In article , Dave Plowman (News)
wrote:
In article , Patrick James
wrote:


The LP does not behave like a diaphram on the platter for the very
simple reason that for an LP to behave like a diaphram it would need
to be *secured* at the edge, like a drum skin for example.

Really? Is a loudspeaker cone 'secured' at the edge? Hint. It's not - if
anything it's secured by the spider in the middle. But works very
effectively as a microphone. In just the same sort of way as a pickup
does on a poorly supported disc.

The problem does seem to be that Patrick has simply defined the word
'diaphragm' simply so he can say that an LP isn't one. Thus evading the
more significant point that the LP mounted a la the Transcriptor can indeed
vibrate in response to acoustic energy.


Another in the thread has pointed out that when the turntable was
introduced and sold records were much thicker than those sold, say, in
the eighties or nineties. This is very true indeed, and the very thin
records of the eighties were a major reason why turntable
manufactureres stopped using point suspension or ridged suspension.

Actually he said "pre 73" not "mid eighties" IIRC.

Err, what other maker used it? The vast majority have conventional
turntables. For good reasons. Oh - I've been buying records from *well*
before the 'eighties and nineties' and there wasn't a universal
reduction in thickness.

I have a feeling that the highly regarded audio maker, Amstrad, also made a
look-alike with multiple point support for the LP. They came up with a
hilarious technogabble description of it IIRC. I'll see if I can find a
copy of the advert I have in mind as it was very funny. This was about the
time Alan Sugar was apparently telling his 'engineers' that if other makers
had four knobs on their amp, he had to have five or six. Didn't matter what
they did, just more knobs. :-)

As a return to that issue it is worth remembering that in the
seventies (and indeed early eighties) point or ribbed suspension was
considered a good thing because it meant that the record was not
sitting right on top of a potential dusty platter. Build up of dust
on records was a great concern in the seventies because people were
not as precious with them as they are today.

Worth remembering something you've just invented? Mats on turntables
come in all varieties. Some using just plain felt. But a ribbed design
supports the LP over most of its area - not in six points.

Actually my impression is that suspending the LP in open are might make the
dust problems *worse*. Reason being attraction to open surfaces by static.
A good mat may be slightly conductive so tend to remove charge as well as
cover the surface.


David Gammon knew that attaching the mechanism to a wooden box for a
chassis was crazy. The wooden box simply amplifies the sounds of the
mechanism. So with the THR the plinth is plywood laminated with an
acrylic layer creating a highly damped non resonant base. Remember
that this is in the sixties, no other turntable manufacturer was
exploring these ideas.

What noise does a mechanism make?

I'm curious about the common confusion of physics here that a wooden box
will 'amplify' the sounds. No doubt this is due to an inapporiate analogy
with things like acoustic instruments.

First lets look at platter design which has caused such consternation
for some. The common way to make a platter in the sixties was just to
cast one, fairly thin in a drum shape, aka Garrard and others. However
those designs were very resonant, indeed flicking the edge would
cause them to ring sometimes. David Gammon did not want a resonating
platter. He knew that any, even partial, air enclosure within the
platter was a potential cause of resonance, so in fact he designed a
platter which did not enclose air and which was acoustically
inherently "dead".

More ********.

Not necessarily. Maybe he just wanted to focus on allowing the LP to
vibrate. However maybe his idea would have worked if only used by people
living in anechoic chambers. ;- ...oh hang on, bugger, the stylus will
also generate vibrations. So no stylus contact either, I'm afraid, for his
(alledged) idea to work.

The platter is very heavy (12 kg) and most of the weight is at the
periphery. It has a huge moment of inertia compared with other
turntables of the time. In fact the moment of inertia is very great
even by today's standards. This, of course, was to facilitate
exceptional speed stability. Wow and flutter is extroadinarily low
with the THR even compared with many quality turntables in
manufacture today.

I still have a Goldring-Lenco GL75 somewhere. That also had a very high
intertia. Worked quite well in its day. But lacked the eye-appeal of the
Transcriptor I guess. :-)


The THR was and is probably the single most influential turntable
design.

You really must stop believing adverts. And quoting them wholesale here.

Well, Alan Sugar may have been impressed... or at least decided his punters
would be. :-)

The other is the Thorens upon which the Linn Sondek was famously
based. However the Linn is the only turntable inspired by the Thorens
whereas very many turntables available today are facsimiles in one
form or another of the THR.

Erm. I have the feeling that the Linn was also based on another deck whose
name is now largely forgotten. I seem to recall some patent arguments about
this which only stopped when the (probable) real inventor died. There were
some interesting reports on this some years later by Barry Fox IIRC.

Anyway I won't be posting again in this thread so please do enjoy
music no matter what the medium! -- Patrick

Good luck, I'm sure you will find a buyer.

Slainte,

Jim

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