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As an aside, also be aware that some hum may be recorded in the record
itself, and nothing you do with cabling will make that go away. I discovered
this myself once upon a time, when trying to play an AFRS ET.  I could not
discover the source of the hum, until I lifted the stylus off the record to
have everything go quiet. This may or may not apply to what you are doing.

js

----- Original Message ----- 
From: "Richard L. Hess" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 19, 2006 8:32 AM
Subject: Re: [ARSCLIST] Audio equipment cable shielding


> At 08:53 AM 4/19/2006, you wrote:
> >At 01:21 PM 4/18/2006, you wrote:
> >
> >>Kurt Nauck:
> >>
> >> > We are doing some re-arranging of our studio here at
> >> > the shop.  We're encountering hum from the audio
> >> > cables being in proximity of power cables and possibly
> >> > from florescent lighting (!)
> >>
> >>Are the audio cables balanced?
> >
> >No, unfortunately. If I use an rca to xlr cable converter, can I
> >carry a balanced signal from my turntable to my preamp, or do I need
> >a special device?
>
> Balance is more than the cable type.
>
> The preamp needs to be very close to the turntable - preferably
> 3-feet or less.
>
> Let's look at your issues for a moment.
>
> You say you're getting hum. Is it just in the turntable or in the
> entire line-level system?
>
> Turntables are very, very fussy because the signal levels are low,
> the impedance is fairly high, and the signals are unbalanced.
>
> All three of these work against you.
>
> The turntable needs to be separately grounded (not via the cartrdige
> cables), the cables need to be short, and preferably grounded at the
> preamp only - let the shields connect to the cartridge, but not the
arm/TT.
>
> Then, if your preamp is unbalanced, go into something like an Aphex
> 124A balancing box, then balanced to your sound card (hopefully you
> have a balanced input sound card like the CardDeluxe, most of the
> MOTU boxes, or RME boxes or better).
>
> But, the biggest risk is in the TT->preamp area. I would not try and
> run that through a patch bay or switch or long cables. I suspect you
> might have multiple TTs and preamps and want to switch. At the
> moment, I cannot think of very many good ways to do that. Perhaps I'd
> use a small BNC patch panel, perhaps with all the grounds tied
> together--it depends--one can argue it both ways. I do not tie the
> line-level unbalanced shields at my patch bay.
>
> Cheers,
>
> Richard
>
>
> Tape Restoration Seminar:    MAY 9-12, 2006; details at Web site.
> Richard L. Hess                   email: [log in to unmask]
> Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
> Detailed contact information: http://www.richardhess.com/tape/contact.htm
>
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