Re: Advice needed from audio grounding experts

[Dave, G4AON]

Hello Paul

I took the pre-wired cable that came with my PTC-IIex and terminated the
cable in a plastic project box, I connected all 4 of the braid of the
screened leads to/from the K3 to the braid of the cable to the SCS
modem. The white wire (pin 2 of the DIN plug) on the cable from the
modem also connects to the braid at that common point.

You might at some stage consider making a switch box to avoid needing to
keep swapping those audio plugs when using sound card modes, a cheap 4
pole 3 way rotary switch works well, just needs a few sockets on the
rear panel of a small box and you're in business. It saves wear and tear
on the rear sockets of the K3.

73 Dave, G4AON
K3/100, SCS PTC-IIex
---------------------------------

>I am making up a cable set to connect a Pactor modem to the K3 and wish to
>avoid ground loops. The connections to the radio are:


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[Dave, G4AON]

Paul, I think you are looking at the wrong side of the transformer, on
the circuit diagram the right hand side connects to the rear panel
sockets via J91 and is "floating" with respect to DC ground.

73 Dave, G4AON
--------------------
 >According to the schematics one end of the K3 line out isolation
transformer
 >is DC grounded and the line in transformer is DC floating (just to be
clear
 >I am talking about the windings for external connection).
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[Paul Fletcher]

Dave G4AON wrote

Paul, I think you are looking at the wrong side of the transformer, on
the circuit diagram the right hand side connects to the rear panel
sockets via J91 and is "floating" with respect to DC ground.

Doh.

You are quite correct. Thanks for pointing this out Dave. Makes things much simpler.

Cheers,
Paul.

[David Woolley (E.L)]

Paul Fletcher wrote:
>
>
> Dave G4AON wrote:
>> Paul, I think you are looking at the wrong side of the transformer, on
>> the circuit diagram the right hand side connects to the rear panel
>> sockets via J91 and is "floating" with respect to DC ground.
>>
Doh.
>
> You are quite correct. Thanks for pointing this out Dave. Makes things much
> simpler.

Note that this list's real expert on audio grounding would claim that
the inclusion of the transformers is a design flaw, and the the real
solution is good ground bonding and the use of twisted pair cables.
Ideally these should have balanced drivers and receiver, but, if I
understand him correctly, even unbalanced they help.

--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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