Recently my zkit developed a buzz. It’s always had a low level hum that is tolerable, hardly audible from the listening seat with no music playing. But this new noise is a higher pitched buzzing that increases as I turn the volume up. I tried switching tubes, no difference. I took off the anniversary mods thinking maybe something got hot there with all those big caps packed in, but no change in the buzzing.  Preflight voltage checkpoints are fine.
Any ideas? I feel like since the buzzing started with no change by me that it is an early part failure? Before I repurchase the basic caps and resistors I would scan the group here in case anyone else has experienced this. Hopefully not a transformer issue.

Thanks 4krow. I tried a different outlet, different circuit, and different service and same buzzing, coming from both speakers. Nothing new, no new gear or anything, and still buzzed when no other components are plugged in to the circuit or the amp.  I’m guessing it is coming from the amp. I have triple checked all the solder points and did the chopstick test. I noticed one of the tube sockets is slightly loose and rattly (the socket itself, not the soldered connection) but I don’t have another on hand to replace it today.

I used the parts express gold pin sockets Steve recommended in the instruction manual.  For better or worse I just ordered three new ones of the same. Reordered new sets of the original caps and a new volume pot too. The volume pot is suspect as the buzzing get wonky at about 70%. Seems like 40% is the sweet spot in my system- that’s where I usually run it. I’ll keep you posted.

Some of my parts arrived today. I replaced all the caps except the 3.3ufs in the preamp power (arriving on a different order) and replaced the volume pot. The hum is quieter and the buzz is quieter but both are still there. Much better though.
I first did the caps and plugged it back in and it was the same. Then did the volume pot and that’s where the improvement was made. I think what is happening is that the board flexes when I change tubes (i roll tubes often, especially preamp tube which is right there close) and that flex pushes the pot, which is fixed to the board, up against the hole in the chassis and is flexing the pot. I reamed out the hole for the pot while I was in there so it no longer makes contact with the chassis.
Mounting the pot off the board would be an easy solution, but more likely my next project will be just rebuilding the amp as a point-to-point.
When the other order arrives I’ll install those two last caps and replace the wonky tube socket too. Then maybe I’ll be good as new.  8-)

Lol, no doubt. My Pearl 2 has been flawless but then you have all the LP monkey business.
Point to point would solve most of my problems, but I would add tube rectification if/when I do it so that will create as many problems as it would solve. Most likely. Sigh is right.

Manny,

Waaay back in the day, AC was set at 25hz! I had better qualify that by saying this was in the lab so to speak when AC was being developed. Interestingly, much lower voltages were suggested for industrial use. Don't know why. That didn't last of course for a number of reasons and the higher frequency of 60hz, and a higher voltage was chosen. We have lived with its downsides ever since. Who hasn't heard hum even in our childhood? That is NOT an acceptance of it on my part, but rather a wondering why it couldn't have been addressed more successfully in a lot of cases. No doubt, there are consequences of most any 'answer' to it. It is simply what the general public will put up with overall.
Now, since I had a career in the Bell System, I have had the opportunity to observe other things that are tolerated by people over the years. Way back when copper was king, most every phone line was dead silent. Being a field troubleshooter, I saw all of the exceptions. Usually a ground was causing a hum, but not always. My point here is that dead quiet was normal, and a hum wasn't, but Many people out there didn't care too much (unlike me). Now, let's fast forward to even 20-30 years ago when cell phones became a thing. Yes, I am well aware of the many crappy technologies in between. Dropped calls, inconsistent service, high or at least unacceptable amounts of spiking distortion, and I could go on. The people have 'spoken'. I guess that they are willing to accept this as normal. And so it isn't a big leap to see that they feel the same about audio and a lot of other stuff too.
Then there are the very few of us that don't want what is popular, hum included. Apparently, the price is high to get that box checked.
I will end by saying that in spite of my many efforts to reduce or eliminate it, the results vary. Good equipment, matched with anything from the AC power to the equipment that feeds it (and a hell of a lot more!), can just be a PITA.
As of yesterday, I am moving to an integrated amp design in hopes of a better outcome.

I may be able to help. Or at least offer a suggestion to save your amp I had a similar problem with my zkit and with 100+bd sensitive speakers, I agree, the slightest hum can be maddening. I tried every grounding scheme I could think of and had all but given up;  accepting that my amp would have a mild hum forever.

Digging through the depths of the hum threads one day, I came across a thread that suggested eliminating the ground trace from the RCAs to the potentiometer on the circuit board (which runs directly thru the entire board), by connecting each RCA jack shield directly to its corresponding ground lug  on the pot. The thread suggested solid core wire and I didn’t have any on hand so just used fairly heavy gauge hook up wire to test the theory, and low n behold… IT WORKED!! I can now run my amp wide open without a sound and adjust the volume with my pre

Hope this helps!