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How to prevent amplifier from picking up interference from computer? - Page 3

post #31 of 50
Quote:
Originally Posted by stv014 View Post

 

From the OP - which states that the problem is fixed by a cheap ground loop isolator transformer, and nothing else - it is already quite clear that the noise is indeed caused by a ground loop. Another simple test is to connect the headphones directly to the sound card (which could possibly drive the headphones fine in the first place).

 

Thanks for clarifying. Good to know in case I have to troubleshoot, too.  have a Little Dot I+ getting here this week. I knew that the Little Dots are prone to ground loop problems, but am hoping I don't have to deal with it. 

post #32 of 50
Thread Starter 
Quote:
Originally Posted by cel4145 View Post

 

Thanks for clarifying. Good to know in case I have to troubleshoot, too.  have a Little Dot I+ getting here this week. I knew that the Little Dots are prone to ground loop problems, but am hoping I don't have to deal with it. 

I don't think it's just the Little Dots that are prone to picking up noise and/or suffer from ground loops. I've read that tube amps in general easily pick up interference noise.

 

Let us know if you run into any problems when you connect your Little Dot I+ to your sound card.

post #33 of 50
Quote:
Originally Posted by boyyo View Post

I don't think it's just the Little Dots that are prone to picking up noise and/or suffer from ground loops. I've read that tube amps in general easily pick up interference noise.

 

Let us know if you run into any problems when you connect your Little Dot I+ to your sound card.

 

Thanks! I should probably be OK. I can hook it up to the headphone output on the STX, or I have an HK 3390 receiver plugged up to the line outs on the STX running my speakers. The Little Dot can plug into the tape out on that if need be. 

post #34 of 50
Thread Starter 

Just to confirm what other people have said about it being a ground loop:

 

Other sounds can be picked up via a ground loop, as well: these include the sounds of your hard drive when its heads move around accessing different files; the scratchy sounds that you sometimes hear when you move your mouse; or those clicks caused by your graphics card re-drawing part of the screen display on your monitor screen. 

(from http://www.soundonsound.com/sos/nov04/articles/computerproblems.htm)

 

All of which are symptoms that I suffer from whenever I have my amp connected to the sound card. So this rules out, I would say, RF interference and so forth.

post #35 of 50
Thread Starter 

I have also read that A/C Isolation Transformers should be another problem solver to ground loops; which often is overlooked by consumers but preferred by musicians according to some source (I will try and find the website I was reading from)

 

Apparently it is preferred in computer systems and medical equipment. I could pick one up in my own country and try it out, then return it if it has no effect on my system.

post #36 of 50

I got the Little Dot I+, and I do get a little interference when plugged into my headphone jack (have not tried the other yet). It's not audible except when nothing is playing--very faint. I'll try to hook it up directly to the line out in the next few days and see what happens. 

post #37 of 50
Thread Starter 
Quote:
Originally Posted by cel4145 View Post

I got the Little Dot I+, and I do get a little interference when plugged into my headphone jack (have not tried the other yet). It's not audible except when nothing is playing--very faint. I'll try to hook it up directly to the line out in the next few days and see what happens. 

Does the noise get worse when your GPU is under stress? I.e. whenever you open a 3D application or any other program that puts load on the graphics card.

post #38 of 50
Quote:
Originally Posted by boyyo View Post

Does the noise get worse when your GPU is under stress? I.e. whenever you open a 3D application or any other program that puts load on the graphics card.

 

I'll have to try later on see. I don't normally keep games on my PC (or they keep me from getting work done smile.gif). 

post #39 of 50

Well, I didn't get to installing a game yet, but I did try my Little Dot I+ with the headphone output on the STX. Sounds great. No interference whatsoever. Dead silence.

