Twin Master Volume Modifications?

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Twin Master Volume Modifications?

Post by dragonbat13 » Wed Sep 13, 2017 1:53 pm

I got a 72 twin reverb with non pull master volume. While doing some other work I overheated the pathetic excuse for coax to a short, so I have pulled the wiring and knob and am gonna replace with RG174. I like to use the master volume. As long as your not going for any form of overdrive it turns the twin into a very usable bedroom amp. However, I was wondering about the other types of master volume. Most of the ones I saw concentrate on overdrive tones, if I read correctly.

Should I go with the factory setup or look into something else? Keep in mind that I don't really go for overdrive, I mostly like the headroom of the 4 x 6l6 setup. If I could improve on the headroom at lower volumes (which seems like an oxymoron to me) I would like to do that. I guess what I am asking is if there is any way to improve the FEEL of more headroom at bedroom levels with a different master volume.

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Re: Twin Master Volume Modifications?

Post by Roe » Wed Sep 13, 2017 2:36 pm

try a larmar MV with a dual 100k pot with 220k security resistors connected to the viper for a total of ca 68k ... zuo2xPgrM:
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s

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Re: Twin Master Volume Modifications?

Post by Stevem » Wed Sep 13, 2017 3:21 pm

Bed room amp? If you do not mind not having Reverb then the reverb driver is already a 1 watt amp SE amp!
Just hook the reverb drive cable up to a 8 ohm speaker .
Most times with good Amps just like it is with sex, it's best to just plug straight in!

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Re: Twin Master Volume Modifications?

Post by xtian » Wed Sep 13, 2017 3:45 pm

IMO, a MV is not going to help you achieve low volume levels with any kind of preamp overdrive or harmonics. Just use the Volume control for that. Maybe you need a better, more logarithmic Volume pot?

I have a ‘71 Twin Reverb that I’ve been playing in my office for the past week. Sounds wonderful at low volume. So good, I decided not to sell it!
I build and repair tube amps.

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Re: Twin Master Volume Modifications?

Post by dpin » Wed Sep 13, 2017 4:47 pm

Here's 3 easily reversible moves to drop some db's and retain "headroom"
- Pull 2 6L6's
- Add a switch so you can drop one speaker when you pull those tubes
- Replace the PI tube with a 12AU7

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Re: Twin Master Volume Modifications?

Post by dragonbat13 » Wed Sep 13, 2017 8:31 pm

Maybe I should have been clearer, I like the way the amp sounds with the stock master volume. I am in the process of fixing it. I was just wondering if there was any other MV that was worth trying to see how I like it.

It seems that alot of people equate the master volumes only use is for added preamp gain with low listening levels. I like to run the channel volumes at about halfway and use the master volume to manage the sound level. There is a lot of harmonic rich tome in the pre amp , even when playing clean. The master volume allows me to achieve that without knocking down walls.

I actually removed the master volume on this amp and sent the reverb channel straight to the phase invertor. Quite loud, and unusable to me. Perhaps there may be more needed that just moving wires, but it did what I needed to do for troubleshooting.

I am gonna put it back to factory specs for now.

Edit: I just noticed that somebody posted swapping to a better spec pot. Im gonna look into that.

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Re: Twin Master Volume Modifications?

Post by JD0x0 » Wed Oct 04, 2017 6:55 pm

FWIW, I am getting a nice preamp overdrive with my master volume twin, on the vibratochannel. It does have the push/pull master, but the push-pull function is not needed to get the overdrive. I am using significantly different circuit values for more gain and clipping, though..
It's true i've lost my marbles and i cant remember where i put them

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