2 Channel Fender Silverface Question...

Kevin Mincke · Post by **Kevin Mincke** » 4 Apr 2005 1:29 pm

I have a 71/72 Twin. I'd like to see the mod please......& thanks Uncle Ken Good thing we still have some knowledgable "Tube Heads" around!!

Mark Herrick · Post by **Mark Herrick** » 5 Apr 2005 10:43 am

Got 'em both now...

Thanks!

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Ken Fox · Post by **Ken Fox** » 5 Apr 2005 11:03 am

It is in the mail, Kevin!

Mark Herrick · Post by **Mark Herrick** » 13 Apr 2005 12:46 pm

Now that I am getting close to performing this two-channel reverb mod, I have a question.

The next to last paragraph in the instructions states:

Oh, you thought I forgot the little 1 inch piece of wire? ... Just put it down on the other 220k resistor there and reduce the series resistance into the driver stage. A simple, easy trick for a hotter sound, and a little more "presence."

Will doing this increase the potential for distortion? I was already planning on doing the 56k slope resistor replacement.

Any advice on connecting the two 220k resistors?

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Ken Fox · Post by **Ken Fox** » 13 Apr 2005 3:24 pm

I do not do that part of the mod.

Andy Zynda · Post by **Andy Zynda** » 13 Apr 2005 7:15 pm

Hey Ken,
I've seen some of your work, and you obviously care a great deal about what you do, and make every effort to do quality work.
And you do your work in the spirit of Leo Fender's creed, as I do.
Be glad that you've never seen a Torres modded amp. Oh my god, so ugly you can't beleive it. Holes drilled in the chassis in some cases, labelling done with Dymo hand labellers, switches sticking out in the most awful places.
Be afraid.... you'll know one when you see one..
-andy-

Paul Honeycutt · Post by **Paul Honeycutt** » 14 Apr 2005 10:01 am

I had my Bandmaster Reverb modded to have the reverb on both channels AND the channels in phase. I don't believe that the "Torres" mod will take care of the phase problem. My amp was worked on by Bruce Collins at Mission Amps in Arvada, CO and he's a great tech and all round good-guy.

I've had dealings with Dan Torres over the years, some good, some less then good. I think he knows quite a bit, but his mod kits are usually poorly constructed and only give your amp a "can of bees" tone. on the other hand, he went through my Kitty Hawk Quattro preamp and upgraded components and tweaked the sound of it doing an awesome job. So, if you do anything to your amp that includes any Torres mods, get a second opinion.

Mark Herrick · Post by **Mark Herrick** » 14 Apr 2005 12:02 pm

Thanks, Ken.

About the "in phase" issue; if you are using only one channel at a time, wouldn't the phase issue be moot? I would think the two channels would only need to be in phase if you were using both channels simultaneously.

T. C. Furlong · Post by **T. C. Furlong** » 14 Apr 2005 6:50 pm

Nice to mod one channel with a 56 K slope resistor

I used to be a mountain climber, but now I'm just a slope resistor.

Rob van Duuren · Post by **Rob van Duuren** » 14 Apr 2005 11:46 pm

Ken, could you send me the mods too? Thanks
a lot, Rob.

Ken Fox · Post by **Ken Fox** » 15 Apr 2005 10:53 pm

For one channel at a time, you are right no big deal. Adding reverb to channel one will put the channel in phase with channel two.
Without the mod channel one gets two gain stages. Every time the signal see a gain stage (half of a 12AX7 tube) it is inverted 180 degrees. The second channel see three gain stages, due to 1/2 of tube #4 being used to mix the dry signal from tube #2 with the wet signal from 1/2 of tube #4. Three gain stages makes it 180 degrees out of phase with channel 1.

Adding the reverb mod to channel 1 get the third gain stage added, as it is now going thru 1/2 of tube #4.

Colin Alder · Post by **Colin Alder** » 18 Apr 2005 5:13 pm

Ken
Will you please email me the mod.
Thanks, Colin

Ken Fox · Post by **Ken Fox** » 18 Apr 2005 6:34 pm

It is in the mail!

Drew Howard · Post by **Drew Howard** » 27 Apr 2005 4:29 am

Ken,

I'd like to add this mod to my recently acquired Twin. Can you e-mail the mod to me?

much thanks,
Drew

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Drew Howard - website - Fessenden D-10 8/8, Fessenden SD-12 5/5 (Ext E9), Magnatone S-8, N400's, BOSS RV-3

Ken Fox · Post by **Ken Fox** » 27 Apr 2005 6:32 pm

Man, that is a thing of beauty! You got to get a Paisley Tele and get a shot of them together!!

Bud Musgrave · Post by **Bud Musgrave** » 27 Apr 2005 7:33 pm

Ken,could you please send me the Fender two channel mod also. thanks

Ken Fox · Post by **Ken Fox** » 28 Apr 2005 5:43 am

It's in the mail!

George Duncan Sypert · Post by **George Duncan Sypert** » 29 Apr 2005 6:44 pm

Ken I would also like that info. Did you get an email I sent you a week or so ago? If not I will resend. I used the email address here on the forum. Thanks, George

Ken Fox · Post by **Ken Fox** » 29 Apr 2005 10:27 pm

Sent it to you. Did not get the other email. My email here on the Forum is correct.

Mark Herrick · Post by **Mark Herrick** » 30 Apr 2005 5:32 pm

I just tried this mod this afternoon on my '74 SFTR. I found the correct wire and unravelled just enough of it to move it over to the new location. When I turned the amp on it had way more noise in both channels than it had before. I switched the wire back to the original position and it was quiet again.

I guess this amp is just going to have reverb on one channel...

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Ken Fox · Post by **Ken Fox** » 1 May 2005 7:19 am

Never had that problem! Interesting. Has anyone else tried the mod and can give us their feedback! I have done a bunch and never experienced that yet.

Jon Light · Post by **Jon Light** » 1 May 2005 7:24 am

No. I've done this on a Dual Showman Rev and a Deluxe Rev. with no issues. Is the lead running as directly as possible? (I recall that there isn't much you can do wrong there--just uncoil a bit of wire, just enough to loop it back to the new solder junction.
Ken--would a bad driver tube be exaggerated by this process? Maybe try a new tube there.

Ken Fox · Post by **Ken Fox** » 1 May 2005 8:55 am

I would not think the driver tube would make a difference. I would re-check where the wire connected again. Also lead dress is important and could make the difference.

Mark Herrick · Post by **Mark Herrick** » 1 May 2005 3:11 pm

...just uncoil a bit of wire, just enough to loop it back to the new solder junction.

Yep. That's exactly what I did. I didn't want to unravel the whole wire, but maybe that is what is causing the noise. I did try several different tubes in the V1 - V4 slots and it didn't effect the noise in any way.

I have the chassis out again and maybe I'll try it once more with a whole new wire.

I have another question relating to plate voltage and the Weber Bias Rite, but I have to leave the house right now. Will log on later and post that question in a separate thread...

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