MM Petrucci Hum

[Hexa]

Hello,

I'm the owner of a fabulous black MM Petrucci with Piezzo option ... but since one week I getting a really strange issue.
Actually when I'm not touching any metallic part of the guitar, a kind of small hum can be heard ... This hum disappear immediately when touching any of the metallic parts (switch, knobs, jack ... even strings )

I was first thinking about a ground problem ... but after testing, all cables are looking OK
Is it possible this issue comes from a bad soldering somewhere (I know the main switch has been changed) ??

Many thanks in advance for any idea

PS : to be more accurate there this no hum when using piezzo only + the hum can be heard the same in the two outputs of the guitar

 

[Banger]

Hi Hexa,
actually this is nothing unusal to passive guitar electronics; your body is like an antenna radiating in to the electronics. As soon as you touch the metal parts, you ground yourself, which leads to beautiful silence

A solition (besides switching to active electronics, of course) would be to shield every cavity containing electronics with adhensive copper foil or shielding laquer (don't forget to ground the shielding, too), which worked so fine on my strat, I could even do without grounded strings.

 

[Hexa]

I'm maybe wrong but all cavities are not shield by default on MM. ??
For instance if I do the test with my MM Steve Morse in exactly the same condition I can hear a relative silence
I've a big doubt , as I'm now obsessed by this hum on the Petrucci ... but to me it appears only one or two weeks ago and it was really more quiet in the past (but not sure if it was totally ...)

 

[Mick]

Hey Hexa, it´s like Banger explained. But maybe you were lucky until now.
There is surley no prob with your GTR, maybe something in the electrical environtment of your House or room changed.
Could be a lamp or some unperfectly grounded equipment.
I would recommend trying the setup in another room and you will see.

And the Pet is more attracted to noise pollution because of the preamp/active system of the piezo. Keep cool, in one room in my house it´s hell too. Until I discovered it´s the power supply (external) of my notebook.


Hope that helps a bit
Mick

 

[Hexa]

Hey Mick ... You maybe put the finger on it ...
Two weeks ago I moved my laptop just near my amp ... and of course the power transformer was plugged all the time when I was doing my tests
That could be the culprit ... I'll have a look on that side
Thank you very much

 

[eliot323]

Hi there Hexa
I agree with all that's been said - I have 3 Pets and they all do it to a greater or lesser extent.

I found that using a proper mains conditioned power supply to run amps and FX from helps a lot - I've also removed virtually all my pedals off my pedal board except my wah and choralflange and delay (which I run through my amp's FX loop) and noticed a big reduction in noise.

The Lehle amp splitter I was using was not very good on the noise front...and even more surprisingly the MXR Noise Gate was one of the worst culprits.

Also check out for local fluorescent lights, including energy saving bulbs; other power supplies etc.

If you check in the back cavity of your Pet, there should be a wire coming from the ground lug that lodges onto the shielding on the the back of the cavity cover. Make sure that is making a good contact.