2Ch-Triple Recti: Reduce power to 50W by taking out tubes?

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DocSauerkraut

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Hi guys!

I have a 2-Channel Triple Recti (150W) that i really love but i find it really hard to play this amp at home, simply because it's too loud.
Now i just started thinking about selling this amp and replacing it with a 50W Rectoverb, when i heared about a possibility to reduce the power of a Triple-Recti to ~50 Watts simply by taking out the two inner power tubes.

I already found some post on this board that seem to support this idea but before i try it out, i'd like to ask if anybody can confirm this.

Thanks for your help!

Tom
 
this can be done on dual rectos by taking out either the inner or outer power tubes (i dont think it matters which, but im not sure), but it will cut the output impedance in half. to do this on the triple, youd have to take the 4 outer power tubes out, which would cut the impedance by 3. but, the speaker outputs arent divisible by 3 tho, so i dont think this can be done with the triple. if youre thinking of selling it to get a new amp, id recommend a new multi-watt rectifier. they sound awesome, are incredibly versatile, and can go down to 50 W with a flick of a switch.
 
o and btw, impedance aside, taking 2 power tubes out would only bump it down to 100 W. and i failed to mention that for every 2 power tubes that you take out, you will need to take out 1 rectifier tube.
 
You can take out 2 power tubes, but by no means take out 4. What RnR was saying is correct. I don't recall the exact details right now, but taking out 2 tubes would lower the 8 ohm impedance down to something like 5.3 ohms, which you could run on safely, but taking 4 out would cut it down to 2.6 or so, which isn't safe.

So yeah, don't do it.

Also, removing tubes does not substantially cut down on the volume. It cuts down your headroom...IE, the amp will go into power tube distortion sooner.
 
Thank you guys for your help!
So i guess i will continue with my plan and try to get a new amp.

Cheers!

Tom
 
Hold on! :) You certainly *can* pull four power tubes (and two rectifiers) and run it at 50W - it's perfectly safe.

Yes, the result is that the effective output impedance of the amp triples, which makes it not exactly match any standard cab impedance, but it's not remotely critical - Mesas are not very impedance-sensitive anyway, and when running at only 1/3 of the power, even a serious mismatch couldn't develop enough voltage or current to harm anything. (Well, possibly the tubes if you were to get it the wrong way round, but even then they tend to be self-limiting.)

The 4-ohm outputs effectively become 12-ohm outputs, so you can run either an 8-ohm or a 16-ohm cab safely from these, since either way it's well within the factor-of-two mismatch that is safe with any Mesa (and almost any amp). You could also run a 16-ohm cab from the 8-ohm outputs (which are now 24-ohm outputs) because a slightly low mismatch like this is also not harmful.

In any case, accurate matching only matters if you're really driving the power stage hard, so if you're trying to reduce the volume for home playing this is unlikely anyway. I agree with mikey that it won't *substantially* reduce the volume, but it will help, and it might let you get the amp up above that 'step' where it starts to sound good. If not, you probably should look into an attenuator... cheaper than anew amp, anyway.
 
94Tremoverb said:
Hold on! :) You certainly *can* pull four power tubes (and two rectifiers) and run it at 50W - it's perfectly safe.

Yes, the result is that the effective output impedance of the amp triples, which makes it not exactly match any standard cab impedance, but it's not remotely critical - Mesas are not very impedance-sensitive anyway, and when running at only 1/3 of the power, even a serious mismatch couldn't develop enough voltage or current to harm anything. (Well, possibly the tubes if you were to get it the wrong way round, but even then they tend to be self-limiting.)

The 4-ohm outputs effectively become 12-ohm outputs, so you can run either an 8-ohm or a 16-ohm cab safely from these, since either way it's well within the factor-of-two mismatch that is safe with any Mesa (and almost any amp). You could also run a 16-ohm cab from the 8-ohm outputs (which are now 24-ohm outputs) because a slightly low mismatch like this is also not harmful.

In any case, accurate matching only matters if you're really driving the power stage hard, so if you're trying to reduce the volume for home playing this is unlikely anyway. I agree with mikey that it won't *substantially* reduce the volume, but it will help, and it might let you get the amp up above that 'step' where it starts to sound good. If not, you probably should look into an attenuator... cheaper than anew amp, anyway.
Click to expand...
i stand corrected. i thought it divided the impedance :?
but you said that you could plug a 12 ohm output into an 8 ohm cab? i thought the cab's impedance had to be greater than or equal to the output's impedance.
 
