stereo power amp output to a mono cab?

[ylo]

Bridging a stereo power amp to mono is NOT a good idea. You will probably blow up the amp unless it has a switch to do this. Before trying to wire the outputs together, contact the amp maker to be sure this is safe.

The better thing to do is open up your 4x12 cabinet and rewire it for stereo, or better yet, get something like the jackplate that Mesa uses on its 4x12s, which give you the option of stereo or mono (although not necessarily with the impedances that you want).

 

[reo73]

Just use one channel of the Power Amp and make sure to turn the volume and presence to 0 on the side not connected. Mesa speaks about this in all their power amp manuals and I have been running only one side of my 50/50 without a problem for a couple years.

 

[reo73]

Just use one channel of the Power Amp and make sure to turn the volume and presence to 0 on the side not connected. Mesa speaks about this in all their power amp manuals and I have been running only one side of my 50/50 without a problem for a couple years.

when you do this, is the other unused side on and in standby? if so, this is bad for the tubes (cathode poisining)...

I don;t know what is happening electronically when one side is not used and there is not dedicated standby switch per side but Mesa has designed their power amps to be able to run one side only and they tell you to turn the controls for the unused side to 0. I have never noticed greater than usual tube wear on the unused side but it is good to change sides every so often to keep things even.

 

[Jakem]

Just use one channel of the Power Amp and make sure to turn the volume and presence to 0 on the side not connected. Mesa speaks about this in all their power amp manuals and I have been running only one side of my 50/50 without a problem for a couple years.

The side which is not connected to a load should have the volume set to 0 and presence should be MAXED!

-Jaakko

 

[reo73]

Just use one channel of the Power Amp and make sure to turn the volume and presence to 0 on the side not connected. Mesa speaks about this in all their power amp manuals and I have been running only one side of my 50/50 without a problem for a couple years.

The side which is not connected to a load should have the volume set to 0 and presence should be MAXED!

-Jaakko

I think the 20/20 manual is the only one that states this about the Presence but it is probably true of the other power amps as well. The presence is not a load issue though, just a potential feedback one.

 

[RJ2213]

i believe its also in the manual for the 2:90. and a mesa tech i talked to on the phone confirmed this for me. volume should be min, presence should be max.

 

[Jakem]

I think the 20/20 manual is the only one that states this about the Presence but it is probably true of the other power amps as well. The presence is not a load issue though, just a potential feedback one.

Mesa speaks about this in ALL their power amp manuals...

:shock:

 

[FastRedPonyCar]

I was under the impression that running any tube power amp with no load attached to it is leathal for the output transformers.

Does setting the volume at zero somehow negate this rule? Or are mesa amps engineered specifically to be able to do this?

It's not really an issue for me as I use a bridgable mono or stereo carvin 50/50 but if it's a universal truth, it'd be nice as it means I could use my amp with a single 50 watt output into my 4X12 rather than having to use a single bridged 100 watt output.

And +1 for retrofitting or rewiring the cab to be used stereo/mono.

Tim at earcandy sent me this new speaker jack plate to put into my buzzbomb 2X12 so I could use the cab in stereo or mono.

 

[reo73]

I think the 20/20 manual is the only one that states this about the Presence but it is probably true of the other power amps as well. The presence is not a load issue though, just a potential feedback one.

Mesa speaks about this in ALL their power amp manuals...

:shock:

Am I not making sense? Mesa speaks about the Volume to 0 for the unused side in ALL their power amp manuals and many times more than once. They only speak about the presence being maxed in a select few, the 20/20 being one of them.

 

[reo73]

I was under the impression that running any tube power amp with no load attached to it is leathal for the output transformers.

Does setting the volume at zero somehow negate this rule? Or are mesa amps engineered specifically to be able to do this?

I think Mesa has engineered them so that if the volume is set to 0 it puts that side in a sort of stand-by mode.

 

[unconventional]

From the 2:100 Manual.

The amplifier is stereo, offering two separate channels of
amplification. If you wish to use only one of its channels, it is necessary
to: 1 ) Make sure a speaker (or load resistor) remains connected
to a speaker jack on both channels, including the unused
one; or 2 ) Turn the LEVEL Control of the unused channel to zero.
(This is necessary because an amplifier channel receiving any amount
of signal at its input will require a “load” at its output - or damage will
most likely result.)

 

[PC Biz]

I got a stereo jack plate from Mesa for my 4x12 steel grill cab. They emailed wiring instructions by way of photos. I like it that way. Sorry about the oversized photos. I'll figure out how to shrink them down to size next time.

[/img]

 

[unconventional]

If you go on the mesa website and download the manual for the 2:100 it includes all types of speaker diagrams and how to wire.

http://www.mesaboogie.com/manuals/2-100.pdf

 

[CudBucket]

Wow. Those Mesa jack pics are a short waiting to happen with no jackets on the hard lines.

 

[FastRedPonyCar]

They can't wire it for you and just let you hook up the speaker cables inside the cab to the plate??

 

[PC Biz]

They can't wire it for you and just let you hook up the speaker cables inside the cab to the plate??

I'm pretty sure they would. It would just cost more.

 

[PC Biz]

Wow. Those Mesa jack pics are a short waiting to happen with no jackets on the hard lines.

I was wondering about that, too. However, I have seen exposed hard wiring like this before from other 4x12 boxes. I guess the space between them is insulation enough. Since I don't have any hard wiring as in the diagrams, covered lines it is.