Running one side of the Mesa Fifty/Fifty

[highgainer]

Hello guys !
I plan to use only one cab with the Mesa Fity/Fifty, I checked the manual and here's what I found :

"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 else damage will most likely result.)"

Now, I know that I should turn down the level control of the unused channel, but how do I do to keep a speaker (or load resistor) connected to a speaker jack on both channels, including the unused one while I have only one jack input on my 2X12 cab ?

In other words, when I connect say the right channel of the poweramp to the only input of my cab, what should I do with the unused left channel of the poweramp other than turning the level control to zero ?

 

[mnemonic]

I believe mesa’s position is you just leave it with nothing plugged in. I think I’ve also seen them say (maybe in a different rack amp manual, or maybe on that online help desk page they have) that you can plug a shorting jack into the speaker jack of the unused channel (a jack with + and - tabs soldered together).

If Mesa recommend it it’s probably fine but I would still be nervous of high voltage on the tubes with no load on the output transformer. If it were me I would either make a little metal box with a 50 or 100 watt resistor in it and plug that in, or if I was only ever gonna use that one side, pull the tubes on the unused side (this will cause plate voltage to go up a little on the remaining side though).

 

[trey85stang]

The unused size can't be turned off you need a load hooked to it.

 

[Snave]

It's fine to leave the unused side without a speaker connected. Just turn the volume all the way down and presence all the way up.

This is Mesa's recommended protocol and how I ran a 2:50 for years.

 

[mixn4him]

Just pull the 2 tubes for the channel you are not using, no need for a load once the tubes are pulled. Did this for years...

 

[highgainer]

It's fine to leave the unused side without a speaker connected. Just turn the volume all the way down and presence all the way up.

This is Mesa's recommended protocol and how I ran a 2:50 for years.

I think this is the method that most people recommend, including Mesaboogie crew.

 

[highgainer]

Just pull the 2 tubes for the channel you are not using, no need for a load once the tubes are pulled. Did this for years...

Are you sure it's safe to run the amp that way minus two tubes ?? When the tubes are pulled off should I also turn the volume down and presence up on the unused channel from which the tubes are pulled ?

 

[mixn4him]

Just pull the 2 tubes for the channel you are not using, no need for a load once the tubes are pulled. Did this for years...

Are you sure it's safe to run the amp that way minus two tubes ?? When the tubes are pulled off should I also turn the volume down and presence up on the unused channel from which the tubes are pulled ?

Yep nothing to damge since there are no tubes in play. Just run both the level and presence fully off on the unused channel..

 

[Panzer917-30]

For my Mesa 20:20 I use a Mesa 2x12 with input jumper cut so that it makes it a Stereo 12 so I can use it to run 1 or both sides of the 20/20. Fun to run wet/dry.

If I dont use that Cab I use a Hot Plate attenuator to act as a dummy load.