livewire

Now there is a great idea for an IEM design. Call em "dikhedz".

What (if any) is the sonic difference between the ixys and the 2SA1968 current sources? Any other benefits of the ixys over the other? (besides price)

The comp caps exist on the last design. KG didnt put them on the schematic. They do show on the BOM and the board overlay jpeg drawing. FWIW if the latest outboard heatsink design sees the light of day, sign me up for a board set and some sexy heatsinks!

What (if any) is the sonic difference between the ixys and a1968 current sources?

We have one of those da Vinci robots where I work. Got to play with it once, kewl stuff. Also had to troubleshoot the Da Vinci power supplies a few times. Not so kewl stuff....especially when there is a pissed-off doctor standing over you wanting to use the damn thing.

Back in the day she used to turn me on! Doesnt she do Boniva commercials now?

Lenovo PC Pentium Dual Core 2.5Ghz > Foobar 2000 > FLAC > Neko Audio D100 DAC A few things I've noted, When I power it on, the living room lights go dim for a second. Them big caps are thirsty! Cased up it runs relatively cool. After a few hours, it's just warm to the touch. Dead silent noise floor. Zero hum or static no matter what the volume setting. Being a "one box build", I took the extra precaution of ordering a toroid with a "core band". Minimal shielding around the periphery, it helps cut down on EMI radiation. I like my new toy. Next up is a better attenuator, although the RK27 dont sound bad. Eleven or twelve o'clock on the volume control is the sweet spot for me. This thing has mucho grunt to spare.

Been listening to the HGSSHV non-stop. Sure is different having a fully balanced rig. Mucho mas detail and headroom to spare. Now I need some better Stax....

KG is doing some minor revisions to the board design. A few silkscreen changes and reroute the input fet traces on the amp boards.

As a footnote, I used nylok "aircraft" style nuts. Both the screws and the nuts are non-magnetic stainless steel.

I know nothing about silicone foil or it's ability to insulate under pressure where the sharp edge of a transistor mounting tab may cut through. I've had good luck with the fiberglass reinforced products they sell here and bad luck with cut-through using the very thin non-reinforced thermasil backing material. The alumina ceramic product you reference looks to be the right stuff. The one on the left appears to be correct for use with the TO-220 transistor package. Generally I do not use metric stuff, so I'll leave it up to you to figure out the fit up of the products you might consider for use over there in Europe. I can tell you what I did using American inch standard products. The 7721-3PPSG did not fit inside the hole of the TO-220 mounting tab. I used a dremel grinder to enlarge the hole diameter a few thousands of an inch. Then the plastic shoulder washer slipped right in. The heatsink I used came tapped for a 6-32 screw. I used a smaller diameter 4-40 screw that fit through the 6-32 heatsink hole without threading into it, The screw entered from the backside of the heatsink and was nutted from the front side of the transistor. (with the nut resting on the plastic flanged shoulder washer) To make the screw fit between the heatsink fins from behind, I parallel ground the screw head flat on two sides. I assembled it all together in this order: screw > heatink > thermal coumpound > ceramic pad > more thermal compound > transistor > plastic flange washer > nut. The 7721-3PPSG washer when used with the alumina ceramic backing plate protrudes through the transistor tab (and fits) into the hole of the ceramic plate. This insures that there is no electric arc-through between the screw threads and the hole in the metal transistor mounting tab. The normal short shoulder plastic flange washers are not deep enough to insure that there are no exposed screw threads in this critical area.

In fact any sand with an exposed metal mounting tab that is used throughout this build should be mounted in this fashion. If you notice, KG has silkscreened the alumina pad locations on the pc boards. At the risk of sounding redundant, In practice any of the transistors or FETs that have exposed metal mounting tabs which are affixed to any of the heatsinks, mount them this way. Silkscreened location or not, the alumina pads will fit in there. (you may need to resolder or replace the transistors to get the correct hole height matchup) The only exception to this rule are the +/- 15 volt regulators.

