Date:         Fri, 17 Oct 2008 19:27:00 -0400
Reply-To:     Association for Recorded Sound Discussion List
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From:         Tom Fine <[log in to unmask]>
Subject:      Re: Aren't recordings original sources?
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Mal, and others, I highly recommend you read writings about grounding available from the AES. All of 
this stuff is addressed.

This is a great place to start:
http://www.aes.org/sections/pnw/pnwrecaps/2005/whitlock/whitlock_pnw05.pdf

-- Tom Fine

----- Original Message ----- 
From: "Malcolm Rockwell" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, October 17, 2008 12:09 PM
Subject: Re: [ARSCLIST] Aren't recordings original sources?


> Thanks, Bob.
> There are at least two other problems I've dealt with as well.
> I owned and operated one of the last analog pro studios in Northern California for a few years and 
> was plagued with intermittent ghost hums and other ills. It wasn't until I put a large 1:1 
> isolation transformer between the pole and the main power feed that much of that went away.
> Still there were some problems. We discovered, through the highly scientific hit-or-miss method, 
> that ground for a rack is not necessarily ground for the power system. That there can be a 
> potential voltage difference not only there, but difference in resistance depending on where the 
> copper ground stakes for each separate circuit are placed in, well, the ground!
> Once we discovered that some time, persistence and a good voltmeter banished the problems. Now all 
> we had to deal with were any parallel voltage feeds to other, outside circuits and noisy client 
> amplifiers. The iso transformer took care of the first, and individual attention, the second.
> The point of all this is as I said before - one power cord will not make any appreciable 
> difference in frequency response - including 60 cycle hum - for an individual unit in the chain, 
> unless it is flawed (said flaw would include its being under-gauge for it's application).
> Mal Rockwell
>
> *******
>
> Bob Olhsson wrote:
>> -----Original Message-----
>> >From Tom Fine: "... do you think powerline fuzz and hash matter more, less
>> or none to modern gear that uses cheaper/lightweight and switching-type power supplies? I'd think 
>> the
>> old-school stuff wouldn't care, it was designed to operate on the principle of an over-spec'd 
>> power supply
>> providing a large reserve for peak-power demands after the conversion to DC. But some of these 
>> modern
>> devices -- including well-rated professional gear -- seem to have such flimsy power supplies, I
>> wonder if all this matters more in that world. Plus, there are arguments to be made about the
>> quality of internal power and the performance of digital devices, but again what is provided on 
>> the
>> gear may well be up to the job in the case of professional-grade equipment. Bottom line, I highly 
>> doubt
>> what sort of power cord you use as long as you're using properly-spec'd gauge wires, matters in 
>> any
>> of this..."
>>
>> I've heard power cords make a surprising difference especially shielded vs.
>> non-shielded. Tying every neutral in an audio system together at one point
>> makes a bigger difference as does cleaning and tightening every single AC
>> connection all the way back to the power pole. Doing both in my experience
>> has reduced the effect of AC cords considerably.
>>
>> You can ask anybody in the touring sound business and they'll talk your ear
>> off for an hour about the incompetent power supply and grounding design
>> found in most of the past 40 years worth of so-called "pro" audio gear and
>> there is no reason to expect consumer audio to be any better. When you
>> consider how little AC wiring has even been touched in a half century and
>> how poorly designed most gear is, it shouldn't be surprising that anything
>> that alters the frequency response of an audio grounding system may well be
>> audible due to different flavors of RFI. Obviously if you can hear anything
>> change, all flavors are wrong but those of us who hear this stuff aren't
>> lunatics and at least some of us are pretty happy with a heavy duty, well
>> shielded $20 power cord.
>>
>>
>> Bob Olhsson Audio Mastery, Nashville TN
>> Mastering, Audio for Picture, Mix Evaluation and Quality Control
>> Over 40 years making people sound better than they ever imagined!
>> 615.385.8051 http://www.hyperback.com    http://www.thewombforums.com
>>
>>
>>
>