Had another go at trying to identify an "LP" sized disc I picked up
somewhere. I found this reference
http://www.ips.org.uk/audiocompendiu....php?title=MSS

"“Direct Cut Acetate” a system that used a cellulose acetate medium
coated onto an aluminium disc which, though soft enough to cut, was
sufficiently hard to withstand playbacks without excessive wear"
is exactly this description, acetate film over thick Al disc.
It has a small hole on the underside , presumably to drive the disc
around and resist the cutting force.
Unusually this is marked 50RPM, agreeing with the 120 band strobe ring
(uk 50 Hz mains) and you play from the inside to outside, has some
ragtime like piano music on it, well one track anyway, seems to be 2 tracks.
Dated by rubber stamp and endorsing ink, 11 Dec 1944 and AY 1, may have
had another letter beforethe A.
There isa letter D impressed in the aluminium on the underside near the
drive dog hole.
I must get around to taking a recording off this disc by modding a vinyl
record deck to play it properly.
Did the BBC modify their ones to 50 rpm?

N_Cook wrote:

Had another go at trying to identify an "LP" sized disc I picked up
somewhere. I found this reference
http://www.ips.org.uk/audiocompendiu....php?title=MSS

""Direct Cut Acetate” a system that used a cellulose acetate medium
coated onto an aluminium disc which, though soft enough to cut, was
sufficiently hard to withstand playbacks without excessive wear"
is exactly this description, acetate film over thick Al disc.
It has a small hole on the underside , presumably to drive the disc
around and resist the cutting force.
Unusually this is marked 50RPM, agreeing with the 120 band strobe ring
(uk 50 Hz mains) and you play from the inside to outside, has some
ragtime like piano music on it, well one track anyway, seems to be 2 tracks.
Dated by rubber stamp and endorsing ink, 11 Dec 1944 and AY 1, may have
had another letter beforethe A.
There isa letter D impressed in the aluminium on the underside near the
drive dog hole.
I must get around to taking a recording off this disc by modding a vinyl
record deck to play it properly.
Did the BBC modify their ones to 50 rpm?

The Marguerite lathe offered 60 rpm as an alternative to 78. I have
never heard of one running at 50 rpm. The strobe was sometimes marked
"50 c/s", but the disc ran at 60. rpm.

Yes , the BBC did use 60 rpm for a while, but no disc from this era will
have been recorded with the RIAA characteristic, so you will need
specialist equipment for correct playback (initially try a Blumlein
300c/s characteristic, it suits most UK recordings of that era). More
info on this wil be found at:

http://www.bl.uk/reshelp/findhelpres...aloguesoundres
toration.pdf

There was a later BBC characteristic known as the "D" system, but this
did not come into use until 1949 (so the "D" stamped in the disc is
unlikely to refer to this).

You will not get many plays before the quality begins to deteriorate, so
make sure you have everything in place before you let a styus touch the
surface, so you stand the best chance of getting a good transfer
straight away. If the nitrate surface has deteriorated, there are ways
of improving it by replacing the missing plasticiser molecules with
other chemicals. (If the surface is mud-cracked or there is red powder
on it, the disc will be in a dangerous condition and you need to seek
specialist help to avoid starting a disastrous fire.)

Generally a 0.0028" stylus is about the right size, but if the nitrate
has shrunk, you might need to try a range of sizes to get the best
results - or to avoid 'bottoming' on the aluminium if the bottom of the
groove has split. Deep spiral scratches are a nightmare because they
drag the stylus across the grooves; there are a whole range of
techniques for dealing with that situation, ranging from tiltng the deck
or playing the disc backwards, to re-cutting the grooves by hand under a
microscope.

There is some info about MSS in "Audio Biographies" by Briggs and I
believe Cecil Watts's wife published a biography of the firm, although I
have never seen a copy.

If you want more help with this, please contact me (I live in the UK).


