pulling tubes in a Twin to cut the power

[olejason]

A few people have mentioned to me that I could pull two tubes in a twin and drop it down to 40w or so. Which two do I need to pull and will I need to rebias the amp?

Thanks

[Blue Strat]

1 or 2 AND 3 or 4...or to make it simpler, inner or outer pair.

Rebiasing isn't critical but it would be good to check just to be sure.

[olejason]

Does pulling tubes make it only one channel? So if I normally use the vib channel I'd pull 1 & 3?

Thanks

[Blue Strat]

Originally Posted by olejason

Does pulling tubes make it only one channel? So if I normally use the vib channel I'd pull 1 & 3?

Thanks

No, all power tubes are used for both channels. Both channels will still work but at half power. You'll probably be surprised at how loud half power is.

[olejason]

Yeah I know it will be a minimal reduction in volume but I just want to tinker around with it when it arrives.

[BadCat]

doesn't that also change the impedance?

[olejason]

Yes it does... that's the other thing I meant to ask. I'm not sure what it changes the impedence to. It should be 4ohm w/ all of the tubes in if I remember correctly

[BadCat]

sorry, I just saw the thread down below

[metz420]

Originally Posted by Blue Strat

No, all power tubes are used for both channels. Both channels will still work but at half power. You'll probably be surprised at how loud half power is.

BlueStrat is right, even at half power, my TR still blows out my windows at a volume of 5.

[deeval]

Make sure you disconnect one speaker its best to run 8ohm load with just two tubes being used,and it will still be loud but you will get bit earlier breakup,also you will need to rotate the tubes as you will be wearing one pair out more then the ones you pulled out that way if you go back to using all four again they at least they will be same match.

[Blue Strat]

Originally Posted by deeval

Make sure you disconnect one speaker its best to run 8ohm load with just two tubes being used,and it will still be loud but you will get bit earlier breakup,also you will need to rotate the tubes as you will be wearing one pair out more then the ones you pulled out that way if you go back to using all four again they at least they will be same match.

On the other hand, the mismatch is safe (2:1) and the mismatch will create less power transfer which may also create earlier breakup.

Try it both ways.

[FrankieSixxxgun]

I tried it on my 100 watt Marshall and the volume reduction, which was minimal, wasn't worth the tone loss, which was noticeable. Plus, even at 40 watts that twin is gonna be LOUD.

[John Coloccia]

Post back how you like it.

My Red Knob has a 25W switch and it's still LOUD....I mean LOUD. What you get @25W vs 100W, is it breaks up early enough that I can actually get a bit of grit from it at reasonable volumes.

The 25W switch works differently than pulling tubes, though. It actually changes the voltage that the tubes are operating at, if I remember correctly. IMHO, this sounds way better than pulling two tubes, so if you're looking for a bit of early breakup with reasonable volume, you may want to consider a mod along these lines, especially if you don't like where you end up tone-wise with two tubes pulled. On the other hand, you may really dig how it sounds with pulled tubes, so you never know.

[The Golden Boy]

Originally Posted by FrankieSixxxgun

I tried it on my 100 watt Marshall and the volume reduction, which was minimal, wasn't worth the tone loss, which was noticeable. Plus, even at 40 watts that twin is gonna be LOUD.

I used to use 100w MV Marshalls. I wanted to run less loud, so I did the tube pulling/halving the impedance thing. I really didn't notice much of a drop in volume (if any), but I thought it sounded thin and wussy. I just rolled with all 4 tubes, then got a 50w.

[grayeyes777]

i don't think that pulling tubes on a twin will make it sound much better. twins don't usually sound best driven being that their made to be a clean sounding amp. good luck though.