Running Dual Rec at 50W

[stadidas]

I just today got Dual Rectifier R-001967 (Blackface ). I want to run it in 50W mode by removing two power tubes. I think I read somewhere that I would then need to use a 16 Ohm output to my 8 Ohm 4x12 (the rec has two outputs that say 8-16 Ohm so I take it that would be ok). Does anyone know if this is correct?

 

[Zoomzilla]

You will not hear a great difference in volume drop by doing this. You WILL hear a difference in tonal quality. Why do you want to run it in 50W mode anyway?

 

[stadidas]

... volume drop. More gain at lower volumes preferably.

Maybe I shouldn't bother.

 

[mikey383]

No, that is not correct. You'll need to use the 4 ohm outs.

Also, there's nothing wrong with running a Dual in 50w mode...don't let anyone tell you there is. The tonal change of running 50w is worth it to me. Give it a shot and see what you think.

 

[MikeK]

I run mine with the center pair pulled out, half of the fuse value (from a 4 amp down to 2 amp, I think?). I could have also pulled one of the rectifier tubes, but I like the way it sounds running two, it feels a little tighter. I went down on the impedance from the 8 ohm speaker out to one of the 4 ohm outs for my 8 ohm cab. I was running it at 8 for a while, but then some one here told me that I needed to do this to match the output transformer to the power tube removal. I found that this opened the tone up almost dramatically.

I run it this way @ 50 watts because it gives me a little more manageability at the volume I run at without burning up the extra pair of valvesI don't really need. But it's really nice to have the choice to go back up to a hundred watts when I want the extra head room. As far as I know this doesn't hurt the amp in any way ...

If anyone out there knows something about this that I may be missing, I'd really like to hear it.

 

[stadidas]

Well the tonal difference between this and my Single Rec is pretty big, but then that will be down to the fact this is an old Dual more than anything else, rather than the difference in power.

 

[Sustain]

I run mine with the center pair pulled out, half of the fuse value (from a 4 amp down to 2 amp, I think?). I could have also pulled one of the rectifier tubes, but I like the way it sounds running two, it feels a little tighter. I went down on the impedance from the 8 ohm speaker out to one of the 4 ohm outs for my 8 ohm cab. I was running it at 8 for a while, but then some one here told me that I needed to do this to match the output transformer to the power tube removal. I found that this opened the tone up almost dramatically.

I run it this way @ 50 watts because it gives me a little more manageability at the volume I run at without burning up the extra pair of valvesI don't really need. But it's really nice to have the choice to go back up to a hundred watts when I want the extra head room. As far as I know this doesn't hurt the amp in any way ...

If anyone out there knows something about this that I may be missing, I'd really like to hear it.

You need to remove one of the rectifier tubes.

I refer you to the user manual, it states this plainly that if you do this you should remove a rectifier tube to prevent a mismatch. I guess it has something to do with the way its routed to the rectifiers, 2 tubes per rectifier tube. when there is only 1 tube the 2 power tubes cant get confused about which rectifier to send to.

 

[mikey383]

I run mine with the center pair pulled out, half of the fuse value (from a 4 amp down to 2 amp, I think?). I could have also pulled one of the rectifier tubes, but I like the way it sounds running two, it feels a little tighter. I went down on the impedance from the 8 ohm speaker out to one of the 4 ohm outs for my 8 ohm cab. I was running it at 8 for a while, but then some one here told me that I needed to do this to match the output transformer to the power tube removal. I found that this opened the tone up almost dramatically.

I run it this way @ 50 watts because it gives me a little more manageability at the volume I run at without burning up the extra pair of valvesI don't really need. But it's really nice to have the choice to go back up to a hundred watts when I want the extra head room. As far as I know this doesn't hurt the amp in any way ...

If anyone out there knows something about this that I may be missing, I'd really like to hear it.

You need to remove one of the rectifier tubes.

I refer you to the user manual, it states this plainly that if you do this you should remove a rectifier tube to prevent a mismatch. I guess it has something to do with the way its routed to the rectifiers, 2 tubes per rectifier tube. when there is only 1 tube the 2 power tubes cant get confused about which rectifier to send to.

This is completely incorrect. There is no need to remove rectifier tubes. The power tubes don't "send" anything to the rectifier tubes. The rectifiers convert AC current to DC current for the amp to use. There is no impedance mismatch or anything. The only result is less sag due to the decreased load through both rectifiers.

 

[Elpelotero]

Regardless of the interaction b/w the power tubes and rectifier tubes, you still got to remove a rectifier tube.

I run my amp at 50w often b/c it had less bass...Bass is what mostly causes the walls to shake, so it works for me.

 

[Sustain]

well i never said I had the theory correct, but I did get it directly from mesa engineering to remove 1 rectifier tube.

They said it doesnt matter which one, but to remove one. So does the manual.

 

[njsurf]

You do have to remove one of the rectifier tubes. I like running mine in 50 watt mode as well. Makes the volume and tube distortion alot more manageable, but that just my preference.

 

[RoadKinger483]

im interested in running my DR in 50 watt mode also. So what do i have to run my 4x12 cab at??? what input do I use???

 

[mikey383]

The only reason behind removing one of the rectifier tubes is so that you get the sag. They are wired in parallel, and the only thing that will happen by not removing one is a tighter tone.

 

[MikeK]

You need to remove one of the rectifier tubes.
I refer you to the user manual, it states this plainly that if you do this you should remove a rectifier tube to prevent a mismatch.

I believe you've taken what the manual says about this, out of context.

It actually says .. "Remove one of the Rectifier tubes if you are using the Tube Rectifier setting to assure a correct match." .. It says this coming out of an explanation about rectifier tube sag. The "correct match" its talking about is the amount of sag two rectifier tubes give to a quartet would be the same as one rectifier would give to a pair. There is no mention of a "mismatch" to be "prevented".

Anyway, I also believe as mikey383 and his explanation of the parallel wiring of the tubes.

RoadKinger483: I run my 8 ohm cab from the 4 ohm out on the amp.
It sounds the best to me and I don't believe it harms the amp or the cab in any way.