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

On 13/12/2015 11:18, Adrian Tuddenham wrote:
N_Cook wrote:

Had another go at trying to identify an "LP" sized disc I picked up
somewhere. I found this reference
http://www.ips.org.uk/audiocompendiu....php?title=MSS

""Direct Cut Acetate” a system that used a cellulose acetate medium
coated onto an aluminium disc which, though soft enough to cut, was
sufficiently hard to withstand playbacks without excessive wear"
is exactly this description, acetate film over thick Al disc.
It has a small hole on the underside , presumably to drive the disc
around and resist the cutting force.
Unusually this is marked 50RPM, agreeing with the 120 band strobe ring
(uk 50 Hz mains) and you play from the inside to outside, has some
ragtime like piano music on it, well one track anyway, seems to be 2 tracks.
Dated by rubber stamp and endorsing ink, 11 Dec 1944 and AY 1, may have
had another letter beforethe A.
There isa letter D impressed in the aluminium on the underside near the
drive dog hole.
I must get around to taking a recording off this disc by modding a vinyl
record deck to play it properly.
Did the BBC modify their ones to 50 rpm?

The Marguerite lathe offered 60 rpm as an alternative to 78. I have
never heard of one running at 50 rpm. The strobe was sometimes marked
"50 c/s", but the disc ran at 60. rpm.

Yes , the BBC did use 60 rpm for a while, but no disc from this era will
have been recorded with the RIAA characteristic, so you will need
specialist equipment for correct playback (initially try a Blumlein
300c/s characteristic, it suits most UK recordings of that era). More
info on this wil be found at:

http://www.bl.uk/reshelp/findhelpres...aloguesoundres
toration.pdf

There was a later BBC characteristic known as the "D" system, but this
did not come into use until 1949 (so the "D" stamped in the disc is
unlikely to refer to this).

You will not get many plays before the quality begins to deteriorate, so
make sure you have everything in place before you let a styus touch the
surface, so you stand the best chance of getting a good transfer
straight away. If the nitrate surface has deteriorated, there are ways
of improving it by replacing the missing plasticiser molecules with
other chemicals. (If the surface is mud-cracked or there is red powder
on it, the disc will be in a dangerous condition and you need to seek
specialist help to avoid starting a disastrous fire.)

Generally a 0.0028" stylus is about the right size, but if the nitrate
has shrunk, you might need to try a range of sizes to get the best
results - or to avoid 'bottoming' on the aluminium if the bottom of the
groove has split. Deep spiral scratches are a nightmare because they
drag the stylus across the grooves; there are a whole range of
techniques for dealing with that situation, ranging from tiltng the deck
or playing the disc backwards, to re-cutting the grooves by hand under a
microscope.

There is some info about MSS in "Audio Biographies" by Briggs and I
believe Cecil Watts's wife published a biography of the firm, although I
have never seen a copy.

If you want more help with this, please contact me (I live in the UK).



wow, what a lot of info
that pdf would seem to be now on
http://www.bl.uk/britishlibrary/~/me...estoration.pdf
not read it yet.
I'll take a pic of the label and also the reverse with spindle hole and
the drive dog hole.
Label says "SPEED 50 R.P.M"
At the moment I was only trying to think how to fudge a deck to play it.
Hang the motor upside down and a 50/45 scaled from the 45
pulley,replacement pulley, if I can find one. I seem to remember not
only inside to outside but counterclockwse rotation.
Hopefully minimum stylus pressure
No idea about antiskating and handedness of the arm at the moment.
May end up replaying in reverse and then electronically reversing it.
No intention of even applying distilled water to the surface for the moment.

3 pics of this disc
http://www.diverse.4mg.com/marguerite1.jpg
http://www.diverse.4mg.com/marguerite2.jpg
http://www.diverse.4mg.com/marguerite3.jpg
the third is the reverse, the label on the front is covering over the
drive dog hole, viewed from the rear.
The tearing around the spindle hole is the only obvious failing of the
film, clumsy positioning over a spindle in antiquity?
Film laid down like silicone slivers and resist etc in chippery
production? spun at high speed with a dot of liquid on the disc?
The colours are about right, plum-brown in flat light and coppery tone
with slanting light reflecting off the aluminium. The apparent grooves
on the rear is probably machining marks of the Al blank.
Perhaps the 50rpm business was a "pirated" manufacturer trying to escape
patent infringement, I suppose patent library is one route to look into.
I'll check again , but the blank space between 2 tracks, with
continuation groove, spirals in such a fashion that playing from sinside
to out , the disc would be spinning normal clockwise , so hopefully
normal handedness of the tonearm and normal antiskating weight.

