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Noises when using receiver through PC

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Hi all. Basically my audio setup goes FLAC/320K MP3 > X-Fi Titanium (Sound Card/PC) > Sansui R-50 > Audio-Technica ATH-AD700

Here's where the problems start. When I'm using the receiver with the PC, moving the mouse, scrolling on a web page, or generally doing anything generates an audible buzzing/mosquito noise through the headphones. This noise is non-existent when I'm using the cans straight from the PC, but obviously, audio quality suffers because of that.

Listening to the receiver through FM produces no such noises.

Apart from some minor issues (crackling when adjusting volume/treble, easy fix for that, and the Channel A speaker in/out doesn't work) everything works fine.

What's the issue here? From my limited understanding (I'm mainly a PC guy) it's a grounding or interference issue. The noise is only there once the receiver is introduced into the system.

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Sounds like a ground loop to me. I had this exact issue with my USB DAC and my PC. I now use a USB isolator to eliminate the problem.

I believe that there are also line-level isolators that will eliminate your problem, but I have no experience with them.

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How would you suggest I fix this? What is a ground loop? What is a USB Isolator and what exactly does it do?

Thanks.

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Guess I'm off the Jaycar on Monday. Thanks.

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I just got one of these to isolate noise coming in to my miniDSP analogue in from my Sony TV.

 

Seemed to sound a bit "tizzy", so I measured it in Room EQ Wizard plugged into a USB soundcard.. seems to have quite a bit of 3rd harmonic distortion, especially in the lower frequencies (i.e. 5% at 40hz).

 

graph of it's frequency response, in REW, with the lower lines being THD, 2HD, 3HD, etc...

http://pix.minirig.org.au/main.php?g2_itemId=5044&g2_imageViewsIndex=2

 

same measurement done with just a short RCA cable in loopback, dead flat response and much lower distortion (would be the THD of the A->D and D->A rather than the RCA cable).

http://pix.minirig.org.au/main.php?g2_itemId=5049&g2_imageViewsIndex=2

 

hitech measurement rig:

http://pix.minirig.org.au/main.php?g2_itemId=5034

 

Note that apart from sounding a bit rough, it did get rid of the noise leaking into my miniDSP from the TV. Since TV is rubbish anyway I'll keep using it until a better solution presents itself.

 

why don’t I use the digital out from the Sony TV? because the miniDSP only does PCM SPDIF, so whenever the Sony TV goes to a HD channel with dolby encoded digital audio we get a blast of noise... so back to analogue stereo audio it is.

Edited by zog

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Zog,

 

Is the annoying noise present when the tv is on and no sound playing? 

 

If yes, what happens when you disconnect the antenna cable?

 

If that fixes the problem it may be a better solution to get an isolation transformer on the antenna cable rather than on the single ended stereo cables. I am waiting on them to come back in stock here - http://www.bluejeanscable.com/store/rf/index.htm (see bottom of page) I believe that Hills also make an isolation device that protects against surges and needs a connection to the mains earth. I couldn't get my hands on one because I don't have the requisite licenses so I think you'd need to get a licensed electrical contractor to fit them.

 

Which minidsp are you using? It may also be a PSU grounding problem.

 

I have a similar problem and once my workbench is clear of a few other projects I'm planning on trying both of the above.

 

Cheers,

Chris

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Zog,

 

Is the annoying noise present when the tv is on and no sound playing? 

 

If yes, what happens when you disconnect the antenna cable?

 

I haven't checked the antenna cable, but the extra bit of info here is the TV gets main use nowadays as a PC monitor (youtube, big web browser, and flac playlist manager has been taking over from TV). It is connected via HDMI to the PC, and a lot of the noise is related to moving and resizing windows when it's in use as a monitor.

 

If that fixes the problem it may be a better solution to get an isolation transformer on the antenna cable rather than on the single ended stereo cables. I am waiting on them to come back in stock here - http://www.bluejeanscable.com/store/rf/index.htm (see bottom of page) I believe that Hills also make an isolation device that protects against surges and needs a connection to the mains earth. I couldn't get my hands on one because I don't have the requisite licenses so I think you'd need to get a licensed electrical contractor to fit them.

 

Which minidsp are you using? It may also be a PSU grounding problem.

