Is it safe to remove 2 tubes from my 100watt Marshall?

G

GuitarDemon666

New member
I read all over the place about people taking 2 tubes out of their 100 watt amp to make it a 50 watt. Is this really safe? I don't wanna screw up my amp.
 
you would be better of with an attenuator, as going from 100watt to 50 watt would only reduce loudness of 3 dB. The ear is not a linear organ, it follows a logarythm curve.
dB formula: dB=10log(W1/W2)

so 10log(100W)=20dB
10log(50W)=17dB

(that value needs to be added to the speaker value, which would probably be arround 90dB, 1W,1meter)

so you would go from 110dB to 107dB with volume at 10.

or directly 10log(50/10)=-3dB
 
little mistake... 10log(50/100)= -3dB .... not 50/10....

and by now you should realize mesa boogie with their tripple rec is just a marketing affair based on missbelieves.

10log(150/100)=+1,76 dB .... wow what an loudness increase!!! (just kidding)
and
10log (150/50)=+4,77 dB................
 
I failed algebra!! But thanks wannabecomedeat. I'm considering the ateunator.

Yeah, I want things to break up sooner. Which two tubes should I remove?
 
I've had friends that did this years ago-probably before attenuators were easily accessible and it did drop the volume and caused breakup earlier. Just be sure to remove the pair of tubes that are coupled in the push/pull power tube circuit and for sure don't remove preamp tubes!
 
I won't remove the pre-amp tubes... But I don't know what the push/pull power tube circuit even is...

Maybe I should just not try it.
 
GuitarDemon666 said:
I won't remove the pre-amp tubes... But I don't know what the push/pull power tube circuit even is...

Maybe I should just not try it.
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The power tubes are the four big tubes that are all the same model. Pull the outside two tubes (far left and far right), or the two inside tubes. Don't worry, you ain't gonna hurt the amplifier or the transformer by doing this. Hell, you can even pull 3 of the 4 tubes if you want a really dirty sound. It'll sound like shit, but you won't hurt the amp.

The way it works is pretty simple:

It's called an AB circuit, which means that at very low volume, each tube is putting out the whole signal (the positive part of the signal that goes up, AND the negative part that goes down). That's called Class A mode.

Above a certain level, the two left hand tubes switch over and put out just the positive part of the signal (that goes up), while the two right hand tubes handle just the negative part of the signal (that goes down). That's called Class B mode.

If you pull one of the tubes from each pair, the whole signal will still be there, but with half the power. If you pull 3 of the 4 tubes, it'll put out the whole signal at very low level (class A), but will only put out the positive or negative half at high volume (depending on which 3 of the 4 you pulled out).

Regardless of which power tubes you pull, you ain't gonna hurt anything. Most people pull either the middle pair, or the two outside tubes.
 
Harvey Gerst said:
If you pull 3 of the 4 tubes, it'll put out the whole signal at very low level (class A), but will only put out the positive or negative half at high volume (depending on which 3 of the 4 you pulled out).
.
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sorry harvey but i dont think this is true.... the tube that is left would still turn off .... leaving just half the wave form...
 
dementedchord said:
sorry harvey but i dont think this is true.... the tube that is left would still turn off .... leaving just half the wave form...
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You may be right; I haven't looked at a Marshall schematic, but most Class AB amps, at very low levels anyway, do tend to operate in Class A mode. Pure Class B is more of a switching mode, at least that's how I remember it.

I may be wrong though; it's been a long time. But, either way, he ain't gonna hurt the amp. I think we agree on that.
 
Harvey Gerst said:
But, either way, he ain't gonna hurt the amp. I think we agree on that.
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agreed....

BTW there are some true class A amps that are push pull in nature... those new crates as an example... also if under biased an AB section will push beyond it's normal shut-off...
 
I would think it's the slow blow fuse at most.

don't freak out too much before first checking that fuse and if it's good you can also try to put all the tubes back in and run it normally.
 
GuitarDemon666 said:
I read all over the place about people taking 2 tubes out of their 100 watt amp to make it a 50 watt. Is this really safe? I don't wanna screw up my amp.
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Here is something else you might consider:

http://www.thdelectronics.com/products/yellow_jacket.htm

They convert your EL34's, 6650's, 6L6's, etc. to lower powered EL84's. No bias change necessary; just pull the power tubes and drop them in. I've got an old 50w Marshall that I tamed considerably with a pair of these.
 
makes me wonder too, my marshall amp schematic = pcb board, is the same for the 20watt and the 40 watt version, my 40 watt having 2 more power tubes is all I see, as a difference?.... so I could go 20 watts from 40 apparently?

not sure why I would want to, but there seems to be some truth to the 2-tubes removed equals 1/2 wattage. A person could save $$ on tubes I guess.:confused:
 
ermghoti said:
LOL. How "creative" did you get?
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I don't wanna talk about it.

Definately gonna research those Yellow Jacket things.. Thanks for the suggestion.

When I was taking out my tubes, I noticed that two of them appeared to be more 'worn out' than the others. By that I mean the Groove Tube logo was Orange on 2 of them, and faded on the other 2. Is this normal?
 
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