Hum and noise problems

Q & A for building and interfacing your rack gear with Ground Control Pro and GCX-based systems.
andefeldt
Posts: 25
Joined: Mon Feb 20, 2017 3:59 am

Hum and noise problems

Post by andefeldt » Wed Mar 15, 2017 8:44 am

Hi,

I've connected all the pedals and cables in my system (8 pedals connected to GCX and GCX out to TC G-Force).

To my surprise I have a large amount of hum when I turn it all on. I've been trying to figure out where the hum was coming from. I tried eliminating pedals and bypassing my power conditioner (Samson PowerBrite PB10) but that did nothing.

I noticed that the same hum (although lower volume) also was present from the rack itself. It turned out to be the power supply to the GCX that was humming. If that's the same hum that's amplified in the GCX through the cables, I don't know, but it's the same frequency as far as my ears can hear. I guess it's 50 Hz hum.

Is the power supply the cause of my problems with hum?

Also, when turning on a loop it results in a "pop" sound, quite noticeable. However, this is mostly noticeable when turning on a loop placed later in the chain than the current effects, eg:

Loop 1,2 and 3 are on. Pop sound occours if turning on loop 4, 5, 6, 7 or 8.

Loop 6 is on. Pop sound if turning on loop 7 or 8. Almost no pop sound if turning on loop 1, 2, 3, 4 or 5.

What could be the cause of this?

- My rack units are all separated from each other and I've placed plastic washing between each unit and the rack mount.
- All pedals are powered by Voodoo Lab PP2+ (except for Chandler Tube Driver and Whammy which both have their own power supply).
- I've tried connecting guitar in Guitar In, Loop 1 and via Guitar Out/Feedthrough. Nothing helped.

I hope someone can help out.

andefeldt
Posts: 25
Joined: Mon Feb 20, 2017 3:59 am

Re: Hum and noise problems

Post by andefeldt » Wed Mar 15, 2017 11:05 am

Forgot to mention that the power supply for the gcx is labeled "Sceptre" 9VAC, 3.4A, so the hum isn't due to lack of current.

JohnClark
Posts: 7092
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: Hum and noise problems

Post by JohnClark » Wed Mar 15, 2017 12:12 pm

Does the noise change if you move the power supply away from the rack?

3.5A!? I'm not so sure that is the power supply that came with the GCX. Ours are 1A or 1.2A depending on the country it is going to.

andefeldt
Posts: 25
Joined: Mon Feb 20, 2017 3:59 am

Re: Hum and noise problems

Post by andefeldt » Wed Mar 15, 2017 1:30 pm

I bought it all second hand, so I guess it's not the original power supply.

But I just tried moving the power supply out of the rack and boom, almost no noise at all. A little hum very faint in the background back nothing besides that. Broken power supply or should I just try different locations in my rack?

And what about the pop noise? That's still there :cry:

andefeldt
Posts: 25
Joined: Mon Feb 20, 2017 3:59 am

Re: Hum and noise problems

Post by andefeldt » Wed Mar 15, 2017 1:57 pm

Ok, just had a few more tests.

With my strat with active PU's I experience a little hum and then just the normal hiss from pedals. But with my Les Paul (humbucker) I got a lot of hum and noise when not touching any metal parts on the guitar. Ground loop?

When turning down the volume on the guitar it self the hum disappears. I have another guitar with humbucker PU's that acts the same as my Les Paul.

So where do I go from here?

bettsaj
Posts: 190
Joined: Fri Jun 11, 2010 12:13 pm
Location: Darkest Suffolk UK
Contact:

Re: Hum and noise problems

Post by bettsaj » Thu Mar 16, 2017 7:27 am

andefeldt wrote:And what about the pop noise? That's still there :cry:
Have you got the G-Force going through one of the GCX loops??
"My technique is laughable at times. I have developed a style of my own, I suppose, which creeps around. I'll never be a very fast guitar player."

David Gilmour

andefeldt
Posts: 25
Joined: Mon Feb 20, 2017 3:59 am

Re: Hum and noise problems

Post by andefeldt » Thu Mar 16, 2017 7:37 am

Nope. G-Force is connected after loop 8.

Chain is:

Board: guitar-Tuner-wah-buffer -rack

Rack: gcx - G-Force - output
Gcx:
#1 whammy
#2 demeter compulator
#3 ibanez ts7
#4 chandler tube driver
#5 byoc large beaver
#6 boss ge-7
#7 EHX small Stone
#8 boss Ce-5

JohnClark
Posts: 7092
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: Hum and noise problems

Post by JohnClark » Thu Mar 16, 2017 10:11 am

The hum that happens when you aren't touching the guitar could be the guitar itself... it shouldn't be a ground loop, rather its more likely a lack of a solid ground connection somewhere. Can you try plugging the guitar in further down the line as a test to find if it is in fact happening in the rig?

For instance, skip the pedalboard and connect your guitar straight to the rack and test. If it still doing the same thing skip any front end effects and connect the guitar to the front of the amp.

Let us know what you find!

andefeldt
Posts: 25
Joined: Mon Feb 20, 2017 3:59 am

Re: Hum and noise problems

Post by andefeldt » Fri Mar 17, 2017 2:06 am

Ok, tried it all now. All is when not touching strings

1: Through board: Noise and hum
2: Straight into GCX (skip board): Noise and hum
3: Straight into G-Force (skip board and GCX): Noise
4: Straight into computer soundcard (all running on the same power outlet): Noise

The noise level is the same so I guess that's the "normal" noise level frmo the guitars when not touching the string.

When touching the strings the hum is still present in scenario 1 and 2, but no hum at all when skipping the gcx. This is with the power supply outside of my rack. If I move the power supply back into my rack (tried various places) the hum level is increased many times.

If I listen to the power supply (outside the rack), I notice it makes a constant humming (sound higher in frequency than the hum I get in my speakers - but that could just be my ears playing tricks on me :-) ).

So, do I have a faulty power supply?

JohnClark
Posts: 7092
Joined: Tue May 05, 2009 2:33 pm
Location: The Lab

Re: Hum and noise problems

Post by JohnClark » Fri Mar 17, 2017 1:12 pm

The power supply... I have no idea what you actually have there. It is not the power supply that we ship with the GCX. That it is rated for 9VAC @ 3.5A could mean that with a load of only about 600mA the voltage might be rather high. I would recommend getting a replacement power supply from us or at least finding one that is spec'd similarly to the original of 9VAC @ 1A.
Also, if you can hear noise from the power supply itself, I'd dare say it needs to go away.

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