[DaftFader]

I've built and been using a pair of these for some weeks now without major issue, but suddenly in this session I'm working on the left compressor started to randomly make some bursts of noise. It would go away after a bit then come back, and eventually it became constant. And now I get a constant noise on my left comp which gets louder the more I turn up the output gain. It also goes away if I put it in bypass (although, when it first started doing bursts, I'm not sure if it did go away in bypass, I think it's only now it's constant that bypass removes it, but I'm not 100% sure about that as when it was making burst of noise I was running it into a bunch of saturation and clipping, so even the noise floor was audible and it might of just been that in bypass I was hearing, but I tested it afterwards and bypass makes it go away). Also If I put it into "LINK" mode it's the same as "IN" mode and the noise is there.

Here is a recording of it with both input/output dials roughly half way.

https://we.tl/t-7hnRoujobX

Thanks
DF

[JPK]

Try removing the jumper JMP1 and listen if it is still there. This would show that it doesn't come from the side chain.
Try tapping various components (tube, electrolytics, pots) with a pen to hear if it increases the noise.
Is the noise level dependent on the input pot, the output pot?

[DaftFader]

It seems to stay the same or get slightly better with incereased input at 0 output gain, but increasing the output increases it regardless of where the input is set.

This morning I did some more testing. Here are some screen shots of plug in doctor and REW of both my left and right comps so you can see the differance. It seems like the noise gets worse after prolonged use in a session. As I started them up fresh today and the noise was way less than it was yesterday, and yesterday it got worse the longer I used it, so I assume if I left them running for a couple of hours hte left would continue to get worse.

For the record, these tests are being done using the same slot and cables, the same output and input of my interface, with nothing else in the rack and in the furthest slot from the power supply.

Left no input gain with 100% output gain...



And the right...



Left with full output and and a little input to bring it into the frame, but no compression happening (it looks basically the same with no input, just half is off the screen)....



And right ...



And these are the left and right with input gain up but no output gain....
L


R




I'll have a play about and see if anything looks off with the componants ... and try the jumper thing. I'll get to work on that and get back to you a bit later. Ta

[DaftFader]

So removing the jumper doesn't change anything, and it doesn't appear that moving any componants make it worse. It just has these random "fizzle" sounds (like in the recording) ontop of the background noise that don't seem to coincide with anything I'm doing and are there even if I'm not touching the board.

I will continue to play about to see if I notice anything, just pulling the board off the back pannel to have a look at the board and the solder on the back first.

[DaftFader]

OK I've found the source I think. Moving the trimmer +/- on TR2-Bal 1 pot makes the noise really loud when moving it. It's coming from that pot. Luckily I have spares, so I can replace it if you think that will solve it (or could it be something else that the pot is controling the voltage to?).

[DaftFader]

Ok I replaced the trim pot, and although it still makes some noise when moving it, the other comp does too. It's no where near as bad as it was before I chnged the trimmer though, and both comps now are in line with each other with regards to the noise floor. I also removed and re-incerted the tube (after testing it in the other comp to make sure it wasn't the cause) as there may of been a bad connection as the leeds are quite oxidized.

I think it's solved, although I'll leave them powered for a bit just to make sure. (EDIT: So far so good!)

Ta for your help!

[JPK]