tone stack mod's AB763

tone stack mod's AB763

Postby tatittle » Thu Aug 29, 2013 3:08 am

I would swear I had seen detailed explanation of modification's done to Jerry's tone stack in the Fender Twin AB763 amps somewhere (Wald.) but cannot seem to find it now.

I am looking into modding my Tremolux tonestack along with a vibrato off pot and would love some guidance. The Tremolux has no midpot so changing the resistor there (thus default setting) may be important. A quick search of the archives here yielded nothing...but that seems to happen all the time for me so may be my error. Thanks.
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Re: tone stack mod's AB763

Postby Banana Boat » Thu Aug 29, 2013 4:20 am

ditto on that.
started a cap job on my 70 deluxe reverb and figured it was time to go all the way.
haven't been able to find what I know I've seen countless times on waldos site.
I think it's been taken down.
I know there is much appreciation for all of the information contributed by the senior gurus on this board.
puzzling...
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Re: tone stack mod's AB763

Postby cmc64 » Thu Aug 29, 2013 5:48 am

Yes, it does appear that the section with the info on the "Post-Alembic Mods" seems to be MIA.
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Re: tone stack mod's AB763

Postby Smolder » Thu Aug 29, 2013 6:17 am

.
Last edited by Smolder on Mon Nov 25, 2013 5:17 pm, edited 1 time in total.
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Re: tone stack mod's AB763

Postby gpilcher2001 » Thu Aug 29, 2013 11:21 am

Allen bradly milspec 100ks on the power rail and tantalum bias caps..... something like that. Greg....
good to know you got shoes to wear when you find the floor.....
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Re: tone stack mod's AB763

Postby softmachine72 » Tue Sep 03, 2013 4:32 pm

I too was wondering what happened to the diagram on Waldo's site also just used a few weeks ago. I just did a Jerification on a dual Showman AB 763. In addition I totally removed the trem. circuit and added a Parallel FX loop after the 2nd stage pre amp tube. Everything discussed so far is true but, in the tone stacks he used 225p's and used the 715's for the pico values (in 2 places if i remember). Use Sprague solid 25uf tantalum for the cathode bias caps and replace the 100k plate resistors W/ 1% metal films (where the 100k res. make a triangle at B+). As far as i remember the values on the tone stacks were not changed just replaced w/ (sprague) the 225p's . I also changed the sliver micas and I reduced the bright switch cap to 68p to take the edge off. Also I think it was wired for 220v and there was some modification to the rectifier circuit.(my amp was a 69 so did not encounter). also all the pot were replaced. I just did the vibrato side with new PEC mil spec pots.
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Re: tone stack mod's AB763

Postby Smolder » Tue Sep 03, 2013 6:51 pm

the tone stack in one channel was definitely changed.
Last edited by Smolder on Mon Nov 25, 2013 5:17 pm, edited 1 time in total.
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Re: tone stack mod's AB763

Postby softmachine72 » Wed Sep 04, 2013 1:47 am

i guess those were the small value 715's . can you post the copy of the schematic? i thought jerry only used the vib channel anyway.
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Re: tone stack mod's AB763

Postby Smolder » Wed Sep 04, 2013 6:45 am

not sure who 'owns' these, but until they claim and object, I'm happy to make them available here. They are wide so on this site, you'll have to stretch out your browser window. The 225p's were typically used in the tone stack and where they sound right. The 715/716's are a different material and sound sterile, so they are used elsewhere - or when that's all that is available. Lastly... as I recall, Jerry went into both channels, and went out in stereo to the two channels of his Mac. I'm not an expert, but I did read Waldo's site a number of times.

Edit: images removed.
Last edited by Smolder on Wed Sep 04, 2013 7:52 am, edited 1 time in total.
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Re: tone stack mod's AB763

Postby waldo041 » Wed Sep 04, 2013 7:27 am

If I wanted them posted, I would have them posted.

~waldo
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum
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Re: tone stack mod's AB763

Postby Smolder » Wed Sep 04, 2013 7:53 am

waldo041 wrote:If I wanted them posted, I would have them posted.

~waldo



done
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Re: tone stack mod's AB763

Postby hippieguy1954 » Wed Sep 04, 2013 11:36 am

Why wouldn't you want them posted?
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Last show: 1994
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Re: tone stack mod's AB763

Postby Smolder » Wed Sep 04, 2013 12:51 pm

I thought that there might have been a problem with the site they used to reside on, which is why I offered to help. I still don't know who owns them, but they are in the public domain at this point. All one has to do is use the way back machine at archive.org (which we are all pretty familiar with for music downloads) to find them. That can't be erased.
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Re: tone stack mod's AB763

Postby waldo041 » Wed Sep 04, 2013 2:36 pm

Unlike the majority of the information i have posted on my webpage, these layouts were a culmination of intense research and some first hand info from insiders but not definitive. Meaning, they did not come from actual peeks inside the twins or mac. Therefore, i chose to remove them until such a time possibly happened.

Although, after using and listening to those who do use what i have gathered it is pretty hard to argue against the info, especially, from a stock view.


~waldo
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum
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Re: tone stack mod's AB763

Postby hippieguy1954 » Wed Sep 04, 2013 3:00 pm

I hear ya, Waldo. Perfectly logical. :smile:
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