Upgrade from TW Acustic Raven AC-3 to what?

Response to Aoliviero

Motor is AC, large ( weighs around 10kg in gunmetal case ), driven by what is described as an oscilater preamplifier, this has sine/cosine outputs, feeding a power amp of which the outputs go back into the preamp and out to the AC motor. The controller has separate infinite speed adj for 33/45 and has a torque control so you can adjust it.

Dertonam

What turntable/arm/cartridge are you using. Is it the one you built yrs ago and described in various threads ?

Having ben a high end dealer and set up many turntables - Linn, Pink triangle, Roksan, Sota, Oracle, SP10's, Mapleknoll ( Walker ) etc yrs ago my conclusions are as follows ; go back to first principles - the stylus, arm, platter AND motor drive MUST be absolutely rigid and referenced to each other to obtain ultimate pitch stability. I have found that most suspended tables suffer considerable wow. Similarly if you consider the first princiles I espoused - air bearings are out, not rigid, that rules out the Walker, Da Vinci & Air bearing micro seiki's. You need to consider the bearings - the Raven has a teflon thrustpad as do many high end decks, thats like playing your record on a spongy pudding - the platter and cartridge coupling are not rigid. I currently run a Final Audio Parthenon - high mass, copper platter, all chassis components made of composite gunmetal, totally rigid and massive ac motor with a power supply that includes power regenerator for accurate voltage and hz etc. This designed in the 70's ( Absolute Sound ultimately wrote it off as they mounted it on an air bed - completely against the designers philosophy ). It is mounted on a custom stand with true mechanical grounding ala Goldmund. The only turntable I lust after is the Verdier - with ball installed in the bearing so it is grounded - but dial the air pressure so that the grounded bearing only sees 4-5 lb ala the Continuum. Tonearm recommendations - no air bearings again not rigid - I use Naim Aro as the unipivot has true single point grounding and is rigid given correct arm/cartridge matching. Cartridge recommendation - currently use an Ikeda - no cantilever slewing around creating time distortion, diamond mounted n a hoop - so speed of a Decca without the hassles. Direct drives - have 2 friends with SP10 MkIII's in custom plinths - I'm not convinced - the sound is chopped up ala digital - have reservations about direct drives with constant speed correction impacting stability. Non air bearing Micro Seiki's and Melco's are also on my list of resonable decks.

Laws of physics say that for every action there is a reaction, therefore any "give" in a bearing means you are losing the leading edge ( I think you will find the downwood pressure/energy of the minute stylus tip is surprisingly high ). For an air bearing or magnetic bearing to be completely rigid they would have to have infinite pressure - impossible. The only benefit of air bearings is that they are much cheaper than a decent mechanical bearing that does not induce vibration and noise, they dont wear out and they are more forgiving of poor set up ( soft bearing = soft sound ). Remember Enid Lumley of TAS - drop the air pressure until it fouls and then raise it slightly - this gives you the softest mushiest sound possible.
Lewm
I can only draw on experience - listening to the L07D demonstrated the later Goldmund direct drives were cogging, similarly when comparing the SP10 Mkiii against the Mkii you can clearly here the instability of the Mkii. The mkiii is the best dd I've heard - I'm just not totally convinced. I would not be averse to picking up an SP10 mkiii for experimentation to find out more.

"We will never see a lightweight TT nor an unsuspended one, with a platter less than 30-50 lbs coming anywhere near the point of closing the book on TT nor approaching its true frontiers.
As we all will see - as they will come and go in half years turn.
The same they have done so for the past 40+ years in high-end."
You misread my comments - my turntable is the Final Audio Parthenon - 25kg+ platter, massive bearing and composite gunmetal rigid plinth and armboards, along with massive motor using power regeneration and power amp for the motor. If you do a search on the net you will find that the top brinkmann's etc are still catching up to my turntable which was built in the 70's. Final used to "upgrade" the big micro's as well as build their own turntable. I dont like the SP10 mkiii just said it was the best dd I've heard. And yes I've had the air bearing tables, arms and moved on. I seem to be sensitive to speed stability, timing and compression - dont want a rose tinted front end with timing issues.

Regarding string Drive - my experience with the final audio ( high mass/ac drive ) was a big improvement in stability going from cotton ( slippage and stretch ) to surgical silk.
I'd really like to get a version of this with no knot if possible as I believe the knot is the weakness - anyone got any suggestions.
I also aligned the position of the drive string to be at the bearing point ( this is an inverted bearing design ) - again this seemed to be an improvement.
With regard to torque - my experieicnes using the adjustabe torque on the speed controller of the final are that there is definitely an optimum - the sound is much smoother at the optimum point, ie I go for the highest torque until the sound goes off.

lastly a question for Dover, what do you think of someone dumping a Walker Black Diamond for a refurbished Technics SP10 MKII ?????
My view would be use the money leftover to buy a high mass rigid turntable as mentioned in the threads above.