They can safely handle a mismatch of one step in either direction. You can plug an 8 ohm cab into either the 4 or 16 ohm spots...that's from the user manual for every Mesa.
 
mikey383 said:
Also, removing tubes does not substantially cut down on the volume. It cuts down your headroom...IE, the amp will go into power tube distortion sooner.
Click to expand...

+10000000

There really is no worthwhile reason to do this.
 
Why not? It *does* definitely reduce the headroom somewhat, the overall volume sightly, and changes the tone in a way that some people will like (and others not, that's true). And there is no harm it could cause or reason *not* to do it, and it doesn't cost anything, so why might it not be worthwhile to at least try?
 
94Tremoverb said:
Why not? It *does* definitely reduce the headroom somewhat, the overall volume sightly, and changes the tone in a way that some people will like (and others not, that's true). And there is no harm it could cause or reason *not* to do it, and it doesn't cost anything, so why might it not be worthwhile to at least try?
Click to expand...

Because he's not looking for a tonal change.. he said it's "too loud" for home. Most people that look into doing this sort of thing think that it'll substantially reduce the volume, but you know as well as I do that really what it does is take away some headroom (which makes the amp sound less ballsy IMO) and make the volume go from "window shattering" to "wall rumbling".
 
That's absolutely true, but it does reduce the overall volume very slightly too - not much, but for most people who are finding their Recto too loud for the house, it's just because that 'step' in the MV response where it suddenly kicks in and sounds good, is still just too loud - not because the amp is too loud when it's cranked, since they're not going remotely near there. Anything that gets that step down even just a little bit quieter is worth trying, and since pulling tubes costs precisely nothing, why not try it? If you don't like it, just put them back.

It also has two other advantages - it wears the tubes out at half (four-tube amp with two pulled) or one-third (six-tube amp with four pulled) the rate, simply because some of the tubes are not in the amp! The wear rate on the ones that are in is the same as normal, if you're not cranking it. And secondly, it biases the two tubes very slightly hotter - not much, but the plate voltage does rise by a few volts while the bias voltage stays the same, and again anything that gets you closer to the magic 'kick in' point where the amp starts to sound good is worth trying - particularly as I think that the very cool bias is one of the reasons for the not-so-great very low volume tone of these amps.

Personally, I agree with you about the tone shift - I prefer the sound of four power tubes to two. My chosen method is an attenuator, but they cost a couple of hundred dollars or more. And I know at least one person on this forum who actively prefers the two-tube sound, so it's purely a matter of taste and definitely *not* "not worthwhile" until you've at least tried it. Who knows? Even though he wasn't looking for a tone shift, he might actually like it too.
 
Two tubes are brighter, clearer, and tighter. Enough said!
Four tubes sound much beefier, especially with a 4 x 12, but you need a venue that will support that amount of horsepower!
 
94Tremoverb said:
That's absolutely true, but it does reduce the overall volume very slightly too - not much, but for most people who are finding their Recto too loud for the house, it's just because that 'step' in the MV response where it suddenly kicks in and sounds good, is still just too loud - not because the amp is too loud when it's cranked, since they're not going remotely near there. Anything that gets that step down even just a little bit quieter is worth trying, and since pulling tubes costs precisely nothing, why not try it? If you don't like it, just put them back.

It also has two other advantages - it wears the tubes out at half (four-tube amp with two pulled) or one-third (six-tube amp with four pulled) the rate, simply because some of the tubes are not in the amp! The wear rate on the ones that are in is the same as normal, if you're not cranking it. And secondly, it biases the two tubes very slightly hotter - not much, but the plate voltage does rise by a few volts while the bias voltage stays the same, and again anything that gets you closer to the magic 'kick in' point where the amp starts to sound good is worth trying - particularly as I think that the very cool bias is one of the reasons for the not-so-great very low volume tone of these amps.

Personally, I agree with you about the tone shift - I prefer the sound of four power tubes to two. My chosen method is an attenuator, but they cost a couple of hundred dollars or more. And I know at least one person on this forum who actively prefers the two-tube sound, so it's purely a matter of taste and definitely *not* "not worthwhile" until you've at least tried it. Who knows? Even though he wasn't looking for a tone shift, he might actually like it too.
Click to expand...

You're right, and you're correct in that it's easy and simple to do, but the pessimist in me still says it's like putting a bandaid on a gunshot. I have an RKII and I leave the thing running on all six power tubes even when I'm playing at whisper soft volumes.

Not trying to be overly pessimistic though. I hope it works for the OP, but I still have my doubts.
 

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