"N_Cook" wrote in message ...

3 pics of this disc
http://www.diverse.4mg.com/marguerite1.jpg
http://www.diverse.4mg.com/marguerite2.jpg
http://www.diverse.4mg.com/marguerite3.jpg
the third is the reverse, the label on the front is covering over the
drive dog hole, viewed from the rear.
The tearing around the spindle hole is the only obvious failing of the
film, clumsy positioning over a spindle in antiquity?
Film laid down like silicone slivers and resist etc in chippery
production? spun at high speed with a dot of liquid on the disc?
The colours are about right, plum-brown in flat light and coppery tone
with slanting light reflecting off the aluminium. The apparent grooves
on the rear is probably machining marks of the Al blank.
Perhaps the 50rpm business was a "pirated" manufacturer trying to escape
patent infringement, I suppose patent library is one route to look into.
I'll check again , but the blank space between 2 tracks, with
continuation groove, spirals in such a fashion that playing from sinside
to out , the disc would be spinning normal clockwise , so hopefully
normal handedness of the tonearm and normal antiskating weight.




You might only get one shot at playing this disc, it may be destroyed by
that process, as has been suggested.

This may not be your world, but I would take Adrians advice and try and take
a digital recording via a normal turntable at 45rpm, if the handedness and
anti skate should work the same.
Speed/EQ adjustments and even reversing the audio can be done later, much
more safely, in software.


Cheers,


Gareth.

N_Cook wrote:

3 pics of this disc
http://www.diverse.4mg.com/marguerite1.jpg
http://www.diverse.4mg.com/marguerite2.jpg
http://www.diverse.4mg.com/marguerite3.jpg

Typical centre-start transcription disc of the period. Broadcasters
sometimes used centre-start to make sure the louder climax of a
performance was recorded at the highest surface speed to give best
quality.

Common practice for continuous programmes lasting longer than one disc
side was to use two recording machines (often with a single common
amplifier). Sometimes thesae were set up so that one recorded
outside-in and the other inside-out, this meant that the changeover on
playback was less noticeable because the surface noise didn't suddenly
change its quality. This system was not popular with the playback
operators, who had to check each side carefully and often made mistakes.

The label suggest that there is no question that the intended playing
speed was 50 RPM - but it is definitely non-standard.

To vary the speed without a lot of butchery, connect the turntable motor
through a step-up auto-transformer to the 100v output of a large P.A.
amplifier. Feed the amplifier from an audio signal generator and adjust
the frequency to get the required speed change. Carefully monitor the
motor current and adjust the amplifier gain so that it is maintained at
a similar value to the normal 50c/s current, otherwise you will burn out
the motor at low frequencies.

Alternatively, look out for a secondhand Lenco turntable with infinitely
variable speed.


The tearing around the spindle hole is the only obvious failing of the
film, clumsy positioning over a spindle in antiquity?

No, these discs weren't played many times, so it is more likely to be
caused by shrinkage of the laquer film pulling away at the centre. It
also appears to have delaminated at the rim for the same reason.

Film laid down like silicone slivers and resist etc in chippery
production? spun at high speed with a dot of liquid on the disc?

....or edge dipped into a bath of laquer whilst rotating slowly. Both
techniques were used.

The colours are about right, plum-brown in flat light and coppery tone
with slanting light reflecting off the aluminium. The apparent grooves
on the rear is probably machining marks of the Al blank.

They weren't usually machined, the blanks were stamped out of sheet
aluminium. Without examining this one closely, I wouldn't like to guess
at what caused that.


Perhaps the 50rpm business was a "pirated" manufacturer trying to escape
patent infringement, I suppose patent library is one route to look into.

