On Thu, 10 Sep 2009 18:15:09 +0100, "Keith G"
wrote:


"Keith G" wrote in message
...

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
All sounds typically very scary, but my suspicion is that no normal
person would be able to tell the difference between a record played
directly on the mat/platter/whatever and the same record lifted up on,
say, only three bearing points.

You certainly will if you wind up the wick. It will feed back. Unless in
a
well sealed enclosure. It acts beautifully as a diaphragm.


Well aware (after nearly half a century as a user) that a record deck can
act as a transducer but the question is still the is any FB discernable
in normal use or even wicked up?

I might give it a go later but I notice the mint imperials haven't been
opened and I don't like them anyway, so it'll have to be with Tic Tacs...



OK, I have recorded identical samples with and without Tic Tacs and there's
not an iota of difference that I can hear.

Pic of the *unopened* Mint Imperials and the Tic Tacs in situ on my Show N
Tell page, along with the samples which, unfortunately, all have a ton of
hum that I didn't know I was getting! (Hasty wiring to this computer - I was
cutting grass at the time!!)

But hum or no, the samples are of an identical recording setup and are good
enough for a quick comparison!



I've done the same thing here, but I've measured what happens.

Two recordings, both of the same piece of silence between tracks 1 and
2 of a typical record. Then invert one channel and sum to mono. That
gives the vertical movement of the stylus - which is what this is all
about.

Now downsample to 200Hz to see low frequencies nicely, and take an FFT
of both recordings. Here is the result:

http://81.174.169.10/odds/six.gif

First, at the expected 3.3Hz, we have a level about 22dB higher on the
point-suspended disc (that is nearly ten times the voltage for the
preamp to contend with), but a similar difference continues all the
way down in the general subsonic rumble area. I have to say I wasn't
actually expecting it to be quite that much worse. I now think I
wouldn't take one of these turntables as a gift.

d

"Patrick James" wrote In fact the
unconventionl appearance of the

THR is because it is the first turntable in which form follows function.
Previously turntables had been designed firstly with a view to how they
look, then the mechanism fitted into that design.


Well that is *definitely* nonsense! Turntables are pretty functional things,
which look how they do because that's what they are. Form has *always*
followed function.

David.

On Thu, 10 Sep 2009 18:45:27 GMT, (Don Pearce) wrote:

On Thu, 10 Sep 2009 18:15:09 +0100, "Keith G"
wrote:


"Keith G" wrote in message
...

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
All sounds typically very scary, but my suspicion is that no normal
person would be able to tell the difference between a record played
directly on the mat/platter/whatever and the same record lifted up on,
say, only three bearing points.

You certainly will if you wind up the wick. It will feed back. Unless in
a
well sealed enclosure. It acts beautifully as a diaphragm.


Well aware (after nearly half a century as a user) that a record deck can
act as a transducer but the question is still the is any FB discernable
in normal use or even wicked up?

I might give it a go later but I notice the mint imperials haven't been
opened and I don't like them anyway, so it'll have to be with Tic Tacs...



OK, I have recorded identical samples with and without Tic Tacs and there's
not an iota of difference that I can hear.

Pic of the *unopened* Mint Imperials and the Tic Tacs in situ on my Show N
Tell page, along with the samples which, unfortunately, all have a ton of
hum that I didn't know I was getting! (Hasty wiring to this computer - I was
cutting grass at the time!!)

But hum or no, the samples are of an identical recording setup and are good
enough for a quick comparison!



I've done the same thing here, but I've measured what happens.

Two recordings, both of the same piece of silence between tracks 1 and
2 of a typical record. Then invert one channel and sum to mono. That
gives the vertical movement of the stylus - which is what this is all
about.

Now downsample to 200Hz to see low frequencies nicely, and take an FFT
of both recordings. Here is the result:

http://81.174.169.10/odds/six.gif

First, at the expected 3.3Hz, we have a level about 22dB higher on the
point-suspended disc (that is nearly ten times the voltage for the
preamp to contend with), but a similar difference continues all the
way down in the general subsonic rumble area. I have to say I wasn't
actually expecting it to be quite that much worse. I now think I
wouldn't take one of these turntables as a gift.

d

I recorded the on-platter version again. Having left the record
sitting on a nice firm platter for a while, the kinks, which obviously
formed while it was resting on the lumps, flattened out again and now
there is no trace at all of 3.3Hz.

d

On Thu, 10 Sep 2009 19:35:18 +0100, Patrick James
wrote:

On 2009-09-10 10:06:56 +0100, "Dave Plowman (News)"
said:

In article ,
Patrick James wrote:
On 2009-09-10 00:26:48 +0100, "Dave Plowman (News)"
said:

A prime example of design over engineering. Ideal coffee table exhibit.
Just don't try and use it.

I've used it for over twenty years and found it to be quite superb.

You can't be serious? Unless only using headphones. Mounting the disc like
that turns it into a near perfect diaphragm. Causing feedback at very
modest levels. Then there's the likelyhood of smashing the pickup to bits
if being slightly careless when playing a 7". Then there's the care needed
when closing the lid to avoid the pickup jumping - those soft springs
cause the whole unit to tilt alarmingly.

