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i'm on a roll... the kgsshv


kevin gilmore

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I hooked my completed kgsshv onboard final version power supply to its SumR transformer this evening and fired it up one circuit at a time. Everything looks good. + / - 453 VDC on the high voltage outputs and + / - 15.0 VDC on the low voltage. I could not measure the bias as my meter only goes to 500VDC. No sparks or smoke though.

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I hooked my completed kgsshv onboard final version power supply to its SumR transformer this evening and fired it up one circuit at a time. Everything looks good. + / - 453 VDC on the high voltage outputs and + / - 15.0 VDC on the low voltage. I could not measure the bias as my meter only goes to 500VDC. No sparks or smoke though.

Are SumR ok transformers. I read some posts with failures? I am not speaking from my own experience, only posts I have read from other KGSShv users.

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ON-BOARD or OFF-BOARD?

He guys. I am not a tech, so bear with me. Is the design philosophy of the

on-board and off-board the same? I am thinking (in physical terms) the off-board

design should be able to shift more heat, which may allow more amps on the grid?

 

If this is true, does this in turn mean an off-board could sound better as it 'can/could' have more

dynamics, more effective head room.

 

My other theory, was, can one KGSShv sound better than another depending on parts

qualities? I have some 300B monoblocks, and they are at level 3, the level 5 versions

have better transformers, and do sound nicer, sweater.

 

If all this is true or possible, it would be really interesting to build an ultimate KGSShv with no

holes barred parts, where the design can be taken to the max. Has such an amp ever been built?

 

Fascinating subject. To my tiny exposure to the KGSShv it has really impressed me as being a classic

amp design that will around for years to come. it is also fantastic that it is available to the DIY community,

as some like to build for themselves, but it also allows those on a tight budget (me) to get a taste of the high end.

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The on board version can only handle so much power because of the heatsink size.

The default is 5ma, which at 450V is 9 watts total for the output stage which is

2.25 watts per output device.

 

The off board version is limited by only 2 things, the size of the heatsink and the

maximum amount of power the output devices can handle. So yours is 14ma

which is 25 watts per channel.

 

The effect of the higher current is to extend the high frequency response well

past 50khz. So the amp will definitely sound different.

 

The choice of resistors will likely not make a change that you can ever hear.

Except that a few of the trendy and expensive resistors cannot handle the voltage

and cause all sorts of trouble.

 

An lsk389 is going to be better than 2 x 2sk170 from an electrical drift standpoint.

Not going to make any difference in the sound.

 

Now the pot makes a big difference. RK50 and P&G are definitely the best of the

bunch, rk27 and tkd less so. Mainly in channel to channel matching.

dact will do better on matching. digital attenuators are even better.

Edited by kevin gilmore
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The on board version can only handle so much power because of the heatsink size.

The default is 5ma, which at 450V is 9 watts total for the output stage which is

2.25 watts per output device.

 

The off board version is limited by only 2 things, the size of the heatsink and the

maximum amount of power the output devices can handle. So yours is 14ma

which is 25 watts per channel.

 

The effect of the higher current is to extend the high frequency response well

past 50khz. So the amp will definitely sound different.

 

The choice of resistors will likely not make a change that you can ever hear.

Except that a few of the trendy and expensive resistors cannot handle the voltage

and cause all sorts of trouble.

 

An lsk389 is going to be better than 2 x 2sk170 from an electrical drift standpoint.

Not going to make any difference in the sound.

 

Now the pot makes a big difference. RK50 and P&G are definitely the best of the

bunch, rk27 and tkd less so. Mainly in channel to channel matching.

dact will do better on matching. digital attenuators are even better.

Thanks Kevin, that is great to know.

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The on board version can only handle so much power because of the heatsink size.

The default is 5ma, which at 450V is 9 watts total for the output stage which is

2.25 watts per output device.

 

The off board version is limited by only 2 things, the size of the heatsink and the

maximum amount of power the output devices can handle. So yours is 14ma

which is 25 watts per channel.

 

The effect of the higher current is to extend the high frequency response well

past 50khz. So the amp will definitely sound different.

 

The choice of resistors will likely not make a change that you can ever hear.

Except that a few of the trendy and expensive resistors cannot handle the voltage

and cause all sorts of trouble.

 

An lsk389 is going to be better than 2 x 2sk170 from an electrical drift standpoint.

Not going to make any difference in the sound.

 

Now the pot makes a big difference. RK50 and P&G are definitely the best of the

bunch, rk27 and tkd less so. Mainly in channel to channel matching.

dact will do better on matching. digital attenuators are even better.

 

Default for onboard 450V version is 5mA, then what about the default for the 500V version?

 

Which resistors I need to change to increase the output current?

 

Also, where can I find LSK389/LSK170? Any alternative that's available at Mouser?

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default for 500v is the same 5ma. you change the emitter resistors at the bottom of the output stage.

and you want a lsk389B.

 

the lsk170B is available from diyaudio.com

 

Thanks for the reply.

 

By the emitter resistors at the bottom of output stage, do you mean lowering R5 and R6 in this schematic: http://gilmore.chem.northwestern.edu/kgsshvproductiondual.pdf, which are both 180 ohm?

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Well my huge hv uses the LSK389A's (the A is on ujamerstand's BOM too). Seems the only difference between the flavors is the Idss range.

 

Edit: Realized I answered my own question.

Edited by s_r
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It's quite cramped, that's how.  :)  Here is the latest version:

 

aeACidbh.jpg

 

0obulOSh.jpg

 

Only major change is the voltage selector PCB which makes the AC wiring all neat and tidy.  Nearly every centimeter is used now and I'm up to 9 pcb's per amp.  ;D

 

The bigger changes are outside as I changed the layout a bit from the one above:

 

9v7sIgEh.jpg

 

ik3lCQnh.jpg

 

It's very hard to photograph the chassis as it's so reflective... 

 

Thanks for the offer but I do have a Wordpress site up and running but it appears to be down now.  My friend hosts it and he's been having some issues due to some of the other stuff being hosted there.  It's mjolnir-audio.com and .net when ever it is up again.  Haven't done a whole lot with it yet but I need to add all the DIY stuff and what stuff I have in stock. 

Let me know if I can help Birgir. I hosts quite a few WordPress sites. Call it FOC if you need help. I think it is good to help in the cause if I can.

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