Mk11 C+ Hum / Noise w guitar plugged in

[krsmusic]

I have a 1984 MK 11C+ that was moded from a 11c. The input is sensitive to any guitar plugged in and I live with Hum and noise that goes away when the guitar is not plugged, turned down or improves some if I stand away from the amp.
The num /noise is there but barely noticable in the rythem mode. It is most noticable in the lead mode or as gain and volume is turned up. I think the problem has always been there but may have gotten worse now that I'm more aware of tone etc.
Any suggestions. I sthis typical ?
The output tubes are new and the pre amp are two years old. I tried two guitars one with humbuckers and one a mix of single coil and HB

 

[Jim Ed Love]

I have a 1984 MK 11C+ that was moded from a 11c. The input is sensitive to any guitar plugged in and I live with Hum and noise that goes away when the guitar is not plugged, turned down or improves some if I stand away from the amp.
The num /noise is there but barely noticable in the rythem mode. It is most noticable in the lead mode or as gain and volume is turned up. I think the problem has always been there but may have gotten worse now that I'm more aware of tone etc.
Any suggestions. I sthis typical ?
The output tubes are new and the pre amp are two years old. I tried two guitars one with humbuckers and one a mix of single coil and HB

Are you running any effects. Those always add noise. My MKIIC+ makes noise when I put the guitar in. I figure since I'm running it high gain with a bunch of effects there is going to be noise.

 

[DaveP]

I have owned 4, currently have 2 Mark IIc+'s. Everyone of these has/had a hum in the high gain channel with the volume 1 up past 7-8 and the treble and lead drive about the same. It's just nature of the beast. You can eliminate some by reducing the gain, treble and drive some.
Unless of course you have something beyond that. If you call Mesa support they will conclude the same thing.

 

[Fronzil]

ISP gstring..or another good noise gate

 

[krsmusic]

Thanks for the feedback so far.
I believe the amp has a an inherent hum ( sounds like A/C noise ? ) that starts when a guitar is plugged in irregardless of where or what effects are plugged in. The hum is there with the guitar pick ups turned off
I have to keep the amp gains minimized to make the hum noise not so annoying.
Hum / Noise gets magnified especially in the lead mode and adding effects makes it worse, however my acoustic simulator when on reduces the noise - it's in the fx loop now.

I'm bummed - I'm calling mesa again - I'll update

 

[Boogiebabies]

You may have an off balanced heater circuit. When one of the two ground reference
resistors is bad, it will hum badly as they are needed not only fro ground, but to keep the heater voltage at 3.2V per side.
These usually get taken out when a 6L6 blows in one of the inner sockets. They are the two Brown/Black/Brown/Gold 100 Ohm carbon comp resistors just to the right
of the three speaker jacks. They act as ground reference to the heater circuit and as a hum trimmer.
In parallel they will read 50 Ohms. If not, your heater circuit is unbalanced and amplifying the
hum from the increased voltage and imbalance. It gets way worse in lead mode as the amplification/gain is dramatically increased.

 

[krsmusic]

Thanks again for comments.
After much isolating, I have learned more about all the noise I hear and concluded that the MK 11 C+ combo with EQ, Simulclass, Rev is not the cause of excessive hum and noise I have.

There are two conditions causing the hum and noise I know of.
The Fender Telecaster thinline MM w dual humbuckers produces some hum. Moving away from the amp and turning at certain angles reduces the noise. Its manageable

Most of the hum / noise is associated with the use of the Roland Gr 20 synth unit when plugged into the mesa / acoustic amp
MY guitar is plugged into the Gr20 via 13 pin conncector. When "guitar out" from the GR 20 is plugged into the MK11 input, the hum starts but not too bad.
When the second line out from the Gr 20 is plugged my acoustic amp for the synth sounds the hum becomes much worse. The gr20 output is set to guitar
Can't seem to make it go away when using the Gr 20. The acoustic amp is really the biggest hum initiator . I tried two differnt amps ( Peavy Ecoustic FX 12 ) and differnt 120v outlets, grouds etc

 

[Boogiebabies]

It would have been easier to diagnose if you said you were using two amps.
All pickups make some noise and every one will have a ground loop hum when using two amps
with the same ground input. It turns all the cabling into a giant antenna and in overdrive amplifies the issue
exponentially.

 

[CoG]

You may have an off balanced heater circuit. When one of the two ground reference
resistors is bad, it will hum badly as they are needed not only fro ground, but to keep the heater voltage at 3.2V per side.
These usually get taken out when a 6L6 blows in one of the inner sockets. They are the two Brown/Black/Brown/Gold 100 Ohm carbon comp resistors just to the right
of the three speaker jacks. They act as ground reference to the heater circuit and as a hum trimmer.
In parallel they will read 50 Ohms. If not, your heater circuit is unbalanced and amplifying the
hum from the increased voltage and imbalance. It gets way worse in lead mode as the amplification/gain is dramatically increased.

Man, I wish Boogiebabies lived in my town.

 

[krsmusic]

small update
I have found out I still get hum in my C+ when I add any 2nd device such as amp or PA mixer out of the GR20. The adding of the second device really increases the hum, which I think may be there to begin with in a small amount, so I should check that heater circuit.
Note:
If I connect a jumper wire on the outer portion of a quater inch jack on both devices the noise is reduced. But hum still a problem especially with gains up.

Any new thoughts with this ?

Thanks for all

 

[zebpedersen]

Whenever I run multiple amps I've always had hum issues. The solution, for me, to make it manageable has been to invest in a high quality switching unit - however as far as I'm aware unless you get a managed power supply/conditioner with all equipment in the chain plugged in you can't get rid of it all.

And yes, it always gets worse with more gain.