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PC sound in signal path

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Re: PC sound in signal path

Postby Hugh Robjohns » Sun Aug 18, 2019 8:52 pm

Leftyjay wrote:Even if the Atomic amp is off? I mostly play through headphones, with the Atomic amp at off.

Yes. It's not about whether the amp is on or off. It's the physical connection to it that makes the Ground loop. The connection via the audio connection cable's screen and the amp's mains safety earth.

The transformers in the isolation box break that direct connection and thus remove the ground loop.

If you mostly use headphones, then try unplugging the audio feed to the amp, or unplugging the amp from the mains outlet. If the unwanted noise is due to a ground loop I will go away when you unplug the amp.

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Re: PC sound in signal path

Postby Leftyjay » Mon Aug 19, 2019 4:00 am

I will check more in depth this week, but FYI, when I unplug the USB cable in the back of the eleven rack, both anyone noises goes away completely.
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Re: PC sound in signal path

Postby CS70 » Mon Aug 19, 2019 6:41 am

Leftyjay wrote:I will check more in depth this week, but FYI, when I unplug the USB cable in the back of the eleven rack, both anyone noises goes away completely.

Many cheap USB cables aren't shielded well or at all, which could be the source of your problem, or at least a contributing factor if they act as an antenna. The challenge is that it's hard to say which ones are which without measuring or opening them up - price alone is not a proxy for quality unless you get the ones which gold-plated connectors which are very expensive (and even then). You could try to google for specific brands.

Worth a try if you have other cables laying about.
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Re: PC sound in signal path

Postby ef37a » Mon Aug 19, 2019 8:40 am

Late on parade I know but these,
https://www.amazon.co.uk/AV-Link-Ground ... th=1&psc=1

Are surprisingly good for the money. They are cheap enough to buy in as a test device and if they fix the earth loop problem, fork out for better. Note, although the audio performance might not be top class they do just as good a job of isolating grounds as expensive transformers. (but then this IS only guitars!)

Point about self built PCs. Check that all the MOBO mounting screws are present and correct. Even if they are, check with a meter that the PCB pad is indeed grounded by the screw, a layer of resist can prevent this and, AFAIK the EM spec' of a computer depends upon complete bonding of the MOBO ground plane to the case? (Please do NOT tell me you embarked on PC fettling without a DMM?!)

Also, if chicken foil fixes the PC radiation you could seek out some Perforated Zinc. Still see the pretty lights through it but the holes are around 1.5mm so a "stop" up to several Gigs.

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Re: PC sound in signal path

Postby ef37a » Mon Aug 19, 2019 8:49 am

CS70 wrote:
Leftyjay wrote:I will check more in depth this week, but FYI, when I unplug the USB cable in the back of the eleven rack, both anyone noises goes away completely.

Many cheap USB cables aren't shielded well or at all, which could be the source of your problem, or at least a contributing factor if they act as an antenna. The challenge is that it's hard to say which ones are which without measuring or opening them up - price alone is not a proxy for quality unless you get the ones which gold-plated connectors which are very expensive (and even then). You could try to google for specific brands.

Worth a try if you have other cables laying about.

I have a couple of USB A to Bs that have a transparent cover so it is obvious that they have a shield, a good quality braided shield in these cases (these are clear but I have seen red and blue see thru' jobbies) . Another trick is to try some clip on ferrites. Maplin (GRTS. Joney Mitchell had it right!) used to do a range but I dare say 'Zon have them.

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Re: PC sound in signal path

Postby Hugh Robjohns » Mon Aug 19, 2019 9:46 am

Leftyjay wrote:...but FYI, when I unplug the USB cable in the back of the eleven rack, both anyone noises goes away completely.

Yes, I appreciate that... but it's very hard to break a ground loop via a USB cable, and much easier via the audio cables feeding other equipment...

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Re: PC sound in signal path

Postby CS70 » Mon Aug 19, 2019 10:14 am

Browsed thru the thread and just realized you gave an important clue some posts ago - the sides of your pc case aren't metal but acrylic or glass.

