Look what Santa brought!

Rob11966 · 27th December 2007, 02:13 AM

Hi all,

I have just completed my second amp after about 200 hrs of work!

It is stereo amp based on the Mark III KT88 monoblock with 6AN8 drivers, a couple of NOS Mullard GZ34 rectifier tubes and some Genelex 'Gold Lion KT88 tubes. Used new components throughout with sprague orange drop caps.

All hand made apart from the SDS Caps board. I have also added (this is going to drive a stake into the heart of the purists, sorry) digital bias meters for both channels - don't crucify me for this one....

The chassis is aluminum with the base and transformer covers black nickel plated and the top is plated with 18ct Gold.

It sounds great, but to be totally honest maybe not quite as good as my first project (with EL34 output tubes), seems t be a bit less punchy with the bass - or maybe I was expecting too much - I really couldn't fault my first amp for sound.

It also has one small problem that I don't seem to be able to solve. With no input signal, when I turn the volume pot, there is a very slight 'crackling' through one of the channels as the pot rotates, especially at high volume. The channel is silent even at full volume when the pot is stationary and sounds fine when playing sound. I have changed the pot but the problem remains so I think that the issue is downstream of the pot and only in one channel!? It doesn't cause a problem when listening to the amp but I am a perfectionist at heart, so any ideas will be acted upon.

Enjoy the pictures and thanks again for the advice along the way.

Cheers,

Rob

Rob11966 · 27th December 2007, 02:14 AM

Here is the inside

MJL21193 · 27th December 2007, 02:15 AM

Stunning! Well done.

Rob11966 · 27th December 2007, 02:15 AM

The evil LED's

Rob11966 · 27th December 2007, 02:17 AM

Hopefully I can pass some knowledge onto the next generation of hollow state builders. You can see the gold top a little better on this one.

Cheers,

Rob

kuroguy · 27th December 2007, 02:31 AM

Quote:

Originally posted by Rob11966
Here is the inside

You are a perfectionist. Nice.

Wavebourn · 27th December 2007, 02:36 AM

Very nice look, Rob!

HollowState · 27th December 2007, 02:40 AM

Rob, That's a superb wiring job! Truly it is. But what's that I see...several evil ground busses? Oh dear. (just being a wisenheimer) For the noisy control, check for any DC on it. Even a little can make it sound scratchy.

Victor

Richard Ellis · 27th December 2007, 02:43 AM

Congrats Rob!!
Your second build is even better than your first (Followed your first!)
The gold plating is very tasteful & elegant.....the black nickel sets off the gold superbly!
Now the question...do you have a place in the home for it?
I see audio sprouting thruout the house......all different decor to match(?) the amps....??
You didn't want to string speaker wire in all the rooms now did you!................Sooo you have two now...and how many rooms are left?
_____________________________________Rick......... ..

AudioFreak · 27th December 2007, 02:48 AM

Sounds like there is DC on the pot. You need to have the pot at a point in the circuit that doesn't see any dc or there will always be scratchiness when you adjust the volume.

27th December 2007, 02:36 AM	#7
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	Very nice look, Rob! __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

27th December 2007, 02:40 AM	#8
HollowState diyAudio Member Join Date: Aug 2006 Location: Taxland, New Jersey	Rob, That's a superb wiring job! Truly it is. But what's that I see...several evil ground busses? Oh dear. (just being a wisenheimer) For the noisy control, check for any DC on it. Even a little can make it sound scratchy. Victor __________________ "The supercomputer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required." ~ Professor of Electrical Engineering, New York University

27th December 2007, 02:43 AM	#9
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	Second build Congrats Rob!! Your second build is even better than your first (Followed your first!) The gold plating is very tasteful & elegant.....the black nickel sets off the gold superbly! Now the question...do you have a place in the home for it? I see audio sprouting thruout the house......all different decor to match(?) the amps....?? You didn't want to string speaker wire in all the rooms now did you!................Sooo you have two now...and how many rooms are left? _____________________________________Rick......... ..

27th December 2007, 02:48 AM	#10
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	Sounds like there is DC on the pot. You need to have the pot at a point in the circuit that doesn't see any dc or there will always be scratchiness when you adjust the volume. __________________ - Dan

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27th December 2007, 02:15 AM	#3
MJL21193 Account disabled at member's request Join Date: Mar 2007	Stunning! Well done.

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