[78-L] Turntable vibration isolation

[Don Cox]

On 03/08/2010, Sammy Jones wrote:
> Mike Biel wrote:
> 
>> We had an Audiophool join over at the ARSC-List last week, and I bet
>> he could recommend some turntable isolation feet that would run a
>> couple of
>> hundred bucks.
> 
> I tried a $500 power cord, but I still get vibrations!
> 
> I was around for that discussion, but kept my head down. Seriously
> though, I'm not interested in "improving the soundstage" or anything
> like that, but are the products on Nauck's, KAB, or Esoteric Sound
> likely to help my particular problem? Somebody recommended concrete or
> marble slabs to me off-list, but I'm not sure that's practical in my
> apartment.
> 
Heavy slabs on their own will do nothing. What you need is a very low
resonant frequency (less than 0.5 Hz), with plenty of damping. The point
about the frequency is to get it below the driving frequencies, which
are 78 RPM (0.77Hz) and any rumble that is on the disc. And rumble from
traffic etc.

A heavy slab or thick piece of wood, mounted on a softly inflated inner
tube, will do this. Suitable inner tubes are made for cars with small
wheels.

You can also add, in series, some rubber mounts or feet which are
stiffer and will absorb some higher frequencies. These are available at
sensible prices for mounting electric motors in workshops etc. 

Rubber is your friend as it gives good damping. 

A person who wants to sell you rubber feet for hundreds of dollars is
not your friend.



>> If we did that in my daughter's 4th floor Brooklyn apartment the
>> turntable would be dancing a jig every ten minutes when the subway
>> rumbled by under her building.  It's amazing how the frame of her
>> building transmits the vibration.
> 
> The ceiling above me is just as creaky. I routinely hear the upstairs
> neighbors coming in from the bar at 2 AM, getting up for a midnight
> snack, etc.
> 
> I'm in Atlanta, so no subway to worry about, though I do hear a
> freight train off in the distance sometimes!
> 
> Sammy "Treading Lightly" Jones
> 
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Regards
-- 
Don Cox
doncox at enterprise.net