[Paul Stamler]

Hi folks:

Here's a weird one, for those interested in 78s. (Well, this is an audio
production newsgroup.) I'm working on cleaning up a 1923 Gennett record,
acoustically recorded, and when I look at the spectral view of the whole
song

http://twin-x.com/groupdiy/displayimage.php?pos=-2689

I see a pair of lines beginning in the upper left-hand corner and going
diagonally to the right side, about halfway down. Zooming in to about a 1.5
second slice of the song, taken about halfway through

http://twin-x.com/groupdiy/displayimage.php?pos=-2688

you can see that in fact it's a tone which alternates pitch between high and
low, once per revolution. (It may help to click on the image for a cleaner
view.) At the start of the recording, the lower pitch is at about 20.5kHz,
while the upper pitch is above the Nyquist frequency of this 44.1k sample
rate and so is not recorded. By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Those of you famiiar with disc cutting -- what could possibly be the cause
of this? I can see a tone sneaking in through the drive mechanism of the
turntable, I can see it being different as the turntable rotates...but what
could cause the pitch to lower by about 50% in the course of the recording?

There are four Gennett sides in this set of records. Of the four, one has no
tone, two others have tones that mimic the descending frequency as the side
progresses, but the alternation as the disc turns is less regular. None of
the other records in the collection (all on other labels) seem to have it.
I've observed this a few times in the past; don't remember whether the
recordings were on Gennett or not.

Peace,
Paul

[Don Pearce]

Paul Stamler wrote:
Hi folks:

Here's a weird one, for those interested in 78s. (Well, this is an audio
production newsgroup.) I'm working on cleaning up a 1923 Gennett record,
acoustically recorded, and when I look at the spectral view of the whole
song

http://twin-x.com/groupdiy/displayimage.php?pos=-2689

I see a pair of lines beginning in the upper left-hand corner and going
diagonally to the right side, about halfway down. Zooming in to about a 1.5
second slice of the song, taken about halfway through

http://twin-x.com/groupdiy/displayimage.php?pos=-2688

you can see that in fact it's a tone which alternates pitch between high and
low, once per revolution. (It may help to click on the image for a cleaner
view.) At the start of the recording, the lower pitch is at about 20.5kHz,
while the upper pitch is above the Nyquist frequency of this 44.1k sample
rate and so is not recorded. By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Those of you famiiar with disc cutting -- what could possibly be the cause
of this? I can see a tone sneaking in through the drive mechanism of the
turntable, I can see it being different as the turntable rotates...but what
could cause the pitch to lower by about 50% in the course of the recording?

There are four Gennett sides in this set of records. Of the four, one has no
tone, two others have tones that mimic the descending frequency as the side
progresses, but the alternation as the disc turns is less regular. None of
the other records in the collection (all on other labels) seem to have it.
I've observed this a few times in the past; don't remember whether the
recordings were on Gennett or not.

Peace,
Paul




Not a clue as to what could cause that, but at least you can safely
filter them off.

I suppose you need to start an investigation. Are they still there in
the lead-out groove. Are they there if you lift the stylus off. Are they
there on some other player - etc. At least you would know if they were
genuinely artefacts on the discs.

As these were acoustic recordings I'm assuming that something was
squeaking in the clockwork mechanism prior to the speed governor and the
frequency reduction is a wind-down effect. Probably everyone in the room
was old enough that nobody could hear it as it started (high frequency).

d

[Edi Zubovic[_2_]]

On Thu, 23 Oct 2008 08:30:35 +0100, Don Pearce
wrote:

Paul Stamler wrote:
Hi folks:

Here's a weird one, for those interested in 78s. (Well, this is an audio
production newsgroup.) I'm working on cleaning up a 1923 Gennett record,
acoustically recorded, and when I look at the spectral view of the whole
song

http://twin-x.com/groupdiy/displayimage.php?pos=-2689

I see a pair of lines beginning in the upper left-hand corner and going
diagonally to the right side, about halfway down. Zooming in to about a 1.5
second slice of the song, taken about halfway through

http://twin-x.com/groupdiy/displayimage.php?pos=-2688

you can see that in fact it's a tone which alternates pitch between high and
low, once per revolution. (It may help to click on the image for a cleaner
view.) At the start of the recording, the lower pitch is at about 20.5kHz,
while the upper pitch is above the Nyquist frequency of this 44.1k sample
rate and so is not recorded. By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Those of you famiiar with disc cutting -- what could possibly be the cause
of this? I can see a tone sneaking in through the drive mechanism of the
turntable, I can see it being different as the turntable rotates...but what
could cause the pitch to lower by about 50% in the course of the recording?

