Hum stops when I touch the strings... but not only !

[TheDams]

Hi all,

I am new to this forum (I am French, and live in Minneapolis).

A little bit about me:

I play since 20 years, mostly for myself in my tiny man cave

. I used to have a couple of 50's/60's rock bands in France before I moved here.

My gear (sorry... no real Les Paul, maybe one day I'll afford it !)

- Agile AL3100 P90
- Agile AL3010SE humbuckers (50's wiring)
- Fender Stratocaster Classic 50's w/ 57/62 pickups

My amp is a "hot rodded" Blackheart BH5H that has now a point-to-point board, NOS tubes (RCA/Ge tubes, including a GZ34 rectifier), plugged into a BH112 cab w/ a WGS Reaper speaker

My pedalboard is: Wilson WMA Wah -> Fulltone Deja Vibe Stereo -> Fulltone 69 MKII -> Fulltone OCD MKIV -> Malekko 616 delay -> Mr Black Deluxe Plus (reverb/tremolo)

Here is my "problem":

When I don't put my hand on any part that is grounded (strings, tuner pegs, stop bar, etc.) there is a slight buzz.
I can ear it especially with the AL w/ humbuckers, as they are by nature quieter (to other parasitic noises) when string/stop bar are touched... so it is more obvious when I get my hands off any grounded parts.
I can ear it also on the strat' or the P90 AL, but it is less obvious, as the single coils are noisy by nature.

Now I know it is not a missing ground problem (or the noise would be worse if I touch a metal part on the guitar, right ?), and I know that every guitar, even loaded with humbuckers is subject to that king of noise... depending of where you play, the electrical installation and such (BTW, my amp is plugged on a properly grounded prong).

What is weird, is that when I don't touch any grounded part on my gear (on the guitar, or on my pedalboard, or my amp chassis and such), but I touch other thing that are grounded in my room (and again, they are NOT linked to any part of my gear !), the buzz stops !

I found that if I get my guitar further from my body (when using a strap), and I don't touch any grounded part, the buzz is quieter.

So, should I conclude that my body acts like an antenna, and brings that noise even when I am NOT touching any grounded part of the guitar ?

Any idea of how to deal with that ? shielding the cavities with copper tape ?

I've checked all the guitars' wiring... no cold solder joints, no missing grounds, etc.

Thanks for your help

 

[snow and steel]

Yes your body does act as a poor antenna, and if you touch metal and the hum goes away then your ground is functioning as is should.

If you are playing with high gain, the hum is going to be very common and noticeable.

Is the hum worse at home than at another location? If so, you might consider shielding the cavities.

Hope that helps.

 

[TheDams]

Thank you for your answer

I don't really play high-gain (mostly blues and 50's/60's rock)... my dirt boxes are an OCD (and the gain is usually set between 8:00 and 12:00), a Fulltone 69 Fuzz and a Dallas Arbiter Treble Boost.

Unfortunately, I didn't try other locations. As I said, I mostly play for myself now, in my "man cave" (which is in my attic, with a pretty poor electrical installation I'm affraid).

I'll try to shield the cavities, as I have some copper tape.

 

[snow and steel]

Also try another location, preferably even a whole new building just to check to see if its the house wiring. Keep us updated.

 

[TheDams]

Thanks for the advice... I'll see if I can try another location.

Right now, further investigations:

- cables are OK. Evidence Melody instruments/amp cables and Evidence Monorail patches. All tested with DMM and ok.
- guitars are OK, especially grounding (or the noise wouldn't disappear when I touch sonething grounded).
- Plugged in bathroom, where grounding is supposed to be good (with these "test/reset" prongs). Same thing... well, almost: amp is less noisy, I suppose because my bathroom has less parasitic stuff around.
- I checked my amp, which is a pretty simple 5W class A build (ptp board), all the grounds are fine. Solder joints look good, shinny and clean. I also tried, just to be sure, other tubes... no change, except that I found that one of my GE Blackplate is slightly microphonic

.

As far as I can tell (and according to your opinion), I guess it is just myself acting as a poor antenna in my attic, where electrical installation/isolation is unfortunately not very good... prongs are grounded, but there are wire running in the ceiling (lights) and I suspect other badly isolated stuffs that potentially emit some sh*tty waves.

I might act as a big capacitor, emitting parasitic "radiations", and when I touch something grounded, I ground myself... then bye-bye buzzz, et voila

.

I'll consider shielding the cavities.

Thanks for your answers

 

[snow and steel]

I'm still highly suspicious that there is some electrical or RF noise, so before you spend any money - again, check another location. IF it goes away then the answer is to shield it.

Another thing you could check is another amp and or guitar at your lacation, but I sort of doubt that's it.

Keep us updated.

 

[TheDams]

Yep, as I said, that's what I think too... I'm just amplifying this electrical or RF noise with my body.

I'll try to bring my gear to another location when I'll have the time (lotsa work right now !).

Anyway, I'll shield it just to be sure... I have some copper tape leftover, it might be enough to shield the potz cavity, and maybe the jack and toggle switch's.

(If shielding's not enough, I could consider an EHX Hum Debugger. I heard it's a nice little add-on in a noisy gear... but, I can also live with that noise, it's not that bad, especially because I play for myself and don't do any recording)

Thanks again

 

[TheDams]

Just came back from a camping trip in South Dakota...

This morning, I spent 2 hours shielding cavities (that includes: potz, toggle switch AND jack cavities). I took my time to do it clean.

and........ hum is gone

So basically, that graphite paint is not enough to shield the electronic. A real shielding is needed.

 

[onegoodtrick]

Cool. Well done. And welcome to the madhouse. Perhaps you brought a friendly spirit back from the Dakotas that dosen't dig static.


onegoodtrick