ThePhoenix

Sounds reasonably easy, thank you for your help!

Thank you; I didn't know about needing to turn it all of the way down (good thing I haven't tried anything yet). Do you have any idea what I might be looking for to actually do the adjustment?

The amp has been back in my hands for a couple of weeks now and sounds great; there was a scare the static was returning one evening, but I think that was something else as I haven't heard it since (knock on wood). That said, it was recommended to me by the forum member who worked on it to swap out the generic transistors they used with a pair of THAT340s once I could get my hands on a pair and, once I had them, to make sure I check the DC Offset and adjust as necessary. I'm assuming I measure off of the volume pot like I did when we first started troubleshooting; what is it, exactly, that I should be doing to adjust it?

I've heard back from the awesome forum member who's checking out the amp. They found that three of the four MAT BJTs were bad, which is why I didn't notice a difference when I swapped them around. They've replaced them, adjusted the output, and have the unit on its way back to me as I type this out. So, thanks again to them and everyone else here! I can't wait to have it back and look forward to hearing it without concern of that awful static.

So, a small update. A very kind forum member offered to take a look at the amp and see if they can find the issue and rectify it. I'm very thankful to them and everyone else who's offered their advice and hope the problem can be eradicated. I will update this thread with anything they find. Thanks again!

That's a good idea on taking it out of the enclosure. I'll look at it and do some soul-searching. I love the darned thing when it's quiet and performing correctly, but it sure is annoying to know something's not right and, of course, have one's music interrupted with a bunch of static. That said, maybe this is the universe's sign that now isn't the time to upgrade and I should just sell it, cut my losses, and move on. Thanks again, everyone, with your suggestions and contributions! I'll report back what I decide to do and, later, if I get any resolution on the matter.

Okay, so I can report back with static updates (yay, what fun this is - not). After doing some listening, I'm not wholly convinced the imbalance is outside of the norm or that it isn't something wrong with me physically. It seems to come and go, but that could also be the music, so I'm going to ignore this for the time being and focus on the static. Anyways, while testing the above, I finally got some static. I quickly shut the amp off, swapped the L/R channels on the left side of the pot (that go to the circuit board), and turned the amp back on. The static remained with the left channel. [I think I've noted it before, but if I swap my headphone connections from L to R, the static does follow.) With that discovery, I think it is safe to say that the issue is somewhere in the left channel circuitry (or even the XLR out). Is there anything else I can measure/test, or should I start packing it up to ship to an expert? [I also have half a mind to sell it to an intrepid DIY'er who wants to deal with it. We'll see what happens.]

That sounds like it's above my abilities. Hmm.... Well, I need to determine if the initial issue is resolved/gone or not and go from there. I'm switching the wires back this morning and do some A/B-ing between the BiPolar and my old amp to see if I am hearing a channel imbalance or not (I was very sure of it the other day, less sure yesterday). Obviously, if the static returns we know I just got absurdly unlucky last night (the story of my life with nice things). Also, I know I've said it already, but thank you so much for sticking with me on this. I really appreciate it.

Well, for the two hours I tried, I got no static. Which is either insanely "lucky" OR the part finally failed OR the static was caused by a dodgy connection to the volume pot. So, I'm going to switch everything back to how it should be tomorrow morning and I guess keep waiting to see if any static comes across. With the potential of it being a problem (if not THE problem) and there being the believed channel imbalance, I'm considering replacing the volume pot just to be safe. I know these vary wildly in price from "reasonable" to "are you kidding". Right now it looks like there's an Alpha brand pot in there; I know Alps and TKD are the names thrown around here most often; is there one I should look at/consider if I go this route for peace of mind?

Okay, so I've played around with the wiring a bit. Naturally, the problem didn't immediately hold its hand up and reveal itself. First, I swapped the L/R wires leading from the pot to the circuit board. The "pop"/static with the volume pot stayed with the left channel. The channels were definitely swapped, so not sure why that didn't change. After playing around with it for a few minutes, I shut the amp back off and switched those first wires back around. Then, I swapped the wires coming in from the XLR inputs. Still no change as far as the turn-on noise (which isn't a big deal) and volume pot static go. Again, the L/R audio is definitely swapped. I didn't notice any of the static I've been having in the few minutes I tested, so once I'm done writing this post, I'm going to just listen to silence and wait/see if that issue has swapped channels or not. I would guess from the results of the testing above, that it will not, but I'll report when I get some (damn these intermittent issues!). I believe the channel imbalance remained on the left side. That said, I'm second-guessing everything I hear and I can't measure it, so maybe I'm just nuts (very possible). I've been listening to an old amp to compare/try and placate myself that I haven't damaged my headphones, and I do think there is an imbalance of some kind.

Awesome, thank you. I'll try it out when I have a chance and report back (crossing my fingers this is the whole issue!).

I did not attempt to separate the BJT sockets, but I'll fiddle with them to make sure they didn't separate. For the volume control, are you saying I should switch the two L wires with the two R wires on the left of the pot? Or, that I should swap all of the wires from the left side (going to the circuit boards) to the right (from the XLR inputs)?

In the central bit of Missouri, USA (specifically, around the Lake of the Ozarks). I knew asking for help with this particular issue and getting it resolved would be a long shot; I'm so thankful Spritzer and the rest of you have offered advice already.

All right; I took a number of photos (yay, 30s exposures!) from different angles in an attempt to be as helpful as possible. I've posted them all to an Imgur folder; please let me know if a Google Drive or something similar would be easier for you to use. I think everything is pretty logically organised, but let me know if you have any questions. I don't have a macro lens, so I did what I could with what I had readily available. Imgur LINK (it's private, only those with the link should be able to view it). I will reiterate that everything is exactly as it's been since I got it a couple of weeks ago (other than the swapping of the BJTs); I only mention it in case you see anything and go, WTF.

Doing some more listening; I'm more and more convinced there's a channel imbalance between the L/R channels (L being weaker). I'm not sure if I just simply didn't notice or if it's gotten worse over time, but I just swapped back to my previous amp to see if I was going crazy (or possibly damaged my headphones) and I'm confident it's there. While I'd love to believe it's all due to the potentiometer, would it also be possible for whatever resistor/transistor (not sure how many transistors there are or if it's just the BJTs) causing the issue to have failed completely and is now not amplifying the channel fully? [Also, I'm working on those photos. I'll have them up in a bit - sorry for the wait!]