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.