I seem to remember a time when stereo records were incompatible with
mono cartriges, which lacked the vertical compliance necessary to
avopid damage to the grooves. Sometime in the late 60's or early 70's,
howvere, I remember "compatible stereo" records being introduced. About
this time, the appearance of the records also seemed to chamge. Before
this, stereo discs looked quite different. I remember having Peter Paul
& Mary records in both mono and stereo, and the stereo ones looked
quite different. The grooves appeared 'deeper'.

wrote in message
...
I seem to remember a time when stereo records were incompatible with
mono cartriges, which lacked the vertical compliance necessary to
avopid damage to the grooves. Sometime in the late 60's or early 70's,
howvere, I remember "compatible stereo" records being introduced. About
this time, the appearance of the records also seemed to chamge. Before
this, stereo discs looked quite different. I remember having Peter Paul
& Mary records in both mono and stereo, and the stereo ones looked
quite different. The grooves appeared 'deeper'.

I'd like to know more about this. I remember a "compatible" record acquired
in 1965, at which time I was very young but very interested in all things
electronic. I wondered at the time if it was really different or if they
were just telling the user not to worry, it will sound OK on your mono
phonograph, and never mind that subsequent stereo playback will be impaired.

As for the appearance of the records, of course the number of grooves per
inch is something the maker can adjust freely; a record with 30 minutes of
music per side will have them closer together than a record with 15 minutes
of pop songs. You are no doubt already familiar with this. I wonder if it
had something to do with the change you noticed.

On almost all the LP records I've ever owned, the grooves look more or less
uniform all over the record. A strking exception is the "Basic Library of
the World's Greatest Music" circa 1961. These are classical records, in
mono, and the grooves look very different as you go along from one musical
passage to another. So you get a pattern of irregular concentric stripes.
What does this tell us about how they were made, I wonder?

"M. Covington" wrote in message
...
wrote in message
...
I seem to remember a time when stereo records were incompatible with
mono cartriges, which lacked the vertical compliance necessary to
avopid damage to the grooves. Sometime in the late 60's or early 70's,
howvere, I remember "compatible stereo" records being introduced. About
this time, the appearance of the records also seemed to chamge. Before
this, stereo discs looked quite different. I remember having Peter Paul
& Mary records in both mono and stereo, and the stereo ones looked
quite different. The grooves appeared 'deeper'.

I'd like to know more about this. I remember a "compatible" record
acquired
in 1965, at which time I was very young but very interested in all things
electronic. I wondered at the time if it was really different or if they
were just telling the user not to worry, it will sound OK on your mono
phonograph, and never mind that subsequent stereo playback will be
impaired.

As for the appearance of the records, of course the number of grooves per
inch is something the maker can adjust freely; a record with 30 minutes of
music per side will have them closer together than a record with 15
minutes
of pop songs. You are no doubt already familiar with this. I wonder if
it
had something to do with the change you noticed.

On almost all the LP records I've ever owned, the grooves look more or
less
uniform all over the record. A strking exception is the "Basic Library of
the World's Greatest Music" circa 1961. These are classical records, in
mono, and the grooves look very different as you go along from one musical
passage to another. So you get a pattern of irregular concentric stripes.
What does this tell us about how they were made, I wonder?


In the mono days, most of the groove adjustment was done manually by the
mastering engineer, based on the loudness/dynamic range of the music being
played. Stereo made this much more complicated, but only a few years after
stereo records started being produced the first crude "feed-forward" lathes
were introduced, creating a semi-automatic way of adjusting groove spacing
dynamically. Then later, of course, more sophisticated servo-adjustments.

I suspect the difference he is refering to (and you in the lst passage
above) was the difference between early manually cut records and later,
servo-adjusted ones. Perhaps even two different pressings of the same
recording done a few years apart.

M. Covington wrote:

I'd like to know more about this. I remember a "compatible" record acquired
in 1965, at which time I was very young but very interested in all things
electronic. I wondered at the time if it was really different or if they
were just telling the user not to worry, it will sound OK on your mono
phonograph, and never mind that subsequent stereo playback will be impaired.

I'm pretty sure "compatible" stereo discs had mono bass.
One of the reasons mono cartridges destroyed stereo records
was that they weren't designed to respond to vertical modulation
and would tend to destroy grooves with much L-R (vertical) bass.

Peter.
--

Peter Irwin wrote:
M. Covington wrote:

I'd like to know more about this. I remember a "compatible" record acquired
in 1965, at which time I was very young but very interested in all things
electronic. I wondered at the time if it was really different or if they
were just telling the user not to worry, it will sound OK on your mono
phonograph, and never mind that subsequent stereo playback will be impaired.

I'm pretty sure "compatible" stereo discs had mono bass.

That was one possibility that crossed my mind. Bass tones, being the
largest in magnitude, would cause the most vertical displacement of the
stylus. Would mixing the bass to mono cause the records to look
different? I think it might. I know that stereo records definitely
looked different in the mid-60s. They looked much 'duller' and darker
than monos of the same music. If this is what happened, did this
practice become standard? Is the bass on stereo records today still
mixed to mono? If so, does this make the records easier to press?

One of the reasons mono cartridges destroyed stereo records
was that they weren't designed to respond to vertical modulation
and would tend to destroy grooves with much L-R (vertical) bass.

Correct.

I did find this:

http://www.stevehoffman.tv/forums/sh...ad.php?t=38101


Peter.
--

wrote:
Peter Irwin wrote:

I'm pretty sure "compatible" stereo discs had mono bass.

That was one possibility that crossed my mind. Bass tones, being the
largest in magnitude, would cause the most vertical displacement of the
stylus. Would mixing the bass to mono cause the records to look
different? I think it might. I know that stereo records definitely
looked different in the mid-60s. They looked much 'duller' and darker
than monos of the same music.

Some record sleeves on early London-Decca stereo discs had
the notice:

"When held at certain angles the surface of this FFSS record
looks different from that of a monaural disc . . . It may even
appear to be worn. Of course, this is only an illusion caused
by the unusual way in which the grooves of this FFSS record
are cut."

So you aren't the first person to notice this.

If this is what happened, did this
practice become standard? Is the bass on stereo records today still
mixed to mono?

There's a second reason for mono bass on stereo LPs.
The space available for vertical modulation is only
a little over 0.1 mm. On records cut at a fixed pitch
of around 240 grooves per inch, this is not a limitation
at all: there is the same amount of room for horizontal
and vertical modulation. But when variable pitch systems
which automatically adjust the groove spacing to allow more
bass are used, you can get a lot more horizontal room for
the bass, but are still restricted to the same amount of
vertical room. Mixing the bass to mono solves the problem.

It is possible to build a system which would limit L-R bass
only when necessary, but since the effect of stereo bass
is fairly subtle if it can be heard at all, making the bass
mono seems the easiest solution.

If so, does this make the records easier to press?

I doubt it makes any difference.

Peter.
--

Peter Irwin wrote:
wrote:


It is possible to build a system which would limit L-R bass
only when necessary, but since the effect of stereo bass
is fairly subtle if it can be heard at all, making the bass
mono seems the easiest solution.

So, the 'compatible' method is now the standard? All stereo LPs are
mixed to blend the bass to center?



If so, does this make the records easier to press?

I doubt it makes any difference.

Peter.
--