"hubert pellikaan" wrote in message
...
Hi everybody,

Rethinking garrard 301 technique using a high power motor with a idle
wheel I came to some ideas:

1 An electric motor reacts immediately to applied variation in load.
The higher the motor power, the stronger it reacts.

2 An idle wheel has low elasticity compared to a belt drive. This means
variations in speed are transmitted most instantaneously to the motor
and thus compensated very fast.

3 everything should be mounted on a verty heavy plynth.

4 So I would say:

the variable load by a stylus should me small compared to:
a: platter mass kinetic energy
b: platter bearing load

Motor power should be high compared to platter kinetic energy
Transmission of power should be a very stiff spring,

The problem with this is that unless the motor is *very* quiet, motor noises
will find themselves superimposed on the audio. This is particularly
noticeable with direct-drive turntables. I happen to like the idea of
direct drive, but it *does* need a superb motor.

Arm bearing tot platter bearing flexibility/rotatability should be very
low, or very high mass.

So for reengineering a thorens 160 to garrard 301 behaviour it would be
good to:
1 increase the motor power a lot
2 increase the belt thickness (put more belts on top of each other)
3 increase the subchassis mass at the arm pivot a lot (this is nothing
now!)

Why would you want to do this? The Thorens approach is a high-mass flywheel,
with a good bearing, so it only needs a low power (and hence low noise-
although that's not always true) motor to maintain speed. Starting speed is
slow, but for domestic use, that's not much of an issue.

I already did try to thicken the belt by stacking more on top (1, 2 ,
3).
This does have a serious impact on the sound, even without glueing them
together!

Probably for the worse, as it allows more of the motor noise to work through
to the turntable, and hence the record.

I think turntable behaviour is more physics than magic

Absolutely. *All* audio is more physics than magic, but you need to
understand the design concepts behind different designs. The 301 and the 401
that followed it had powerful motors with an eddy-current brake permanently
applied to adjust speed. They needed a very heavy plinth to sink the motor
energy (something that SME with their plinth system seemed to have got
wrong) and a heavy turntable to smooth out the speed fluctuations. Thorens
worked on the opposite principle of a very free-running turntable, with
minimum motor power to keep it turning at the right speed. They both had
massive turntables to reduce speed variations, but Thorens (and AR, Ariston,
Linn et. al.) thought it better to isolate the turntable from external
vibrations and have low-power motors to keep the thing turning, whilst
Garrard preferred mass in the plinth. Both are capable of good results, but
which was easier to achieve and hence more commercially successful must be
obvious. As an aside, my preferred method is of a light platter, driven by a
superb direct-drive motor under servo control. It allows very fast start-up
and stop, although I accept that is an affectation on my part, as it doesn't
make much sense for domestic music reproduction.

S.