Screeching from speakers with new amp

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25 Apr 2009
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It even screeches if I touch the audio cable to the outside of the MOBO(onboard sound). I've tried moving the speakers to the other side of the room, no difference. It's better with the treble and bass turned all the way down, if I turn it up too far horrible bassy crackling.

I also tried it on my music computer running through a Native instruments sound card, same thing.

VIDEO:http://sendvid.com/8niefhhg

My speaker specs:
Max power 240 watts
Minimum power 5 watts
Nominal impedance 8 OHMS
Frequency response 35-22 KHZ
Sensitivity 92db per watt

s-l1600.jpg


Specification:
S/N: More than 70dB
Speaker impedance: 4 - 8 Ohm
 
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try taking the amp off the big metal comp case

amp isnt earthed may be something funny happening earth wise
may also be faulty its a £15 chinese job.

you also had the amp volume up too high - start with volume on 0 then turn up

edit its actually a £10.31 Chinese job

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Soldato
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Could be a few things. Could be a ground loop.

As lude says, take the amp off the PC case for a start, or at least place something underneath like a book or something. If there's no change, then it would be a good idea to connect the amp to a portable device. A smartphone or anything as long as it's not connected to mains.

Trying with something like a smartphone will give a better indication whether the problem lies with the amp itself, or whether the noise is coming from a possible ground loop.
 
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I only had it on the PC case for the vid, it's usually on a wooden desk. With the PC output set to headphones I still get the same sound, it goes in sync with the volume knob, off, no noise etc. And it was £7.57 :p UK.

try taking the amp off the big metal comp case

amp isnt earthed may be something funny happening earth wise
may also be faulty its a £15 chinese job.

you also had the amp volume up too high - start with volume on 0 then turn up

edit its actually a £10.31 Chinese job
 
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Posts
2,132
try amp volume to a third
headphone volume on 0,
gradually turn up the headphone / pc volume
does the sound start off clear then get all 'distorted'?
£7.57 :p
 
Soldato
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I only had it on the PC case for the vid, it's usually on a wooden desk. With the PC output set to headphones I still get the same sound, it goes in sync with the volume knob, off, no noise etc. And it was £7.57 :p UK.

Can't you connect a smartphone or tablet then try it?

That will go some way to determining whether there is a fault with the amp or not.
 
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Just plugged my smartphone into it, sounds fine. What does that mean though? It's not my new amp, but both my PC's do it, I have ordered a 3.5mm to RCA cable, maybe that'll do something?

Can't you connect a smartphone or tablet then try it?

That will go some way to determining whether there is a fault with the amp or not.
 
Soldato
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It's a ground issue. I didn't actually get as far as suggesting a ground loop isolator. :p

As above though; that's what you need to try.

Link

The RCA to 3.5mm cable you've ordered should just plug straight into the RCA female sockets and the RCA male plugs go into the amplifier.
 
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Ok thanks for the help, it's all sorted. Got the isolator which removed the horrible noise and the RCA cable I bought fixed the feedback, cheers.:D

EDIT: It's only partially fixed. With the noise of the PC running you can't here it anymore, but as soon as I shut it down there it is, but it is much better. It seems to make the exact tone of the PC fans running.
 
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EDIT: It's only partially fixed. With the noise of the PC running you can't here it anymore, but as soon as I shut it down there it is, but it is much better. It seems to make the exact tone of the PC fans running. Would getting another isolator make an improvement, or is one the limit?

That's good news. :)
 
Soldato
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I'm guessing that adding another won't make any difference, but I'm not certain about that. They aren't a complete remedy. Sometimes noise is completely removed, sometimes not.

If your motherboard has optical; another thing that can be tried, is a DAC connected to the PC via optical. That will decouple the DAC and amp from the PC electrically. Interference travels along copper wire and optical uses fibre.

You'll need one that comes with mains power plug though. Some come with just a USB cable for power, which could be used if you've already got a USB mains plug. Connecting to a PC for power with USB cable may defeat the purpose.
 
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