Strange interference, here's a challenge for you!

P

Phil66

Member
Hello everyone,
To save me typing everything out to try and explain, please visit my thread Which Recording Interface? where I've posted this issue after getting advice on which recording interface to get.

I'm baffled by this, hopefully someone here won't be.

Thanks for your time folks :)

Phil
 
The description of the problem on the linked site is not helpful to me, perhaps someone else can follow it. However, anytime you can bypass a piece of equipment and the problem is no longer present, you have successfully found the offending device. I wish your signal chain was stated more clearly but if I followed the summary, the signal is quiet as expected when you bypass something. Time to have that something looked at.

Best of luck!
-PC
 
The noise sounds similar to the computer noise I have via my monitor controller when one input is from a separate PC than my recording PC.

I am sure that doesn't help at all...
 
cecerre said:
The description of the problem on the linked site is not helpful to me, perhaps someone else can follow it. However, anytime you can bypass a piece of equipment and the problem is no longer present, you have successfully found the offending device. I wish your signal chain was stated more clearly but if I followed the summary, the signal is quiet as expected when you bypass something. Time to have that something looked at.

Best of luck!
-PC
Click to expand...

Thanks,
I think I'll bin it :)
Ok, signal path. Guitar into Art Coolswitch. Outputs from Coolswitch: one goes into Focusrite Scarlett (via a desktop effects processor), the other goes to an amp head. It's when I plug the output into any of heads that I get the noise. The Vox gives more noise than the Peavey head BUT what I find odd is that the noise has evidence of the effects being used in the effects processor, you can hear that more on the soundcloud player that says "Vox various patches" here Which Recording Interface?
The thing is, the effects processor is only routed into the Focusrite interface, it's not sent to the Coolswitch.
Very odd.
Thanks
 
Phil66 said:
Thanks,
I think I'll bin it :)
Ok, signal path. Guitar into Art Coolswitch. Outputs from Coolswitch: one goes into Focusrite Scarlett (via a desktop effects processor), the other goes to an amp head. It's when I plug the output into any of heads that I get the noise. The Vox gives more noise than the Peavey head BUT what I find odd is that the noise has evidence of the effects being used in the effects processor, you can hear that more on the soundcloud player that says "Vox various patches" here Which Recording Interface?
The thing is, the effects processor is only routed into the Focusrite interface, it's not sent to the Coolswitch.
Very odd.
Thanks
Click to expand...
Still no clear signal path (and WTF is the FX processor?) !

Does the AI plug into a desktop PC or a laptop? If the latter, is it mains powered and if so does the noise cease if you run on battery power?

I am sure you have an earth (aka, ground, hum) loop that is manifesting itself as digital hash.
You need to break the earth path to one device, either AI or head. Best done with a 1:1 transformer unit (Google Orchid Electronics) but you would need some form of buffer on the guitar to give a low impedance feed.
You could try removing the screen from one end of say, the amp feed cable.

DO NOT UNDER ANY CIRCUMSTANCES REMOVE ANY MAINS EARTHS. No matter WHAT you might read or be told!

Dave.
 
The fx processor is a Boss GT-001. The AI plugs into a PC. When these noises are created the guitar and amp volume are both fully down.
How is the effected signal from the GT-001 getting to the monitors when I plug a cable into the other output socket on the Coolswitch?
Cheers
 
Phil66 said:
The fx processor is a Boss GT-001. The AI plugs into a PC. When these noises are created the guitar and amp volume are both fully down.
How is the effected signal from the GT-001 getting to the monitors when I plug a cable into the other output socket on the Coolswitch?
Cheers
Click to expand...

ACTIVE! Monitors? (ffs!) Another potential earth loop path.
The good news is theta the BOSS FX box is almost certainly fully buffered so you could put a transformer "braid breaker" just after that.

Ground loop noise is often very counter-intuitive and demands a cut and try approach. So long as you keep safe, what works....Er...WORKS!

if you Google "earth isolator" you should find a black cylinder device with two pairs of RCA phono leads. This is a "low fi" loop isolator and woks well as such. Once you have proved the problem, buy better. Should get the cheapy well under $10 ppaid.

Dave.
 
Plug the guitar straight into the Focusrite. If that's clean, start adding your bits and pieces one at a time until you find a culprit. If that's not clean, find something else to plug into the Focusrite to see if it's the interface or the guitar/pickups.

My personal guess (and only a guess) is that you have too much processing going on, mostly unbalanced, and there's interference or a mismatch somewhere along the line.
 
Bobbsy said:
Plug the guitar straight into the Focusrite. If that's clean, start adding your bits and pieces one at a time until you find a culprit. If that's not clean, find something else to plug into the Focusrite to see if it's the interface or the guitar/pickups.

My personal guess (and only a guess) is that you have too much processing going on, mostly unbalanced, and there's interference or a mismatch somewhere along the line.
Click to expand...

Thanks Bobbsy,

Yeah it only happens when I plug an output from the Coolswitch into any of the heads. I'm just worried about buying a better switcher if it is somewhere else and the Coolswitch is highlighting it. Even if I plug the guitar in an analogue drive (I use one of these HOT BIRD) without much gain just to add a bit of responsivness, before the Boss the sound is clean.

Cheers

Phil
 
OK, I've sorted the noise problem. I tried the Ground Loop Isolator in between my Boss GT-001 and my Focusrite and it made it worse so I put one of the leads from one output of the switcher to the input on my Focusrite. The other output goes to my head. All noise gone except for the usual gain hum that you get.

Only problem is, when I switch from output to just the amp to outputting to both amp and interface I get a volume drop AND a tonal change from the amp. Any ideas?

Cheers folks, Here is a soundcloud first with single output second with output to amp AND interface.

You can hear the sound here >>>> Which Recording Interface?
 
You must log in or register to reply here.
Back
Top