There are four Gennett sides in this set of records. Of the four, one has no
tone, two others have tones that mimic the descending frequency as the side
progresses, but the alternation as the disc turns is less regular. None of
the other records in the collection (all on other labels) seem to have it.
I've observed this a few times in the past; don't remember whether the
recordings were on Gennett or not.

Peace,
Paul
-- I think this could be a sort of cutter pinch or some other
cutter/lacquer issue. You see it beginning in the ultrasonic area at
the outer rim of the record, and falling down as the cutter travels to
the end of the record. First I thought that the two walleys would
roughly co-respond to the two geometrically most clean spots of an
record but it seems that they rather change with dynamics. The pitch
is IMO lowered as the cutting geometry changes towards the end of the
recording. At the other hand, I've seen mirror reflections near the
Nyquist frequency when analysing a high frequency sweep tone.

-- Just a guess --

-- Edi Zubovic, Crikvenica, Croatia

[Adrian Tuddenham]

Paul Stamler wrote:

Hi folks:

Here's a weird one, for those interested in 78s....
[...]
you can see that in fact it's a tone which alternates pitch between high and
low, once per revolution. (It may help to click on the image for a cleaner
view.) At the start of the recording, the lower pitch is at about 20.5kHz,
while the upper pitch is above the Nyquist frequency of this 44.1k sample
rate and so is not recorded. By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

It often occurs very noticeably at the end of 8" 'Broadcast" records
made by the UK branch of the Vocalian Co. For a long while I thought it
was because the Marconi recording process, which is what they used,
might have been equipped with a long whippy cutting tool which began to
chatter at slow surface speeds near the end of the disc.

Some time ago, I discussed this matter with two disc cutting engineers,
the late Peter Copeland and (the still very much alive) Sean Davies.
They came to the conclusion that it was mainly due to the wax cooling on
the lathe turntable during the cutting session (no nitrate in those
days).

It would be useful to keep a note of these examples and try to relate
them back to the recording conditions. Were any know to occur during
summer or were they all recorded in winter? Were they more common on
location and/or in a recording van, where the air temperature would be
lower or the wax ovens less effective?

An interesting project for anyone with enough time to spare.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Don Pearce]

Adrian Tuddenham wrote:
Paul Stamler wrote:

Hi folks:

Here's a weird one, for those interested in 78s....
[...]
you can see that in fact it's a tone which alternates pitch between high and
low, once per revolution. (It may help to click on the image for a cleaner
view.) At the start of the recording, the lower pitch is at about 20.5kHz,
while the upper pitch is above the Nyquist frequency of this 44.1k sample
rate and so is not recorded. By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

It often occurs very noticeably at the end of 8" 'Broadcast" records
made by the UK branch of the Vocalian Co. For a long while I thought it
was because the Marconi recording process, which is what they used,
might have been equipped with a long whippy cutting tool which began to
chatter at slow surface speeds near the end of the disc.

Some time ago, I discussed this matter with two disc cutting engineers,
the late Peter Copeland and (the still very much alive) Sean Davies.
They came to the conclusion that it was mainly due to the wax cooling on
the lathe turntable during the cutting session (no nitrate in those
days).

It would be useful to keep a note of these examples and try to relate
them back to the recording conditions. Were any know to occur during
summer or were they all recorded in winter? Were they more common on
location and/or in a recording van, where the air temperature would be
lower or the wax ovens less effective?

An interesting project for anyone with enough time to spare.