It always amuses me how on Usenet people will present themselves as
experts on things that they have so little knowledge about.

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.


So the disc is insufficiently well secured to qualify as a diaphragm?
Ok, if you want to be pedantic you are right, but as I hope you can
see, this turntable is actually worse than a properly secured
diaphragm. The record is simply flapping in the breeze.

Your imagination is running away with you.

The Transcriptor Hydraulic Reference does not have soft springs at all.
The later Michell versions did have leaf springs which were soft, but
the Transcriptor Hydraulic Reference sits on three fairly hard feet
which have rubber at the bottom.


So he wasn't interested in decoupling the unit from
chassis-transmitted vibration? Is that supposed to be a plus?


So here in Daves post are the usual tedious things people say about
Transcriptor turntables when they have no experience of them or perhaps
just saw one in a shop once.


We were addressing the physics of the thing, which from the picture is
clearly exactly as we supposed.

I am going to address a couple of other points I saw in the thread.

The turntable was not designed to be a prop for a set used in Clockwork
Orange. Kubrik loved this turntable and used it a set.

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.

The difference is merely one of degree, not principle.

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.


This is forty years later - I would hope we have learned at least
something.

Now I hope to give a brief idea of just how great an advance in
turntable design the THR represented. It was in fact the brain child of
a brilliant engineer called David Gammon, who very sadly passed away a
few months ago. It was David Gammon's intention to make a turntable
which provided better speed stability and minimised rumble to an extent
far greater than that of any other available turntable. He achieved
this by applying plain engineering science to the device with an
uprecedented thoroughness. In fact the unconventionl appearance of the
THR is because it is the first turntable in which form follows
function. Previously turntables had been designed firstly with a view
to how they look, then the mechanism fitted into that design.

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.


Simply gibberish. Had he been concerned with resonances he would have
made sure that the one thing in contact with the stylus - the record
- was secured and not simply making a very passable imitation of a
microphone.

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".

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.


Go to all the trouble of making a heavy platter, then don't actually
connect the record to it. That has to be one of the stupidest ideas
ever.

To give you an idea of the attention to detail on these issues. The
pinion for the belt on the motor is attached using a screw aligned with
the axis. Other belt drive turntables would attach the pinion with a
grub screw at 90 degrees to the axis. That was easier, but if you
attach a pinion the second way the tightening of the screw moves the
pinion off-axis such that it become eccentric, albeit to a tiny degree.
However David Gammon would not have even the possibility of that kind
of speed instability even that small.


It is always a winner when someone corrects a "fault" that nobody else
suffers from.

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

If you do get hold of a THR in good condition (not necessarily mine)
and you set it up correctly then you will be simply amazed at how good
it sounds. You will be immediately in love with it.

A good record deck doesn't sound amazing. It simply fails to impart
further faults to the vinyl.

The record won't magically become a diaphram, it won't wobble around in
some mysterious way, the stylus won't mysteriously dive bomb the
platter...


Oh yes it will. It has no choice in the matter.

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

What is that supposed to mean? Are you saying that your statements and
assertions are gospel and not open to challenge?

d

On Thu, 10 Sep 2009 18:15:09 +0100, "Keith G"
wrote:


OK, I have recorded identical samples with and without Tic Tacs and there's
not an iota of difference that I can hear.

And here's another pair of traces of difference, this time microphony.
The turntable is not spinning - the stylus is simply sitting on a
stationary record, responding to reasonably loud room noises.

The blue trace shows the flat platter, the green is the six-point
suspension. So much for the record not acting as a diaphragm in this
condition.

There is a little hum spike there that I really ought to deal with.


http://81.174.169.10/odds/microphony.gif

d

On 2009-09-10, Jim Lesurf wrote:
In article , UnsteadyKen
wrote:
Don Pearce said...

Hold an LP up balanced on two fingers at opposite edges - you will see
how much it sags quite easily. Obviously it doesn't sag as much as
that with six suspension points, but it sags much more than enough to
generate a huge signal.

The Hydraulic was designed for the thick'n sturdy pre 73 oil crisis
discs which are a totally different animal to the later floppies.

My unreliable recollection is that many 'pre 73' LPs were far from flat, or
even very thick.


I obviously don't know what records you bought in that era but I bought
(and still own and play) roughly 500 or so records made pre 73. I've
just rechecked a ramdom sample (20 or so) and all without exception
are very flat and quite thick. Most are UK pop/rock but I also have a
fair few classical and some US rock imports. Even the very cheap classical
(eg Fontana and Marble Arch) are flat and are thick enough not to droop.


I got a couple of lp's last week, a Decca ffrr from 1965 and a bog
standard EMI Columbia from 1966 and neither droops on your finger tip
test,

Weird. Most of the pre 73 LPs I have are ones I bought when they first came
on sale! :-)


It would be interesting to know which labels made the "floppy" pre 73
LPs you have - if I have any of the same I'll dig them out and check
mine.

I do have a fair number of thin floppy LP's but these I'm fairly sure
date from the mid to late 70's.