No chance, hardly anybody but the BBC and GPO could get hold of MSS
blanks during the war; the GPO ran the factory. By 1944 aluminium was
in very short supply, so private recordings, when they could be made at
all, were being made on glass and even galvanised iron blanks (they were
heavy!). The BBC monitoring services recorded onto wax cylinders.

I'll check again , but the blank space between 2 tracks, with
continuation groove, spirals in such a fashion that playing from sinside
to out , the disc would be spinning normal clockwise , so hopefully
normal handedness of the tonearm and normal antiskating weight.

A centre-start disc still rotates in the conventional direction, it is
one of the few conventions in the recording world that never seemed to
be flouted. The only time you would need a reversing turntable is if
you needed to play it backwards to recover a lost turn because of a
jumped groove.


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

On 13/12/2015 14:43, Adrian Tuddenham wrote:
N_Cook wrote:

3 pics of this disc
http://www.diverse.4mg.com/marguerite1.jpg
http://www.diverse.4mg.com/marguerite2.jpg
http://www.diverse.4mg.com/marguerite3.jpg

Typical centre-start transcription disc of the period. Broadcasters
sometimes used centre-start to make sure the louder climax of a
performance was recorded at the highest surface speed to give best
quality.

Common practice for continuous programmes lasting longer than one disc
side was to use two recording machines (often with a single common
amplifier). Sometimes thesae were set up so that one recorded
outside-in and the other inside-out, this meant that the changeover on
playback was less noticeable because the surface noise didn't suddenly
change its quality. This system was not popular with the playback
operators, who had to check each side carefully and often made mistakes.

The label suggest that there is no question that the intended playing
speed was 50 RPM - but it is definitely non-standard.

To vary the speed without a lot of butchery, connect the turntable motor
through a step-up auto-transformer to the 100v output of a large P.A.
amplifier. Feed the amplifier from an audio signal generator and adjust
the frequency to get the required speed change. Carefully monitor the
motor current and adjust the amplifier gain so that it is maintained at
a similar value to the normal 50c/s current, otherwise you will burn out
the motor at low frequencies.

Alternatively, look out for a secondhand Lenco turntable with infinitely
variable speed.


The tearing around the spindle hole is the only obvious failing of the
film, clumsy positioning over a spindle in antiquity?

No, these discs weren't played many times, so it is more likely to be
caused by shrinkage of the laquer film pulling away at the centre. It
also appears to have delaminated at the rim for the same reason.

Film laid down like silicone slivers and resist etc in chippery
production? spun at high speed with a dot of liquid on the disc?

....or edge dipped into a bath of laquer whilst rotating slowly. Both
techniques were used.

The colours are about right, plum-brown in flat light and coppery tone
with slanting light reflecting off the aluminium. The apparent grooves
on the rear is probably machining marks of the Al blank.

They weren't usually machined, the blanks were stamped out of sheet
aluminium. Without examining this one closely, I wouldn't like to guess
at what caused that.


Perhaps the 50rpm business was a "pirated" manufacturer trying to escape
patent infringement, I suppose patent library is one route to look into.

No chance, hardly anybody but the BBC and GPO could get hold of MSS
blanks during the war; the GPO ran the factory. By 1944 aluminium was
in very short supply, so private recordings, when they could be made at
all, were being made on glass and even galvanised iron blanks (they were
heavy!). The BBC monitoring services recorded onto wax cylinders.

I'll check again , but the blank space between 2 tracks, with
continuation groove, spirals in such a fashion that playing from sinside
to out , the disc would be spinning normal clockwise , so hopefully
normal handedness of the tonearm and normal antiskating weight.

A centre-start disc still rotates in the conventional direction, it is
one of the few conventions in the recording world that never seemed to
be flouted. The only time you would need a reversing turntable is if
you needed to play it backwards to recover a lost turn because of a
jumped groove.



