have. Anyway, un related sort of.) So could this somehow be part of my grounding? OR is this just bad practice in general?

[sluckey]

Put a bypass cap on the cathode of V1A. 1, 2, 4, 10µF, whatever you have. Short out that 470K that goes to relay 1A. Do these one at a time. If still not enough gain then do both.

[hesamadman]

My issue isn't so much that it doesn't have enough gain for my taste. It's that it doesn't have the gain it had before I took it apart. This was a working amp that I'm trying to configure for two channels. Right now the amp is assembled "exactly" like it was before the mods. Only I have an error somewhere. With gain know all way up there's hardly any gain at all.

[sluckey]

Keep looking. You'll find it.

[hesamadman]

Keep looking. You'll find it.

Check out my gain pot 


That took care of that issue.

[sluckey]