[78-L] Removal of hiss on 78 transfers

[Michael Biel]

Jeff Lichtman wrote:
>> 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.
>>     
>
> The first thing to do for noise reduction is to clean the record. 
> There shouldn't be any dirt.
>
>   

The needle can pull debris out of a shellac record even if it is clean.  
It is made up of filler that is just held together by the shellac like 
an asphaltic compound.
>>  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.
>>     
>
> My practical experience (and that of many others) is that the stylus 
> tip size usually makes a huge difference in signal to noise ratio. I 
> could theorize about why this is true, but I'd be talking through my 
> hat. 

I wasn't discounting that at all.  All needles need to fit the groove 
size, and that is what is happening with selection of different points 
and shapes of points.  But we have been trained that in the case of LPs 
the point might also be chosen to miss worn parts of the groove walls, 
but these records are always played with points that hit only a part of 
the wall.  Some people have also taken it to mean that this is the 
situation with 78s,   Later 78s might have been played with jewelled 
points and might actually show wear on just a part of the walls or only 
one wall, so point choice there can be affected by trying to miss a worn 
portion.  But 78s that have been played mainly with steel needles are 
different.  The wear should be to the entire groove wall, but portions 
of the different fillers in shellac records can cause microscopic 
differences which result in crackle and little particles that have 
popped out.  There are also needle digs and gouges.  . 
> I'd think the best way to understand what's happening would be 
> to play records with steel needles and examine the results under a 
> microscope. Someone must have already done this, but I've never seen 
> microphotographs of groove wear.
>
> I'd expect, BTW, that the fact that a steel needle covers so much of 
> the groove wall would help eliminate some noise but make other noise 
> worse. A steel needle should be more likely to track properly over a 
> pit in a groove wall, but it would also be more likely to be 
> deflected by a protrusion in one part of the groove wall.
>
>
>                         -        Jeff Lichtman

And that is where the laser can come in.  If it is looking at only the 
part of the groove where the protrusion will appear, it will hear it 
just like a stylus point that is also touching only that section of the 
wall.  But if it can look at the whole wall, it could know that the 
protrusion is not in keeping with the shape of the recording stylus and 
would ignore it. 

Mike BIel  mbiel at mbiel.com