Tinkerer

Got mine today. Everything looks good. Can't wait to try it out.

Shipping paid.

Awesome. Those quads look nice. Can't wait to get this stuff in.

Any word on when the TDK pots might come in? Seeing all the lovely boards is making me itch to get started on project stuff.

Boy, those HV900 wound up being pricey but if they're done right, it will be worth it. Kinda surprised nobody else jumped in for even one set since the original run was around a dozen folks IIRC.

You know, the Selectric that ball comes off of has compatible keycaps with the IBM beamspring terminals, the most valued terminal keyboards in modern history. Very nice.

The HV900 revised boards still aren't up on the sheet yet. I know I might be the only guy that wants them, but I will pay the price for a set even if it's kinda high. I need it to finish my build, and it would sure be nice to get them with the couple other things I want in this GB.

So the fat are the ones that can be used with bracket mounts. I must be confusing it with the old KGSSHV where fat was both halves together. Cool. I do think those are better as well. But I got all I need in that department so that's for you guys to hammer out.

Current GRHV split is the V6 or V7 I think. It has silk options for 400V and 450V. The people wanting the fat supply want the +/- combined in one board which is a little different. Circlotron HV900 is definitely it's own PSU. Each board is like 2 KGSSHV +'s duct taped together for 900VDC and you need four of them. I had a question on the TKD 4CP601 pots though. For a stat amp, is the 10K or 50K preferable? Because 'll grab one of those.

I'm interested in HV900 single V2's for the Circlotron. Not sure how many other people are looking at building but they're 4x of the same board for a set so hitting minimums should be a little easier.

Went ahead and did one last thing as a check. Moved one of the HV900's directly under an output board with another flipped directly next to it for minimum lead length and had all leads HV900 shortened to <5 inches. Got the exact same sound. No louder. No less. The new HV900 boards look good to me. Parts match what they should. I didn't go through every trace though. If they look clear, anybody else interested in having them made? I'll chip in for two sets to start it along. Somebody else would probably need to run the buy though, since my experience with PCB houses at this spec is nill.

I remember I tried that at the primary end once at it didn't change noise behavior in either channel, but not sure how I'd do it at the secondary. With 4 secondary pairs in a channel set and no oscilloscope, I'd probably need to go through all 16 combinations and hope one cancels like how a balanced cable works. Is there a smarter way to go about it?

Dumb question but what's that fifth thing on the bottom side that's not the STN0214 or STN9360?

The normally open power mosfet mounted on the +900 out with a resistor picked for gate voltage to hit at a little under 50mA current to the output board. Just a second safety pretty much. IXTH6N100D2 I think. On the mounting front for the singles, longer is perfectly fine for me, it's just wider I can't do. My side sinks are three separate 6" wide aluminum blocks stacked side to side and the current HV900 singles take up pretty much all of one 6" block per mount horizontally.

If I had a wishlist on a HV900 V2, it would probably be: Each still split into a separate board for four total (mostly so I don't have to make a new set of brackets or drill new holes in the heatsink and easier to service if one blows) Transformer inputs on the front like you posted instead of the side like in the first run boards (shorter transformer secondary leads and easier to get to) Integrated current limiter (would help shorten leads for whole output stage) Ground plane (I know it's not a ground part of the circuit but wouldn't it still need a terminal to ground?) Change the 4.42K Xicon to 4.32K Dale resistor so it's closer to 900VDC even instead of a little higher. But you know better than me. I can just put stuff together and troubleshoot a little bit, read specs on parts or whatever. Design itself is not something I really understand.

So, been kinda beating my head against a wall with this like usual, shielding stuff and whatnot but I found something by accident that may be helpful. I was bringing up the GRHV main transformer on a variac to make sure things still started up right on the first half of the amp after all the redoing of cables and was getting the exact same noise as when I would bring up the output stage as I raised the voltage. Same drifting from right to left channel buzz to both, same tone. After some digging around, I had forgotten to reconnect the PSU star ground to the chassis. So everything was floating. Once I connected it back, dead silence again. And that got me thinking about the HV900's/Output floating and doing the same thing. So what I thought was, is there any way to do a ground plane with the HV900's/Output with ultra thick boards and/or really wide spacing around HV rails? Because I think that would probably solve the final noise problem I'm having.

