Direct drive vs belt vs rim vs idler arm

Hi Tonywinsc/Henry et al.

Thanks for publishing that excellent information Henry !

From Dr. Feickerts website.
------------------------------------------------------------

The optimal Azimuth can be found reliably using a systematic analysis of the values of level and phase angle of the crosstalk signal against different azimuth settings.
But this is not the complete functionality you get. You can also measure dynamically using Pink Noise to see how your cartridge reacts under complex signals. Additionally you can measure the frequency response of your cartridge/phono-stage with Pink Noise (dynamic) or with a sine-wave sweep (static). In both cases also in left or right channel only mode.

Setting up turntable speed now is an easy task as you don’t need to use inaccurate strobe discs. Simply use Adjust+ and enjoy additional benefit from the built-in wow&flutter analyzer – now even evaluating according to DIN IEC 386 (formerly DIN 45507)! Now you can test how good your turntable spins your discs….

------------------------------------------------------------

To All.

Would I be correct in assuming that if we wanted a real apples to apples comparison of the data, turntable to turntable – then Halcro (Henry) needs to use the same tonearm/cartridge on each table ?

Did u use different tonearms and cartridges on the two turntables Henry ?

From Dr Feicket’s website again. Btw - I am not affiliated with Dr. Feickert.

Another feature is the fres task. You can measure the resonance frequency of your cartridge/tonearm combination, something very, very rarely found nowadays. Adjust+ helps you to see if your chosen combination works in the recommended range of 8-12 Hertz. Well, and if you are not sure if you have additional resonances in your tonearm resulting from tracking you can measure in the range from 30 to 500 Hertz and see…..

Back in the 70- 80’s when vinyl was at its peak, Bruce Thigpen did a number of wow and flutter tests, without an Android or I phone :^) ........ on various tonearms using the same table.

But this a turntable thread...

Cheers

wow and flutter defined

Halcro, thanks for your interesting post. I wonder if you would get different test results on your Raven if you used one motor? Any thoughts?

Hi Tdaudio,
I tested the Raven with one, two and three motors using the Timeline......and two motors gave the most stable and consistent speed using this method?

Hi Chris,
I will be testing azimuth and arm resonances via this App when I get some time?
Seems like a pretty good investment for under $20 incl delivery from Dr Feikert?
Gotta love the audio community? :-)
Regards

Richardkrebs
"The perfect TT has absolute speed stability under all load conditions"
I would draw your attention to the following :

Newtons Second Law of Motion - Force = mass x acceleration

or Acceleration = Force/mass

In other words deceleration due to an external force is inversely proportional to mass. The moment of inertia for the following TT's are -

Final Audio high inertia TT - 3920kg/cm2
Kenwood L07D - 1025kg/cm2
Technics SP10mk3 - 1100kg/cm2

This means that the high inertia Final Audio TT requires a 300% increase in stylus drag variation compared to the L07D and SP10mk3 to achieve the same loss of speed.
In other words for a given additional force due to stylus drag variation the Technics SP10mk3 and Kenwood L07D will have a deceleration 4 times higher than the Final Audio high inertia TT.

Now if we look at the design intent of both the Technnics and Kenwood we find some interesting facts :

Kenwood L07D Manual

A moment of inertia of 1025kg-cm2 is obtained ( when the turntable sheet is attached ), resulting in high kinetic energy of rotation. Therefore the platter rotates stably even if the transient load from the stylus varies.

The L07D uses double servo coupling which automatically switches the control method when the speed difference is beyond +-3% from the rated speed: when the speed difference is beyond +-3% the speed is controlled to obtain a large torque and, when it is less than +-3%, the phase is controlled to obtain a wide lock range and large phase gain

Clearly the Kenwood designers believed that the magical figure for moment of inertia of 1000kg/cm2 was sufficient to overcome stylus drag fluctuations.

Now let's look at the Technics SP10mk3 Sales Brochure

Technics SP10mk3 Brochure

1.1 ton-cm2 Moment of Inertia
Huge moment of inertia results from the 10kg platter made of diecast aluminium with a 15mm thick copper alloy surface layer. Therefore there is no change in speed with any fixed load up to 10kg-cm – equivalent to 1000 tonearms tracking at 2g each. Of course, the real benefit is that the platter keeps rotating at exactly rated speed even if you accidentally touch it during play.

Wow and Flutter 0.015% WRMS, Speed Accuracy +-0.001%
Besides the huge moment of inertia of the heavy platter itself, our full cycle detection FG also contributes to rotational accuracy by supplying a more reliable signal for phase comparison with the reference

So the Technics designers have a foot in both camps. On the one hand they believe that a moment of inertia of 1100kg/cm2 will support 1000 tonearms tracking at 2gm but then they go on to say that the fast error correction helps to maintain speed.

Furthermore the Technics SP10mk3 Brochure also explains that purpose of the high torque motor is to ensure for that the platter can be brought up to speed within 0.25seconds and reverse torque can stop the platter in 0.3seconds to meet the requirements of Radio Stations.

With regard to your comments on the Techdas, I would draw your attention to the design. Although the Techdas has a 30kg platter, the motor drive is low torque. They deliberately drop the torque as low as possible just to keep the platter spinning accurately and no more. They have done this to minimise noise and vibration. This is explained on their website.

To reiterate my earlier posts on cogging -
The torque ripple or cogging torque will be lower on a high inertia thread drive because a Direct Drive motor is running much slower.
For example
DD - 33.33rpm x 20 poles = 20 poles per revolution of record.
AC/thread drive - 1800rpm x 4 poles = 216 poles per revolution of record.

In summary then, the benefits of a high inertia thread drive over direct drive are :

Final Audio High inertia TT has a resistance to stylus drag variation 4 times higher than the SP10mk3 & Kenwood L07D
Final Audio High inertia TT has less cogging effect ( and lower amplitude ) due to the higher motor speed.

Speed correction is required on Direct Drive TT's due to insufficient moment of inertia which is required to resist to transient load fluctuations.