How does this work? Is it that the wax forms tiny ripples or wrinkles as
it cools? Assuming they formed in lines across the disc, that would
explain both the variation in frequency with each turn and the drop in
frequency towards the centre.

d

[Adrian Tuddenham]

Don Pearce wrote:

Adrian Tuddenham wrote:
Paul Stamler wrote:

Hi folks:

Here's a weird one, for those interested in 78s....
[...]
you can see that in fact it's a tone which alternates pitch between high
and
low, once per revolution. (It may help to click on the image for a cleaner
view.) At the start of the recording, the lower pitch is at about 20.5kHz,
while the upper pitch is above the Nyquist frequency of this 44.1k sample
rate and so is not recorded. By the end of the tune, the high pitch is
about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

It often occurs very noticeably at the end of 8" 'Broadcast" records
made by the UK branch of the Vocalian Co. For a long while I thought it
was because the Marconi recording process, which is what they used,
might have been equipped with a long whippy cutting tool which began to
chatter at slow surface speeds near the end of the disc.

Some time ago, I discussed this matter with two disc cutting engineers,
the late Peter Copeland and (the still very much alive) Sean Davies.
They came to the conclusion that it was mainly due to the wax cooling on
the lathe turntable during the cutting session (no nitrate in those
days).

It would be useful to keep a note of these examples and try to relate
them back to the recording conditions. Were any know to occur during
summer or were they all recorded in winter? Were they more common on
location and/or in a recording van, where the air temperature would be
lower or the wax ovens less effective?

An interesting project for anyone with enough time to spare.



How does this work? Is it that the wax forms tiny ripples or wrinkles as
it cools? Assuming they formed in lines across the disc, that would
explain both the variation in frequency with each turn and the drop in
frequency towards the centre.

I think the wax stays smooth but becomes too hard for the cutting tool
to work smoothly. The tool chatters as it tries to cut the hard wax.
If it has been heated or cooled unevenly, the effect will vary around
the axis of rotation.

If you have ever tried to machine a very hard material in a conventional
metalwork lathe, or machined something that was running too slowly with
an incorrectly set tool, you will have experienced the effect. The
drop in frequency relates to the surface speed and the changing
mechanical impedance of the mechanical resonant circuit, which includes
the wax.

The biggest component on the disc is probably longitudinal ('Z'-axis)
modulation which would give a frequency-modulated effect, but this won't
be visible or strongly audible. Any lateral component of the chatter
will be much more audible. and may be visible under the right
conditions.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Adrian Tuddenham]

Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]



--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Scott Dorsey]

Paul Stamler wrote:

Those of you famiiar with disc cutting -- what could possibly be the cause
of this? I can see a tone sneaking in through the drive mechanism of the
turntable, I can see it being different as the turntable rotates...but what
could cause the pitch to lower by about 50% in the course of the recording?

The cutter is worn and is not making a clean cut, instead it is causing
the top edge of the disc to deform and ripple. This happens with acetates
as well as with wax.

It's the same basic mechanism that makes a fiddle or a cello work... the
bow alternately sticks to the the string and lets go.

There are four Gennett sides in this set of records. Of the four, one has no
tone, two others have tones that mimic the descending frequency as the side
progresses, but the alternation as the disc turns is less regular. None of
the other records in the collection (all on other labels) seem to have it.
I've observed this a few times in the past; don't remember whether the
recordings were on Gennett or not.

Look at the groove under a microscope and I bet you see the groove walls
are rippled... it may only be the horn that is the problem, so playing with
a smaller stylus could cause the noise to go away.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Don Pearce]

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]




Looks pretty much identical - sounds awful too. You'd have thought that
would have been heard and sorted early on.

d

[Don Pearce]

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]




BTW, nice to see that you turn off the stereo pilot tone while
broadcasting those mono pieces.

d

[Adrian Tuddenham]

Don Pearce wrote:

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]




Looks pretty much identical - sounds awful too. You'd have thought that
would have been heard and sorted early on.

What can a recording engineer do when faced with an artiste waiting to
record, a cold room and a company with no resources that is struggling
to keep its head above water in a depression?

The customers for that sort of material probably weren't terribly
discerning about sound quality.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Don Pearce]

Adrian Tuddenham wrote:
Don Pearce wrote:

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.
Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]



Looks pretty much identical - sounds awful too. You'd have thought that
would have been heard and sorted early on.

