Tranfiguration Orpheus description

Speedy, the 7 or so people I've assisted in following my procedure for establishing zero SRA, have then set their stylus rake angle to a nominal 1.5 degrees (+/_ .20 degree) and found it to yield the best sonics achievable simply using measuring tools and mechanical adjustments. It is possible to refine the SRA (and the sonics) further on a record-by-record basis, the way Doug likes to do, however that requires you have a tonearm that permits easy SRA/VTA adjustments on-the-fly.

I don't have a tonearm that allows me that luxury-cum-obsession, however, it is possible to achieve almost the same results (as adjusting VTA on-the-fly) by increasing/decreasing VTF slightly:

If one normally runs their MC cartridge at the high end of the recommended VTF range say 2gms, then adding or subtracting 0.2 gms won't substantially alter the alignment of the coils in the flux field, but it will change the SRA by a tenth of a degree or more, for high compliance cartridges like van den Huls, somewhat less for Transfiguration, Dynavector, ZYX and other low-to-med compliance designs.
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Andrew,

Your increase in VTF (1.92 to 1.97) had sonic effects that would be similar on our cartridge, or maybe any cartridge. A slight increase in overall heft, sturdier bass, less edginess in highs. Those are fairly normal effects when you move from near the mistracking point to very slightly higher.

A spot some few hundredths of a gram above the mistracking point is the sweet spot for every LOMC we've used. On a UNIverse the spot is about .02-.04g above the mistracking point. Apparently on an Orpheus it's about .05g above the mistracking point. Different suspensions, different results, but not by very much.

We're obviously both splitting hairs to maximize the performance of extraordinarily sensitive and responsive cartridges. As Raul observed during his visit here, we play right on the edge. Our bass was a touch light at one point so I replaced a thick O-ring with a thin one, increasing VTF by about .02g. He was fairly amazed at the audible improvement from such a tiny adjustment. This degree of nuttiness is the only way to get the most from these cartridges, at least in our experience.

BTW, don't think that just because it sounds perfect at 1.97g today that it will do so forever. That kind of stability will probably never happen. Weather will change it. Amount of use or lack thereof will change it. We often find ourselves reducing VTF by .02-.03g after the cartridge warms up from playing several sides. The sweet spot is always a moving target.

You're right that VTF must be absolutely spot-on before you can truly optimize VTA/SRA. Doing that by ear requires listening for:

a) the integration or timing of fundamentals vs. harmonics (what Frank Schroeder and I hear) or,

b) the quickest rise/fall times and greatest amplitudes of individual notes, especially bass notes (what Paul hears).

Best,
Doug

Nsgarch,

Your suggestion to use small VTF adjustments as a proxy for fine-tuning VTA/SRA would indeed have the effect you described. Unfortunately, VTF fine-tuning does more than center the coils in the magnetic field. A fairly large increase like .2g would cause other effects that might fairly swamp the VTA/SRA change.

As Andrew described and I affirmed, a change of .05g or even .02g can have a significant impact on sonics. These tiny changes barely effect the coils/magnets relationship, yet if we're near the cartridge's VTF sweet spot they have significant sonic effects. Why?

I believe the reason has to do with a kind of mechanical damping. Increases in VTF increase pressure between the suspension and cantilever, by definition. Once we have sufficient downforce to assure clean tracking, additional pressures very quickly become detrimental. HF response is dulled, micro-dynamic shadings are lost, the music goes dull, drab, lifeless - in a word, overdamped.

Our anti-skating experiments (described on other threads) support this understanding. Anti-skating, like VTF, increases pressure between suspension and cantilever. Using more than necessary to maintain clean tracking sounds exactly like using too much VTF. HF response is dulled, micro-dynamic shadings are lost, the music goes dull, drab and lifeless - in a word, overdamped.

For the sufficiently obsessed (Andrew and I know who we are!) increasing VTF as a proxy for adjusting VTA/SRA would produce unacceptable side effects. Of course Raul did observe that Paul and I play our rig right on the edge. He was certainly right about that. ;-)

Doug

Thank you, SirSpeedy.

Best wishes for the holidays and the new year,
Doug

Doug, you and Andrew have Triplanar tonearms, so you can have perfect SRA at all times no matter the record thickness or the engineering preferences of the lathe operator. In any case, even .2gms wouldn't make enough of a difference with most of the top cartridges which are low(ish) compliance (except for vdH).
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