Hey rille I think that I see the problem. The 10M90S should have better isolation from the heatsink. I assume that you used the short thermasil plastic washer and a thin backing pad between the sand and the heatsink. This may not be enough to prevent a high voltage breakdown (arc path) between the metal mounting tab and the grounded screw/heatsink. To insure complete isolation between the two, one needs to use an aluminum oxide ceramic backing pad with a deeper shoulder plastic washer instead.(along with dielectric heatsink grease) A discussion of this has been covered in this thread. (click on my thumbnail pic above to see the enlarged detail of the mounting) The Mouser part numbers are: Alumina Pad: 532-4170 Insulating Shoulder Washer: 532-7721-3PPS

Wow! I have that album. Your post made me dust it off and listen to the whole thing. The chilhood memories came floodin in... Oh and btw, it sounded great on my new amp! Now back to your regularly scheduled dynahi discussion. Great stuff! Keep it coming.

rille, looking good! I hope all tests ok, looks like it will. Somebody wanted to be able to read the Stax tribute on one of the amp boards?

Here is a pic of the kgsshv on the bench while doing final testing. Please note that I was doing a lot of unhooking and reconnecting of the wiring during board removal. I do intend to clean up the wiring before casing it up. Still need to paint the cover, then will post more pics.

@KG - ygpm

Awesome! Cant wait to hear some impressions from the cognoscenti.

Thanks! I may be a fool for attempting KG's high voltage madness, but no April's Fools. It's the real deal, finally. WOW! That Khozmo looks like it could withstand a nuclear blast. That is what I call "over-engineered". Tis a thing of beauty indeed!

That BOM is for the 500 volt version with the T2 / BHSE style external heatsinks. I built the 450 volt version with internal heatsinks. The BOM for it is much different and has fewer parts, but count em -> 27 heatsinks! And yes, there are a few revisions to be made. KG is aware of them, I dont think anything new has been posted recently. I would be glad to proofread it when posted.

Good to hear of your progress! I really dont remember who I bought the fake 2SK389's from. I do remember they took six weeks to get here. What kind off attenuator did you get? Mine is a POS ALPS job. I intend to upgrade it in the near future. I went the "econo route" on my build. Plain Jane stamped chassis, I'm gonna dress it up with some bumper stickers. The theme is "Back To The Future" as in paying homage to the orignal KGSS.

Thanks guys for the good words. Thank you Doctor G for bestowing your latest SS design on me. FINALLY! IT LIVES! OMFG I CANNOT BELIEVE IT! After three months of blood, sweat and tears I can hear music through my Stax on my KGSSHV. The 2SK170 sand did the trick. The +/- bias sits right on zero volts now. I still need to do a little tweaking on the +out to ground zero bias. Pics to follow in a few days...

So my struggle continues....more observations below. The power supply is working fine now. I also checked my attenuator connections, they are correct. If I ground the amp inputs (as in zero volume / resistance on the attenuator), the LED in the third stage current source shuts off. (see attached amp pdf below) When I turn up the volume control about a third of the way,(about 15K ohms above ground) the 3rd stage LED lights up. I also tried unhooking the volume control completely and ran wires from the amp pcb inputs directly to the xlr input jack and applied a signal from my DAC.(variable strength signal with the DAC's digital volume control) That also shuts down the 3rd stage LED. The third stage LED stays on with nothing hooked to the amp inputs.(except for the onboard 500k resistors to ground.) I performed the +/- output zero bias procedure, the amp board did respond to adjusting the RV2 trim-pot, but would then drift as much as 10 volts one way or the other. The +output to ground bias was a similar failure. With the RV1 trim-pot pegged to the stop clockwise, I could only get it to within 10 volts above ground (0V). The reading would then drift upwards to about 20 volts. Letting the amp warm up more and re-adjusting had the same effects. At this juncture I suspect that I have some bogus input FETs (2SK389) I noticed that the front side of the plastic package has been abraided, maybe relabeled fakes? I bought them on ebay back in November 2010 from a chinese vendor. I paid $12 each. Today I picked up some 2SK170 sand. Gonna try them and see if things get better. Stay tuned! kgsshvproduction-final amp.pdf

@UV88 - if you read back in this thread, there are some answers to your questions. 507 + 323 = good stuff. But dont take my word for it. I've heard neither.

Whoa dude! Datz beta dan foe foety ana somolian.