What can a recording engineer do when faced with an artiste waiting to
record, a cold room and a company with no resources that is struggling
to keep its head above water in a depression?

The customers for that sort of material probably weren't terribly
discerning about sound quality.



Come to that you probably couldn't hear it on the average gramophone of
the day.

d

[Adrian Tuddenham]

Don Pearce wrote:

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.

Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]




BTW, nice to see that you turn off the stereo pilot tone while
broadcasting those mono pieces.

I agree that it's the right way to do it, but I don't deserve the
credit; those MP3 were generated from my backup AIFF files. To save
space, I only made them in stereo when the programme contained a stereo
item, and then it was used throughout the file, not item-by-item.

When those programmes were broadcast, they were posted to the station on
CDRs (which were always two-track) and I had no control over what
happened after that - except that I made it very clear that I would be
on the 'phone to them as soon as I heard the slightest trace of
automatic volume pumping. They were very good and kept the levels set
to a sensible setting.

(I had threatened to put line-up tones on the first track of each disc,
but they were afraid that Continuity would not recognise them and would
accidentally broadcast them as part of the programme)


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Don Pearce]

Adrian Tuddenham wrote:
Don Pearce wrote:

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.
Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]



BTW, nice to see that you turn off the stereo pilot tone while
broadcasting those mono pieces.

I agree that it's the right way to do it, but I don't deserve the
credit; those MP3 were generated from my backup AIFF files. To save
space, I only made them in stereo when the programme contained a stereo
item, and then it was used throughout the file, not item-by-item.

When those programmes were broadcast, they were posted to the station on
CDRs (which were always two-track) and I had no control over what
happened after that - except that I made it very clear that I would be
on the 'phone to them as soon as I heard the slightest trace of
automatic volume pumping. They were very good and kept the levels set
to a sensible setting.

(I had threatened to put line-up tones on the first track of each disc,
but they were afraid that Continuity would not recognise them and would
accidentally broadcast them as part of the programme)



Sort of opposite problem that the Beeb had one Nov 11th when they tried
to broadcast the minute's silence and most of their transmitters dropped
into auto fill-in music.

d

[Scott Dorsey]

Adrian Tuddenham wrote:

I think the wax stays smooth but becomes too hard for the cutting tool
to work smoothly. The tool chatters as it tries to cut the hard wax.
If it has been heated or cooled unevenly, the effect will vary around
the axis of rotation.

Yes. I blame a poor tool as much as I blame hard wax for this, though.
You can even make it happen with a lacquer if you use a worn cutter,
even hot.

The biggest component on the disc is probably longitudinal ('Z'-axis)
modulation which would give a frequency-modulated effect, but this won't
be visible or strongly audible. Any lateral component of the chatter
will be much more audible. and may be visible under the right
conditions.

Yes, the longitudinal vibration is manifested as a kind of flutter that
produces sidebands around pure tones. But there will also be lateral
vibration too, and it should mostly be at the top of the groove where
the wax is more free to move up and down.

I have never actually cut wax... it would be really fun to try and see
how different it is than a modern lacquer.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Adrian Tuddenham]

Don Pearce wrote:

Adrian Tuddenham wrote:
Don Pearce wrote:

Adrian Tuddenham wrote:
Paul Stamler wrote:

....By the end of the tune, the high pitch is about
12kHz and the low is about 10kHz, both quite audible despite the record's
surface noise.
Is it similar to the sound from 16'45" to 17'30" in this recording?

http://www.poppyrecords.co.uk/lifebeforevinyl/MP3s/LBV28(2-13).mp3


[More info at:
http://www.poppyrecords.co.uk/lifebeforevinyl/P28.htm ]



BTW, nice to see that you turn off the stereo pilot tone while
broadcasting those mono pieces.

I agree that it's the right way to do it, but I don't deserve the
credit; those MP3 were generated from my backup AIFF files. To save
space, I only made them in stereo when the programme contained a stereo
item, and then it was used throughout the file, not item-by-item.

