Earthing problem? Odd warbling noise

[Chris Whitworth]

Hi;

I've just rearranged my home studio a bit to take into account the Edirol
UA-5 I've just bought, and I think I've got a bit of a strange earth loop
problem.

If I connect the output from my mixer (Samson 16->4 of some description,
the model number escapes me 'cos I'm at work) to the inputs of the UA-5,
I get a strange high-pitched warbling sound from the UA-5 - it sounds
like a sine wave being pitch-modulated by a couple of semitones at about
5-8Hz. The connection is via two 1/4" unbalanced jack leads (although the
problem still occurs if only one is connected), although both the mixer
and UA-5 support balanced jack connections (I haven't got any suitable
leads at the moment).

It happens when the mixer is turned on or off, which leads me to think
it's an earthing problem - both the mixer and the UA-5 are plugged into
the same ring main, as I currently have no easy way of providing isolated
power supplies.

The warbling is definitely not present on the output of the mixer if it
is not connected to the UA-5, and the UA-5 is completely silent if it is
not connected to the mixer.

Any thoughts/suggestions as to what could be up, and what I could do
about it?

Thanks;
Chris
--
Chris Whitworth | GT/AC Name: parm
http://home.parm.net | AC Town: Markham

[R. Foote]

Chris Whitworth > wrote in message >...

> If I connect the output from my mixer (Samson 16->4 of some description,
> the model number escapes me 'cos I'm at work) to the inputs of the UA-5,
> I get a strange high-pitched warbling sound from the UA-5 - it sounds
> like a sine wave being pitch-modulated by a couple of semitones at about
> 5-8Hz. The connection is via two 1/4" unbalanced jack leads (although the
> problem still occurs if only one is connected), although both the mixer
> and UA-5 support balanced jack connections (I haven't got any suitable
> leads at the moment).


You will definately want to try a balanced connection. Reason being,
you can break the shield connection at the mixer end, which might fix
your problem. They are easy to make, but if you buy them ready made,
you will have to cut the shield wire yourself, meaning the cables will
have to be made with connectors that you can dis-assemble.

Here is a link that will cover this:

http://www.rane.com/note110.html

Good luck

Roger A. Foote

[R. Foote]

Chris Whitworth > wrote in message >...

> If I connect the output from my mixer (Samson 16->4 of some description,
> the model number escapes me 'cos I'm at work) to the inputs of the UA-5,
> I get a strange high-pitched warbling sound from the UA-5 - it sounds
> like a sine wave being pitch-modulated by a couple of semitones at about
> 5-8Hz. The connection is via two 1/4" unbalanced jack leads (although the
> problem still occurs if only one is connected), although both the mixer
> and UA-5 support balanced jack connections (I haven't got any suitable
> leads at the moment).


You will definately want to try a balanced connection. Reason being,
you can break the shield connection at the mixer end, which might fix
your problem. They are easy to make, but if you buy them ready made,
you will have to cut the shield wire yourself, meaning the cables will
have to be made with connectors that you can dis-assemble.

Here is a link that will cover this:

http://www.rane.com/note110.html

Good luck

Roger A. Foote