Dual Rec Tech - How to reduce power by removing tubes

I'm reposting this from another thread since it seems to be a (understandably) popular configuration, with limited information available outside of calling Mesa.

I've heard of some players removing 2 of the power tubes in recto heads to achieve a 50 watt solution.

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It is true and it works! I've been running mine (Tremoverb) with two EL34's for about 5 years now. It is very simple. Here is what you need to do.

Remove two power tubes in pairs, either the two outter or two inner pair. I removed the two inner since I figured it would space out the other remaining tubes and maybe offer better heat dissipation. Also remove one Rectifier tube. It doesn't matter which one. I left the one closest to the power tubes.

There is one other consideration - your speaker jack impedences double. So you basically have one 32 ohm, two 16 ohm, and two 8 ohm jacks now. I applied some masking tape above the jacks and relabled mine to reflect the new values.

This effectively reduces your output to 50 watts +or-. It is still a loud amp - this isn't a 50% reduction in volume. Your bold/spongy and vintage/modern settings will reduce wattage more, and I believe if i remember correctly, that you can actually get it down to about 20 watts or so, depending on switch position.

If you have any questions, I'll be happy to help.

Uhh, you half the speaker impendence jacks instead of doubleing them. You won't hurt the amp if you do this because the output transformer won't be seeing any extra stress. You'll just work your power tubes harder.

If you have an 8 ohm cab, you run it from your 4 ohm out on the amplifier.

If you have a 16 ohm cab, you run it from your 8 ohm out on the amplifier.

Dale

Dale B. said:

If you have an 8 ohm cab, you run it from your 4 ohm out on the amplifier.

If you have a 16 ohm cab, you run it from your 8 ohm out on the amplifier.

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We're saying the same thing. Except the jack values don't half, they double (your 4 ohm out becomes the 8 ohm out). See the silver tape? Those are for plugging my 8 ohm cab in to the correct jacks when there is not enough light to read the numbers. Those two jacks used to read 4 ohms. If you double 4, you get 8. I'm looking at it from the amp side, I think you're looking at it from the speaker side.

Once you pull the tubes, the amp output impedence figures stay constant, thats why I prefer to re-label them. Its a little more foolproof than not having them labeled and stopping to think about how many ohms your cab is and then what jack to plug it into. If you switch cabs with different impedences I think its easier this way.

Obviously you shouldn't use a 4 ohm cab in this configuration.

I gotcha now. I just look at it a little differently.

Like I said, you don't have to do this if you don't want to as it won't hurt your Output Transformer. It'll just run your tubes a little hotter and in a Recto, that isn't a bad thing if you doesn't have the bias mod done.

Dale

I assume this can also work with 4 EL84's right? Just pull either the inner pair or the outer pair. I figure I better check before I do it. I've been thinking about doing this or getting a hotplate for my Nomad 45.

zakk615 said:

I assume this can also work with 4 EL84's right? Just pull either the inner pair or the outer pair. I figure I better check before I do it. I've been thinking about doing this or getting a hotplate for my Nomad 45.

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check the pic - those are EL34s.

jong said:

zakk615 said:

I assume this can also work with 4 EL84's right? Just pull either the inner pair or the outer pair. I figure I better check before I do it. I've been thinking about doing this or getting a hotplate for my Nomad 45.

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check the pic - those are EL34s.

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You misunderstood. I'm talking about my amp which uses EL84's. All I'm asking is if I can do the same thing with my amp which runs 4 EL84's without ruining anything. I figured I better ask before going ahead and doing it.

I don't now about just plugging the EL-84's into the amp, but I'm running THD YellowJackets in my DR. They are about $80 if you get them new. They are also self biasing and convert the amp to Class A operation.

zakk615 said:

jong said:

zakk615 said:

I assume this can also work with 4 EL84's right? Just pull either the inner pair or the outer pair. I figure I better check before I do it. I've been thinking about doing this or getting a hotplate for my Nomad 45.

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check the pic - those are EL34s.

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You misunderstood. I'm talking about my amp which uses EL84's. All I'm asking is if I can do the same thing with my amp which runs 4 EL84's without ruining anything. I figured I better ask before going ahead and doing it.

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absolutely

I've also been wondering about this with my 1x12" combo.

Can I pull out f.ex. the 2 outer EL84 tubes and plug the 8Ohm speaker into the 4Ohm jack without problems?

I have to be 100% sure before I do it...

*bump*

Can I do this for a Triple Rectifier?? I've heard yes and no, anyone doing it? If I remove 2 tubes, 100w..... If I remove 4 tubes 50w? That'd be great if it did, but I really doubt it is possible.

tele_jas said:

Can I do this for a Triple Rectifier?? I've heard yes and no, anyone doing it? If I remove 2 tubes, 100w..... If I remove 4 tubes 50w? That'd be great if it did, but I really doubt it is possible.

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nope cant do it, it would create speaker impedences of really odd values.

Once again, can I pull out two EL84's and put the 8ohm speaker jack into the 4ohm jack?

I have been told you can drop the Triple to a 100W but not a 50 Watt because of the reason above.

Just remove the 2 outter tubes and one of the rectifier tubes, was told it didn't matter which one I could be wrong though. I use silicon diode option anyways.

If you usually use the two 8 ohm outs then use the two 4ohm outs

I have not tried this but the person who told me this has used this method several times never having any problems.

mrdylan said:

I have been told you can drop the Triple to a 100W but not a 50 Watt because of the reason above.

Just remove the 2 outter tubes and one of the rectifier tubes, was told it didn't matter which one I could be wrong though. I use silicon diode option anyways.

If you usually use the two 8 ohm outs then use the two 4ohm outs

I have not tried this but the person who told me this has used this method several times never having any problems.

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Its still an impedence mismatch at only 2 tubes, running a mismatch isnt a guarantee for instant disaster, but its just a matter of time.

Removing the 2 outter tubes leaves 4

The Triple has 6 power tubes removing 2 is supposed to be the same as removing 2 from the Dual. but you can not go down to 2 tubes. You are correct that it is still a mismatch at some .3 (like removing a third) or something but it is not enough to cause damage.

The guy says he has done it for years now and has had no problems

He also says it doesn't make much difference since the Triple is so loud

an impendance mismatch is in no way a road to 'disaster'. yes, you may be putting excess strain on the tubes, but no more than having the amp cranked all the time anyway.

mrdylan said:

Removing the 2 outter tubes leaves 4

The Triple has 6 power tubes removing 2 is supposed to be the same as removing 2 from the Dual. but you can not go down to 2 tubes. You are correct that it is still a mismatch at some .3 (like removing a third) or something but it is not enough to cause damage.

The guy says he has done it for years now and has had no problems

He also says it doesn't make much difference since the Triple is so loud

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in any given circuit design that is 150w, putting it down to 100w isnt going to make a huge difference volume wise to begin with, if you understand the dB to w relation, that change in incriment is practicaly nothing. Practicaly speaking, a tri rec is barely louder than a single rec. The differences are going to be more in the dynamics of how the amp breaks up, ie more headroom, granted there will be a slight tonal difference as well.

If you feel comfortable making the mismatch, nevermind what I or anybody else tells you. Go for it!

jong said:

Your bold/spongy and vintage/modern settings will reduce wattage more, and I believe if i remember correctly, that you can actually get it down to about 20 watts or so, depending on switch position.

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How do you get it down to 20 watts? I didn't realize that the bold/spongy settings affected the output. I've played with the various switches and it didn't really seem any quieter. But, I'd love to figure out how to bring this down to 20 watts. Thanks.