My 2:90 hums

[mARKw]

Hi there,

Does anyone know why my new Simul 2:90 would produce a hum? It gets louder as the volume goes up. It's a little bit annoying. I am running a vox tonelab > JMP1 > 2:90.

Cheers

 

[phantomlord2oo]

I don't know the solution but I've got the same problem too. It's pretty annoying! I'm running a Triaxis and a bunch of other gear but it's always made the humming noise even when it was just the Triaxis --> 2:90. I've got a Furman Power Conditioner and noise supressors but nothing stops it. Everything's grounded too. No clue what it is but it's definately the 2:90. I retubed it recently too and same problem.

+Mike+

 

[maeshuggah]

have you checked the input jacks? what cables are you using?

I know when I was using TRS cables in my rack I got hum using my Mesa Quad/295 Rig. when I switched to Monster Guitar cables It went away.

Check those input jacks.

 

[phantomlord2oo]

I've been using all Monster Cables since I got the Triaxis/2:90.

+Mike+

 

[mARKw]

Yeah bizarre.

I asked the shop for the best cables they had - They're called "Climb. Noise reduction cables."

:?

 

[mARKw]

Is there any Mesa support email or phone numbers?

...though the phone call would be a little expensive from Aus.

 

[disassembled]

Does the amp hum by itself? Try this: plug in the 2:90 to your cab, do NOT plug anything else into the power amp, and then turn the volume up on the 2:90. If the 2:90 still hums it is isolated to the 2:90, speaker cables, speaker cabs, and power/ grounding source.

 

[Tuna141]

It sounds like a ground loop problem to me.

I suggest taking the JMP and the 2:90 out of the rack to see if the hum goes away. Don't let their chassis touch when you do this test.

 

[maeshuggah]

If its ground loop hum, then try an ebtech Hum eliminator.

They have rack and non rack versions.
The non rack version is only $60 USD.

 

[mARKw]

I have been in contact with Australia's rep for Mesa.

I tested the power amp without any inputs connected and turned the volume up and there was no hum. Then I plugged the preamp back in and turned it up and the hum was there again.

After this I plugged my guitar straight into the 2:90 one channel at a time. Firstly I set the Line/Instrument switch to Instrument. Nice and quiet both channels - no hum. When I switched to Line - There was only a little bit (an acceptable amount) of hiss/crackle noise.

So, apparently, I might have an impedance mismatch between my JMP1 preamp and the 2:90 poweramp. Has anyone ever heard of an impedance mismatch between preamp and power amp?

Cheers

 

[Tuna141]

I'm still betting it's a ground loop hum. When you switch from Line to Instrument input on the 2:90 you just change the input gain. I think that's why the hum seems to away when you flip this switch. It's a similar phenomenom as the hum getting luder when you turn up the gain on your preamp.

Did you try turning the volume back up on the 2:90 and different gain settings on your preamp in the "quiet" input switch setting? Does the hum come back?

 

[maeshuggah]

Maarten from Tubefreak.com has extensive information on this subject. :?

Check it out in the articles section.

http://www.tubefreak.com/farticles.htm

 

[disassembled]

So now that we know you don't have a problem with the amp itself you can start troubleshooting. Firstly, make sure that all of the pieces are grounded and are plugged into the same outlet or power strip. Check the grounding switch on the 2:90, make sure it has a grounding prong then do the same for the preamp. Use a known good cable to do the testing.

 

[JAZZGEAR]

Well...I definitely have had the same experience. I have a 2 yr old Traixis 2:90 combo which hum'd excessivey and required a noise gate -- gated to the point where playing was no longer dynamic and choked all of the natural feel and dynamics of the guitar. Spent an enourmous amount of $$ buying high end cables, power conditioners and voltage regulators.

I even tried grounding everything to a central ground in my rack to no avail.

I even dismantled every thing and tested each individual piece outside of thre rack.

I isolated the problem to the Triaxis. Purchased new tubes...Nothing --same hum. Finally decided to send it in to Mesa for warranty repair.

They confirmed the unit was out of spec with the noise level. They fixed the unit in 2 days.

Verdict: Power transformer in Triaxis needed additional shielding.

I am now a happy camper and my rig is as quiet as can be.

 

[bobmeredith]

Try isolating the power amp from the rack rails and casing of the other rack units. This often causes a ground loop. You can buy "Hum Frees" (no, not a fun loving bear) from Pro Audio in Canberra

 

[phantomlord2oo]

I'm going to check out what Jazzgear said. My 2:90's in a separate 4 space rack that only holds the power amp and a 2 space drawer. It's also on the same power strip as my Triaxis.

+Mike+