Re: (idm) my apologies

From Et Pharmacistic Paradoxia
Sent Thu, Sep 3rd 1998, 03:02

On Wed, 2 Sep 1998, Alex Reynolds wrote:

> My apologies for being stupid. I am obviously not a Professional.
> 
> I was imagining 300-odd multiple tracks, each starting as an individual
> spiral among 300-odd possible, interwoven spirals on the record.

Those would certainly spiral inward pretty sharply!

> On another note -- and while this (like every other one of my posts) has
> nothing to do with idm in particular -- is it possible to change the
> handedness of the spiral groove on a record, so that a track starts from
> the inside and works its way out? Are the dynamics of the needle on the
> groove such that this inversion would cause technical problems, i.e. is the
> needle engineered with chirality in mind:
> 
>                                            v    <- needle
>       --------------------n-------------------- <- record
> 
>       less relative force this side -> v <- more force the other side -- as
> the needle travels along the groove -- so the engineers think, "ah, let's
> make this half of the needle last longer, as it will encounter more
> stress"? Are the individuals pressing records thinking along the same lines?

Not really, in fact, there is an adjustment called "anti-bias" or
"anti-skating" that tilts the tone arm such that, on a frictionless
surface (ie, not touching the record or a record with no groove) can make
the tonearm weighed to move toward the left or right.  The function of
this is to defeat skipping tendecies.

In your example, you must remember that the needle is intersecting the
record at a tangent and the curve of the groove vs the centripital force
is not very strong, especially since the tonearm is very light (depending
on how you set it.)  I imagine that the engineers don't have to design the
needle to be different on each half.

Ectomorph, on Interdim. Transmissions has a track that not only starts on
the inside, but ends in a lock groove in the middle of the record right
next to the lock groove that ends the track that plays from the outside
in.

My question is: has anyone made a record with two parallel grooves that
spiral inward between each other that have different tracks with the same
bpm that have the their cue points line up, such that if the needle skips
to the other track  (the one in parallel, not one groove ahead or behind)
it is still in time and in sync?  Whew!


solenoid