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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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Hello all!

I assembled Power Suplly on board version 450 V. Output shows +457 V , -457 V. Bias equal ~580 V after 30 minutes worked.

But I worry about temperature regime. Especially about R7,R10,R18,R20 . It consists from two 120K resistors = 120K + 120K = 240K. But the temperature is still hot, about 75 degrees. Is it ok? What temperatures other members has?

And could somebody say what temperature on 2sa1968, C4686A off board mafia version?

 

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Nice build, @samsie! Are you noticing any noise on your Carbon from having the transformer so close to the amp boards, inputs, and outputs?

 

I do not hear any noise even when I turn the volume all the way up.

I am impressed with the circuit design and the quality of transformer ( the transformer was custom-made in China for  $20 dollar-  the guy completed and shipped out the transformer including the resin filled process in 48 hours).  He was either super efficient or he had no other order to do.:D

Edited by samsie
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the case is from taobao, the Chinese version of ebay.  they even  cut a stepped hole for me for the stax socket

http://world.taobao.com/item/39957531066.htm?fromSite=main&spm=a312a.7700846.0.0.Fa8iz2&_u=421pt7g7143

That's amazing!  and shocking too considering the cost of such things in Europe. These are no doubt made in quantity, but a bespoke case made here (such as this) would be ten times the price.  My heatsinks were more meaty though

psXUsT0.jpg

Edited by headinclouds
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That's amazing!  and shocking too considering the cost of such things in Europe. These are no doubt made in quantity, but a bespoke case made here (such as this) would be ten times the price.  My heatsinks were more meaty though

 

this is really good looking.  I wish I could get someone to do the engravement like yours.

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It is done by an engraver literally a mile from my house.  He does tons of cups and trophies for schools and sports clubs, and labels and warning signs etc.

He also has a little milling machine with an old pc that does a limited range of fonts which he uses on my engraved panels.  You might be able to find somebody doing similar work.

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  • 2 weeks later...

Hi all,

I'm having a problem with a rev 0.4 offboard amp 450V.

Power supply is known to be good and powered another board with no problems. When I fired it up R11(175K) and R10(175K) cooked immediately. D10, D13 and D2 did not light up. All new sand.

I checked all the resistors before building. Balance trimpot was set to the middle and offset was set to max.
I crossed over the 50k resistors. I just checked the bottom of the board and no shorts.
Thanks for any feedback

http://imgur.com/xeWBpku

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Hi all,

I'm having a problem with a rev 0.4 offboard amp 450V.

Power supply is known to be good and powered another board with no problems. When I fired it up R11(175K) and R10(175K) cooked immediately. D10, D13 and D2 did not light up. All new sand.

I checked all the resistors before building. Balance trimpot was set to the middle and offset was set to max.
I crossed over the 50k resistors. I just checked the bottom of the board and no shorts.
Thanks for any feedback

http://imgur.com/xeWBpku

Why the crossing of the 50k's??

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  • 2 weeks later...

Better late than never... I am getting near to finishing my KGSSHV and I would really appreciate it if anyone can spot anything incorrect before I fire things up. (I still have to put in the op amps and remove the servo jumper on the amp boards).If I could do it again it would be with RN60D resistors. I know - the dissipante case for on board version is a bit unnecessary, but it was never going to be portable B)

24aOojJ.jpgX6crC6v.jpgKnZlPHH.jpgRBkbJRS.jpg

5ybFtJQ.jpg

 

 

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  • 2 weeks later...

I just got set of the onboard heatsink boards, mostly populated and the enclosure mostly already put together. I just needed to check if everything was set up for 450v and global feedback and if anything obvious is missing since I don't know what's different between versions. It's revision .61 so I think a bit older than current?

 

BkD5R3p.jpg

 

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uWVVHAB.jpg

 

5v6vOGY.jpg

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Did you elevate the big power resistors on the PSU board a bit? I cannot tell from the pictures. They should be a bit above to board, for better heat dissipation.

 

On the Amp board two disc caps are missing in the input section.

The PSU board also misses a few part (one film cap and two diodes)

Furthermore it looks like you are using non-isolated diodes in the bridge rectifier part (although I am not totally sure form the pictures). If so, it will arc and blow up...

Edited by insanity
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Yeah, definitely wanted to go over this thing with a fine tooth comb before putting any power through it. This was one of those projects that was 80% done that I picked up because I figured it would be easier than starting from scratch, especially with the case stuff almost all done already. I just need to tap holes for the case feet and enlarge the tap for the volume pot a hair.

 

Also, looking closer at the transformer and comparing to the website specs, this is the 500v version after all, not the 450v. The amp boards look to have the correct IXTP01N100D for it installed as well. I think 500v means I need a jumper in place of one of the missing film caps? I'm still trying to puzzle out the rest.

 

I'm getting a mouser order together for what I lack. So far I know I still need 8 STM STTH512FP to replace the Vishay ETF12's in the rectifier bridges.

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It looks like this thing was built with the 4686 as output devices which as far as I know are suitable for the 500V version. If you want to go for 500V, you would need to replace them with ixys parts. Which I would not recommend, since the 4686 is definitely superior sound wise (I changed my kgsshv from ixys to 4686 some time ago, but I ran it at 450V anyways). 

I would rather get a transformer suitable for the 450V version and rebuild the PSU board for 450V as well. 

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Two of the devices on each amp board are IXYS. The rest are the 4686. The PCB below seems to match that but I don't know if that's correct or not.

 

If I'm reading the website stuff right, and I very well might not be, the amp boards still need to be fully populated as well no matter what which means I still need 4x 175k 1/2 watt resistors, 2x 1k 1/2 watt resistors, 2x 1.2k 1/2 watt resistors (board says 500 but BOM says 1.2k if using the IXYS), 2x .47uF/50v caps (ceramic/mica), 2x 5pF caps (ceramic/mica), and two LED's per amp board. Comparing to the BOM here https://docs.google.com/spreadsheets/d/1tQvwqsARXGge6Tw6edqicCDti6Mite2F24T5YddyEEc/edit?pli=1#gid=0 that means I need.

 

8x 273-174K-RC Xicon resistors (nonstock mouser) I'm guessing you can't swap in the Dale CMF55174K00FHEB because it's only rated 250v instead of 350?

4x 273-1K-RC Xicon (in stock mouser)

4x 273-1.2K-RC Xicon (in stock mouser)

4x 810-FK16X7R1H474K TDK cap (in stock mouser)

4x 75-561R10TCCV47 Vishay cap (in stock mouser)

4x 859-LTL-307ELC LED's (in stock Mouser)

 

Also found the jumpers for Local/Global feedback. They're currently set to local. I remember how terrible the no-feedback sounded on my 727A with my SR-007 and I think the mod that fixed it changed that to global. What would be recommended here? I think the global/local option later got removed entirely in later revisions of these boards right? So there should be a clear better option.

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