Re: Pitch Issues on Rega (Or Any) Turntables


"Trevor Wilson" <trevor@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
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"ScottW" <ScottW48@xxxxxxxxxxx> wrote in message
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"Trevor Wilson" <trevor@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
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"ScottW" <ScottW48@xxxxxxxxxxx> wrote in message
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On Jun 26, 2:42 am, "Trevor Wilson" <tre...@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
"Bret Ludwig" <bretld...@xxxxxxxxx> wrote in message

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If the pitch of the turntable is off, the speed is. We are really
talking about a speed issue.

If the table uses an AC motor, unless it has its own oscillator/
amplifier or PLL switchmode power supply, the motor speed is a direct
function of frequency. AC frequency in any normal country does not
vary enough to be audible for all intents and purposes. If the speed
is then off it's a mater of pulley diameter. One or the other pulley
must be increased or reduced in diameter.

If it's a DC motor, we have two things to look at. One is the exact
speed of the motor. how is it set? Usually there's a feedback loop and
some adjustability. Otherwise we are bacl to the above, unless it's
direct drive.

Direct drive tables are usually undesirable for audiophile use.

**Bul***! As usual, you introduce your own weird-sit ideas and promote
them
as fact. Companies like Denon and Technics have produced quite excellent
direct drive motors, suitable for turntables. FAR better than, for
instance,
the popular Papst, DC motor used in early Sotas and Oracles. The Papst
motors in question exhibited significant drift problems, whilst the Denon
motors were three pahse, AC driven beasts, with a feedback (crystal
locked)
system which ensured that corrections (if required) were applied around
500
times per second. The Denon and Technics motors delivered impressive
torque
figures and inaudible levels of wow and flutter.

I'll point out that my LT-30 motor has delivered excellent performance
for
26 years now and I do appreciate that torque. Comes in very handy
for a the obligatory pre-play dusting. Wow, flutter and rumble are
inaudible and while the isolation is poor as Trevor mentions, this is
easily remedied if one feels the need. I've had the opportunity
through
work to obtain samples of various density isolation materials which
when
stacked are highly effective. One layer has a transmissibility band
outside another so when used in layers they are extremely effective.
However, They provide no audible difference to me. Footfalls and the
like are
not an issue in my current room, no dancing though :).

Their failing, IMO, lay
with the poor isolation of the turntable itself.

My ideal turntable would be a Sota, belt driven with a Denon motor. Ideal,
because I like the idea of a main bearing whose centre of gravity was
above
the main mass of the platter and the superbly simple, easily tunable
suspension of the turntable.

Rubber belt drives can only pull and require the bearing to
convert a linear force to rotation. A knit perhaps but
I like the balanced forces inherent in DD.

**You miss the two, very important, advantages of the Sota.

* The fact that the bearing's centre of gravity is above the platter (IOW:
The platter 'hangs' off the bearing.

That isn't the way Sota describes it.

"Located at the very center of gravity on the SOTA platter is the synthetic
Sapphire crystal thrust plate (ground to one wavelength of light accuracy),
which balances the platter and rotates on a chrome steel ball bearing."

http://www.sotaturntables.com/Sound%20Engineering.htm

The difference I see is the platter spins on the ball while usually
the ball spins with with the platter. I think this is why they call
it inverted.

**Wrong. My description is more accurate. Yours is just wrong.

My first paragraph is a quote from Sota's web site. I hope you're not
arguing with that?
The second is a simple description of a cross section depiction
also on their site. Please describe the construction in that image
that has the platter hanging off the bearing.


But all this extraordinary balancing is irrelevant when you're tugging
on the edge of a platter with a belt.

**No, it is not. The Sota system makes for an inherently stable system.

I'm sure it is. But there are inherent inbalances in belt drive that can only be
opposed by friction which makes it hardly ideal.

ScottW


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