Laptop to Amp interference

[anonymous-user]

I have just purchased an old amp to run a pair of speakers my dad gave me, its a Trio KA-1500.
I brought a connector off ebay so I can plug my mp3 into it, running my ipod with the new amp produces fantastic sound quality.

The problem is, as soon as I plug the connector into the headphone jack on my computer I get masses of interferance.

Would any one be able to advise me on what might be causing this and how I can stop it?

[EliseNick]

I'm not an expert, but you could try muting the "CD volume" in the Master Volume control. It helps on my laptop.

Cheers,

Nick

[anonymous-user]

I've tried that, but even when the sound is muted the interferance remains.

Some websites suggest a ground look isolator may get rid of this problem, possibly correct?

[TonyRPH]

This sounds like a ground loop.

A ground isolator would probably do the trick.

Edited by TonyRPH on Sunday 1st August 16:04

[headcase]

You cant get a ground loop from a laptop its running from an isolated PSU. Without actually hearing the problem its hard to diagnose. Are you using the same cable to connect the lappy as the ipod? or are you using a different one. Ususly with a laptop the output from the headphone jack is less than line level even at full volume so you have to wack up the external amp volume to compensate and that is where you hear the excess noise, if the cable you are using is ropey or the jack plug dosent connect properly it makes it worse. Sometimes the jack plug dosent align properly with the contacts inside the socket, if that is the case then you may get away with pulling it out ever so slightly.

[TonyRPH]

headcase said:

You cant get a ground loop from a laptop its running from an isolated PSU. Without actually hearing the problem its hard to diagnose. Are you using the same cable to connect the lappy as the ipod? or are you using a different one. Ususly with a laptop the output from the headphone jack is less than line level even at full volume so you have to wack up the external amp volume to compensate and that is where you hear the excess noise, if the cable you are using is ropey or the jack plug dosent connect properly it makes it worse. Sometimes the jack plug dosent align properly with the contacts inside the socket, if that is the case then you may get away with pulling it out ever so slightly.

The OP made no mention of a laptop.

Overlooked the subject of the post - how the heck did I do that...

Perhaps it was these words..

champ54321 said:

... headphone jack on my computer ...

So...

However.. you can still get interference from laptop PSU's as well, as most of them have a capacitor (usually around 1nF - 10nF) connecting the live side of the PSU to the low voltage side for EMF discharge IIRC.

This can induce all sorts of noise.

I suggest unplugging the laptop charger, and see if the noise goes away?

But as the OP appears to be using a PC, I stand by my original suggestion of an earth loop.

My son plays and records his own music, and has his PC connected through a mixer, ADC and various guitar pedals.

We experienced similar issues.


EDIT: correct my dopey moment.

Edited by TonyRPH on Sunday 1st August 19:48

Edited by TonyRPH on Sunday 1st August 19:49

[anonymous-user]

I'm using the same 3.5 jack cable for the mp3 and laptop

TonyRPH said:

I suggest unplugging the laptop charger, and see if the noise goes away?

Yup, when I unplug my laptop charger it plays perfectly clear.

[TonyRPH]

champ54321 said:

I'm using the same 3.5 jack cable for the mp3 and laptop

TonyRPH said:

I suggest unplugging the laptop charger, and see if the noise goes away?

Yup, when I unplug my laptop charger it plays perfectly clear.

Some laptops have a "figure of eight" mains connector that looks like this...



If so, try unplugging it and connecting it the other way around, this will reverse the Live / Neutral connections (quite harmless in this case) but may remove the interference.

If that doesn't work, are there any other devices (e.g. turntable, other source) plugged into the amp?

You could try disconnecting these one by one as a process of elimination?

[headcase]

champ54321 said:

I'm using the same 3.5 jack cable for the mp3 and laptop

TonyRPH said:

I suggest unplugging the laptop charger, and see if the noise goes away?

Yup, when I unplug my laptop charger it plays perfectly clear.

Noisey PSU then, could be a fault with the psu, could just be a crappy psu design, only way to find out would be to swap it out for another one.

[dans2]

Have you tried using a different 'figure of eight' lead?
I have a MacBook Pro. With the lead that came with it I get the same noise, but with a different one or the compact version that also came with it, I get none.
The lead that produces a noise is grounded, while the others are not.

Edited by dans2 on Thursday 3rd March 17:18

[koenig999]

I had some of this with a Dell laptop I use for recording.

Solution was to cut off the mains plug and replace it only connecting the live and neutral, missing the earth off, cured the ground loop.

ps only do this if you are not cack handed with electrics.

Koenig

[Dave 500]

We get this all the time at work nearly every laptop will do it.

To sort it you need to use something like this

http://hiveindustries.com/component/virtuemart/?pa...