When those programmes were broadcast, they were posted to the station on
CDRs (which were always two-track) and I had no control over what
happened after that - except that I made it very clear that I would be
on the 'phone to them as soon as I heard the slightest trace of
automatic volume pumping. They were very good and kept the levels set
to a sensible setting.

(I had threatened to put line-up tones on the first track of each disc,
but they were afraid that Continuity would not recognise them and would
accidentally broadcast them as part of the programme)



Sort of opposite problem that the Beeb had one Nov 11th when they tried
to broadcast the minute's silence and most of their transmitters dropped
into auto fill-in music.

One Nov 11th I was driving somewhere and happened to switch on the car
radio in the middle of the one-minute's silence. I didn't remember what
day it was, so I was puzzled by the sounds of an open mic being
broadcast.

After a few seconds I started winding up the gain, trying to hear if
there was anything that would give me a clue about what was happening.
I had just reached maximum gain when the end of the silence was marked
by a cannon shot....


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Paul Stamler]

"Don Pearce" wrote in message
et...

Not a clue as to what could cause that, but at least you can safely
filter them off.

Well, fairly safely. There's signal on this disc at 8kHz, so I'll have to be
careful if I want to chop 10kHz. Probably use a noise-reduction program
rather than a straight filter, but we'll see. I'm more curious right now
about where it came from.

I suppose you need to start an investigation. Are they still there in
the lead-out groove.

Yes.

Are they there if you lift the stylus off.

No.

Are they
there on some other player - etc. At least you would know if they were
genuinely artefacts on the discs.

That, I couldn't tell you, because I only have one 78 turntable. But I
transferred several dozen discs for this project, all at roughly the same
time and under roughly similar conditions, and only the four Gennett sides
have this oddity.

As these were acoustic recordings I'm assuming that something was
squeaking in the clockwork mechanism prior to the speed governor and the
frequency reduction is a wind-down effect. Probably everyone in the room
was old enough that nobody could hear it as it started (high frequency).

Quite likely. Or perhaps it was entirely internal, and not audible from more
than an inch or two away.

Peace,
Paul

[Paul Stamler]

"Edi Zubovic" wrote in message
...

-- I think this could be a sort of cutter pinch or some other
cutter/lacquer issue. You see it beginning in the ultrasonic area at
the outer rim of the record, and falling down as the cutter travels to
the end of the record. First I thought that the two walleys would
roughly co-respond to the two geometrically most clean spots of an
record but it seems that they rather change with dynamics.

There aren't any particular dynamics on this disc -- everyone plays at the
same volume throughout, as is often the case on acoustic recordings.

The pitch
is IMO lowered as the cutting geometry changes towards the end of the
recording. At the other hand, I've seen mirror reflections near the
Nyquist frequency when analysing a high frequency sweep tone.

Well, the cutting geometry *shouldn't* change at the end of the recording,
since it's a straight-line lathe. On the other hand, there does seem to be
more loss of high-frequencies than usual toward the center grooves, which
suggests that the cutting assembly may not have been mounted at the proper
angle. Whether that has anything to do with this artifact, I don't know.

Peace,
Paul

[Paul Stamler]

"Adrian Tuddenham" wrote in message
id.invalid...

It often occurs very noticeably at the end of 8" 'Broadcast" records
made by the UK branch of the Vocalian Co. For a long while I thought it
was because the Marconi recording process, which is what they used,
might have been equipped with a long whippy cutting tool which began to
chatter at slow surface speeds near the end of the disc.

Some time ago, I discussed this matter with two disc cutting engineers,
the late Peter Copeland and (the still very much alive) Sean Davies.
They came to the conclusion that it was mainly due to the wax cooling on
the lathe turntable during the cutting session (no nitrate in those
days).

It would be useful to keep a note of these examples and try to relate
them back to the recording conditions. Were any know to occur during
summer or were they all recorded in winter? Were they more common on
location and/or in a recording van, where the air temperature would be
lower or the wax ovens less effective?

An interesting project for anyone with enough time to spare.

