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i'm on a roll... the kgsshv


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After 5 years from the time I acquired the PCBs and parts, I finally took advantage of the free time created by the pandemic and completed my KGSSHV.  This is the offboard version with +/-500V supply.

Not sure if we have a KGSS thread but I'll just post this here.  So last year it dawned on me that I built my first KGSS amp 15 years ago and something had to be done to celebrate that.  It started of

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All you'll be listening to is the sound of the pot. I have no scientific rationale for why these sound just as awful as they do - tearing one apart the design principles and construction look superb. But they sound dreadful. For a more sane price than the RK50, go for a DACT - knocks the RK27 into a cocked hat.

It is really astounding just how bad they are. Not a DACT fan but the TKD 601 is excellent and bloody tiny.

Ohh and if anybody needs a cheap 4-gang pot then drop me a line. I still have some Alpha's left from my bulk order and to these ears they are a large step up from the RK27 and cheaper too.

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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!::

My 20-16164 is the same configuration, only two lines of ventilation holes on the bottom.

I am using this case for my breadboard-KGSS

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Bom:

Bridge 747desp12-12a quantity is 8. Should be 2.

Mouser has nil stock of the following parts

273-120-rc. They ran out between me putting them on my order and the checkout....

273-300-rc. nil stock

75-561r10tccv50 nil stock

273-20k-rc. nil stock

273-100-rc. nil stock

667-eet-uq2w681lf. nil stok

661-esmh41vnn101mp3. nil stock

647-ups1h101mpd. nil stock

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Bom:

Bridge 747desp12-12a quantity is 8. Should be 2.

No its 4 individual diodes, so the quantity is correct.

Any 1200 volt fast recovery diode works. Actually any 1000 volt to220 diode works.

Used to be the st parts, those are out of stock too there are new versions of the st parts in stock.

updated bom with a couple of fixes.

alternate 680uf cap in stock is

667-eet-uq2w681ea definitely fits.

like the T2, some parts were on backorder.

Just spent 2 hours stuffing resistors. somehow forgot to order 3 values.

more parts stuffing later today.

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747-dsep12-12a dioded are restricted export from Mouser. Digikey has 497-5150-5-nd TS devices.

Digikey also has 4171G al oxide washers. Problem is minimum ammount is 1,000 pieces. Not too good if 3 or 7 are required.

2SC3381 were available on ebay from little-diode.

Neither Mouser or Digikey had 100uF 50V caps. Will source them locally, probably WES Electronics.

Digikey has lm4040-10

ixtp01n100d is restricted on Mouser, none at Digikey.

The saga continues.....

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747-dsep12-12a dioded are restricted export from Mouser.

ebay. search for dsep12-12a.

Digikey also has 4171G al oxide washers. Problem is minimum ammount is 1,000 pieces. Not too good if 3 or 7 are required.

Try mouser 532-4170 (smaller size) or here.

Neither Mouser or Digikey had 100uF 50V caps. Will source them locally, probably WES Electronics.

I doubt. there should be a boatload of these caps. very standard values.

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Neither Mouser or Digikey had 100uF 50V caps.

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.

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BTW, I'm confused about the 4171G 'washer'.

Also, should the nuts be something special or just a standard one would be just fine?

Having been down this track with the T2, what you need is an insulating bush that goes through the transistor tab, and then well into the 4171G. If it is a short bush, the transistor tab isolation is compromised. You have to draw a cross section picture to see this clearly.

The ones that work well are the Aavid 7721-3PPSG. These can be a tight fit in some TO220 holes, but the bush length is 1/8" (3.18mm), which is more than enough with conductive (steel) screws and nuts. I prefer steel fixings because you can get the torque required - I tried plastic screws, but they always strip at a small fraction of the recommended TO220 package fixing torque.

Future have 675 in reserve stock and 14,000 on order.

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Having been down this track with the T2, what you need is an insulating bush that goes through the transistor tab, and then well into the 4171G. If it is a short bush, the transistor tab isolation is compromised. You have to draw a cross section picture to see this clearly.

The ones that work well are the Aavid 7721-3PPSG. These can be a tight fit in some TO220 holes, but the bush length is 1/8" (3.18mm), which is more than enough with conductive (steel) screws and nuts. I prefer steel fixings because you can get the torque required - I tried plastic screws, but they always strip at a small fraction of the recommended TO220 package fixing torque.

Future have 675 in reserve stock and 14,000 on order.

i suggest you buy ceramic screws @ $5 each. otherwise you'll be MAGNETIC!!!

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Amazon.com: Ceramic Socket Cap Screw, Slotted Drive, #4-40, 3/4" Length (Pack of 1): Industrial & Scientific

i really underestimated the price...

but with no shoulder washer needed you can probably fit #6-32 in most transistor tabs

I've never touched a ceramic screw before. Are they brittle? Do you end up breaking them with too much torque? They look like you would have to use a torque wrench with them?

Those are kinda high Dollar items!

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I've never touched a ceramic screw before. Are they brittle? Do you end up breaking them with too much torque? They look like you would have to use a torque wrench with them?

Those are kinda high Dollar items!

If they use the same sort of ceramic used in knives it will be much harder than a stainless steel one.

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If they use the same sort of ceramic used in knives it will be much harder than a stainless steel one.

That's my point though.

Drop a steel knife on the floor, it may bend. Drop a Ceramic knife, you have a high chance of it breaking.

You wouldn't want ceramic Head Bolts on your car either.

I'm just wondering how these tighten up. A lot of metal bolts "hold" be using stretch.

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Having been down this track with the T2, what you need is an insulating bush that goes through the transistor tab, and then well into the 4171G. If it is a short bush, the transistor tab isolation is compromised. You have to draw a cross section picture to see this clearly.

The ones that work well are the Aavid 7721-3PPSG. These can be a tight fit in some TO220 holes, but the bush length is 1/8" (3.18mm), which is more than enough with conductive (steel) screws and nuts. I prefer steel fixings because you can get the torque required - I tried plastic screws, but they always strip at a small fraction of the recommended TO220 package fixing torque.

Future have 675 in reserve stock and 14,000 on order.

So, basically any shoulder washer that has enough length would be just fine? I still a bunch left from my Beta22 build. Wondering if I could use them...

Also, would this aluminum oxide insulator work for lower voltage MOSFETs like the ones in the Beta? If it's better, in term of heat transmitting, than the thermasil I'm using, I'll just buy a bunch and replace the thermasil.

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That's my point though.

Drop a steel knife on the floor, it may bend. Drop a Ceramic knife, you have a high chance of it breaking.

You wouldn't want ceramic Head Bolts on your car either.

I'm just wondering how these tighten up. A lot of metal bolts "hold" be using stretch.

I've never seen a ceramic knife break, these are harder than steel, not just a regular ceramic used in planes and bowls.

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