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On Thu, 10 Sep 2009 11:53:17 +0100, "Keith G"
wrote:


"Don Pearce" wrote


Any deck that supports the record on six points can never be described
as "right". It is a ridiculous thing to do. The record must sag
between the points


This is a joke - right?


Of course not. How could a flexible plastic record not sag between
those suspension points? Remember that we are talking thousandths of
an inch to create a big signal, not a sag like a row of bunting. A
record needs to be supported over its whole surface, as flat as
possible.

d

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"Don Pearce" wrote in message
news:4aa8db1e.1466875@localhost...
On Thu, 10 Sep 2009 11:53:17 +0100, "Keith G"
wrote:


"Don Pearce" wrote


Any deck that supports the record on six points can never be described
as "right". It is a ridiculous thing to do. The record must sag
between the points


This is a joke - right?


Of course not. How could a flexible plastic record not sag between
those suspension points?


Stiffness.


Remember that we are talking thousandths of
an inch to create a big signal, not a sag like a row of bunting. A
record needs to be supported over its whole surface, as flat as
possible.


And yet they are so often not, for one reason or another - without any truly
discernable effect on the sound....

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On Thu, 10 Sep 2009 12:24:00 +0100, "Keith G"
wrote:


"Don Pearce" wrote in message
news:4aa8db1e.1466875@localhost...
On Thu, 10 Sep 2009 11:53:17 +0100, "Keith G"
wrote:


"Don Pearce" wrote


Any deck that supports the record on six points can never be described
as "right". It is a ridiculous thing to do. The record must sag
between the points


This is a joke - right?


Of course not. How could a flexible plastic record not sag between
those suspension points?


Stiffness.

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.

Remember that we are talking thousandths of
an inch to create a big signal, not a sag like a row of bunting. A
record needs to be supported over its whole surface, as flat as
possible.


And yet they are so often not, for one reason or another - without any truly
discernable effect on the sound....


You won't hear it, because the frequency is too low, but what it does
is create a huge subsonic signal that the preamp has to cope with.
That eats into the overload margin, and can result in premature onset
of distortion with loud bass notes. So as a piece of engineering, it
is ****. Some may consider it pretty, but I'm not among them because I
can't separate form from function that easily. If I can see why it is
bad, it will not please me aesthetically.

d

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"Don Pearce" wrote in message
news:4aa9e20e.3243421@localhost

You won't hear it, because the frequency is too low, but
what it does is create a huge subsonic signal that the
preamp has to cope with.

The flexing also creates wow.

I don't know whether or not it is audible given all the other speed
variations that are inherent in LP playback, but its there.

Transcriptor Hydraulic Reference on sale at UK
 

In article ,
David Looser wrote:
It was a triumph of style over function, designed to appeal to those
(who are still with us today, of course) to whom what a HiFi system
looks like is more important than what it sounds like.

In one. The ideal, of course, is something which works well *and* looks
good.

And you have to admit it does look "special".

Yes. I actually have one. Was given it broken. But don't use it. It just
looks nice on a shelf. Along with a Nagra. Which does work well.

The reason it was broken? It belonged to a mate who was so fed up with the
faults in performance I described earlier, that he through it out of a
window...

--
*How many roads must a man travel down before he admits he is lost? *

Dave Plowman London SW
To e-mail, change noise into sound.

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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.

--
Ken O'Meara
http://www.btinternet.com/~unsteadyken/

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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.

--
*Experience is something you don't get until just after you need it *

Dave Plowman London SW
To e-mail, change noise into sound.

Transcriptor Hydraulic Reference on sale at UK
 

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 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! :-)

However, a sensing system like a stylus might be able to detect variations
from flat thay you can't see using your mark 1 eyeballs. So your "neither
droops" may simply tell us something about your eyes, not the LP. :-)

You could check by holding a straight-edge just above the LP, touching at
the suspension points. Then see if daylight floods though the gap. That way
you may be able to see a droop which your eyes would otherwise not notice.

That said, since most LP sensors are essentially velocity sensitive that
might help here given the low frequency of 6-point support at 100/3 rpm. I
guess it then depends on the suspension of the cantilever and the response,
etc, of the preamp. And with luck the unwanted ripple will be below the
arm/cart resonance, not spot-on that value!

on the contrary significant pressure has to be applied to deform
them.

....to the extent you find visible.

I have a vague feeling this topic did feature in a magazine set of
measurements a few decades ago. If I can find that sometime I'll let people
know.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

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"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...

Transcriptor Hydraulic Reference on sale at UK
 

"Keith G" wrote in message
...


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. Might try it later with mint imperials....



Using the mint imperials will indeed sound dreadful.. Unless of course you
use a green marker pen on the edge of each mint prior to placement.. ;-)