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Strange alt whine when more than 2 channels (LONG)

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  • Strange alt whine when more than 2 channels (LONG)

    All –

    My alternator whine issues continue. As some of you know, I have a two page thread now as folks have tried to help troubleshoot this. In light of the fact that I’ve performed additional troubleshooting recently, as well as identified a peculiar problem which did not exist previously, I wanted to start a new thread, and hopefully I can get the same quality assistance I’ve had.

    I’ve quoted the relevant parts of my original post below. I have tried virtually everything I can think of, and I can’t fix this problem – completely, anyway. Here’s something interesting, though: before, as noted below whenever I had just one cable plugged into my PC and driving two channels on my amp, I had a loud humming noise, that went down to the usual high-pitched whine when I plugged in additional channels. NOW, when I have just one channel plugged in, the hum AND THE WHINE is virtually gone – but if I plug in additional channels the whine is back! Now I have replaced the amplifier, but in light of the fact that I’ve basically ruled out the amplifier as the source of my problem (when all channels are active, I get the same level and type of high-pitched whine – regardless of which amp I am using). I’ve switched cables and also the channels driven and the behavior stays the same – drive 2 channels, beautiful, drive 4 or 6 (depending upon which amp I am using at the time) and the whine is very clearly there.

    So, I have a Shuttle-type AMD64 Sempron w/Nvidia 5200, Audigy 2 NX USB, SIR-ALP1 Sirius receiver, wireless card, USB Bluetooth dongle, and Xenarc touchscreen running off of a 400W Coleman inverter. It feeds into an Audiobahn 6601X 6-channel amp which is then wired back into my factory harness to output to the 6 factory speakers on my Chrsyler 300C. I disconnect the Sirius, etc. when troubleshooting to minimize the number of connections and possible sources of problems.....

    Here is what I’ve tried and what I know:

    1) engine off, no whine, sounds AWESOME, even with the cheapo factory speakers
    2) engine on, whine present, remove RCAs in to amp and no more whine (this means the amp and speakers have no loop, anyway)
    3) plug in RCAs, whine present again. NOTE: changing cables (I have Monster cables 3.5mm to RCA) doesn’t help. When plugging in, if only 1 cable (pair of RCAs) feeding any two channels is present, I hear a LOUD hum in amp….sound drops to the standard high-pitched whine when 2nd RCA pair is plugged in. Is this evidence of the ground being worse until the 2nd pair permits additional flow THROUGH the amplifier? Dunno, I’m EE challenged…)

    4) All RCA ends plugged in, I next remove the 3 3.5mm ends from the Audigy 2 – no whine. I plug them into 3 turned off mp3 players I have just for grins to see if it is some strange electrical ghost – STILL NO WHINE. Looks like it is the PC or USB adapter…. Plug it back in to USB adapter, whine returns….

    5) Screw wire into outside of case of PC where it also screws into PSU and ground to car… improvement.

    6) Disconnect Audigy 2 NX from PC and disconnect power from USB sound card as well. WHINE STILL PRESENT! As best as I can tell, this is a plastic case, and it is not making contact with anything metal that might be an alternative ground, so what the heck????

    Does anyone have any other ideas? FWIW, I have also previously plugged the 3.5mm jacks into the onboard sound of the PC motherboard (it supports 6-channel, just not powerful enough for good loud sound) and the whine was there, so it almost seems to me that it is something about the amp flowing current back through any device plugged into it with more than one cable.
    I’ve tried all of the following as well to troubleshoot the behavior, to no avail.

    1. Replaced the amplifier.
    2. Replaced the 3.5mm to RCA Monster cables.
    3. Snipped the ground in the USB cable to the Audigy NX. (Has since been replaced w/ a normal cable.)
    4. Uninstalled the amp, reinstalled, uninstalled.
    5. Tried 3 ground loop isolators.
    6. Separated power wires from audio wires.
    7. Tried using the onboard audio as well as the USB soundcard.

    So, does anyone have any theories as to why I still have problems and why this unusual situation exists?

  • #2


    • #3
      what about grounded RCAs?


      • #4
        I noticed with my wife's Pioneer DEHP-8600MP I had to flop the front left and rear left channels because if I hooked it all up 'straight', I'd get really nasty noise, by flopping the channels to the inputs (front left to 3 instead of 1, rear left to 1 instead of 3) and just rearranging where the speakers were wired into the amp, it went away. No idea why...try switching around where you plug in the RCAs into which channel to see if there's a certain combination that'll work, and just rewire the speaker outputs accordingly.


        • #5
          I'm suffering a similar !%&*£$&ing problem which is slowly !%£$&*ing me off!

          I'm only running a four channel set up though. I have two 3.5mm to RCA cables coming from my PC onboard sound card going into a four channel amplifier. Without the RCAs plugged in there is no whine. With only three RCAs there is no whine, but as soon as there are four plugged in a get a whine in my rear left speaker. It's always the rear left speaker that whines regardless of which RCA is plugged/unplugged. Also, sometimes the rear right whines aswell. I aslo get a whine if using an MP3 player as a tester. I have replaced the cabled to gold plated shielded *****es but they havent made any difference. Also, I got a ground loop isolator from eBay which aslo makes NO difference (it gets worse in some cases). I do notice that the whine is louder if I put the RCA cable closer to the power cables so I have made sure they are nowhere near each other but I still cannot get rid of the rest of the whine.

          Any help would be great!

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