I think I'll go with the larger pulley, even if not giving exactly
50rpm it will be constant at a measurable speed.
The other letter in front of AY 1 may be a J, so JAY 1,
a ragtime pianist of 1940s called Jay Something ?
The blemish at the rim on the front face is a splodge of powdery paint
or tippex, easily removable if/when I dare to clean the disc.
No damage on the active face film, a few spots missing on the rear.
I'd played it sometime for about 5 seconds, the track stayed intact,
played well enough to tell by my nonmusical ears it was a pleasant piece
of ragtime piano or some such style of music.
I suppose they were double sided discs but only one face recorded on
this. But the exposed Al on the rear near the spindle hole does not show
machining marks. Perhaps there was an attempt at recording on the rear,
but at too low a pressure, it feels smooth to the touch, and the film
patterning goes right to the centre.
I wonder if the use of Persian blue, endorsing ink (stains well into
paper fibres for legal document use) is relevant or that is just the ink
pad they had there then.
Another recovery program I must get back to sometime is 3 spools of used
taperecorder wire that came with a rusted up Magnetophon , circa mid 1950s.
one of these
https://www.soa.hr/galerija/6/m/1-1_...sa_zicom_b.JPG
Hardly anyone could afford one of those pocketsize (well greatcoat
pocket) covert recorders, then.
It would be unlikely they were erased (unless it was a dismissible
conduct if not erased before disposal ) as required the use of batteries
only, and no fast erase. 3 batteries to power the peanut valves and motor.
I got the motor and mechanics free running again, but ran out of time ,
before cross-connecting the head to the head wiring of the R/P head of a
modern cassette recorder, to hear what,if any, is recorded on the wire.

On 13/12/2015 14:43, Adrian Tuddenham wrote:
N_Cook wrote:

3 pics of this disc
http://www.diverse.4mg.com/marguerite1.jpg
http://www.diverse.4mg.com/marguerite2.jpg
http://www.diverse.4mg.com/marguerite3.jpg

Typical centre-start transcription disc of the period. Broadcasters
sometimes used centre-start to make sure the louder climax of a
performance was recorded at the highest surface speed to give best
quality.

Common practice for continuous programmes lasting longer than one disc
side was to use two recording machines (often with a single common
amplifier). Sometimes thesae were set up so that one recorded
outside-in and the other inside-out, this meant that the changeover on
playback was less noticeable because the surface noise didn't suddenly
change its quality. This system was not popular with the playback
operators, who had to check each side carefully and often made mistakes.

The label suggest that there is no question that the intended playing
speed was 50 RPM - but it is definitely non-standard.

To vary the speed without a lot of butchery, connect the turntable motor
through a step-up auto-transformer to the 100v output of a large P.A.
amplifier. Feed the amplifier from an audio signal generator and adjust
the frequency to get the required speed change. Carefully monitor the
motor current and adjust the amplifier gain so that it is maintained at
a similar value to the normal 50c/s current, otherwise you will burn out
the motor at low frequencies.

Alternatively, look out for a secondhand Lenco turntable with infinitely
variable speed.


The tearing around the spindle hole is the only obvious failing of the
film, clumsy positioning over a spindle in antiquity?

No, these discs weren't played many times, so it is more likely to be
caused by shrinkage of the laquer film pulling away at the centre. It
also appears to have delaminated at the rim for the same reason.

Film laid down like silicone slivers and resist etc in chippery
production? spun at high speed with a dot of liquid on the disc?

....or edge dipped into a bath of laquer whilst rotating slowly. Both
techniques were used.

The colours are about right, plum-brown in flat light and coppery tone
with slanting light reflecting off the aluminium. The apparent grooves
on the rear is probably machining marks of the Al blank.

They weren't usually machined, the blanks were stamped out of sheet
aluminium. Without examining this one closely, I wouldn't like to guess
at what caused that.


Perhaps the 50rpm business was a "pirated" manufacturer trying to escape
patent infringement, I suppose patent library is one route to look into.

No chance, hardly anybody but the BBC and GPO could get hold of MSS
blanks during the war; the GPO ran the factory. By 1944 aluminium was
in very short supply, so private recordings, when they could be made at
all, were being made on glass and even galvanised iron blanks (they were
heavy!). The BBC monitoring services recorded onto wax cylinders.

