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Most likely for my build. At extreme left I got some ground hum, so justin suggested putting in 100ohm resistors after the pot. Dead silent at both extremes now so no complaints. Might put up a pic of my kgsshv's inside a few days from now, since I reworked the wiring a bit since the last pic I have up here. Edit: Here's that pic

Shaping up to be quite nice there. If only my wallet would have allowed a T2 build...

So I take it that figure of 0.0009% THD+N isn't exactly accurate?

Are you going to post schematics & some measurements for the LL once all is said & done? Also, silver & amber sounds like a good idea to me.

I feel like kicking myself now. I had -15V hooked into the - pole instead of ground. How the LED worked for so many hours with such a dumb mistake is beyond me... Anyway, do you have any of those orange switches you were planning on getting spritzer?

I'm getting some weird behavior out of the latching switch on the front of my kgsshv. I noticed the LED is dimmer than it should be and decided to do a quick check with the DMM to see what's going on. Apparently I'm getting +9V/-15V (relative to star ground) instead of +12V/-12V. Really not sure what to blame here, as the switch LED crapping out on me happened once before. At least it still 'works', for now...

Putting in 100 ohm resistors did the trick, thanks. It's dead silent from extreme left to extreme right now.

I made a few changes to the inside of my HV recently. Put in the much larger encapsulated trafo and tidied up the wiring a bit. However I haven't figured out what to do with the ground hum at the pot's extreme left. Anything I should try first to see exactly where the issue is? Also SoupRKnowva, I'm not sure about pushing it past 10mAx4 with IXYS parts. It would probably drift a considerable amount.

The buzzing was audible with the cover on & a few feet away, so I opted for the encapsulated replacement. Quite a bit larger than the old transformer (133mm OD and 70mm height) but it makes about as much noise on as it does off.

Congrats on the T2, looks beautiful. Before I got a fully encapsulated replacement from sumr (old transformer was buzzing) I measured about 50-60C on the trafo in my KGSSHV. You can shoot sumr an email if you're worried, but it's not too much hotter than what I measured for mine.

Beats me as to what was the problem with the other board. I might put it up for sale for parts if anyone's interested.

So there's one more working KGSSHV in the world. Finally received the last parts I was waiting for to finish the replacement board, and it worked on the first try. Giving it longer on-time the side heatsinks reached ~40C. I got the balance & offset on both boards to zero as well. Not that warm at all considering it's running at 10mAx4. It also makes the SRM1/MK2 look tiny. One thing though, if I turn the volume pot all the way to the left I can hear some ground hum. It's dead silent with a little turn to the right & up to max volume though. The grounding looks the same as I had it in my last internals pic (save for only one ground wire coming off the pot instead of two). This isn't just a quirk of the alpha quad is it?

I'm using the 1968s. So would I lower the value of the 2k resistor then (R26)? I'll probably just leave it at 10mA though, not going to be running anything but a lambda with it for a while.

How much output current could one really get away with for the offboard version? I actually had my working board running at ~10mA by swapping R5 and R6 with 100ohm resistors. After nearly an hour being on the outside of the heatsink reached about 37C, also the lowest I could get the offset was 7V.

Looks mostly the same as how I did my grounding, save for john's suggestion on the inputs and connecting the amp boards to the psu. Any reason you only used one pin on the alpha pot pcb?

Made the changes to the xlr inputs, hopefully the higher res makes details easier to see.

Yea, I have two extra since batchpcb does x2 of whatever amount of boards you order. Once I make those changes to the input grounding tomorrow I'll take a better pic.

I did follow an old pic of your build to ground the inputs Just attach the ground tab to one of the mounting screws for each DLX then?

Probably, they did seem fine when I checked them. I really don't know where the problem is so I'm just going to replace the whole amp board.

Well, I swapped all the sand save for the 1968s & 4686s and the board still doesn't work (same behaviour). Would anyone be kind enough to spare some 4686s? I'm building a new amp board at this point since it seems like it might be the output transistors that are the problem (or who knows what). On a positive note I've done all the wiring (feel free to point out any stupids).

D13 is right beside the 2SC1815 (Q20). I'll try swapping a few 4686's with spares, and D10 too since that looks suspicious to me (since it's right beside the +15 input). Edit: Well it's not any blown LEDs, they all light up after applying voltage directly to them. Still puzzled as to what would cause only D13 to light up. Also, measuring the -HV input on the problem board I get about -63V (-459V on the working board).

Well, there are no burn marks or anything visual that would indicate a bad part. I'll try and see if any of the 4686/1968's are blown (sure hope not though). Edit: It doesn't seem like the output transistors are the problem, their hfe all check out according to the spec sheet and unless I'm reading my multimeter wrong they seem to pass the diode test. Only D13 lighting up seems a little weird to me though, shouldn't D10 be lit as well?

I shut it off right away when I didn't see every LED light up, but remeasuring I got +457V on both +/- outputs of the problem board (while I get -a few volts on the good board since I set the balance/offset while it was warmed up).

So after testing the boards I got one to balance & offset fine. However there's a problem with the other board. Only one LED lights up (D13). I checked beforehand for possible shorts and didn't see anything, also made sure to hook the signal inputs to ground. Any obvious spots I should check first?

I let it stay on for another hour or so and those measurements didn't budge.