what's that noise

[gordiji]

Hi all, My amp makes a noticeable constant noise when switched to the higher gain channel which is a bit like the sound one hears when mistakenley telephoning a fax machine, screeching kind of sound.Not really heard over playing but very apparrent when not. This sound ONLY occurrs when i use my boss compresser before the pre amp i.e.between my guitar and amp. The compresser is always switched off when i use this channel(obviously). I don't want to use it in the effects loop as it ruins the effect but need the compresser for clean sounds and solos.Amp engl screamer 50 vgc. Strat with (IT's) .Unplug the compresser from the chain and no probs . Any ideas ?

[Jonny]

I think you have your amp positioned near somewhere that's emitting a radio signal.

That's the only thing I can think of. Some amps if close enough can radio coming out of them.

[Ratrod]

Is there a mobile phone in the same room?

Do you have a rediculously expensive or rediculously cheap cord?

[gordiji]

thanks for your suggestions, but no mobiles or wireless connections anywhere. leads good quality.Why would radio signals or similar only effect when the compressor is in the chain? Unplug compressor and no problem. Compressor works fine , i don't think it's at fault.Somehow a small white noise is generated ,only when the compressor is in the chain and with the hi gain channel it's amplified enough to be irritating.

[maverickf1jockey]

Is the compressor true bypass?
It could just be a poorly designed bypass like the one in the Boss SD-1 (Distortion sound is never truly muted and can be heard clearly under cleans with the pedal on high settings.).

[gordiji]

I wouldn't know if it's true bypass, it's a BossCS2 so quite old but in vgc.I did some more poking about today and the 'noise' seems to be there when my delay(old Boss PS2) is in the effects loop and compressor in front of the amp.Both are coonected to the same power supply with a boss multipedal lead.If i take out the delay so nothing is in the loop the noise ain't there, even with the compressor staying connected infront.But if i want the delay to stay in the loop,which i do then i must leave out the compressor.So infact it's a combination of the delay in the loop and the compressor in front but not the fault of either alone.And to reiterate the 'noise' is only a problem when i select high gain channel.     

[BigB]

I did some more poking about today and the 'noise' seems to be there when my delay(old Boss PS2) is in the effects loop and compressor in front of the amp. Both are coonected to the same power supply with a boss multipedal lead.If i take out the delay so nothing is in the loop the noise ain't there, even with the compressor staying connected infront.

Looks like a typical ground loop problem.  Try putting one of the offenders on batteries. If this solves the issue, then you probably need either a way better power supply (one with decoupled isolated outputs), or at least two distinct power supplies (one for the "front" pedals and the other for the "fx loop" pedals).

My 2 cents.

[hunter]

I did some more poking about today and the 'noise' seems to be there when my delay(old Boss PS2) is in the effects loop and compressor in front of the amp. Both are coonected to the same power supply with a boss multipedal lead.If i take out the delay so nothing is in the loop the noise ain't there, even with the compressor staying connected infront.

Looks like a typical ground loop problem.  Try putting one of the offenders on batteries. If this solves the issue, then you probably need either a way better power supply (one with decoupled isolated outputs), or at least two distinct power supplies (one for the "front" pedals and the other for the "fx loop" pedals).

My 2 cents.

This happens a lot if pedals in front of the amp and in the loop have the same power supply, it creates a ground loop as the FX loop cable is grounded and the power supply too, try getting them isolated for separate power supply or create a ground lift in the loop.

[gordiji]

thanks hunter and big b, this crossed my mind, i'll try a batterie and isolated power sources

[gordiji]

yeh, it's a ground problem. Dissappears when i use a batterie in compressor. i'll need to get another power supply.
                                                           Thanks all, g

[hunter]

yeh, it's a ground problem. Dissappears when i use a batterie in compressor. i'll need to get another power supply.
                                                           Thanks all, g

Or this: http://www.thomann.de/gb/ebtech_hum_line_level_shifter_2.htm

It's the magical box for all loop level or ground issues.

[BigB]

Or this: http://www.thomann.de/gb/ebtech_hum_line_level_shifter_2.htm

It's the magical box for all loop level or ground issues.

I assume you meant this one: http://www.thomann.de/gb/ebtech_by_morley_hum_eliminator_2.htm

The one you linked to changes the level, which may not be what gordiji is after  8)

[hunter]

Or this: http://www.thomann.de/gb/ebtech_hum_line_level_shifter_2.htm

It's the magical box for all loop level or ground issues.

I assume you meant this one: http://www.thomann.de/gb/ebtech_by_morley_hum_eliminator_2.htm

The one you linked to changes the level, which may not be what gordiji is after  8)

The one I linked changes Level AND eliminates hum, I always want it all ;)

[gordiji]

thanks for the links boys,never even knew this stuff existed and thomann are excellent to deal with.