I'll check again , but the blank space between 2 tracks, with
continuation groove, spirals in such a fashion that playing from sinside
to out , the disc would be spinning normal clockwise , so hopefully
normal handedness of the tonearm and normal antiskating weight.

A centre-start disc still rotates in the conventional direction, it is
one of the few conventions in the recording world that never seemed to
be flouted. The only time you would need a reversing turntable is if
you needed to play it backwards to recover a lost turn because of a
jumped groove.



Found a pulley to give +0.5% of 50 RPM, so within normal mains f variation.
I intend to record on minidisc as stereo from a magnetic pickup. At this
stage not playing around with the EQ of the phono amp, any
recommendations for setting the normal domestic amp bass and treble
controls for this first (only?) recording . After a second or 2 at inner
and outer posistions to check antiskating weight and stylus weight is ok

N_Cook wrote:



I intend to record on minidisc...

No, No, NO!!!

Record in the highest possible uncompressed quality. This may be the
only surviving recording and you don't want to screw up the sound wih
the artefacts of Minidisc or any other compression format.

Even with a high bit-rate digital format, it is best to put right
everything that can be done in the analogue domain before digitising it;
once digital artefacts have been created by digital equalisation or
speed changes, they can never be undone.


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

On 14/12/2015 18:13, Adrian Tuddenham wrote:
N_Cook wrote:



I intend to record on minidisc...

No, No, NO!!!

Record in the highest possible uncompressed quality. This may be the
only surviving recording and you don't want to screw up the sound wih
the artefacts of Minidisc or any other compression format.

Even with a high bit-rate digital format, it is best to put right
everything that can be done in the analogue domain before digitising it;
once digital artefacts have been created by digital equalisation or
speed changes, they can never be undone.



I could certainly take the 1V "L & R" audio feeds to other recorders,
but the only analogue recorder I have is an ordinary domestic cassette
recorder of dubious quality other than it works, no 30 IPS R-R recorder,
plus wav file on a laptop?

N_Cook wrote:

On 14/12/2015 18:13, Adrian Tuddenham wrote:
N_Cook wrote:



I intend to record on minidisc...

No, No, NO!!!

Record in the highest possible uncompressed quality. This may be the
only surviving recording and you don't want to screw up the sound wih
the artefacts of Minidisc or any other compression format.

Even with a high bit-rate digital format, it is best to put right
everything that can be done in the analogue domain before digitising it;
once digital artefacts have been created by digital equalisation or
speed changes, they can never be undone.



I could certainly take the 1V "L & R" audio feeds to other recorders,
but the only analogue recorder I have is an ordinary domestic cassette
recorder of dubious quality other than it works, no 30 IPS R-R recorder,
plus wav file on a laptop?

Stereo WAV file on a laptop is your best option. If you were able to
equalise it and get the speed exactly right before digitising it, you
could used 16-bit 44.1k sampling, but if you intend doing any digital
manipulation, a higher resolution is preferable to keep the artefacts to
a minimum.

If you know what format your processing software needs, record in that
format to avoid the artefacts of conversion - but it is better to
eliminate all that nonsense by getting the analogue signal right in the
first place.


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

So assuming Blumlein 300Hz recording characteristic.
I'll feed a few uV from an audio sig gen parallel with the cartridge and
adjust treble and bass to try to get something like
3dB down at 300Hz , flat between 600Hz and 3KHz, +3dB broad hump between
3 KHz and 7KHz and as little as possible above 8KHz.
Whatever it graphs out as, record the details.
Try a couple of seconds recording at centre, mid and outer, to check for
enough but minimum stylus weight and antiskating , then review those
recordings before going for a full run on 3 recording media.
I've not set modified the deck yet, I'll time the revs when done, but
it should be 50.3 RPM assuming 50Hz mains

N_Cook wrote:

So assuming Blumlein 300Hz recording characteristic.
I'll feed a few uV from an audio sig gen parallel with the cartridge and
adjust treble and bass to try to get something like
3dB down at 300Hz , flat between 600Hz and 3KHz, +3dB broad hump between
3 KHz and 7KHz and as little as possible above 8KHz.

