In article l.net,
Dave Liquorice wrote:
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?
They are all of a foot long. ;-) Speakon 8 and car trailer multi core
cable.
Though ISTR this is an actve
tri-amped speaker system?
Yup. And didn't buzz with the previous X/O which is a direct replacement
Exactly the same physical size, and even the mains in and XLRs in roughly
the same place.
But if you wind up the drive to the speakers, the buzz remains
constant.
Which indicates it's not incoming to that amp.
Quite. Although it does seem to be started by the input signal. Unplug the
XLR to the X/O input, no buzz - at least for as long as I've tried it.
With signal starts in a couple of minutes after power up. And continues if
you then unplug the input.
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-)
I thought I'd seen it all given how many bits of gear I'd plugged up at
work over the years. ;-)
If I unplug the X/O from the amp with the buzz going, the buzz stops.
That's not to say it isn't some form of interaction.
--
*I feel like I'm diagonally parked in a parallel universe*
Dave Plowman
London SW
To e-mail, change noise into sound.