 

So we have the opposite problem. 

post #40 of 50
Thread Starter 
To update: I have tried a medical grade isolation transformer, one running the amp separately, and the other time with the pc: while these devices serve as a galvanic isolator, the buzz and interference was not cancelled out through the ground loop. And having the amplifier on and then promptly disconnecting the AC cord, letting the amp run out on its power supply capacitor totally eliminates the hum and buzz, while still retaining the audio (until the capacitor runs out of power). Also, there is no hum or buzz when connecting the amp directly to my Macbook laptop. But that's a different story, since 1) there is far less noise and interference in that device, and 2) it isn't run from the power outlet, so the only AC power goes to the amp, which makes it impossible for a ground loop to take place.

I'm going to try connecting all devices to the same isolation transformer when I get two more power cables for its outputs. Will not that resolve the problem I will be having an electrician have a look tomorrow and see if he can come up with any clues. But at this stage I do think I will have to run an optical cable through the ST s/pdif to an external DAC, just like Davidzhezhe from Littledot recommended on the official site. I have also tried running the amp through another USB sound device much like a DAC, and the noise is still there. ST will be kept for the DSP, since selling second-hand and then buying a cheaper card will result in like 40 bucks in between anyway (if I decide to buy the cheaper card second hand, as well). I just hoped the A/C Iso transformer would be a solver, since I might run into the same issue when connecting a 5.1 speaker system to the card via the HDAV extension.
post #41 of 50

The important thing is to isolate the computer's ground from the amplifier's one; the only connection should be through the audio cable, once you add another (through the ground wires in the power cords), the interference will appear.

post #42 of 50
Thread Starter 
Yea, I know. That's what I'm trying to work around, which I thought the isolation transformer would help with in order to avoid lifting ground. I'll have to clear it up with my electrician tomorrow, I'm still new to this problem.

On a side note: I picked up an external DAC on demo from my local hifi retail shop and connected it via optical S/PDIF which resulted, as expected, in an elimination of the computer interference noise. I've been looking forward to using the Schiit Bifrost as my DAC while using the soundcard for the DSP effects in movies and games. But if I'm able to isolate the computer ground from the amp with a little help from my electrician I'll save a few bucks for a while... I'm still quite content with the DAC on the ST.
post #43 of 50

i've suffered from the same problem as you. my setup is computer>usb>dac>amp and it has been nightmare with ground loop noise. then i bought a usb isolator from ebay and it eliminated the noise 99% however, i noticed lowered sound quality. the cheater plug thing is dangerous to yourself and the equiments. so i think the viable solution is to buy a usb to spdif converter, like the musical fidelity v link, and that'll solve your problem, although it'll be costly!

post #44 of 50
Quote:
Originally Posted by angelsblood View Post

however, i noticed lowered sound quality.

 

A USB isolator should not audibly lower sound quality unless either the isolator has some problem or you have a poor DAC.

post #45 of 50
Thread Starter 
Quote:
Originally Posted by angelsblood View Post

i've suffered from the same problem as you. my setup is computer>usb>dac>amp and it has been nightmare with ground loop noise. then i bought a usb isolator from ebay and it eliminated the noise 99% however, i noticed lowered sound quality. the cheater plug thing is dangerous to yourself and the equiments. so i think the viable solution is to buy a usb to spdif converter, like the musical fidelity v link, and that'll solve your problem, although it'll be costly!
That's why I try to avoid isolators in general. Though I find it strange that it should affect the sound quality via USB. Could be a bad isolator or the DAC, but I'm certain that the problem lies in the USB isolator.

My electrician said he has a cable he ordered that he wants me to try out which should be shielded against the noise from the PC. I doubt it will help, but he wants me to try it out before he comes over to take a look at my wiring. When or if he resolves the problem I'll let you all know.

In the meantime I'm holding the trigger on buying the Schiit Bifrost and running it as my primary DAC via Toslink from my soundcard--where I might replace my Xonar Essence ST with an X-Fi Titanium for 5.1 surround to my speakers (which are Z906 and won't benefit much from the Essence STs H6 extension) and for CMSS-3D for games and movies. I'm not really a big fan of the positioning and effect of Dolby Headphone.
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