The New VPI Analog Drive System at T.H.E. Show

They are showing this today. Curious to see how audible it is....

 

I'm also curious, and about the price.

 

Pardon my ignorance, but what is it exactly? An external PSU with speed changer?

 

on VPI's forum they said it will be around $900

It's an analog version of their SDS unit. it keeps the speed of the platter stable and locked on either 33 or 45 rpm

 

i wonder how it differs from the SDS in performance, seems similarish in price...

 

It's to replace the current sds which is used for speed control, and has been around a while. Harry Wesfield hinted on it a month ago and started talking about it mid May in Harry's corner in the VPI website. Seems like there will be two versions.

 

Oof, $900. The Phoenix speed control/power conditioner costs about $700 altogether IIRC and is supposed to be very good.

 

This was in the Vpi forum


AnalogDriveSystem is an evolution of the SDS with no digital based electronics utilized in its design. The low distortion analog sine wave oscillators are actually running at 60/81Hz. Functional switching is performed by simple/reliable analogcircuitry. The drive for the motor is a Class A/B amplifier; the power supply is linear design as well. The removal of the digital noise floor is not subtle.
The speed is adjustable through separate 33/45 RPM oscillators and controls. These controls have a center detent position that is calibrated at the factory for 60/81Hz (33/45 RPM) but also allow for fine speed adjustment with the use of a strobe disc.
The question of feedback came up regularly in our design discussions, but we opted for a high current drive approach to minimize the effects of stylus drag on the speed stability. A synchronous motor will run at the speed set by the AC input as long as driving sine wave is stable and it is producing enough torque to overcome the demands placed on it by the stylus drag in the groove. We found the dynamic demands on speed accuracy to be more important, causing us to focus on the drivecapabilities of the ADS circuitry. Any meaningful system that would add effective feedback would drive the cost of the ADS up dramatically, which we did not want to do.
The results relative to the SDS? The ADS presents a smoother, more coherent presentation on complex passages, with a sense of drive and speed stability that is clearly noticeable as the recordings gets more demanding. The ADS imparts a sense of ease and purity that really shines on dynamic recordings. Holding its own up against the Avenger Direct drivesystem on Friday.

 

The SDS is available at $1399, and this will be $900. There will be three models, and this is the middle one. The higher end model which addresses phase and tracks speed via a strobe under the platter, is not yet ready for release.

 

So the higher end model will incorporate feedback? That would be very cool... I'm surprised they would use a strobe vs an encoder. I guess a closed loop encoder creates a bit of extra force and may be expensive, but they can be extremely accurate.

I would love to get into experimenting with motors for turntables myself. Using 3 phase motors with VFDs at work, I'm familiar with applications that require extremely precise speed control. You can very easily run a 3 phase motor from your single phase 120V circuit at home, the controller just needs to be upsized. Since we are dealing with fractional HP, this wouldn't become an issue. Modern speed controllers used in industrial applications have sophisticated torque control that can also be dialled in to keep the rotor at a precise frequency.

Anyway it's cool VPI is also developing different methods and technologies. Thanks for the posts.

 

I'm surprised they went analog instead of digital, I think it is difficult to get the same stability. If the purpose of these power supplies is to provide stability for the motor, I would think performance would suffer.

There is a preliminary review of the ADS here: http://www.turntablepsu.com/vpi.html

 

3 phase motors would be smoother than single as well. I'd venture to guess it'd be the cost. Easy to spend too much per table on a controller and custom wound motor.

Is the tach not worth getting for closed loop operation?