For archive work, don't throw away anything you don't have to. Keep it
wide open and flat (or "Blumleined") from 20c/s to 20Kc/s unless
somethng is overloading. The 300c/s characteristic is easily achieved
with a single RC time constant in a feedback loop (the time constant is
531 microseconds) giving bass bost. This should be sensibly limited by
another pole that comes in around 20c/s, because you do not want to be
calling for infinity gain at D.C.

A straightforward variable circuit that can be connected directly to the
pickup is shown at:
http://www.poppyrecords.co.uk/other/.../Equaliser.gif

The time constant can be read directly off the dial of the multi-turn
pot.


If you want something more elaborate, try:
http://www.poppyrecords.co.uk/other/...MultipleEq.htm

When you have made your 'Archive' copy, you can play that and then limit
the bandwidth or do whatever is necessary to produce a 'Playback' copy
that sounds easier on the ear.

Try a couple of seconds recording at centre, mid and outer, to check for
enough but minimum stylus weight and antiskating , then review those
recordings before going for a full run on 3 recording media.

It is a pity you are using a radial arm, but you can usually get away
with it if you use a conical stylus (rather than truncated elliptical,
which will emphasise the playback 'azimuth error' between the two points
of contact on the groove walls). Do you have a stylus in the correct
range for coarse-groove recordings? A microgroove stylus will give
useless results (unless you happen to be incredibly lucky)

I've not set modified the deck yet, I'll time the revs when done, but
it should be 50.3 RPM assuming 50Hz mains

Why not use the 45 rpm speed and run it from a 56c/s supply? That will
save a lot of hassle - any well-designed amplifier rated at about 100
watts, fed through a suitable reversed mains transformer, will do the
job.


If you live anywhere within travelling distance of Bath, you could bring
the disc here and I'll see what I can do with it.


(By the way, I'm beginning to have my doubts as to whether the blank was
a genuine Marguerite product or whether it was made by some other
company.)

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

Adrian Tuddenham wrote: "(If the surface is mud-cracked or there is red powder
on it, the disc will be in a dangerous condition and you need to seek
specialist help to avoid starting a disastrous fire.)"

😱 ??

Setting a record on fire just by playing it?

Adrian Tuddenham wrote: "(If the surface is mud-cracked or there is red powder
on it, the disc will be in a dangerous condition and you need to seek
specialist help to avoid starting a disastrous fire.)"

😱 ??

Setting a record on fire just by playing it?

If the disc is old enough that the cutting surface was celluloid, or
cellulose nitrate (rather than the cellulose acetate used in later
years) then it might be bad juju!

Celluloid deteriorates with age - the camphor escapes and you're left
with just cellulose nitrate, which becomes increasingly brittle.

Cellulose nitrate is known by another name - "guncotton". Also "flash
paper". It's a primary ingredient in smokeless gunpowder.

If something made of celluloid or cellulose nitrate has deteriorated
to the point where it's forming a powder... well, that powder might be
touchy enough that even a static-electric spark might ignite it, and
FOOM.

I'd also be concerned about diamond-stylus-to-groove friction - there's
a *lot* of pressure on that tiny contact surface. I've heard that the
heat generated during playback of an LP is actually sufficient to melt
a very thin surface layer of the vinyl!

On the other hand, if it's a true "acetate" disc (made with cellulose
acetate rather than cellulose nitrate) the flammability problem would
be much less. If this material is deteriorating there might be a
distinct odor of vinegar, as the acetic acid dissociates from the
cellulose.

As to playing the disc... the cat's meow might be to gain access to an
ELP laser turntable, which doesn't use a physical-contact stylus at
all. No wear... but not cheap nor common.

Dave Platt wrote:

Adrian Tuddenham wrote: "(If the surface is mud-cracked or there is red
powder on it, the disc will be in a dangerous condition and you need to
seek specialist help to avoid starting a disastrous fire.)"

😱 ??

