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