New (Used) Mini Rec Has A Hum - Any Ideas?

[soundchaser59]

Any clue what the hum is from?

All grounded outlets, no fluorescent lights, Strat with noiseless pups, no pedals plugged in, just guitar > amp, nothing else on the circuit, no computers running, shielded guitar cord, etc.etc.etc. Has all the original Mesa tubes in it.

Hum stops as soon as I unplug the guitar. However, my other (Rivera, Vox) amps have no hum at all with the same guitar plugged in.

Was this an issue in the beginning with these Mini Recs? I know Mesa tubes are kinda notorious for being less than perfect, could a tube cause this? Date stamp inside is 1-12-12.

 

[UnderJollyRoger]

Have you tried plugging in/out the guitar cable to the amp repeatedly ? Sometimes the jack can get a little corroded ...

 

[elvis]

If the hum stops when you unplug the guitar, it's probably the guitar. The MR has a LOT of gain, probably more than your other amps.

Does it hum on the clean channel?

 

[D2dark]

i had hum problem with my mini, but it was still doing it with nothing in the front, so i'll say its your guitar or cable.

 

[soundchaser59]

If the hum stops when you unplug the guitar, it's probably the guitar. The MR has a LOT of gain, probably more than your other amps.

Does it hum on the clean channel?

Yeah, the hum is the same no matter which channel or mode I'm in. The guitar is shielded and was already setup for the Fender Noiseless pickups that are in it. Cable is decent quality shielded guitar cord. No pedals, just plugged straight into the amp. Plugged into my Rivera or my Vox there is silence, no hum, no hiss, nothing, even at super loud volumes. I'm not going to be easily persuaded that it's the guitar. 8)


A couple of things, after speaking with Mark at Mesa Boogie today......

The cord should be minimum 16 gauge, not 18, although the Mini Rec is not a huge current draw like other amps can be.

The Mini Rec does not really follow the pattern of other "big boy" rectifiers, the PI or driver tube is not considered a cathode follower, so there is no need to worry about using special 12AX7 tubes in that position. Any good quality 12AX7's will work fine in all positions. The concern with 12AX7's in the "cathode follower" position is intended for dual rec's and above. He did say they prefer not to use Russian tubes in the positions that do have that concern.

Currently the Mesa tubes are (if I understood him correctly) rebranded JJ's. He said, "We are using JJ's." Maybe (cross our fingers) that is one step they took to cut the incidence of Mesa tubes failing prematurely?

If my hum (it's a 60hz hum) goes away when the guitar is unplugged, he said that points to the possibility of a weak preamp tube, assuming the guitar is properly shileded, grounded circuits, etc....i.e. assuming everything else in the room and the signal path is ok. Suggestion was to swap out preamp tubes one by one with a known new tube known good tube and see if the hum can be removed that way. He seemed to suggest that a hum that stays after the guitar is unplugged would point more toward a weak power tube. He also suggested taking the amp to a totally different location (a friends house, etc.) to see if the hum still occurs. I can do some preamp tube swapping tonight.

I'm no expert, so call them if unsure about any of this, I'm just regurgitating what I think I was told. Hope this makes sense.

 

[D2dark]

10W or 25W mod ?

i had a hum with my mesa tubes in 10W mod, the problem was the tubes.

 

[Addictedtokaos]

The Mini Rec does not really follow the pattern of other "big boy" rectifiers, the PI or driver tube is not considered a cathode follower, so there is no need to worry about using special 12AX7 tubes in that position. Any good quality 12AX7's will work fine in all positions. The concern with 12AX7's in the "cathode follower" position is intended for dual rec's and above. He did say they prefer not to use Russian tubes in the positions that do have that concern.

Good to hear. THanks for passing this along.

 

[soundchaser59]

Took the entire Mini rig to rehearsal, came home, plugged everything in exactly the way it was before, and now there is no hum. :shock: :?

 

[Adambomb]

It's crazy how these Mesa's can be. Seems like everybody has tube problems at first but the amp gets good and broke in, it's like the amp heals itself. I've have plenty of Mesa's, only 3 new ones and each one had a preamp tube problem, but went away after a day or so. Even in the Mini Rec manual it says something about tubes shorting out, but then coming back to full capacity (something like that). Enjoy ur Mini dude, I'm just so stoked about mine. Where did you have your Masters running during band practice?

 

[soundchaser59]

Where did you have your Masters running during band practice?

Pushed at about 2 o'clock, Vintage at about 12 o'clock, both on 25w, using a Supernova for a boost, running the guitar volume knob to clean up.....using a little Weber Texas 10 ported.