A good monument company would make a nice marble case for anybody for under a thousand bucks or two anyhow. You could even do most of the fine casework like mounts yourself with regular drill bits as it only has a hardness of 3'ish. That would sure make a pretty DIY T2 or similar.

So separate shielding layers are multiplicative when insulated from each other. That answers my question perfectly. I tried rotating the smaller ones and nothing much happened. Can't rotate the big one as there isn't enough play in the leads, but it never made noise when running the amp just as a Carbon. Kinda wish I had a Gauss Meter with a probe or something so I wouldn't have to do so much guesswork.

The Circlotron has long power leads that pick up noise. I already RF shielded and grounded every major length of wire. Noise at this point is mostly from bringing the center toroid up of the three required for the amp, and I'm pretty sure it's magnetic. Basically, if the amp wasn't so massive, it wouldn't be a problem. But it is, so I'd rather take some time to slap metal on things before I have to do some more extreme case mods. Will probably have to separate the transformers more from each other in any case but might as well try the easier stuff first. What I'm trying to understand how you do the shielding itself though. Most places just have a single layer example. And other places sell dual layer bands and such with minimal overlap. I got an eight pound reel of continuous 50% nickel ribbon (Metglas 2826mb). I know multiple layers and thickness improve the shielding by a lot. What I don't get is if you use a bunch of separate wraps or just keep wrapping a single length? Or if a whole bunch of unbonded layers might hum like a loose transformer core? I just haven't seen any of that. I know when you make a transformer core, you use a single length and have all the layers epoxied together for strength and heat transfer. But I have no idea how hot shielding and stuff gets or what it needs to be connected to either. Seems like with mu metal you just make sure you don't bend it severely or solder directly to it or cause a shorted loop, but that's all the detail given.

I got lucky recently looking for large toroid transformer magnetic shielding stuff and got a huge surplus reel of mu metal transformer core ribbon for cheap. But after looking awhile on the net, I'm still not quite sure how to use it. It seems like you need multiple overlapping enclosures for good magnetic shielding, so do I just cut single circumferences and layer them up instead of wrapping one long ribbon? And unlike electrostatic shielding, you don't add a ground to it correct? Any special heat or lamination concerns?

Those Crees will be back in stock in a month or two. They tend to run out a couple times a year from what I've seen. Looking at Mouser, it says they expect the next big shipment around the end of February.

Looking for those mumetal bands that you wrap around a toroid transformer for extra shielding. Somebody used them in a build thread in here a few months ago and I'm having a hard time finding it again. Can anybody point me in the right direction? Edit: Found that it was actually the oriented grain steel used by rumina from Don Audio https://www.don-audio.com/trafo-shield

Exploding is one thing it's really good at. Well, I went and put some 1 and 3/8" tinned copper braid shielding on the the transformer secondaries. 1/4" quick connectors to ground leads to star ground. Made stuff significantly quieter but hum still there. I'll get around to the primaries and such next. I got 25 feet of the stuff so might as well cover everything. But I wanted to ask if using some kind of high voltage coax cable to replace the unshielded 900V lines might be a good idea? Since that seems to be what is picking up most of the noise in the first place.

Would only be able shorten a few things a few inches, so like 12" instead of 16" on some of the HV900 - leads. The way the boards are laid out necessitate most of those lengths, which are pretty darn long. I might have to try shielding some stuff instead, like the really long transformer leads. The audio input stuff already is and are connected to chassis ground. Any good bulk braid cheap? Heck, I was reading that sort of thing might even be that the diode bridges on the HV900's might be damaged and leaking. They're about the only parts I've never replaced on those things no matter how much they've blown because they still work. Need to check if they're leaking AC I guess. Connections are good. Just rechecked all those from stem to stern.

Link to hum. You'll probably need to turn up the volume a bit since it was recorded with a crappy phone mic. https://www.dropbox.com/s/zomvnhpob9d4dx5/hum.mp3?dl=0 Any help you guys can give hunting this down would be great. If I can just kill this hum and be sure I don't have to reduce the current even further on the Output boards because boy do those things get hot in a hurry then I'm in the clear.