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Well, I thought JoaMats suggestion about it being the 1N4007 was right. I got a voltage going both ways on it on the non working board but only one way on the working one. However I replaced it and it shows the same behavior once in the board. I swapped out the LT1021 in case that had something to do with it but the same result (voltage shown in both directions). Faulty STN9360 maybe?

I've also double checked the current limiting resistor and it's actually 5.1R.

Edited by s_r
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My own Carbon, not going anywhere... IMG_6585 IMG_6590 IMG_6592 IMG_6593 IMG_6595 IMG_6596 IMG_6597

So I finished my my KGSSHV Carbon a few weeks ago. Been too busy listening to it, but I thought I would share my effort and measurements. I am lucky enough to have access to some test gear that allowe

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I've uploaded a few closeup pics here. All I can see is how much cleaner the solder joints of other people here are. :ph34r: I've since cleaned up the residue between the crees joints after seeing how obvious it is in picture.

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The tantalum cap is positioned the same as it is on the working board. As for the voltage setting resistors, they're 680k and 200k. If I recall correctly a special order of a few thousand was needed to get 442k xicons when I ordered the parts.

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Hi everyone. A few questions:

(1) How shall Servo1 and Servo2 be used / connected? In particular, it seems the 5K ohm next to Servo1 is not connected.

(2) Regarding the input JFET (lsk389), what will be the best Idss (for reducing THD)? i.e. Shall we use lsk389a or b or c.

I remember reading somewhere that larger Idss = less distortion, but then it's strange that lsk389a is more expensive than lsk389b/c. Sorry if this is a silly question, as my analog circuits knowledge is quite poor.

(3) Can we reduce the gain of the amplifier? (since my DAC can output quite high levels (+24dBu), and I usually listen at low volume)

Moreover, will this leads to lower THD? It will be great if someone can do a LTSpice simulation...

Thanks.

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14 hours ago, s_r said:

Well, I thought JoaMats suggestion about it being the 1N4007 was right. I got a voltage going both ways on it on the non working board but only one way on the working one. However I replaced it and it shows the same behavior once in the board. I swapped out the LT1021 in case that had something to do with it but the same result (voltage shown in both directions). Faulty STN9360 maybe?

I've also double checked the current limiting resistor and it's actually 5.1R.

If 17V at pin 3 (katode) 10M90S and 1.77V cross 4.7K resistor than you probably have almost 0V at the emitter of STN9360. My next long shot is at the STN936.

Edited by JoaMat
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Diode test? Or, what I have done may times to find issues or faulty parts, is measure resistance at various parts of the circuit between the good and bad boards - not the most accurate and sometimes the values fluctuate at certain parts of the circuit, but differences here can point to the culprit fairly quickly.

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Here is my Carbon build. The layout is a lot like the KGSShv Cube I made in 2014 although this is bigger and easier to assemble. I have dubbed it the “Chunky”.

I have two versions, a black/silver and an all silver and am building two of each.

The Chunky measures  340 wide X 310 deep x 138 high, plus feet and weighs about 10 kg.

As I wish to concentrate on other projects I do not intend to make more amplifiers for other people.  I am intending to do a KGBH for myself.

I have enjoyed the challenge over the last few years and have also met some great fellow head-cases. The KGSShv/KGST/Carbon KG designs I have built have all worked as intended and been easy to set up and all have given great musical pleasure. This is a sign of a great designer and I would like to note again my gratitude for the great gift given to this hobby by Kevin and Birgir, Kerry, Joamat, Jim L and all the others for their contributions and inspiration.

 

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Edited by headinclouds
correction change 2012 to 2014
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Thank you Steve and Kevin, the cardboard models paid off!  It is also a gorgeous sounding amp. I am smiling and tapping my feet again.

I should also point out that the styling; rounded edges, milled detail and switch insert were suggested by Julian,

whose talents are very much in the visual field.

Edited by headinclouds
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3 minutes ago, headinclouds said:

Thank you Steve and Kevin, the cardboard models paid off!  It is also a gorgeous sounding amp. I am smiling and tapping my feet again.

I should also point out that the styling; rounded edges, milled detail and switch insert were suggested by Julian,

whose talents are very much in the visual field.

Very nice!  He gotta be very happy to receive this amp.

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I think anyone would be happy to receive that - beautiful build!.

Geoff, have you got a picture of the back by any chance? (no, I'm not a perv I just want to see how the transformer is mounted :D)

 

//UFN

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1 hour ago, purk said:

Very nice!  He gotta be very happy to receive this amp.

Yes one is in his new shopping trolley eh Wink.

f4pw6SD.jpg  If you ask for a picture of the bottom I'll worry.

The transformer is on a M6 bolt but in case you are wondering is supported at the front by a 6mm thick acrylic piece bolted to a bracket on the base. You should be able to see it in the internal shot.

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Always admire you guys getting silk screen prints/engravings for volume/switch/name labels back and front faceplates.  Look super professional!

Wonder how to get the services done in my local area.  Sending the parts out seems to defeat the idea due to weight.     

 

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Wonderful craftsmanship.    :wub:

 

Only one problem, though     :o

 

There's only one (1) Stax output socket       :rolleyes:

 

I guess, perfection requires great thought, planning and/or outrageous fortune......      :D

9 hours ago, headinclouds said:

Yes one is in his new shopping trolley eh, Wink. (snip)

Wot...?

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