Dual Rectifier 2 channel as a preamp

[analog]

Is There a safe way to use just the preamp of my 2 channel Dual Rectifier.
I want to run my mesa/Rectifier preamp into my Pearce poweramp.


I know you can harm a tube amp by not having a load attached.
And my cab will hooked up to the other power amp.

 

[94Tremoverb]

You must either connect the amp to a dummy load (many attenuators have this function), or remove the power tubes. Removing the power tubes is obviously cheaper (if you don't already own an attenuator) and doesn't wear out the tubes, but it won't quite produce the same sound since the power stage and the negative feedback loop are no longer affecting the tone. With the power tubes in and a dummy load, use the Slave output (or the Line Out from the dummy load if it has one); with the power tubes out, use the FX Send.

 

[msi]

A better method would be to send the FX out into what ever your using to record. The FX send control would then be the volume control, you want to get that as high as you can without clipping your recording device. Then turn the Master Volume on the amp down all the way. You should have the amp plugged into a load, and the tubes installed. Not having the power tubes in the amp will cause the voltages in the amp to be higher and could potentially damage the components as the voltages expect to have the tubes pulling current or it could damage the power amp. Doing so removes the presence control on the orange channel though.

 

[94Tremoverb]

The voltage rise due to not having the power tubes in is insignificant and not worth worrying about - it's well within the ratings of all the components in the amp, and especially so if you run it in any mode other than Bold/Diode. This is a really common myth, and although there are a *very* few amps where you may have to be careful, no modern amp I can think of is under any risk at all from pulling power tubes. Preamp tubes are another matter though (maybe counter-intuitively) since with no preamp tubes in, the voltages at the far end of the B+ chain can certainly rise very significantly and can exceed some component ratings. Maybe this is where the confusion comes from... but pulling the power tubes will cause a rise of no more than a few volts.

I would still prefer to run with the power tubes in though, since the NFB loop and the presence circuit won't work without them. But if you turn down the MV all the way, this still defeats the point because no signal is now reaching the power amp, so there is no negative feedback.

 

[greg_moreira]

this got me thinking, and now Ive got a quick question. If the FX send is used as the output, and there is nothing sent back to the return......does it really even matter where the master volume is set? You can hook the head up to the cab to introduce that load, but if the signal is only sent but not returned, then nothing actually plays through the cab(even with the master volume turned up), yet the preamp is still operating right? or am I thinking about this all wrong.....

 

[94Tremoverb]

You can do that, but if you want no sound to come from the cab you still must turn down the master volume to zero - the FX send jack doesn't cut off the signal. Nor does the return, if just used by itself - the Mix control will then blend between the amp's preamp and whatever is plugged into the return.