feedback tone/whistle

[D Show]

I have a Peavey Session 500 I am using onstage and I am getting a stgrange anomaly. It startedabout a year ago wheree it would feeback at a given frequency and checking last nite seemed to be an Ab (was an A position note but we tune down a 1/2 step for the singer). I eventually thought I cured it as it would only appear if I ran my signal from steel to tuner (Strobotuner) into effects (Boss digital Delay and an overdrive) to volume pedal to amp and I disonnected the tuner when I was performing but last nite just like the scary movies it was BAAACK.. It is not there if I go straght from just guitar to vlo ped to amp (but that doesnt mean it may not occur down the road. I initially thought it was an oscillatio (inaudible) in the tuner that was exciting something in the amp and still think that has something to do with it. What I don't know is if there is something wrong in the amp making it susceptable to this occurring. I also am thinking mabe it is related to the wall wart power supplies I am using but also wonder if the main poswer supply in the club has anything to do with it though it has happened in a number of venues. I am getting ready for a roed trip with thde band and can't have this. I am going to try to get my LTD working (needs a speaker and I have the replacement) but long term I want to get this resolved. Any thoughts?

[Enzo]

Isolate the problem.

Turn the reverb all the way down.  Still feedback?

DOn;t plug ANYTHING into the amp, turn it on and turn th volumes way up.  Still feedback?

[D Show]

with nothing plugged in the amp there is no problem. I have not tried turning down the reverb. I will set up today and check that. currently it seems to happen only when effects are connected.

[Roly]

I disonnected the tuner when I was performing but last nite just like the scary movies it was BAAACK..

Just to clarify, when it reappeared last night, was the tuner connected, or not?

Does the tuner have a microphone in it for tuning acoustic guitars &c?

Which make and model is the tuner?

[D Show]

Peterson strobotuner and it was NOT in circuit just my 2 Boss effects. I don't know if this is a power supply issue, or internol clock of an effects unit triggering something in the amp  or what?

[Enzo]

I would be looking for simpler explanations, at least at first.

[Roly]

I agree with Enzo, and the things you are considering would not be likely to be marginal or intermittent, or even occur at all (never heard of an Fx clock getting into an amp, and normally Fx oscillators are very low or very high, not mid band).

It is not there if I go straght from just guitar to vlo ped to amp

If that is definite then it suggests that it's not the amp itself.

Chasing rare intermittents is almost impossible; can you create a situation at home/workshop where you can make this occur?

Are you in the habit of powering your amp and Fx from the same power board/outlet, or do you plug in wherever is convenient in the situation?  (thinking of your comments about venue power)

What sort of plug pack power supply to you use with your Fx, a light switch mode, or a heavy conventional transformer supply?