Setting a record on fire just by playing it?

Yes, unlikely but possible.


[...]
On the other hand, if it's a true "acetate" disc (made with cellulose
acetate rather than cellulose nitrate)...

It won't be. Cellulose Acetate can only be embossed, not cut. It was
not used for direct-cut discs. (The manufacturers sometimes called
their nitrate discs "Acetates", but this was deliberately misleading
because of the bad reputation that nitrate had gained.)

As to playing the disc... the cat's meow might be to gain access to an
ELP laser turntable, which doesn't use a physical-contact stylus at
all. No wear... but not cheap nor common.

Not all that effective; it plays every bit of dirt the same as solid
groove wall, whereas a stylus will scrape the dirt away as it plays.

A stylus will also scrape the wall away if you get it wrong , so the
optical system has the potential to do less damage; but the cleaning
process needed before optical playback will probably do as much damage
as the stylus. Swings & roundabouts.

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

On 15/12/2015 20:46, Dave Platt wrote:
Adrian Tuddenham wrote: "(If the surface is mud-cracked or there is red powder
on it, the disc will be in a dangerous condition and you need to seek
specialist help to avoid starting a disastrous fire.)"

😱 ??

Setting a record on fire just by playing it?

If the disc is old enough that the cutting surface was celluloid, or
cellulose nitrate (rather than the cellulose acetate used in later
years) then it might be bad juju!

Celluloid deteriorates with age - the camphor escapes and you're left
with just cellulose nitrate, which becomes increasingly brittle.

Cellulose nitrate is known by another name - "guncotton". Also "flash
paper". It's a primary ingredient in smokeless gunpowder.

If something made of celluloid or cellulose nitrate has deteriorated
to the point where it's forming a powder... well, that powder might be
touchy enough that even a static-electric spark might ignite it, and
FOOM.

I'd also be concerned about diamond-stylus-to-groove friction - there's
a *lot* of pressure on that tiny contact surface. I've heard that the
heat generated during playback of an LP is actually sufficient to melt
a very thin surface layer of the vinyl!

On the other hand, if it's a true "acetate" disc (made with cellulose
acetate rather than cellulose nitrate) the flammability problem would
be much less. If this material is deteriorating there might be a
distinct odor of vinegar, as the acetic acid dissociates from the
cellulose.

As to playing the disc... the cat's meow might be to gain access to an
ELP laser turntable, which doesn't use a physical-contact stylus at
all. No wear... but not cheap nor common.


There is also a step and repeat low power microscope multi-capture
system , then auto stitched images, then wiggles converted to sound.

Adrian Tuddenham wrote:

[...]
A straightforward variable circuit that can be connected directly to the
pickup is shown at:
http://www.poppyrecords.co.uk/other/.../Equaliser.gif

I initially uploaded the wrong circuit, the correct one is now shown.

Apologies for any confusion that caused.


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

Does this pic help in relation to stylus tip size
http://diverse.4mg.com/marguerite20.jpg
a crosssed pair of 0.06mm copper wires over the grooves near the centre
of the disc

N_Cook wrote:

Does this pic help in relation to stylus tip size
http://diverse.4mg.com/marguerite20.jpg
a crosssed pair of 0.06mm copper wires over the grooves near the centre
of the disc

The critical factor is the bottom radius, if it is very small you might
be able to play it with a microgroove stylus; direct-cut discs often
have a smaller bottom radius than pressed ones, so you might be lucky.
If the bottom radius is larger than 0.001", a microgroove stylus will
skate around all over the place.

The picture only shows the width of the grooves at the top, to find the
bottom radius you either have to section the disc or play it with a
variety of styli and listen for the smallest one where 'skating'* stops.
The optimum size will usually be a bit larger than the bottom radius, so
that the stylus tip is located positively between the groove walls away
from the bottom. If it is too large, it will sit much higher and then
it will encounter surface scratches and other damage near the top of the
groove wall.


*Skating can be identified by distortion and a hollow burbly quality to
the surface noise, not unlike the effect that bad digital de-noising has
on the music.

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