Direct drive vs belt vs rim vs idler arm

02-11-13: Richardkrebs
Dover.
Are we not getting off topic here?

No. Read the name of the thread.

Lewm -
Re the NVS servo question : please read my posts more clearly.
My post of 02-04-13 explains that the term "17 degrees of freedom" used on the NVS website under the title "Speed Control" indicates they use it. I included an explanation as to why.
My post of 02-07-13 cites the Stereophile Review in vol 35 no 10. "servo controller with an active ultrasonic feedback loop"
If you want to believe black is white, thats fine, but please dont misconstrue my posts. Thank you.

Lewm,
Since this thread was started I have had further opportunity to listen to a Garrard 401/Raven/Zyx, Technics SP10mk2/Raven/Zyx ( both before and after full Krebs mod ) and Kenwood L07D all in the same system.

The Garrard 401 presented a more musically coherent sound than either of the other combinations. Specifically the SP10mk2 sounded like it was slewing around, the Kenwood L07D had a bottom end/midrange/top end that was discontiguous.

I have also had a listen to a Technics SP10mk3 with Ikeda arm/cartridge and SME V12/Air tight in the Porter plinth & Krebs mods and it sounded very good. So the only direct drive I have heard that is ok is the SP10mk3.

There is a vast gap in performance between the Krebs SP10mk2 and the mk3.
Having heard the SP10mk2 with and without the Krebs mods, my conclusion is that a Garrard 401 with decent plinth/arm/cartridge will outperform it.

I'm sure there may be better DD's out there - the Koda Beat looks interesting.
As far as I'm aware the Krebs mods are simple mechanical tweaks - there are no alterations to the error correction and servo system operating parameters which are limited by the 70's technology employed.

As an aside the Technics based cutter lathe SP02 motor had significantly more torque than the SP10mk3 motor, and used a 60lb flywheel in conjunction with the higher torque to achieve stability.

My Final Audio VTT1 with high mass platter/thread drive which came standard with a Sine/Cosine Wave generated power supply that requires a power amplifier to drive the motor, has far more solidity, explosiveness, micro dynamics and cohesiveness than any of the DD's I've heard. My second deck, the Platine Verdier, is unfortunately not in the league of the Final, but at least it has 78rpm and I use it as a test mule ( and it did outperform an SME 20/V in the same system ).

Lewm,
To clarify a few points -
My comment that the best DD I've heard thus far is the SP10mk3 is based on listening, not torque numbers. The Krebs modified SP10mk2 is in my view easily outperformed by a well set up Garrard 401. The L07D has always been one of my favourite DD's, but recent listening tests have led me to disappointment. The L07D was standard with the stainless mat which according to the literature is supposed to provide shielding. It is possible the L07D may not have been operating optimally. I say this because in my experience the power supplies in these vintage decks should be completely rebuilt and calibrated - not just the caps but all resistors should be replaced. For example in my outboard power supply built for my Marantz 7 tube amp, after 12 years I had it recalibrated by my tech. In that short time several mil spec resistors had drifted in value, despite being mil spec and overrated. The caps were ok but replaced with superior caps.
With regards to servo technology, I think we are in agreement in recognising the issues around servos. Significant advances are available in speed response and accuracy, notwithstanding devices now switching at a trillionth of a second. The chips used in the 70's decks are obsolete, non programmable and slow. As an analogy, my Marantz 7 outboard supply, despite using regulation far more sophisticated that the ubiquitous LM317 and its like, would now be obsolete, the use of stacked op amps for regulation would be an example of using different new technology that can be utilised for providing better solutions to old problems.
With regards to the Bill Thalmann/Krebs changes - my understanding is that Krebs has sent his own power supply to Thalmann because he couldn't get it to run, so I assume that he doesn't know how it works and any mods are more likely parts replacements or tweaks rather than a redesign.
I'm also pretty sure in another thread Krebs has stated there are no changes to the servo operating parameters and design.

Lewm -
There are no sides here. I am reminded of the old doctor who unfortunately misunderstood a lady who wandered into the clinic and complained of acute angina.

