Reply to S4 - high pitched sound problem, anyone help

Hi, i tried my s4 at home with no problems, i got to my bar gig and plugged
directly
> into the pa from the rca outs on the s4, when i turned the bars pa up there
was a high
> pitched tone coming from the speakers.
>
> i was using the power supply on the s4, i noticed that when i unplugged my
laptop
> mains lead that the noise stopped, which suggests that it may be a setting on
the laptop.

have been through the system enhance ment tools with no luck, high performance mode on my laptop actually makes the sound louder.

im running a sony vaio with 4gb ram, core duo processors 2.20ghz, im getting no pops or anything else as mentioned in other posts just this high pitched sound.

ive been using this laptop for the past year on other hardware/software combination with no issues.

any help would be appreciated.

ive also went through the manual before anyone starts suggesting the obvious! soz again for the post in general discussion but it doesnt want to let me post in the s4 discussion, unsure why.