high frequency intermittent noise

This RF/EM signal must be picked up by the voice coil in the tweeter and it is likely a powerful megaHz signal and would be inaudible if it didnt cause problems for the amplifier(which tries to surpress distortion with negative feedback so as to match input) and the problem manifests itself in the audible range somehow due to signal saturation in the amp section making it a broadband signal.

Try adding a choke across the speaker wires to short out the HF signal.

http://audiosystemsgroup.com/RFI-Ham.pdf

See Fig 4 for an example...

Try adding a choke across the speaker terminals to short out the HF signal.

@shadorne 

What is a choke?  How would you implement this?  I'm not an electronics guy, learning-as-I-go-here.

I got my phone steaming videos last night and put it INSIDE my F5 right up against the left amp board.

Nelson knows his stuff.

If the amp is not properly stopped, it will be almost impossible to make this problem stop (if you will pardon the expression...).

Sometimes the amplifier circuitry is OK, but RFI gets rectified right at the input. RF beads of the right value can help, if added right where the signal gets to the amp circuit.

If the amp makes this sound with the inputs shorted, there really isn't much you can do about it but replace the amp or have it repaired.

Um, do NOT "short" your speaker wires!

The example in fig. 4 is fine, but it is most certainly NOT a short, it is the opposite, a choke.

Given however that you even have powered speakers having this issue, the problem is probably too late by the time it gets to your speakers. You need to think further upstream.

I did by the way recommend cheap RF chokes above.

Best,

E

A choke is an inductor that chokes off high frequencies.

The reason I think it is coming from the speakers and back into the Amp is because you have tried other steps.

An very strong HF signal hitting the tweeter coil might also cause core saturation (hystersis) in the tweeter and this converts HF to broadband noise.