Modding a Fender Quad Reverb

[C/G]

I have an old silverface Fender Quad Reverb that I want to mod. It is not mint or original by any means. I bought it cheap because there were no speakers and someone cut out the original baffle and screwed a piece of plywood overtop to accomodate a 15" and a 10" speaker. Anyway, I put in 4 Weber speakers and a new baffle made from baltic birch plywood in lieu of the original particle board. Had the amp blackfaced and made the reverb and tremelo active on both channels by a great tech that no longer lives in my city. I Gave it a new tolex skin and it is good to go. It sounds really great but the breakup in a Fender kind of stinks. I want to get the first channel modded for a real nice overdrive and keep the second channel as it is. I know the transformers have to stay to keep the second channel as is, but is there some kind of mod that can be done without me spending a fortune on the Fuchs mod (new transformers, circuit boards, bias pots, ect.) I don't know much about this subject so any info would be great. Not sure if this should be in geekslutz either. Thanks.

[C/G]

Nothing? Come on amp guys.

[Jeff A. Roberts]

Have you swapped out any of the 12AY7's for 12AX7's? That's a 30 db increase in gain right there. I believe that my Weber amp book says that the first gain stage tube is a good tube to swap. I'll check the book tonight for other ideas.

[softwareguy]

Aspen Pittman's "The Tube Amp Book" has an article by Brinsley Schwartz that lays out a great series of mods that can be done to silverface Fenders, with a special emphasis on modding the "Normal" channel for more gain. His mods include a "Hot mod" for Marshall-type voicing and gain, a tweed-style mod and negative feedback resistor mods to change the dynamics of the power amp stage. It's well-written and includes diagrams. If you don't have the book, it's a great read and the tech articles (and schematics) alone are worth the price of admission, not to mention all the slutty pictures of unobtainably classic amps.

On Amazon:

http://www.amazon.com/exec/obidos/tg...books&n=507846

[84K]

Albert Collins did alright with his QUAD Reverb.... I wonder if it was modded... something worth looking into...

[eligit]

Originally Posted by 84K

Albert Collins did alright with his QUAD Reverb.... I wonder if it was modded... something worth looking into...

i think he "modded" his picking hand thumb! that's where that tone came from....

[84K]

Originally Posted by eligit

i think he "modded" his picking hand thumb! that's where that tone came from....

OH YEAH! The Iceman Commeth!

[eligit]

Originally Posted by 84K

OH YEAH! The Iceman Commeth!

he sez his thumb is so callused that it is hard like a piece of bone or (rhino etc) horn.

great tone from that guy.

[softwareguy]

I love Albert Collins. His tone was literally stunning. A bandmate of mine saw his show from the second row and was physically disoriented for a day afterwards.

[C/G]

Originally Posted by Jeff A. Roberts

Have you swapped out any of the 12AY7's for 12AX7's? That's a 30 db increase in gain right there. I believe that my Weber amp book says that the first gain stage tube is a good tube to swap. I'll check the book tonight for other ideas.

Thanks so far guys. There are no 12AY7's in my quad. The only 3 12AT7's are the pi and tremelo tubes and reverb driver I believe. I have tried a 5751 in the reverb slot for more grit but I did not notice anything.

[C/G]

Originally Posted by softwareguy

Aspen Pittman's "The Tube Amp Book" has an article by Brinsley Schwartz that lays out a great series of mods that can be done to silverface Fenders, with a special emphasis on modding the "Normal" channel for more gain. His mods include a "Hot mod" for Marshall-type voicing and gain, a tweed-style mod and negative feedback resistor mods to change the dynamics of the power amp stage. It's well-written and includes diagrams. If you don't have the book, it's a great read and the tech articles (and schematics) alone are worth the price of admission, not to mention all the slutty pictures of unobtainably classic amps.

On Amazon:

http://www.amazon.com/exec/obidos/tg...books&n=507846

Thanks for the tip. I was trying to avoid buying a book hoping someone might have an internet link ect. If I can not find anything I will have to buy it.

[TAVD]

Clip the master volume and either use a hot plate or post PI master volume.

Cathode / fixed bias switch. It's probably fixed bias now.

There's a mod in the Torres book that plays with the driver circuit and is supposed to let the amp break up smoother.

All the above will change the sound of both channels.

Add a tube or fet stage to hit the 1st tube harder.

Maybe cascade the two channels like the mesa mk.1 did.

I'd just put a v-twin or tonebone type pedal in front and not worry about modding the amp.

IIRC, the quad is just a 4x12 twin and twins aren't know for their overdrive.

[polimorfos]

+1 on Cathode biasing. Adds a bit of compression and a smoother transition into distortion. After playing around with the negative feedback, I always wind up putting it back to stock.

Just don't butcher the amp to make it a high gain amplifier. It's a Silverface Fender - use it for what its good for and use pedals if you want to change the tone.

This is probably not the best forum for this kind of question

[cdog]

Fenders were meant to be clean amps, some folks cranked em and thats the sound of rock n roll but you'll need a gain pedal to go over the top.

This is the best one made in my opinion:

www.stephensonamps.com/stagehog

Not all Fenders will break up as smoothly as a Deluxe, I've never used a Quad Reverb so I can't tell you, if its anything like a Twin Reverb you will definitely need a pedal to get a crunchy sound without blowing out your eardrums.

If you can swing it, go for the Fuchs mod I have heard second hand that he does some really good work on modding Blackfaces.... his original amps are really cool but kinda overpriced.

The build quality on those old Fenders is awesome.... and they can be worked on by anyone.

[C/G]

Cdog, I am actually friends with Mark Stevenson. He is the guy that "blackfaced" my quad and brought up to snuff after I saved it from being chopped up and made into a Twin, but he lives half way accross the country now. I posted a link on this forum a while back to his site and the stagehog, and am glad you like it. Mark is an amazing amp designer and tech, too bad he moved away from my home town. Did you buy it direct from Mark? I was going to send him the chassis and let him have at it because the amp is already slightly modified so I figured I might try to screw around with it a bit. I can get crunchy with the Quad, I just think Fender dist. sounds like ass. Having nice nos tubes and 4 Webers in there is definitely a step up from those shitty Jensens or whatever was stock in there. I hated those speakers. I actually forgot about the Stage Hog. Buying that would be cheaper than moding my amp. I am gonna call Mark. Thanks for the reminder Cdog.

[Jim Williams]

Originally Posted by softwareguy

I love Albert Collins. His tone was literally stunning. A bandmate of mine saw his show from the second row and was physically disoriented for a day afterwards.

His tone was OK, but nothing like the meat from that flipped over flying V Albert King played into that Marshall. What a tone! I managed to record one of his last shows here in LA. I met him before the show and requested he play Cross Cut Saw for me.

He did!

Jim Williams
Audio Upgrades

[atticus]

Have you tried swapping out power tubes? I know it is more of a universal mod but it may give you the tone you desire. I've used a lot of Groove Tubes in the past and I like them a lot. Good luck!

http://www.groovetubes.com/tubes_lis...ctGroup_ID=108

[C/G]

I have some NOS Phillips 6L6GC "stubbies" in there. I love the sound of them. With the Weber Thames and Weber California speakers I have in there it sounds kind of similar to my Hiwatt. Not as full and tight in the mids but still shockingly similar.