livewire

The sparks were flying on my kitchen table last night! Truly a Kodak moment (or two). Thought it was the 4th of July. Checked my calendar and I was wrong.... I came home after a long day at work - eight hours of tracing faults in a computerized hospital communications system. I was very tired and obviously not thinking well. I powered up the kgsshv psu and proceeded to check all of the output voltages. Everything was right on the money. Next, it was time to do what KG suggested to tame my perceived grounding gremlins. (actually Craig Sawyers suggested something similar earlier.) But with 180VAC floating around where it shouldnt be, I wasnt ready to go there, yet. So I wired a 1k resistor between the DC ground of the psu board and 120VAC neutral and checked the current. Yup, the Doc was right, it was sitting right at 1ma. No more problem. Everything was now grounded as it should be. Now is where the fun began. As I was looking at my minor accomplishment, with the psu still under power, the snap of a spark with the resulting flash of diying parts erupted from one the 15 volt VR's. Not sure which one yet. I wasnt touching a thing, the sucker just blew. I immediately powered down the psu and unhooked the transformer, ran some resistance checks, didnt find any shorted windings, so I hooked the HV secondaries back up to the psu board while leaving the 15VAC sencondaries unhooked. I wanted to test the +/- 450V outputs to make sure nothing was affected there. I didnt think there would be, with the exception of the trafo, they are two compltetely independent circiuts, just on the same pc bpoard. So I grabbed my DMM, switched it to the DC volts range, put the probes on the -450VDC terminal block and almost went blind from the resulting flash - crackle - pop. Anyone care to guess what just happened? To be continued...

Glad to hear of your conquest! How does she sound?

Ok, I'm still haunted about physically grounding the power supply DC ground plane to chassis (AC) ground. My multimeter shows a difference of 180VAC between the two. Spooky! The meter shows zero differential for DC, so I guess that's OK. I'm running a transformer with separate 475V secondaries, no grounded center tap. Therefore I'm not using the center tap terminals on the power supply board. I'm pretty certain that this is what's messing with my head. The 180VAC component is 1/3 of the unloaded 540VAC of one secondary winding. So, should I just go ahead and connect the two? (AC ground to DC ground) Or maybe reconfigure the separate trafo secondaries as one with a grounded center tap? I'm really not in the mood for seeing fireworks....

Thank you Craig and Spritzer so much for clarifying the above details. I will proceed from there. And thanks to Marc and the others for your input on the inrush. I will leave those things alone for now. Lastly, many thanks to KG for bestowing all of your fantastic designs upon the world. Happy New Years to you all !!!

Correction: XLR pin1=ground

Excuse my ignorance, I've never attempted to build a stat amp before. I have a question for the gurus. What is the best way to ground this thing? I want to avoid ground loops and due to the high voltage on the supply rails, I've got the heebee jeebees about connecting the amp / psu grounds directly to chassis ground. Much of my doubt is due to I've noted that unlike other lower voltage circuit board designs, these boards have isolated mounting pads (isolated from the adjacent pcb ground plane). Therefore I've been wondering if the high voltage circuit ground should be isolated from the mains / chassis ground. Lastly, with the balanced XLR input connectors, does the ground (pin3) connect to the chassis (as seen in other designs) or do I connect it to the amp ground on the pcb, or just float it with no ground while running balanced source inputs?

o.O! See post #1754 - Re: Dalbani

Wow! I feel for you guys. I hope y'all get to the bottom of this slippery slope soon.

Primitive elegance... Some things never change (like the dual FET front end). Love the KG logo too!

Thanks for the recommendations guys. Spritzer the CL60 rings a bell. That is what I used on one of my old tube amps in the past. I'll prolly go that route, it worked well before and the current rating is about right.

Here's a pic of the finished psu after trimming the output. I will check and re-trim once it is hooked to the amplifier pcbs. The pro bias output is at 586VDC, about 1% above nominal. Two things I noted, one - this sucker is HEAVY! I will need to mount some type of center support block under the pcb. Secondly, upon startup the inrush current is substantial. I have not measured it but the transformer makes a loud pulsing hum, like and arc welder would. About a half second later when the caps are charged, the noise stops. I am considering adding a MOV to the hot side supply line. (click or mouse-over to enlarge) [ATTACH=CONFIG]4143[/ATTACH]

Please! I really dont wanna go there. Besides, this build aint no T2 replete with exposed, finicky hollow-state devices. It is supposed to be relatively easy and somewhat foolproof. Right?

Thanks, I thought it might have been already mentioned in some form. I didnt think about it until I saw the word "vendetta".

This might be lame, but have you guys read the old 2006 vendetta thread over at DIY Audio? The original designer chimes in a few times, plus there's a lot of discussion about unobtanium. Link: http://www.diyaudio.com/forums/analogue-source/90900-real-vendetta.html

OMG!!! WTF?? KGSSHV PSU UP & NO BBQ FTW!!! Mission Control, we have lift-off!

4-40 Gag! 6-32 is more like it... At least they ship with "Free Super Saver Shipping"!

I thought that to be strange too. Very common device, everybody is sold out. I remember the Head Amp guy, Justin lamenting that Apple and some other large companies have been hogging stock on many parts, thus depleting inventories for a long time. Try using 100uf 63V caps of the same style. A little taller, a smidge wider. They fit fine, no problemo.

This. [ATTACH=CONFIG]4089[/ATTACH]

Cant afford no $1000 pot. I dont care where they grow it. There are quad RK27 50k on ebay right now for $34. What a deal! Yea, yea, I know what you guys think about those. Let the bashing begin.... I also picked up some cheap chinese 50K dual dact rip-offs that are quad stackable. $20 total. We'll see how that works.

Found another one in the BOM. Line item #5 - 180 ohm, Mouser p/n should read: 273-180-rc

Mine has four on top, two on the bottom, one on each side. See the pic that I posted above. Hmmmm? Maybe I've got a defective case? I'm not gonna lose any sleep over it, the top ones are the most important for venting the heat. It is good to have them along the sides and bottom to pull cool air in. If you've noticed, the boards have vent holes in them too to aid with drawing fresh air up from the bottom, past the fins of the heatsinks. Nice touch. ::two thumbs way up!::

Good point, I thought about that too while I was stuffing the boards. I figured that I've burdened the good Doctor enough already, so I didnt mention it.

Yes it is, but it should work out just fine. When I ordered the enclosure (and didnt have the boards yet) I thought that I might have to overlap the boards a little bit, using different height standoffs. Turns out that wont be necessary. I really like the placement of the vent slots, right above and below and to the sides of the major heatsinks. Should aid in helping the "chimney effect" venting.

Mine is coming together, the boards just fit inside the case. (Par-Metal 20-16164) Waiting for the trafo to get here to finish the build. (mouse-over or click to enlarge) [ATTACH=CONFIG]4017[/ATTACH]

Please keep in mind that the listed price does not reflect a "group buy". I had a small run of these made, therefore the price is substantially higher. No profit is being made by me. I am selling them to recoup my costs. I wanted to sell them here at HC due to the original KGSSHV thread being here but due to my newbie status, I do not have access to the for sale forum on this board. I will not be offering any more board sets when these are gone.