How flat is an LP?
"Soundhaspriority" said:
Not being a vinyl lover, I am confused by the attention given to the
machining of platters, the complex and costly things called turntables,
while the uppermost surface seems to have the flatness of a Kringles potato
chip.
Of the platter or the mat?
For sure, the turntables you've seen, were either of obscure plastic
Taiwanese quality, bought for $9.95 at the 7-11, or they survived a
trip down a 3-story staircase.
All of the decent TT platters including mats I have had here over the
years, and that I observed at friend's and client's houses, were flat
to the eye.
Some even up to the point where one couldn't tell is if was spinning
or not.
That would include Thorenses and Duals from the '60s and '70s.
I have never seen a record that looks flat to the eye, which suggests to me
that perhaps none of them appear flat to a runout gauge. Do records exist
that do not degrade the flatness of the rest of the turntable by a factor of
ten?
The record warp itself becomes an almost inignificant factor when a
mat is used that is a bit concave, ie. the outer side is higher than
the inner side.
A twist clamp is used to put it flat to the mat and platter, and that
is that.
Record warp must be severe to be immune to this treatment, and
usually, it's the owners fault.
Many people simply store their records the wrong way.
Putting them in a closet or on a shelf, under a degree varying between
90 and 5 degrees, is a certain recipe for warped records.
Luxman, amongst others, had a TT with a vacuum pump to suck the record
close to the platter.
Sadly, the platter surface was made of aluminium, which isn't the best
conductor for vibrations icw. vinyl, and the danger of pushing dirt
particles further into the grooves is always there.
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