On 15/04/2019 23:17, tony sayer wrote:
In article , Dave Plowman (News)
scribeth thus
In article ,
The Natural Philosopher wrote:
On 15/04/2019 10:11, charles wrote:
In article l.net,
Dave Liquorice wrote:
On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff 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?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

as I said - check the power supply.

bad decoupling cap feeding high impedance source that picks up hum from
the body once the cap has stopped being a cap.

Did you actually read my post? The buzz stops as you approach the device.
But perhaps your body is out of phase. ;-)


Now thats is odd., Assuming it used the THAT and SMM series of balanced
line receivers they should only see the input differential voltage
unless that differential system isn't working i.e. the common mode side
is up ****e creek.

Electronic balance is fine but it must be isolated from its supply limes
and other odd references around.

Maybe one input side is getting connected to the metal earthwork?.

Bring it up here Dave got the equipment to suss that one out;!.

I also think this is an earthing issue, exacerbated by the new unit's
switch mode power supply.

Hence my suggestion in an earlier post to use cable ferrite chokes that
help to eliminate HF earth and common mode issues.

However the behaviour of connecting an input that causes a 'buzz' that
remains after disconnecting the input does sound more sinister, such as
an instability. I looked up Behringer and their equipment gets mixed
reviews as well as being the wrong end of a few legal issues with
pirating designs.