Since we have published our two previous posts (Part I
, Part II
) on wow and flutter, we had a privilege of talking to a distinguished guest, an AES author Mr. Ray Kilmanas
Mr. Kilmanas did some very interesting work back in 1982, showing that not only the turntable drive, but the tonearm configuration too can have an impact on wow and flutter. As the tonearm traces the warps of the LP, it is "scrubbing" — frequency modulating the signal that's being picked up. We have touched on the subject of scrubbing earlier
. This should have exactly the same effect as the turntable drive errors.
But does the scrubbing exist "in the wild"? It is quite easy to provoke with a specialized test LP
, but the real world LPs have no content below 20 Hz or so. We have prevoiusly shown that the only possible source of such low frequency disturbances are vertical warps
. Unless the LP is completely out of shape, their influence is quite small. Is it enough to induce scrubbing?
How can we test the scrubbing hypothesis? Linear tracking arms, having no headshell offset angle, should be more resistant to scrubbing. What if we could measure two turntables with the same (or very similar) drives but different types of tonearms — one with pivoting, and one with a linear tracker? Will it show the wow and flutter advantage of the latter?