Single channel AB763 question?

[tdvt]

Hi,
A number of "firsts" here.
First post on this forum,
First total build,
First time using a Hoffman board.

Anyway, I'm getting ready to load an AB763 board I got from Doug & I am deleting the "Normal" channel but no deviation otherwise, the reverb & bias trem are exactly what I wanted.
 
But going single channel raises a question regarding the 220k mixing resistors before the PI & whether to keep the remaining 220k or delete it?

I have found posts with differing information; some keep it, some don't & some others about emulating the missing channel's load with additional components. I have also been collecting schematics with all the modded variations of the AB763 & they seem to vary as well.

I plan to try it both with & without, but thought I'd ask too.

Thanks for sharing all your knowledge, I've learned alot already, more than enough to be dangerous.

Thanks, TD

[sluckey]

But going single channel raises a question regarding the 220k mixing resistors before the PI & whether to keep the remaining 220k or delete it?

I have found posts with differing information; some keep it, some don't & some others about emulating the missing channel's load with additional components. I have also been collecting schematics with all the modded variations of the AB763 & they seem to vary as well.

I plan to try it both with & without, but thought I'd ask too.

Trying both ways will tell you what is right for you. There is one more resistor on the Hoffman board you may consider removing also. It's the 47K that connects to the vibrato channel 220K mixing resistor. That 47K mimics the missing 50K Intensity pot from the original AB763 circuit. (Note that Hoffman uses a different tremolo circuit). Removing that 47K will give you a little more gain.

There are many variations on the AB763. "Everybody's right. Nobody's wrong." (Buffalo Springfield, a long time ago)

[tdvt]

Thanks for your reply.

I never thought about that resistor being part of the Hoffmanized version, until you pointed it out. I'll try that both ways as well.

I noticed that 47K resistor is included on a single channel, verb/no trem version (from your site I think?) between two coupling caps but it didn't click.

Which then raises the question of 2 coupling caps in series (if the resistor were removed) but I suppose things could start to drift away from the original design (sound) pretty quickly. 





Thanks, TD

[JayB]

Thanks for your reply.

I never thought about that resistor being part of the Hoffmanized version, until you pointed it out. I'll try that both ways as well.

I noticed that 47K resistor is included on a single channel, verb/no trem version (from your site I think?) between two coupling caps but it didn't click.

Which then raises the question of 2 coupling caps in series (if the resistor were removed) but I suppose things could start to drift away from the original design (sound) pretty quickly.

Just replace them with a single 1meg resistor. There is nothing like a screaming Fender.

{Edit: quote fix -PRR}

[PRR]

> Buffalo Springfield, a long time ago

Stop, hey, what's that sound....

Your quote is Matt Thompson.

BS sang "Nobody's right if everybody's wrong".

Buffalo Springfield - For What It's Worth 1967
http://occupycolleges.org/2011/12/10/1685/

Much like the current presidential hoe-down.

Written for Kent State. Three years before that happened.

Paranoia strikes deep
Into your life it will creep

Maybe I'm missing a joke.

Go home and check yourself, you think we're singing 'bout someone else?

Maybe the man come and take me a-way....

[sluckey]

Mental dyslexia strikes again. 

[PRR]

Mental dyslexia strikes deep,
into your life it will creep...

I remember every word of that doggerel, but can't remember if I took my pills today....

[sluckey]

I remember every word of that doggerel

I thought I did too!  

Wasn't Neil pretty back then!