Low Level Hum? Anyone????

Howdy folks!. I just took delivery on a new Express 5:25 plus head that I'm using with a full stack of mini rectifier cabs. What an awesome combination!. The tones from this head are just incredible and the Express head sits prefectly on top of the mini stack... very sweet! 8) .I've owned a Lonestar Special head for a number of years now and thought I would get an easier to move setup and I'm very happy.

,,,, but.... the amp is producing a low level hum that is audible when the amp is operating (out of standby) even with no guitar plugged into the input.
Sounds like it may be a 120hz hum, coming from the speakers. Anybody else experiencing this? The hum is not terribly loud but can be heard in a quiet room when the amp is taken out of standby. Any thoughts? :?:

No one else with a 5:25 express plus is hearing this?? :?: :?: :?:

Most likely tube related. Try swapping in a good preamp tube in the V2 spot.

Thanks for the reply... I think I'm going to give that a try as well as giving Mesa a call and get their thoughts... really don't want to return it.

I'm wondering since I don't use spring reverb, if removing the reverb tube might help..... not sure which one it is...

jmontgomery said:

Most likely tube related. Try swapping in a good preamp tube in the V2 spot.

Click to expand...

You want your quietest tube in the first gain stages. Any noises just get amplified from there. I had a 5:25+ head, I now have a 5:50+ combo. I'd say they are as quiet as any tube amp I've owned. I do have some noise on the burn channel when cranked, but that's expected when that much gain is cascaded. My clean and blues channel are very quiet.

This is a hum... I wouldn't call it "noise" as in hiss.... it sounds like power supply filter hum. I spoke to Gary at Mesa at the end of last week and he suggested swapping tubes which I did.... no change. I took tubes from my Lonestar Special head because it doesn't have this hum issue. Gary mentioned that all tube amps will have a certain degree of hum/noise which I understand. If that's the way it is, then that's the way it is... I'd like them (Mesa) to plug in a Express 5:25+ head to a cabinet and see if they get the same thing. It's only happening in the 5 watt position.... and I did switch out both power tubes as well.

This wouldn't be an issue for live playing but for recording, it might be.