 

I have the basic miniDSP 2x4, with miniDIGI for extra digital inputs. My DVD player and computer are connected by digital in (optical SPDIF from the PC for maximal noise isolation), and I'm using a jaycar 12V linear power supply with the miniDSP. All amps, and the miniDSP have "groundloop protection" and run quiet except for unavoidable amp hiss (high efficiency speakers direct into class D amps) audible only near the drivers.

 

The TV (with it's connection to the antenna and the PC via HDMI) is the "weakest link" here..

 

Except when I plug the analog ins and get the digital hash audible from the couch, and sound changes as I moved and resize windows...

 

Another solution would be a unit that converts dolby spdif to stereo PCM spdif signals, but these dont appear to exist at affordable prices.

Also a small A-D converter with optical out might help.

 

 

I have a similar problem and once my workbench is clear of a few other projects I'm planning on trying both of the above.

 

Cheers,

Chris

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encoded digital audio we get a blast of noise

 

Shame you cannot set your TV to output PCM, rather than encoded audio.     Most can.

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Shame you cannot set your TV to output PCM, rather than encoded audio.     Most can.

 

I've looked through the menu options and read the manual, nothing apparent. I haven't tried updating the firmware etc, its a Sony LCD a couple of years old now (model KDL-40EX400 I think).

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Is it a wired or wireless mouse? RF or bluetooth? Try disconnecting the HDMI cable between tv and computer, then see if you can reproduce the noise, does the noise still show up?

 

Are the computer and tv and minidsp and amps all connected to the same wall socket?

 

Can you re-arrange the analogue cables to separate them from other equipment?

 

Does the HDMI cable have a ferrite ring on it?

 

 

Basically we need to find a way to decide if it is radiated or conducted noise that is getting into the analogue cable. If removing the HDMI connection fixes the problem, then it is likely conducted noise, if not then probably radiated noise. I suspect it is conducted noise and probably 'blitter noise' is the term for this sort of issue.

Edited by hochopeper

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Here's where the problems start. When I'm using the receiver with the PC, moving the mouse, scrolling on a web page, or generally doing anything generates an audible buzzing/mosquito noise through the headphones. This noise is non-existent when I'm using the cans straight from the PC, but obviously, audio quality suffers because of that.

 

IIRC the fact that the noise stops when you stop moving the mouse (etc) means it is not a ground loop but is interference from the PC power supply, when "doing anything" on the PC causes its PSU to flick into 'high power' mode. I had this once.

 

I can't recall EXACTLY what I did to fix it :( but logically using a digital out from the sound card is a good idea but then you need an external DAC as your receiver has no digital inputs.  :(

 

Other solutions:

 

- swap out the PC PSU for a better one. This is risky that the new one is no better, but if you are a PC guy you may have several to hand and it is a quick operation for you.

 

- try to block any EMI within the PC e.g 'wrapping the PSU or the soundcard or cables.

 

- move the soundcard out-of-box with an extension ribbon, and put it in a metal case.

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Shame you cannot set your TV to output PCM, rather than encoded audio.     Most can.

 

I just looked again (while looking for the firmware upgrade option) and I did find the option for this.. so now I can use my optical cable and get rid of the noise the "proper" way.

 

Thanks Sony for having two completely different audio settings menus in different places with overlapping, but different options available.

 

I've looked through the menu options and read the manual, nothing apparent. I haven't tried updating the firmware etc, its a Sony LCD a couple of years old now (model KDL-40EX400 I think).

 

Correction,  a KDL-40EX500.

 

Is it a wired or wireless mouse? RF or bluetooth? Try disconnecting the HDMI cable between tv and computer, then see if you can reproduce the noise, does the noise still show up?

 

Are the computer and tv and minidsp and amps all connected to the same wall socket?

 

Can you re-arrange the analogue cables to separate them from other equipment?

 

Does the HDMI cable have a ferrite ring on it?

 

Wireless mouse (not bluetooth), the audio and PC gear all on different wall sockets and powerboards, except for the TV.

 

Thanks for the suggestions to try, but I think finding the force PCM option has sidestepped the problem for me.

 

..now maybe I can sell this C9555 "buzz hum isolator" to Portishead for doing the scratchy trebly vocal effects on their next CD...

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I mentioned this happening to me in another thread.

 

I didn't used to get it with my old wireless mouse (2.4Ghz).....................but I got a new fangled 5.00Ghz model to try out and I get the damned noise when making mouse movements!

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