If they're large enough (as they probably are) they will break the Faraday cage made by the case by and cause EMI in the surrounding space. Basically anything that's not a metal case will do that.

In that case, for your playing moments you can simply build a little shield made by aluminium on a light wood frame enclosed in plastic sheets (plastic foil works fine even if ugly :)) and attach it on the side with velcro, so you can remove it when you want the pc to look good.

Also, some motherboards also have options to reduce immediate interference ("spread spectrum") - you could check if yours have it and turn it on in the BIOS.

Good advice on possible ground loops and screws properly set as well. But a non-metal case will cause RFI in almost all cases.
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Re: PC sound in signal path

Postby Leftyjay » Mon Aug 19, 2019 12:51 pm

CS70 wrote:
In that case, for your playing moments you can simply build a little shield made by aluminium on a light wood frame enclosed in plastic sheets (plastic foil works fine even if ugly :)) and attach it on the side with velcro, so you can remove it when you want the pc to look good.

Also, some motherboards also have options to reduce immediate interference ("spread spectrum") - you could check if yours have it and turn it on in the BIOS.

Ill try the setting in the BIOS. as for the case, since the noise goes completely away when simply unplugging the usb cable from the 11r, woulndt that mean that the noise is purely caused by ground loops and not interference (RF, EMI)?
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Re: PC sound in signal path

Postby CS70 » Mon Aug 19, 2019 1:07 pm

Possibly, and could be the issues are related..

by the way, how old is your 11r?
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Re: PC sound in signal path

Postby Leftyjay » Mon Aug 19, 2019 5:58 pm

11R is several years old...but it's irrelevant now since I just bought a Focusrite 2i2. I wanted to buy one to be able to play and monitor in real time at 92khz with low latency. I must say btw, wow. 92khz with less than 5ms and no clipping, that's awesome. I also bought a balance 1/4 cable to hook up the Atomic and the 2i2.

With that being said : the amp still do sounds like crazy, doing all those wierd noises again. Funny though is those noise, even though I was able to control them with the noise gate, are now completely gone when playing with headphones.

I'm getting there I guess.
Next step : now maybe the ART hum eliminator would worth a try since the problem is not there anymore when playing with headphones.
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Re: PC sound in signal path

Postby CS70 » Tue Aug 20, 2019 9:23 am

The reason I asked is because some of 11 rack's first run had a known grounding issue on the "output to amp" jack.
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Re: PC sound in signal path

Postby Leftyjay » Tue Aug 20, 2019 2:13 pm

CS70 wrote:The reason I asked is because some of 11 rack's first run had a known grounding issue on the "output to amp" jack.

I don't think I have this issue since when I unplug the 11r from the pc, it all goes away. Anyway, I just bought a Focusrite 2i2 and I will keep the 11r has a backup for now.

That whole thing drives me nut, but I realize that I probably have the worst environement. Did I told you that the router is 15 feet away? Not helping the noise issue for sure.
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Re: PC sound in signal path

Postby Leftyjay » Tue Aug 20, 2019 6:12 pm

Just in case you still care :)

I've plugged the computer with a cord extension in another. the PC itself hasn't moved, just where it is connected.

90% of that anyoing noise is gone ! I can live with the rest since the noise was a lot more worse on the Amp vs listening directly through headphones.
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Re: PC sound in signal path

Postby Wonks » Tue Aug 20, 2019 7:07 pm

Nice!

It does seem to imply that most of the noise is due to a ground loop, though it is worth checking on the ground connection for the power lead in the original socket, and that the ground for it is connected properly.

Have you got a power socket tester handy?
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Re: PC sound in signal path

Postby Leftyjay » Thu Aug 22, 2019 6:52 am

Wonks wrote:Nice!

It does seem to imply that most of the noise is due to a ground loop, though it is worth checking on the ground connection for the power lead in the original socket, and that the ground for it is connected properly.

Have you got a power socket tester handy?

Even better. A friend that knows more than me about electricity :)

Ill check the socket and identify the culprit but in the meantime, ill just buy an extension to connect the pc at the other end of room (room is pretty large)
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