Malcolm

On 2009-09-10, Eiron wrote:
UnsteadyKen wrote:
Don Pearce said...

Hold an LP up balanced on two fingers at opposite edges - you will see
how much it sags quite easily. Obviously it doesn't sag as much as
that with six suspension points, but it sags much more than enough to
generate a huge signal.

The Hydraulic was designed for the thick'n sturdy pre 73 oil crisis
discs which are a totally different animal to the later floppies.

I got a couple of lp's last week, a Decca ffrr from 1965 and a bog
standard EMI Columbia from 1966 and neither droops on your finger tip
test, on the contrary significant pressure has to be applied to deform
them.

I just rested an LP on two points. The centre drooped by 4mm.
Of course UnsteadyKen didn't measure anything....


I've just rested my LP ("With The Beatles" Mono PMC 1206 pressed
in 1964) on two points. The centre drooped by maybe 0.2mm.

Of course Eiron generalises from his limited personal experience
to the universal...

On Thu, 10 Sep 2009 20:45:07 +0100, Malcolm Lee
wrote:

On 2009-09-10, Eiron wrote:
UnsteadyKen wrote:
Don Pearce said...

Hold an LP up balanced on two fingers at opposite edges - you will see
how much it sags quite easily. Obviously it doesn't sag as much as
that with six suspension points, but it sags much more than enough to
generate a huge signal.

The Hydraulic was designed for the thick'n sturdy pre 73 oil crisis
discs which are a totally different animal to the later floppies.

I got a couple of lp's last week, a Decca ffrr from 1965 and a bog
standard EMI Columbia from 1966 and neither droops on your finger tip
test, on the contrary significant pressure has to be applied to deform
them.

I just rested an LP on two points. The centre drooped by 4mm.
Of course UnsteadyKen didn't measure anything....


I've just rested my LP ("With The Beatles" Mono PMC 1206 pressed
in 1964) on two points. The centre drooped by maybe 0.2mm.

Of course Eiron generalises from his limited personal experience
to the universal...

You have both presented a single figure. But apparently you are
allowed to generalise, but Eiron isn't How does that work, exactly?

d
--
Pearce Consulting
http://www.pearce.uk.com

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
You certainly will if you wind up the wick. It will feed back. Unless
in a well sealed enclosure. It acts beautifully as a diaphragm.


Well aware (after nearly half a century as a user) that a record deck
can act as a transducer but the question is still the is any FB
discernable in normal use or even wicked up?

Yes - because it's not supported properly it can vibrate in tune with the
speakers more easily. Thought you'd have realised that. Of course you can
improve matters by using something underneath the LP to give more support.
After you've adjusted the pickup to suit, obviously.


The word *discernable* (ie by ear in normal use) is where it hangs; not
whether or not the LP is the only thing in a soundfield that might *not* be
vibrating sympathetically!

"Don Pearce" wrote in message
news:4aa94700.29085171@localhost...
On Thu, 10 Sep 2009 18:15:09 +0100, "Keith G"
wrote:


"Keith G" wrote in message
...

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
All sounds typically very scary, but my suspicion is that no normal
person would be able to tell the difference between a record played
directly on the mat/platter/whatever and the same record lifted up on,
say, only three bearing points.

You certainly will if you wind up the wick. It will feed back. Unless
in
a
well sealed enclosure. It acts beautifully as a diaphragm.


Well aware (after nearly half a century as a user) that a record deck
can
act as a transducer but the question is still the is any FB
discernable
in normal use or even wicked up?

I might give it a go later but I notice the mint imperials haven't been
opened and I don't like them anyway, so it'll have to be with Tic
Tacs...



OK, I have recorded identical samples with and without Tic Tacs and
there's
not an iota of difference that I can hear.

Pic of the *unopened* Mint Imperials and the Tic Tacs in situ on my Show N
Tell page, along with the samples which, unfortunately, all have a ton of
hum that I didn't know I was getting! (Hasty wiring to this computer - I
was
cutting grass at the time!!)

But hum or no, the samples are of an identical recording setup and are
good
enough for a quick comparison!



I've done the same thing here, but I've measured what happens.

Two recordings, both of the same piece of silence between tracks 1 and
2 of a typical record. Then invert one channel and sum to mono. That
gives the vertical movement of the stylus - which is what this is all
about.


It is? I thought it was all about what you might or might not be able to
*hear*, not measure...??



Now downsample to 200Hz to see low frequencies nicely, and take an FFT
of both recordings. Here is the result:

http://81.174.169.10/odds/six.gif

First, at the expected 3.3Hz, we have a level about 22dB higher on the
point-suspended disc (that is nearly ten times the voltage for the
preamp to contend with), but a similar difference continues all the
way down in the general subsonic rumble area. I have to say I wasn't
actually expecting it to be quite that much worse. I now think I
wouldn't take one of these turntables as a gift.


I'm not sure ****ing about with the 'silence' is really where it counts -
that's for geeks; I rely on the music to soak up all sorts of **** when I'm
listening to it on LP...!! :-)