Direct drive vs belt vs rim vs idler arm

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 ).

Dear Dover, You wrote, "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."

Yes, the SP02 motor is even larger and has more torque than does the Mk3 motor, so what? The SP02 is designed with a different task in mind, that of driving the cutting of an LP. That said, the Mk3 motor is still the "torque-ist" motor among all the vintage Japanese DD turntables. I however would not use that fact to claim that the Mk3 must therefore be the best of the bunch; the Mk3 motor has to motivate a platter that is the heaviest of the bunch, and I would think that the high torque was deemed to be required to deal with controlling that excessive mass.

Now, as regards your dismissal (or seeming dismissal) of the Krebs mods, it would seem you misunderstand the intent. The Krebs mods are designed in part to stabilize the relationship between the rotor and stator of the motor. When a servo correction occurs that invokes a speed correction, this applies a force that can momentarily disorient the relationship between the two components of the motor (Newton's Third Law of Motion, again). This phenomenon can then induce a "false" signal for servo correction, and so on and on. The net result is frequent servo corrections that emanate from the instability of the rotor/stator interface. Perhaps this is responsible for the coloration that some do hear with the Technics SP10 Mk2 and less so with the Mk3. (I certainly heard it with an unmodified Mk2, much less with an unmodified Mk3 in a 100-lb plinth.) Richard Krebs has devised some methods to stabilize the motor structurally that largely ameliorates the problem and thereby reduces or eliminates it, resulting in much less frequent servo activation. Also, you are not correct in saying that there are no changes made to the power supply/servo module. Bill Thalmann has devised several updates that are part and parcel of a "Krebs mod". And finally, we were not exactly living in caves back in the late 70s and early 80s when these products were devised and marketed. The major improvements in servo technology have more to do with miniaturization than anything else.

Here I feel the need to repeat myself; none of the above is meant to imply that DD turntables, as a class are superior to BD turntables, as a class. I am sure your Final Solution TT is excellent. And I too love idler turntables; I would not ever give up my heavily tweaked Lenco. But I also adore my L07D, so I would like you to amplify on your critique: "Kenwood L07D had a bottom end/midrange/top end that was discontiguous". For example, did the unit you auditioned have a EMI shield between the motor and the underside of the platter?

I find that a fair point about the Sp10 mk3 having a torquier motor due to the heavy platter. It's engineered for purpose so to speak. the ratio of power to weight comes in mind and with it the EMT analogy that a needle/stylus is like driving a car up a hill - if it is small and powerful it can overcome obstacles and undulations quicker and better than say a truck. It is for this reason the EMT 950 platter weighs very little - so I guess it has a very high power to weight ratio. Simply put a single factor of itself needn't and often is not the only factor in an equation.

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.

To suggest the Technics Sp10Mk3, when properly conceived and implemented, cannot during playback recreate an accurate portrayal of an analog recording possessing the appropriate pitch, scale, speed consistency and balance is purely absurd. Numerous random variables come into play when evaluating such precision instruments, let alone vintage designs, especially when individuals are listening in foreign environments. In order to effectively and objectively evaluate two turntable platforms side by side, one must recreate the conditions present identically, period. Arm for arm, cartridge for cartridge and including associated equipment. Even then, doing so may prove less than absolutely precise. Frankly, based on what one individual described above "Tones are changing multiple times, depth and physical presence does not exist" this may indicate the logic / control / drive circuit requires a comprehensive scope bench test followed by servicing. Had these individuals bothered to examine the block diagram and troubleshooting guide printed in the service manual? Bear in mind, the Mk3's were intended to be used for extended periods of time while exhibiting utmost precision and stability during playback, namely in commercial environments, and thus were readily serviceable in the event of a malfunction. Over the years, in addition to the Technics Sp10Mk3, I've personally evaluated, studied and tested numerous other admired vintage designs at length, including the Micro Seiki RX5000 series and RX1500's with flywheel and many idler drive based ie. Lenco L75, Garrard 301/401 and various obscure direct drive based designs for that matter and in my experience none of these classics are entirely devoid of some type of inherent compromise. Fortunately, however, with today's technical resources and understanding of applied engineering principals, including material application, certain vintage based designs can still prove more than relevant and worthy of our praise.

Peterayer, please PM me directly if you wish to know the extent of Artisan Fidelity's electronic service and mechanical upgrade services available for the Technics Sp10MK3 and how it differs from Bill Thalman's services and Krebs modifications.