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Post subject: Amp squealing when connected to computer through AUX
Posted: Mon Mar 09, 2015 11:53 am
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Like in subject. When I'm connecting amp to my computer to play something with mp3 my amp is making constant, very annoying-squealing sound. Only when plugging to computer. When I use my cell phone it does not happen. I can fix this somehow?


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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Mon Mar 09, 2015 3:12 pm
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Dear Eddie The Trooper,

Thanks for your inquiry. Not sure what the problem is but let's try some of these steps. Go to your control panel and adjust the output level of your computer and see if this change makes a difference, If it doesn't I would test it with a secondary computer to eliminate the first , and I would also try different presets and see if that makes a difference, I hope this helps and please let us know if we can assist you further.

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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Mon Mar 09, 2015 6:59 pm
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If that doesn't help, you may have an AC ground loop.
You can remove extra grounds by using a 3 pin to 2 pin AC adaptor available at hardware stores. Put one on each ac cord to your computer system. tower, monitor and printer.
If that doesn't work, remove the adaptors from the computer system and put one on the amp.
The only chassis ground should be through the audio cable.
For safety, don't leave the adaptors on when you don't need them


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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Tue Mar 10, 2015 1:33 am
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I'd agree with TimsAudio that a ground loop is a likely culprit here.

Removing the earth/ground from either amp or computer may be a useful diagnostic, but this is not a good final solution. The ground connections are there for a reason, and you compromise your safety (and that of everyone else in your home, particularly children with prying fingers) if you leave equipment ungrounded that is designed to work with a ground connection.

Thus, I'd propose the opposite to "the only chassis ground should be through the audio cable" (particularly as the audio cable isn't even designed to carry a potentially large earth leakage current). Leave all the mains-supply ground connections in place; the place to break the ground loop is at the audio cable. You can do this quite simply by using an inline audio isolation transformer. Searching online for those three words brings up a plethora of suitable products, so you should be able to find something easily/cheaply.

For completeness, you can also get USB isolating connectors. I mention as if you're getting a ground loop with the audio cable, it's likely you'll also get a ground loop if you connect your amp to your computer via USB. So fitting isolating connectors on both may be a good idea.

Of course, it would be much better if the manufacturers of computers, amps and other audio equipment made their products with mains/ground isolation already built-in, given that their products are always going to be susceptible to this type of problem! (I suppose they don't to save on manufacturing costs and thus keep retail prices a few pence/cents cheaper, which only benefits those customers who then don't have to go and buy extra equipment to work round the problem...)


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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Tue Mar 10, 2015 3:56 am
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TimsAudio wrote:
If that doesn't help, you may have an AC ground loop.
You can remove extra grounds by using a 3 pin to 2 pin AC adaptor available at hardware stores.

There is a reason why those are banned in the EU. But go ahead, make all those nice metal cases ungrounded and hope to hell that no live wire comes loose anywhere, ever.

A better and less potentially lethal advice would be using cables with ferrite cores, and move amp and PC as far apart as possible.


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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Tue Mar 10, 2015 6:00 am
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Thnx for your replies
I'm complete technical ignorant so please forgive me ;) This thing is strange. The squeal before was quite loud to the point that it was very uncomfortable to play that way. However now it is much more quiet and to some level acceptable although it would be better without it. Actually I don't think I have done something. All I did was some random things in control panel :P, which hadn't have any effect at that time. Later I plug it in once more and was much better. But the problem probably was not fixed it will probably return
All I noticed for now: there is no squealing when amp is only plugged to computer through USB without AUX conection. There is very little squealing when Amp is not plugged through USB but connected with AUX. And finally, the biggest noise is when amp is both connected through USB and AUX at the same time.
So right now the easiest way to enjoy playing with mp3 through my amp is to either save currently used presets to amp bank without connecting it through USB and using FUSE or to play mp3 trough my phone which is little bit less practical.
later eventually i will try those audio isolation transformer

Quote:
Go to your control panel and adjust the output level of your computer and see if this change makes a difference


maybe stupid question but what actually should I adjust? I see in my audio control(it's laptop) panel two speaker and phones devices, some SPDIF audio codec(disabled) in playback tab. In record tab there are only two microphones, some high definition audio codec(also disabled) and i can see mustang there when it's plugged through USB

Quote:
and move amp and PC as far apart as possible

oh, i even though that maybe this can be the problem. My amp(Mustang I V1) is on the table next to my laptop. This is quite comfortable for me because i almost don't use amp's knobs, only FUSE ;) and also here I'm practicing with mp3 and guitar pro so it's easier for my to manage all this things. Also I thing that now it's sounds better than when it was on a floor. There is also drawback of such thing, the amp is probably to close to me . Right now i can't put it somewhere else except back to the floor.


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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Tue Mar 10, 2015 7:51 am
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Quote:
the biggest noise is when amp is both connected through USB and AUX at the same time

Keep the audio cable as far away from the USB cable as possible. From the way you describe your setup, the two may be running side-by-side between amp and computer? The USB cable will introduce noise into the audio cable, so move the cables around to minimise this.

Also, keep the audio cable away from mains cables, any other network, computer or audio cables, in fact any other cable at all. Also keep the audio cable away from your computer (except obviously where it plugs in :-), printer, keyboard, monitor, etc, etc. Use the shortest possible audio cable, and keep it straight-ish. Certainly don't coil-up excess cable: a looped cable will have more problems for a variety of reasons, and the more turns in the loop, the worse it gets.


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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Tue Mar 10, 2015 8:17 am
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Eddie The Trooper wrote:
Quote:
Go to your control panel and adjust the output level of your computer and see if this change makes a difference


maybe stupid question but what actually should I adjust?


Turn the volume all the way down on the laptop and turn the MASTER all the way down on the amp. Play some audio on the laptop (like a CD). Then connect the computer to the amp with the audio cable. Turn the MASTER up just a little on the amp, and then turn the volume up just a little on the laptop. Keep repeating the process, turning each up a little at a time until you either hear music or the squealing sound you mentioned.....

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Post subject: Re: Amp squealing when connected to computer through AUX
Posted: Tue Mar 10, 2015 4:47 pm
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scott-uk wrote:
Quote:
the biggest noise is when amp is both connected through USB and AUX at the same time

Keep the audio cable as far away from the USB cable as possible. From the way you describe your setup, the two may be running side-by-side between amp and computer? The USB cable will introduce noise into the audio cable, so move the cables around to minimise this.

Also, keep the audio cable away from mains cables, any other network, computer or audio cables, in fact any other cable at all. Also keep the audio cable away from your computer (except obviously where it plugs in :-), printer, keyboard, monitor, etc, etc. Use the shortest possible audio cable, and keep it straight-ish. Certainly don't coil-up excess cable: a looped cable will have more problems for a variety of reasons, and the more turns in the loop, the worse it gets.


Haha. Simplest solutions are always the best :) Everything is great now. Thnx


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