Actually, what Kurt seems to be getting is audible hum. This is due to
either a broken shield somewhere or a ground loop.
It's removing the buildup of quiet hum that makes it necessary to get a
grounding specialist. It's a one-time cost (in my fairly complex studio it
ran about $ 2,000 including cables and terminals) and makes a huge
difference in how a finished file sounds. My everything attatched and in
line output from my 78 player is -70 to -72 db.
In a crisis, it allows the enginner to function more efficiently since one
variable is eliminated.
----- Original Message -----
From: "Richard L. Hess" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 19, 2006 9:32 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:
>>> > 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
> Balance is more than the cable type.
> The preamp needs to be very close to the turntable - preferably 3-feet or
> 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
> 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.
> 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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