Re: [ARSCLIST] Audio equipment cable shielding

[Steven Smolian <smolians@xxxxxxxxx>]

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.

Steve Smolian


----- Original Message ----- 
From: "Richard L. Hess" <arclists@xxxxxxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxx>
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:
> >
> > > 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: richard@xxxxxxxxxxxxxxx
> Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
> Detailed contact information: http://www.richardhess.com/tape/contact.htm
>
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