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Path: utzoo!watmath!clyde!cbosgd!ihnp4!houxm!mhuxt!mhuxr!ulysses!allegra!oliveb!olivee!greg
From: greg@olivee.UUCP (Greg Paley)
Newsgroups: net.audio
Subject: Re: Turn table isolation methods wanted
Message-ID: <488@olivee.UUCP>
Date: Wed, 25-Sep-85 12:16:43 EDT
Article-I.D.: olivee.488
Posted: Wed Sep 25 12:16:43 1985
Date-Received: Sun, 29-Sep-85 04:41:19 EDT
References: <62@opus.UUCP> <57@unc.unc.UUCP>
Distribution: net
Organization: Olivetti ATC; Cupertino, Ca
Lines: 38

> I have noticed that turntable vibration sensitivity is very much a
> function of the cartridge used.  The one cure to the problem i have
> found is to use a cartridge which has a semi-rigidly attached brush
> ("dynamic stabilizer") providing support for the cartridge on the
> record.  The cartridge i have came from radio shack (model
> RXT5, $30 on sale), and we can all dance in my living room now, no
> problem.
> -- 
> Jim Ericksen
> UNC Chapel Hill

I have a couple of problems with this solution.  The first is the
limitation in choice of cartridges - very few, outside of the Shure
line, have the stabilizing brush.  This leaves out a number of 
cartridges I consider markedly superior to the Shure, including
most of the moving coils and, of the fixed coil variety, such
makes as Grace and Grado.  Secondly, when I was using a Shure V-15-5, I
found the general performance improved when I disabled the brush.

Aside from getting a turntable with inherently better isolation (such
as an AR or the one of the new Thorens 300-series), there are a couple
of things you can do to improve isolation.  The best way I know of,
although it can wreak havoc with your room decor, is to mount a shelf
directly onto your wall studs and place the table on it.  This will
cut out the majority of audible, floor-borne vibrations.  Another way,
less effective but also easier, is to construct a cheap isolation
platform.  To do this, cut a piece of plywood to fit under the turntable,
drill several holes through the center of it, and place it on top of a
very loosely inflated bicycle inner tube.  You'll need a spirit level
so that you can move the tube around under the platform (once you've
seated the table onto it) until you have it in a position in which the
turntable is level.

There are also commercial isolation platforms.  These, at their cheapest,
are considerably more expensive (some of them go more than half way toward
buying an AR turntable!).  I don't have any direct experience with them.

	- Greg Paley


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