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isw

In article ,
wrote:

I've just gotten finished, (or so I thought) upgrading and servicing all the
equipment in my entertainment center. I just replaced my mediocre speakers
with a pair of nice 12 inch JBL's that were abandoned in the building we just
bought. My turntable is an old Thorens belt drive, supported with a spring
arrangement that I thought would absorb any vibration. The turntable is in a
cabinet about a foot off the floor and right next to the left channel
speaker. If I crank up the volume when listening to a record there is
distortion, the severity directly proportional to the increase in volume. At
first I wasn't certain about this but you can actually "feel" the vibrations
on the turntable base. There are these springs supporting the platter and arm
and these springs are "stuffed" with a foam material but this vibration is
coming through anyway. I know that one solution is to relocate the speaker
however the room is not large enough to do this. I was thinking of putting
foam under the speaker which would be easy and perhaps even a soft foam block
under the turntable as well but I'm afraid that trying to support and level a
turntable supported like this could be a nightmare. Does anyone have any
ideas?

You're probably not going to like this, but the easiest -- and maybe the
best -- solution is to digitize the records and play the resulting
files. No acoustical feedback. No (more) degradation from the stylus
damaging the groove, either.

Years ago,when I still used vinyl records, I became concerned about the
exact same phenomenon, but when it was at a level where it couldn't be
*overtly* heard, but still was causing a modification of the desired
output signal. I figured that it just had to be there and I wanted to
measure it.

I came up with a scheme for placing a second cartridge on the record
that rotated with it, and taking the output of that as the signal to be
measured. Not only would it detect the acoustical feedback from the
speakers, but also the direct vibrations of the active stylus in the
groove, which has to be creating stuff that bounces off the edges of the
disc and back to the stylus as distortion.

Then CDs came along, and I totally lost interest in the whole project.

Isaac