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SDS or phono stage

I have a VPI Scoutmaster with Soundsmith Zephyr Mk II cartridge, jmw memorial arm, a stainless steel vpi record clamp, playing through a Musial Fidelity KW500 integrated amp with on board phono stage. Sounds quite good, but my question is this: would I be better off at this point adding an SDS or an outboard phono stage? Or both? In what order? Thanks!
arsh

Showing 1 response by almarg

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almarg
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02-26-14: Lewm
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.)

02-26-14: Mcbuddah
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.
A Variac will provide some degree of filtering of high frequency noise, both ingoing and outgoing. The ability of noise currents to flow in response to noise voltages appearing between the AC "hot" line and either the neutral or safety ground lines will be constrained to some degree by the bandwidth limitations of the Variac, that limitation resulting mainly from the various inductive reactances that are present in an autoformer (or a transformer). The likelihood of that noise reduction being audibly beneficial in a given turntable application is anyone's guess, but personally I wouldn't bet on it.

Variacs are widely used in or in conjunction with test equipment for many electrical and electronic products, where testing requires precise setting and/or variability of the applied AC voltage. As everyone seems to realize, a Variac cannot change the AC frequency, as an SDS or other regenerator can, it can just vary the voltage. But, consistent with the posts by Bpoletti and Hdm, I would by no means categorically rule out the possibility of their being useful in some audio system applications. The leading exception to that being that I suspect their bandwidth limitations would make them unsuitable for use with power amplifiers or other components whose current draw fluctuates widely and rapidly.

Regards,
-- Al
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