[TenTec] Re: Heil ProSet adapter with Orion -- hum

[Robert & Linda McGraw K4TAX]

And they will work great in an unbalanced configuration.

Bob, K4TAX


----- Original Message ----- 
From: "Ron Martin" <royalct at inr.net>
To: "Jim Brown" <jim at audiosystemsgroup.com>; <tentec at contesting.com>
Sent: Thursday, June 24, 2004 10:08 AM
Subject: [TenTec] Re: Heil ProSet adapter with Orion -- hum


> Jim,
>
> Thanks for the information.
>
> I believe that I will rewire the Heil (and the one I built) transition
cable
> to do what you suggest.  I do have some 'old time' balance mikes that I
> would like to try on the Orion.
>
>
> Thanks
>
>
> Ron
>
> Jim Brown writes:
>
> > On Wed, 23 Jun 2004 23:33:10 -0500, George Skoubis wrote:
> >
> >>I shouldn't bring this up again for someone will blame it on the "Pin 1
> >>problem".  The fact is there's typically 4 connections for microphone
> >>audio.
> >>There is the Audio Hi or +,  Audio Lo or -, Audio Ground, and Audio
> >>Shield.
> >
> > I suspect that the problems here may be related to the difference
between balanced and
> > unbalanced audio wiring.
> >
> > Virtually all ham gear uses UN-balanced audio -- as I understand it (I'm
not flush enough to
> > own one), the Orion uses a balanced mic input, which is a nice step up,
but it can lead to
> > problems when you interface an unbalanced mic. A balanced mic uses only
+ and - for
> > audio -- the shield is ONLY a shield.
> >
> > An unbalanced mic uses the shield both as a shield AND as "audio -", so
if you want to
> > use an unbalanced mic with a balanced input, you must connect the shield
to both chassis
> > and "audio -".  The chassis connection terminates the shield, and the
"audio -" connection
> > completes the audio circuit.
> >
> > There's another big advantage to having a balanced audio input -- you
can plug a pro mic
> > directly into it!
> >
> > The Standard wiring (AES and IEC) for a cable-mounted XLR connector is
> >
> > 1  - Shield
> > 2 - Audio high
> > 3 - Audio low
> > Shell - no connection (there are VERY good reasons why this is the
Standard, and they
> > involve the prevention of ground loops in installed systems).
> >
> > The correct wiring for a chassis-mounted XLR connector carrying balanced
audio is
> >
> > 1 - Chassis
> > 2 - Audio high
> > 3 - Audio low
> >
> > The correct wiring for balanced audio is:
> >
> > Shield to chassis
> > Audio High to Audio High
> > Audio Low to Audio Low
> >
> > Much equipment, including all of the pre-Orion Ten Tec gear I have seen,
is built
> > improperly, in that it takes the shield to the circuit board and not to
the chassis. There are
> > two fixes.
> >
> > 1)  Rewire the equipment connector to disconnect the shield (pin 1) from
the circuit board
> > and connect it to the chassis. (Best)  Unfortunately, lots of equipment
use connectors that
> > are mounted to the circuit board, and it is difficult or impossible to
rewire them correctly.
> >
> > 2)  Rewire the cable-mounted connector to connect the shield to the
shell. (Second best,
> > but it fixes all but the most severe problems).
> >
> > Hope this helps.
> >
> > Jim Brown  K9YC
> >
> >
> > _______________________________________________
> > TenTec mailing list
> > TenTec at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>