Mat,
It's been 5 months since you last posted here. Are you any closer to launching the ADS signature version?
MOON wrote:Mat,
It's been 5 months since you last posted here. Are you any closer to launching the ADS signature version?
Peer Gynt wrote:It would be nice to hear the status of this project.
In general, perfect speed control requires closed loop tachometer feedback.
In the Linn product line, at the top level (the Radikal), a marker is installed on the bottom of the platter and it is monitored by an optical sensor. A computer compares the measured signal to a high precision clock, and adjusts the DC motor to correct or maintain 33.333 rpm. I have one. It is as close to perfect speed as I’ve ever seen. The upgrade from the stock AC motor is around $5k in the US. Does it matter? I dunno. The stock table sounds good too.
There is an aftermarket upgrade from Edmund in Hong Kong. For less than $1000, he will sell you a kit to self install. The kit includes a sticker with 16 markers that fits under the platter. Also included is an optical sensor to read the markers. The computer uses a standard post WWII 2nd order closed loop feedback control algorithm to continually adjust the motor speed based on the sensor signal. I’ve got a deck set up with one of these too. Linn say it’s not as good. It measures imperceptibly less good than the Radikal ( you can see it in the second decimal place). My ears tell me it’s quite good, especially for its price point.
In the VPI line, it looks like we’ve relied on the AC synchronous motor with precise pulleys and belts. Sometimes we add a PLC, or SDS, or ADS, but none of these use feedback.
I don’t think you’re ever going get perfect measurements from a system with out feedback. But obviously the tables sound great. There is a school of thought that views feedback as a sound detractor, rather than an enhanced.
FWIW, Rega tables are notorious for running 33.4+ rpm, and people rave about them. So being exactly on 33.333 is nice for test equipment, but if you want to listen to music rather than measure, it might be better to put away the test gear and grab some records.
When I play my HW19 Mk3 or Classic 3SE against either of my LP12s, the VPIs deliver the goods.
Mat wrote:Actually we have a gorgeous 3D rendering of the chassis as well with a lot of other fantastic steps forward... but I'm not posting anything until I'm holding a near finished prototype in my hands
Orchids1 wrote:Peer Gynt, The system you described for maintaining real-time rotational speed accuracy is essentially what was used in the Phoenix products. They were also accurate to the third decimal point. My platter often maintains 33.333 rpm for extended periods using the Phoenix Eagle and tach. Rich
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