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dpwell 27th February 2014 07:46 AM

new here, with a question about distortion
 
hi

New here, and i have a question about a new pair of PSB B4 Image speakers. In the last few days I've been getting some really nasty metallic-sounding distortion. It's in both speakers, and have had it while listening to Youtube, a CD in my computer's CD drive, and music and podcasts in iTunes.

My computer is an iMac running 10.9, connected to a several-years old iMic connecting device that then runs to my 30 year old amp (120V, 120W, 60 Hz) and on through similarly old speaker cable to the speakers. The speakers are 2 months old. As it's in both speakers, I'm wondering if the problem lies in the sound source and not the speakers. Also, it doesn't happen all the time: I've heard distortion, stopped the music, and immediately replayed the same track without a problem. I never had this with the previous speakers (also PSB but much larger)

Any thoughts? Should I march the speakers back to the shop?

I'm not sure which forum section to post this in, but am hoping someone can let me know, or repost it for me.

thanks in advance,
David from Vancouver BC.

wintermute 27th February 2014 08:03 AM

Hi David and welcome to to diyAudio. I wouldn't be too quick to blame the speakers. It could be anything in the chain, including the speakers. The fact that if you stop the music and restart the track it is fine is a bit odd. Perhaps a driver problem on your iMac??

I'm not sure which section is the best to post the question, as there are a number of different areas where the problem could be.

I'd suggest doing some isolation tests. change out one thing at a time (assuming you have something to substitute) and see if the problem persists. If it goes away change the thing back and see if it returns.

This may point to the problem component. It may also point to a problem with interaction of that component with the others too.

If you have some other speakers you can substitute that would be a good start (or alternatively a different source).

Taking a logical approach to changing things out should allow you to track down the source of the problem :)

Tony.

richie00boy 27th February 2014 09:42 AM

Next time it does it, try leaving the music playing and switch the amp off then back on, if that makes it stop then you know its the amp.

dpwell 28th February 2014 06:10 AM

thanks for the replies. Listening to some Debussy right now and the speakers were fine then started to sound weird and metallic again. I tried turning the amp off and on but the distortion was still there when I turned the amp back on. I stop the music and start it again and it's fine. Then a few minutes later more garbling. Weird.

I don't have another other audio equipment here so will probably take them back to the store for testing...

richie00boy 28th February 2014 07:31 AM

When you turned the amp back on, did the problem sound come back on straightaway? If it did then it's leaning a little more towards being the source I would say. Based on that you said the problems always takes a little bit of time to start.

dpwell 28th February 2014 07:36 AM

yes, the problem was there the moment i turned the sound back on.

Could the problem be that the speakers were too close to the computer (they were very close)?

I moved them further away and they've been fine for the last half hour...

dpwell 28th February 2014 07:49 AM

yup, the distortion was there immediately.

The speaks were positioned very close to, and behind, my computer. Could proximity to my iMac have been the problem? I have moved them further away and it's early days but they seem to be behaving themselves now...

dpwell 1st March 2014 11:53 PM

An electrical engineer friend has suggested that the cables may be acting as antennae to the computer, and that my ancient amp isn't designed to be around modern equipment generating such a lot of high frequency noise. So perhaps I just need a new amp. I heard modern amps have way more shielding than old ones. Is this true?

thanks,
david

richie00boy 3rd March 2014 07:28 AM

It's the input cables that are usually the issue for picking up stuff, but it's not impossible for the speaker cables to have this too. I doubt it's the problem as even old designs usually had input filtering to avoid problems with AM radio pickup.

dpwell 3rd March 2014 05:23 PM

Thanks for all the feedback (ha ha)

Well I seem to have found a solution by simply moving the amp and speakers a little further away from the computer. It's not ideal but there we are. Hopefully that resolves it for good.


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