Indeed. This makes sense to me, that some parameters would change as the wax
blank cooled. The recording in question, and its flip side, were cut on
January 23, 1923, while the other two which show (slightly different)
artifacts were cut November 14, 1922. I have no reason to suspect they were
cut anyplace but the Gennett studio in Richmond, Indiana, where it gets
plenty cold in the winter and even in the autumn.

Could there have been some sort of stick-slip (violining) happening between
the cutting stylus and the wax, and would the frequency of that have perhaps
gone down as the wax cooled? The fact that it alternates up and down as the
record turns makes something like this plausible, if the blank started out
cooler on one half than the other.

Peace,
Paul

[Adrian Tuddenham[_2_]]

Paul Stamler wrote:

"Adrian Tuddenham" wrote in message
id.invalid...

It often occurs very noticeably at the end of 8" 'Broadcast" records
made by the UK branch of the Vocalian Co. For a long while I thought it
was because the Marconi recording process, which is what they used,
might have been equipped with a long whippy cutting tool which began to
chatter at slow surface speeds near the end of the disc.

Some time ago, I discussed this matter with two disc cutting engineers,
the late Peter Copeland and (the still very much alive) Sean Davies.
They came to the conclusion that it was mainly due to the wax cooling on
the lathe turntable during the cutting session (no nitrate in those
days).

It would be useful to keep a note of these examples and try to relate
them back to the recording conditions. Were any know to occur during
summer or were they all recorded in winter? Were they more common on
location and/or in a recording van, where the air temperature would be
lower or the wax ovens less effective?

An interesting project for anyone with enough time to spare.

Indeed. This makes sense to me, that some parameters would change as the wax
blank cooled. The recording in question, and its flip side, were cut on
January 23, 1923, while the other two which show (slightly different)
artifacts were cut November 14, 1922. I have no reason to suspect they were
cut anyplace but the Gennett studio in Richmond, Indiana, where it gets
plenty cold in the winter and even in the autumn.

That fit the theory so far. I'll have to start checking my collection
of 'Braodcasts' to see if there really is a correlation. I don't
suppose Hayes, Middlesex (England) got as cold as Indiana, but in wax
terms it was proabaly cold enough to cause trouble.


Could there have been some sort of stick-slip (violining) happening between
the cutting stylus and the wax, and would the frequency of that have perhaps
gone down as the wax cooled?

It's somewhere between 'stick-slip' and 'dig-chip', with the wax and the
cutting tool and possibly the mounting frame oscillating at some natural
resonant frequency.

The fact that it alternates up and down as the
record turns makes something like this plausible, if the blank started out
cooler on one half than the other.

That's probably the reason. The physical properties of the recording
wax (aluminium/lead stearate soap + paraffin wax mixture) alter greatly
over a small temperature range. Both the modulus of elasticity of the
wax and its internal damping factor due to hysteresis would be affected.
That would have a big effect on the frequency (and the amplitude?) of
oscillation.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Mark]

On Oct 23, 4:01*pm, "Paul Stamler" wrote:
"Edi Zubovic" wrote in message

...

-- I think this could be a sort of cutter pinch or some other
cutter/lacquer issue. You see it beginning in the ultrasonic area at
the outer rim of the record, and falling down as the cutter travels to
the end of the record. First I thought that the two walleys would
roughly co-respond to the two geometrically most clean spots of an
record but it seems that they rather change with dynamics.

There aren't any particular dynamics on this disc -- everyone plays at the
same volume throughout, as is often the case on acoustic recordings.

The pitch
is IMO lowered as the cutting geometry changes towards the end of the
recording. At the other hand, I've seen mirror reflections near the
Nyquist frequency when analysing a high frequency sweep tone.

Well, the cutting geometry *shouldn't* change at the end of the recording,
since it's a straight-line lathe. On the other hand, there does seem to be
more loss of high-frequencies than usual toward the center grooves, which
suggests that the cutting assembly may not have been mounted at the proper
angle. Whether that has anything to do with this artifact, I don't know.

Peace,
Paul

well, as I'm sure you know, while the disc RPM remains constant at
78RPM, the TANGENTIAL VELOCITY of the surface relative to the stylus
reduces for grooves closer to the center.

Mark