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in article , Josh Snider at
wrote on 9/11/03 17.19:

Ok here's my query. I've got an Eela Audio console S191 from about 1985.
When I plug my Radial DI into it, I've got no issues at all. Everything
sounds just the way it should, however, upon plugging a cheaper condenser
into it (MXL 990) there was a horrible 60hz hum, which got louder upon
gaining up, and was also audible through the headphones as well as the main
monitoring desk. I disassembled the mic, and noted that pin 1 was tied to
the chassis, disconnected that and the problem got worse, reconnected and
noted that while I was touching the chassis the hum was notably louder.
Now this is a European desk, however it was operating in a Canadian
broadcast station for years before I got it, and I believe had been phase
flipped (at least the mic inputs, the line inputs had not as I came to
find), and it IS a cheap condenser but can anyone tell me what the possible
source of this hum is and how to eliminate it. I don¹t have another mic to
swap out with it at the moment, but the Radial (Passive) DI has no issue
with it so I assume it could be a phantom power issue (although I do measure
+48V across the to legs of the power supply), but it may also be a grounding
issue between the mic and the input, or possibly the signal ground is tied
or leaking to the chassis? Any help would be much appreciated. I'd hate to
have this sitting here useless.

Also I was wondering if anyone could tell me what the wiring convention was
for this desk, I'd like to know which colour wire went to which pin on the
XLR input so I can double check to see if this desk HAS been phase flipped
or not.

Thanks in advance

J

New news, when pin 1 is disconnected completely on the mic cable, there is
no sound, and you get a nasty electric shock upon touching the chassis of
the mic and the chassis of the mixer. As well when the mic in of the eela
desk is connected to the XLR Balanced out of the monitor desk there is a
HUGE pop and constant level jump (+14dBu) on the meter of the MONITOR desk.
Nearly blew out my mains.

This sounds like a grounding problem. But where??

J

--
josh.snider
cave.productions
416.524.6927

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