[Table of Contents]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ARSCLIST] Aren't recordings original sources?

On Fri, Oct 17, 2008 at 12:09 PM, Malcolm Rockwell <malcolm@xxxxxxxxxx>wrote:

> 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.

We in the listening branch of things started doing that twenty-five years
ago. It works, mostly.

> 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!

As well as the depth. Also some saline solution should occasionally be
dumped nearby.

> 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.

There's another factor I am loathe to bring up, because it's so often met
with resistance (as it were). But the fact is, the orientation with which a
piece of gear's plug is inserted in the socket, can make a sonic difference.

Imagine you've cut off the ground prong and filed down the federal side --
this is just a thought experiment, stay with me -- so that the hot and
neutral can be reversed. Then you do so, and voila! It's better... or it's

What's happening here?

Well for one thing, this is measurable. (But first unplug everything else on
the circuit.) Look at the leakage voltage between neutral and a real ground
*both ways* on your DVM; in the "correct" position it reads lower, or zero.
It should be left in the lower-leakage configuration, but it's up to you to
think how to restore the ground.

This maneuver may not be audible on a single piece of gear, but when all
pieces are properly aligned you will most likely hear the improvement. At
any rate you'll have fewer stray voltages hanging around.

Caution: The plug polarity may vary even among units from the same
manufacturer with the same model designation!

>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).

I've not been talking frequency response here.


Mal Rockwell

[Subject index] [Index for current month] [Table of Contents]