[78-L] Removal of hiss on 78 transfers

[Michael Biel]

DAVID BURNHAM wrote:

>>  What I am suggesting is that the groove of a record is scanned 
>> laterally or radially, however you want to describe it.  Assuming 
>> the results of this scan to be shown on a computer screen, what you 
>> should see is a "V" in the shape of the cutting stylus.  If
>>  the actual shape of the cutting stylus is known, the scan can be 
>> compared to it and only the parts of the scan which coincide with 
>> the reference stylus are considered valid and other parts of the 
>> scan are disregarded.
>>     
>
>   
Jeff Lichtman wrote:
> The system in question does do a scan of the playing surface. For 
> lateral-cut records it does a two-dimensional scan and uses 
> differences in reflectivity to isolate the sides of the groove. What 
> you get is an undulating white stripe with a black background. The 
> system interprets lateral displacement of the stripe as if it were 
> stylus motion.
>
> The problem I see with your idea is the main problem with all noise 
> reduction systems: how do you distinguish between signal and noise? 
> In your proposal, when the system is interpreting a noisy section of 
> groove, how is it to tell which undulations to trace and which not 
> to? It's not enough to say that you would use the shape of the 
> original cutting stylus - when the system comes to a lump or pit on 
> the groove wall, it has to decide whether to trace this as if it were 
> signal or skip past it as if it were noise. Imagine, for example, 
> that the system encounters a widening in the groove that *could* 
> indicate impulse noise. Which side of the groove should it trace? 
> There could be a flaw on either side of the groove, and if you pick 
> the wrong side you're eliminating signal instead of noise.
>   

When David discussed this last time I didn't really mean to put you 
down, just to explain like Jeff has done this time that the laser player 
that has been developed has more trouble with dirt and wear than does a 
stylus which can shove aside some of the dirt.  Your further explanation 
this time does have a valid point which I am not sure the ELP takes into 
account -- that there is one NON-variable in the system: the shape of 
the cutting stylus.  If I understand it correctly, your proposal is to 
trace the ENTIRE groove wall, not just a point on it.  Anything that 
changes the straitness of the wall from top to bottom is noise.  The 
white stripe that Jeff describes is too narrow, taking into account only 
a part of the side wall, assuming it is representative of the entire 
wall.  This is similar to a flaw in the use of modern jeweled styli 
points vs. steel needles I discussed a year or two ago and also was 
quickly shot down.  The steel needle is ground into the shape of the 
entire groove and hits the entire groove from top to bottom.  Our modern 
points try to find a "sweet spot" on the walls that has not been hit 
before.  But that is impossible because ALL the wall is hit every time a 
steel needle is used.  This also serves to spread out the stylus 
pressure over a greater area -- you all remember the picture Walco used 
to show with an elephant on top of the tone arm because the effective 
weight of the stylus is greater since it all is concentrated onto just a 
tiny portion of the groove wall.  The Shebata shape tried to overcome 
this somewhat. 
> I imagine that you could build some intelligence into the system to 
> recognize noise simply by what it looks like. A noisy bit of groove 
> might have an irregular surface, for example.

It should be a straight line from top to bottom, but if it isn't it will 
eliminate the parts that don't fit to the original stylus straight 
edge.  This is not what the ELP does and is not what a modern stylus 
point does either. 
>  It would be interesting 
> to do research in this area, but I don't think the problem is at all easy.
>
>
>                         -        Jeff Lichtman
>   

What is needed is not one laser beam per groove wall, but dozens or an 
infinate amount to compare not only lateral displacement but the 
straightness of the vertical edge -- if they all do not displace 
laterally the same way, what is different is the noise. 

Considering what Lennick has discussed, the playing of damaged records, 
the ELP can trace over a crack, even looking thru scotch tape covering 
the crack, but is programmed not to play a record with a rim-chip, even 
in the non-discontinuous areas!  It simply does not accept a record 
unless the outer rim is continuous.  I discussed this with the president 
of the company, that this feature eliminates the use of the ELP from 
it's most important use, and his answer was that it would take $10,000 
of programming to work around this.  Likewise, it just gives up if there 
are portions of the groove that do not line up, such as in dl's example 
of a lacquer with shrunken or missing pieces.  A stylus just goes 
haywire but ideally a laser should be able to jump over the missing 
pieces and continue with the groove it finds at the end of the hole, or 
should be able to put the sections of grooves together like a jigsaw 
puzzle-- or let a human edit the out-of-sequence pieces together like we 
do when we play a broken record and try to get at least one trace of 
each groove section.   When the ELP was designed they did not understand 
that the PRIMARY use of it should have been playing  records that can't 
be traced with a stylus!  They thought  audiophiles wanted touchless 
playing of their perfect records to keep them perfect.  That's the 
LEAST  of our concerns!!

Mike Biel  mbiel at mbiel.com 


>                                  jeff at swazoo.com
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