On Mon, 15 Apr 2019 13:48:21 +0100, Dave Plowman (News) wrote:

its affected by proximity, sounds more like a parasitic
oscillation of
some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running
out
of steam, do the driver chips/transistors get warm/hot?

The buzz is well below peak programme level. On a PPM. I'd guess at it
peaking 2 with the actual mod peaking 6.

Buzz is a symptom possibly caused by the thing oscillating flat out
ultrasonically or in the low RF range... Bung a scope on the output?

Try shorter or different speaker leads? Though ISTR this is an actve
tri-amped speaker system?

But if you wind up the drive to the speakers, the buzz remains constant.

Which indicates it's not incoming to that amp.

Not too keen on breaking into a brand new unit to measure current draw.

Fair enough, scope? AC Volt meter? With no programme there shouldn't
be any "signal" from, DC to light, across the speakers. You should
be able to measure the buzz when present, if it happens with the
meter connected but fairly small not amp supply rails that I'd expect
with the thing "hooting". B-)

--
Cheers
Dave.