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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 1:04 pm
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Ayup......AB165 all the way, with the hallmark Rube Goldberg-esque bias-balance circuit. Pop some new electrolytics under the doghouse and in all the appropriate locations on the eyelet board and it should be good to go for the next two or three decades. And don't sell those Sov-Tek 6L6GC's short -- if the amp is presently sounding good, I'd keep them. At least until they actually crapped out.

Arjay

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Last edited by Retroverbial on Sun Mar 02, 2014 3:33 pm, edited 1 time in total.

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 2:54 pm
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Of any req mod, that won't hurt resale --- prolly the balance-to-bias pot conversion is the best. And most practical. Pretty easy mod to do. Mostly pulling add-on resistors off the board. Makes for neater looking circuit.

This. Note all the resistors added to the board via terminal strips.

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To this:


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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 3:22 pm
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Retroverbial wrote:
Ayup......AB165 all the wall, with the hallmark Rube Goldberg-esque bias-balance circuit. Pop some new electrolytics under the doghouse and in all the appropriate locations on the eyelet board and it should be good to go for the next two or three decades. And don't sell those Sov-Tek 6L6GC's short -- if the amp is presently sounding good, I'd keep them. At least until they actually crapped out.

Arjay


Not intending to toss the Sov-Teks, they are sturdy tubes, but you have given me something to think about. I did have Sov-Teks 5881's in my 2x12 Bantam and these 6L6GB's have a bit more punch to em than those did and they are about as smooth sounding.

T2

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 3:24 pm
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BMW2002Ti wrote:
Of any req mod, that won't hurt resale --- prolly the balance-to-bias pot conversion is the best. And most practical. Pretty easy mod to do. Mostly pulling add-on resistors off the board. Makes for neater looking circuit.

This. Note all the resistors added to the board via terminal strips.

Image




To this:


Image


Steve,

What is the advantage of going this route? Any tonal difference or is it just a board clean up?

T2

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 3:36 pm
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If you're using matched tubes (or nearly so), Steve's mod provides a true idle-bias adjustment for both bottles simultaneously. The original AB165 configuration is a bias-balance adjustment, which just about mandates using mis-matched tubes.

Arjay

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 4:08 pm
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Retroverbial wrote:
If you're using matched tubes (or nearly so), Steve's mod provides a true idle-bias adjustment for both bottles simultaneously. The original AB165 configuration is a bias-balance adjustment, which just about mandates using mis-matched tubes.

Arjay



So does this mod have a tonal advantage? Or just the benefit of being able to use mis-matched tubes? I have several RCA 6L6's but all are singles, no matched sets. Hmmm?

T2

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 5:35 pm
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Tony,

The tonal advantage is you can bias your 6L6GC's. You cannot do this with a balance pot. With this circuit, if you need to increase or decrease the idle bias current of both tubes, you'll need to change fixed resistors in the bias supply circuit.

Since most ppl buy "matched" output tubes, it's better to be able to adjust the bias of both tubes together. Rather than match the idle bias between the two tubes (to a value that maybe out of the ideal bias range of both tubes).


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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 6:25 pm
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BMW2002Ti wrote:
BTW... how do you set Photobucket, so that you can't click onto the photos/links?

Don't want strangers looking at my girly.... uh .... I mean circuit photos. :lol:

There's no security afaik .... here's his collection:

http://s1192.photobucket.com/user/T2Str ... t=3&page=1

T2Stratman, don't you ever think about anything other than guitars and cars? :lol:

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 6:40 pm
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What no females (human, that is)? :lol:

My collection looks like Stratman's. Ain't no cure for the summertime (cars and guitars) blues... :mrgreen:


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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 7:46 pm
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strings10927 wrote:
BMW2002Ti wrote:
BTW... how do you set Photobucket, so that you can't click onto the photos/links?

Don't want strangers looking at my girly.... uh .... I mean circuit photos. :lol:

There's no security afaik .... here's his collection:

http://s1192.photobucket.com/user/T2Str ... t=3&page=1

T2Stratman, don't you ever think about anything other than guitars and cars? :lol:

Image


You mean there are other things to do in this world besides Cars and Guitars? :lol:

T2

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 7:54 pm
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BMW2002Ti wrote:
Tony,

The tonal advantage is you can bias your 6L6GC's. You cannot do this with a balance pot. With this circuit, if you need to increase or decrease the idle bias current of both tubes, you'll need to change fixed resistors in the bias supply circuit.

Since most ppl buy "matched" output tubes, it's better to be able to adjust the bias of both tubes together. Rather than match the idle bias between the two tubes (to a value that maybe out of the ideal bias range of both tubes).


Thanks! Between you and Arjay, I think you dumbed it down enough that I understand it finally! I may have to talk with my tech and do this mod. Will have to think on that for a bit.

T2

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Post subject: Re: NAHD!
Posted: Sun Mar 02, 2014 8:15 pm
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T2Stratman wrote:
You mean there are other things to do in this world besides Cars and Guitars?


Guns.

And whiskey.

:mrgreen:

Arjay

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Post subject: Re: NAHD!
Posted: Mon Mar 03, 2014 12:34 am
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Retroverbial wrote:
T2Stratman wrote:
You mean there are other things to do in this world besides Cars and Guitars?


Guns.

And whiskey.

:mrgreen:

Arjay


Guns...

Whisky...

Cars...

Motorcycles...

Cameras...

Watches...

Airplanes...

Wines...

Cognacs...

Coins...

Baseball Cards...

Vintage LPs...

Military Memorabilia...

Lithographs...

Don't even get me started... :lol: :lol:

cheers!

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Post subject: Re: NAHD!
Posted: Mon Mar 03, 2014 1:00 am
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Jim,

And the biggest $$$ drain... women!

Did those toobz arrive?

Thanks!


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Post subject: Re: NAHD!
Posted: Mon Mar 03, 2014 1:18 am
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BMW2002Ti wrote:
And the biggest $$$ drain... women!


Negative.

One can periodically recoup the outlay for a bad women investment via "creative" amortization.

But horses and boats are the proverbial black hole.

:lol:

Arjay

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