SDS or phono stage

Has anyone actually compared the sonic output of a variac vs. the SDS? From what I have read technically, the SDS is designed to control the speed of the motor by varying the FREQUENCY of the AC current where a variac is just a glorified transformer outfitted with a wiper to adjust the voltage by adjusting the effective number turns in the secondary.

Mcbuddah, The SDS and the Variac are not equivalent devices, as you seem to know; the SDS is an active device whereas the Variac is passive. One small error: the Variac is an autoformer, not a true transformer. Since the primary and secondary of an autoformer have one connection in common, an autoformer does not isolate the primary side from the secondary. So an autoformer will not either block noise on the AC line or prevent tt motor noise from going back into the AC line. (I think this is true; perhaps Al will jump in and correct me, if I am wrong.) On the other hand, the SDS synthesizes "new" AC and both voltage and frequency can be varied. So the SDS can control a motor by varying either of the two parameters and will ameliorate noise, etc. I have a feeling you know all this. Bottom line: I have tried using a Variac, not to control a tt but to reduce bias voltage on an ESL panel, to "rest" the diaphragms when the speakers were not in use. For some reason, I found that it introduced a very objectionable coloration to the sound from the speakers. I don't know whether the same effect would be audible if Variac is used on a tt motor, but my Variac is now occupying a dark and dingy place in my basement.

Brf, What is "Platter Speed"? Since I've spent about ~$100 on the KAB Strobe, why would I want to spend $35 more on a device that does the same thing, or does it? By the way, that's "Lew M". You are not the only one who finds it hard to read "Lewm" and thus calls me "Lewn". On the other hand, I am a bit Lewnie, for sure.

Lew M, sometimes it is better to ask questions than to shout out answers, only to find out the world has moved on. All the variacs I have ever used or even seen have been of below par construction for audio use. I think most are used to control motors in certain kinds of factory production and OEM usaes in the same role, where critical adjustments are either not necessary or are supported with gauges or a servo mechanism. The speed precision needed to properly replay records far more important due to the sensitivity of our ears to even tiny speed inaccuracies. The KAB device used with VPI's SDS is capable of both setting and holding the speed steady, something else that the Variac likely does poorly in that it is set by mechanical means, whereas the SDS resolves in .01hz increments.

Arsh, if you are still looking for a tube phono stage in the $1500 range, you might want to check out the Eddie Current ECPA. This is the same Eddie Current that makes the Zana Deux (and a lot of other) outre-quality headphone amps. The build quality and design quality of their products is extraordinary, and the designer/owner is tube audio legend. I am happy with a 15 year-old Thor in my system, but if it ever needs replacing, I would put the ECPA at the top of my list to audition. Please note that I have no financial interest in that company, just a very happy Zana Deux ZDT owner who has a real appreciation for the work product of fanatics.

Lewm, sorry about the typo. My iPad autocorrects Lewm to Lewn.

I have both the KAB strobe and PlatterSpeed app and Adjust+ disc. I found the platterSpeed to be more accurate and easier to use.

http://platterspeed.com/