Vintage DD turntables. Are we living dangerously?

Halcro.

I re-read my last post and realise that it could be misinterpreted. Clarification here...

BT suggests that when accessing speed accuracy with a pivoted arm, the measured performance is inferior to the actual performance. This due to the geometry of a pivoted arm.

Since you have a rig with three different arms, it would be of interest to run three sequential tests to see if there are any measured differences.
If there are, maybe we could infer that the TT-101 is actually better than the readings indicate.

Richardkrebs,
The measured performance is inferior to actual performance?

Wow and flutter can only be measured with an arm/cart. Timeline measures or illustrates absolute speed. Henry has shown that absolute speed doesn't deviate when using 3 arms simultaneously on his Victor.

W/F is measured with a test record 3150Hz tone. Output is checked for deviation from that frequency.
I think Thigpen must be referring to low torque belt drives, in which case a gnat landing on the arm or platter might upset speed stability.
Regards,

10-23-15: Fleib
Richardkrebs,
The measured performance is inferior to actual performance?
Wow and flutter can only be measured with an arm/cart. Timeline measures or illustrates absolute speed. Henry has shown that absolute speed doesn't deviate when using 3 arms simultaneously on his Victor.

1. There is no such thing as absolute speed. Speed is relative.
2. Wow or flutter can be measured with a rotary function generator connected directly to the platter - this is the method Thigpen uses.
3. Using a record with a fixed tone is prone to error. Any eccentricity or imprecision in the surface of the record will generate wow or flutter.
4.The timeline only measures the arrival of a single point on the platter at the same place at each time. It does not measure what happens in between.

If you take points 2 and 3 above into account, then when playing records there will be more wow and flutter generated by the arm/cartridge than the TT itself.

If you want to relate Direct Drive speed stability to sound quality consider this:
Analogue wow and flutter is similar to digital jitter. Testing of digital systems as regards temporal errors and the effect on sound quality has yielded the following -
1. The lowest level of jitter that affects sound quality is 5 nanoseconds.
2. Using sine waves for testing showed most people could hear errors down to 10 nanoseconds.
3. On recorded music people could here down to 20 nanoseconds.

I have seen some studies that suggest temporal recognition in the brain is triggered at around 4 nanoseconds.

There is no way that the error correction circuitry from these vintage decks is fast enough to be inaudible.

If the listener thinks that their TT "sounds" more speed stable than anything they have heard before, then their perception of their current turntable on its relative merits is limited to a relativity to the inferior tables that they have previously used in that particular system.

Dover,
"There is no such thing as absolute speed. Speed is relative."

That is incorrect. For a turntable, 33 1/3, 45 RPM is absolutely the correct speed.
How it's measured is another story.

"The timeline only measures the arrival of a single point on the platter at the same place at each time. It does not measure what happens in between."

That was my point, commonly referred to as absolute speed vs. wow and flutter.

"Analogue wow and flutter is similar to digital jitter. Testing of digital systems as regards temporal errors and the effect on sound quality has yielded the following -"

Analog wow and flutter is very different from digital jitter. Your analogy is a bad one. Because of the continuous nature of analog, very small amounts of W/F are much less noticeable. Not so with digital. Because the music is chopped up and regurgitated back to analog, any jitter is more prominent, noticeable. This is especially true with harmonics and tonality.

Playing records is harder, more expensive, and a PIA compared to digital. Then why the resurgence, because it's cool? I don't think so.
It's more fun because it sounds better.
Regards,

Fleib.
Copied here the reference to wow and flutter from the ET2 Dampening trough owners manual.

Food for thought.

"WOW AND FLUTTER
Wow and flutter, FM distortion and surface irregularities in the LP should all be grouped
together because, as we will see, they are all tied together.
When you cut a pure tone (say 1kHz) onto an LP and then play it back on a
turntable/tonearm/cartridge system, you would hopefully want 1kHz to come back. Something
close to 1kHz comes back, but rapidly being shifted up and down around 1kHz. If the frequency
is shifted up to 1001Hz and down to 999Hz within a short period of time, the amount of shift is
.1%. If the shift occurs less than 10 times a second, it is considered as flutter. The two measures
are generally lumped together and called wow and flutter.
“Weighting” is applied to the measurement to reduce the measurement’s sensitivity to very
low and very high rate of frequency shift. The actual amount of frequency shift is much greater
than the number implies. The weighting network is supposed to create a number related to a
subjective ability to hear wow and flutter.
Reviewers have incorrectly attributed wow and flutter to the turntable. Since the advent
of the belt drive turntable, wow and flutter has been purely a function of tonearm geometry, the
phono cartridge compliance with the elastomeric damping, and surface irregularities in the LP. In
our own lab we have measured many high quality turntables using a rotary function generator
directly connected to the platters of the turntables.
The measured results are usually an order of magnitude better than the results using a
tonearm and test record (conventional wow and flutter method). Further proof exists if you take
two tonearms, one straight line and one pivoted and mount them both on the same turntable. The
straight line tonearm will give a wow and flutter reading with the same cartridge/test record of
about 2/3 to ½ that of the pivoted arm (.03% < .07% to .05%). This is because the straight line
tonearm has a geometry advantage and lateral motion does not result in stylus longitudinal motion
along the groove of the record.
Another proof is to take two different cartridges, one high compliance and one low
compliance, and take measurements with both using the same turntable and tonearm. The reading
of wow and flutter will be different. All wow and flutter readings are higher than the rotational
consistency of the turntable
A damping track applied to a tonearm (straight line or pivoted), will reduce the measured
wow and flutter usually 10-30% and sometimes as much as 50%. ET-2 wow and flutter readings
with a typical cartridge and good turntable will usually measure (.02 to .04%) which is extremely
low for an LP system. With the damping track installed flutter readings with the ET drop still
lower and with one test record we measured readings as low as .007%.
Surface irregularities on the vinyl of the LP record are the primary cause of rumble or
random low frequency noise, which causes the tonearm/cartridge spring system to start
oscillating. This oscillation occurs continuously during playback. It is a primary cause of wow
and flutter and FM distortion in phono playback. Surface irregularities occur not as a part of the
record cutting process, but result from the molding process used in making the record
You can see visually small ripples on the surface of an LP as it is turning. These continuously
excite the tonearm resonance"