I have been fortunate to acquire an exceptionable turntable that still outperforms anything I've heard, which includes the SP10's, L07D's and the big Micro Seikis. Ironically HP described the sound of the Final Audio VTT1 as "sounding like a direct drive TT" when he auditioned it in the 70's.

Artisan Fidelity does a fantastic job restoring and improving turntables. In my view the old direct drives need to be blueprinted and recalibrated in every respect, both electrically and mechanically, due to age.

The weak point of the SP10mk3 is a substandard plinth system that does not provide loop rigidity between platter/bearing/arm/cartridge. Artisan Fidelity build a new plinth with both far superior loop rigidity and and If you examine the Artisan Fidelity SP10mk3 upgrades - rigid plinth, energy drain to ground, copper record interface mat - the Final Audio had these attributes as standard back in 1971.

In 1971 the Final Audio had a rigid skeletal plinth, the base of which is 40kg slab of Superplastic Zinc Alloy, at room temperature this material grain slides at a molecular level when excited between 10-100hz. The gunmetal arm pod is bolt to this energy sink as is the inverted bearing. A platform made by Otai composed of a constrain layered structure of hardwood plywood and crushed stone ( used as a base under the bullet trains ) was the recommended interface to sink any residual noise to ground (earth).

The platter system uses 4.5kg copper mat and 18kg aluminium platter ( solid profile, not a ring bell shape ) and a gunmetal clamping system to drain unwanted energy from the stylus/record interface to ground. Final claimed at the time that even the shape of the underside of the platter had been designed to squeeze noise out.

The Artisan Fidelity Statement 301 - has a 19lb platter composed of aluminium/copper with an inverted bearing - again the Final Audio had this back in 1971.

As far as drive train goes - the Final implemented, back in 1971, a regenerated power supply that included sine and cosine wave generator, with infinite control of speed ( not stepped ) and control over the level of torque applied. The AC motor locks precisely, if an AC motor lags at all, it corrects sinusoidally, in a very benign manner.

This drive train is more sophisticated than any of the big Micros and Melcos that came about in the late 80's, some years after the Final was built. The energy drain design of the Final again is far more sophisticated the the big Micros and Melcos as is the speed stability ( the Micros use DC motors )

So I am not anti drive of any kind - it is more about implementation. There are only a handful of exceptional turntables out there in my experience.

Fleib/Peterayer/Lewm
Having set up 100's of TT's when I was a high end dealer in the 80's, it became readily apparent to me that suspended TT's with the motor fixed were not speed stable - particularly noticeable on solo piano pieces. Some are worse than others - the worst I had were the Oracle/Pink Triangle with their very lossy suspensions. The major problem with the early Sota's were the PAPST motor board regulators which were unstable. Knocking these out and replacing them with a decent regulated supply cured much of the SOTA instability. Later SOTA mounted the motor on the sub chassis which is a much better solution in terms of loop rigidity between motor and platter.
My experience selling gear is that many folk can't hear poor timing and therefore it is of no consequence to them.
The SME addresses the issue somewhat by using a hanging suspension and the platter is stabilised to some degree by anchoring the bearing using a rubber O ring looped around the bearing and fixed to the chassis on the opposite side to the motor.

Here is a graphic example of what lousy suspension is doing. When I bought a Platine Verdier ( for a second deck, its way behind the Final Audio ) I set it up with the supplied rubber belt. The Verdier has a very lossy suspension. No matter how I set the tension, the rubber belt vibrated and jigged its way through the music. Removal of the suspension and replacement with fixed adjustable feet ( custom inserts with BDR cones ) eliminated over 95% of the belt creep. Of course going to thread drive ( I use surgical silk ) gets rid of the rubber belt compression issue.

Peterayer I have not heard the SME 30, but certainly the Verdier (with suspension still in) outperformed the SME 20/V in the same system, significantly more resolving and music had a much more substantial foundation. The original owner of the Verdier never listened to the SME 20 again, it was consigned to the office. Cartridges used in the evaluation were Lyra Helikon SL, Koetsu Rosewood & Soundsmith Paua in rotation. For your information the Soundsmith Paua was an outstanding match for the SME combo, providing a very musical system.