Mesa Boogie 20/20 power amp - convert to 220/240 Volts

[Snoopy551]

HI Fearless

I use deep mode,
personnaly a prefer both:
Non-deep on clean and Deep-mode on hi gain.

See you
Steph

 

[fearless]

Hey, I think I'll try that. I guess you have installed a relay circuit and hooked up to a footswitch? I've gone really simple and just put a switch in parallel with each of the caps, and mounted them in a little plastic box on top of the amp. My pre-amp is shallow, so I have the room to do that.

I figure that by having a connection in parallel with the capacitor, the cap will actually do nothing - I hope my logic is right. It certainly sounds right when I switch it, going from the standard tight sound to a looser more open sound when the the caps are bypassed.

One mod I'd like to try one day is adding power-scaling to each of the channels, along with a second volume control and then making the combination footswitchable. It would be like having a second channel which produces power-stage distortion. Too much other stuff to do for now...!

 

[Snoopy551]

Hi Fearless

I control the deep mode with my triaxis (it is working with my g-major too)

Check pics
http://www.hiboox.fr/go/images/musique/ ... 4.jpg.html
http://www.hiboox.fr/go/images/musique/ ... 5.jpg.html
http://www.hiboox.fr/go/images/musique/ ... e.jpg.html

The connection of the switch is not in parallel, ther are in serie with the capacitor.

I could use the same circuit to put a potentiometer or resistor in parallel with the volume pot of mesa 20 too.
The only thing on the circuit is to remove the Black capacitors. (last pic, near of orange wires)

Steph

 

[fearless]

Hi Steph,

The picture links are not working.

 

[fearless]

The connection of the switch is not in parallel, ther are in serie with the capacitor.

Hmmm. I see why - you switch capacitance to infinite. My mod switches it to zero. It still sounds better but I should have looked at the circuit diagram more closely. I see it is the 1uF cap and bridging this also shorts the tube to ground. I feel a bit stupid. Fortunately I have mostly left the swich in off position. I will correct it.

I look forward to seeing your pics

I could use the same circuit to put a potentiometer or resistor in parallel with the volume pot of mesa 20 too.

What would be the advantage?

 

[Snoopy551]

http://www.hiboox.fr/go/images/musique/mesa-01,921afa10dc9ff6f22502c31ac4e856a4.jpg.html
http://www.hiboox.fr/go/images/musique/mesa-02,3e0bb058fd70d5464c84424c15209805.jpg.html
http://www.hiboox.fr/go/images/musique/mesa-03,252fb900e49c0e6f2f3b323fb5c4a8be.jpg.html

Second test for Pics

Steph

 

[rvantond]

Hi guys...

I noticed that some of you have the same problem as me. I however would appreciate it if any of you could assist me in changing my triple rect from 120 to 240V.

Cheers

 

[fearless]

I am pretty sure it can't be done without swapping out the transformer. While I was researching changing my 20/20 I remember reading that the 20/20 is one of the few Mesa Boogie products with a multi-tap transformer. Not 100% sure, but 99%. Check with a tech. www.tubeampdoctor.com will probably stock an after market transformer.

On the off-chance you are in Melbourne, Australia, Dale Sherlock is the go-to man I believe.

 

[rvantond]

Cheers for that mate
Unfortunately i am in WA, close to Perth. I had a look at the transformer and it looks like it can be done just need a wiring diagram on how to do it.