My Views and Procedures for Adjusting VTA

[bblue]

HI Biil,
But it is a needle in a haystack. It's the nature of the beast. The challenge is to find it. Your method will not give the precision that is needed. It's not as time consuming as you think especially after you have done it a couple of times. The objective of my procedure is to find the needle without fail. Please, think about the problem and understand the need for an exact groove to stylus fit and the precision required to accomplish this objective.

I can tell you, you have not found the needle which is what I was afraid of.

Yeah, right.

The higher pressure gives a stiffer air bearing. Sonically, the entire presentation solidifies. This is especially true of the image. Bass, thought to be a weak point of the arm, becomes a strong point. The sound stage gains more specific qualities where each instrument can be placed with certainty and the walls and dimensions of the venue become more than abstractions. And the primary image becomes holographic. Other than that, not much.

Well that's pretty significant. I was originally suspicious of the pressure being responsible for soft bass and discussed it with Bruce @ ET. He said no it would not cause that unless pressure was very low, and that the *apparent* reduction of bass was actually more accurate to the source compared to a pivoted arm, which tends to build up bass due to the summation of vertical and lateral arm resonances. The ET arms don't sum those resonance points and therefore paint a much cleaner clearer representation of the original.

Still I have reservations about that taken entirely at face value. Your description is exactly what I would expect from a stiffer pressure. The question is, though, at what point (psi) does it become significant, and above what point (on each manifold type) is further increase irrelevant.

Separately, I found that the biggest factor controlling apparent bass on my arm was the correct matching of mass loading between the arm and cartridge. The manual is not at all clear in that regard, and seems to gloss over the significance of matching the two.

--Bill

[karma]

Still I have reservations about that taken entirely at face value. Your description is exactly what I would expect from a stiffer pressure. The question is, though, at what point (psi) does it become significant, and above what point (on each manifold type) is further increase irrelevant.

Separately, I found that the biggest factor controlling apparent bass on my arm was the correct matching of mass loading between the arm and cartridge. The manual is not at all clear in that regard, and seems to gloss over the significance of matching the two.

--Bill

HI Bill,
I have only run higher pressures with the high pressure manifold even when I had the Wisa.

I found that pressure changes over 25 PSI could not be detected. I run the air system at 27 PSI.

Sparky

[DonH50]

Any thoughts on how the stylus shape impacts VTA?

[karma]

Any thoughts on how the stylus shape impacts VTA?

HI Don (again!),
By the time I developed the procedure described here I had been using fine line contact styli for years. So, anything I say is conjecture. I have never tried the procedure with elliptical styli.

The alternative shapes are pretty much limited to conical and the various forms of elliptical. Conical is not worth considering. Elliptical, however, could be in the conversation. I basically think that the smaller the small radius is, the finer is the resolution of the procedure. But, a good elliptical will still fit into the highest frequencies of the groove modulation which is the key to the procedure. So, I suspect the procedure would work well for elliptical. I don't think the sweet spot would be the same. It seems to me the sweet spot would be wider and not as definitive (not as deep), similar to the results I get from pivoted tone arms.

As for correctness of the VTA, I think it is always correct for it to be right. It's just that elliptical is probably more forgiving but also, does not give as ultimately good results. I'm, as I'm sure you are too, in the fine line contact camp.

Sparky

[DonH50]

Thanks Sparky. I know we (myself, another tech, some friends) tested conical, elliptical, hyper-elliptical, and fine-line styli and my memory of the results matches your conjecture. That was long ago and I do not really recall the details. We were assessing VTA and anti-skate on a variety of arms including an air-bearing linear, electromechanical linear, a modified SME (to make it easier to adjust VTA), my Unitrac, and a couple of others I do not recall. We used three or four turntables and rotated arms and cartridges. Testing used test records and a few musical selections (I know the Sheffield drum record was one, not sure the others); we used test instruments and listening tests. The main cartridge was a Grace, I think, as we could get all four stylus topologies with the same body. We used a few other cartridges (one was a Stanton IIRC, and another a middle of the line Shure) but very few companies offered different stylus tips on the same body so our selection was limited. It took about two - three months to do all the testing and catalog the results. The results were published but not in the AES Journal; Audio, I think or maybe Audio Amateur. I was listed as co-author but in fact did almost none of the actual writing; I was a kid and mainly the lab rat.

One interesting conclusion, based on measurements more than listening, was that it was indeed easier to find the sweet spot using HF test signals. However, most everybody agreed that, outside that very small point of perfection, it was much faster and easier for most people to hear what happened in the midbass; we had to train people to listen for a pure HF signal (we actually used two-tone testing for much of the study). We did find test tones worked much better than music for dialing it in, and IMD was one of the best indicators both by measurement and ears.

Measurements showed a narrow sweet spot; ears were more forgiving. Going from very thick to very thin LPs back-to-back we could see differences in measurements; listening tests were much less conclusive. The only times we got clear recognition was with a two-table setup that we could quickly switch between; even from very thick to very thin records most people could not tell which was "perfect" with a minute or two gap between trials while we switched records and replayed the test. Shure had a hand in making the test recordings on thick and thin blanks; a Shure VP lived in KC at the time.

[karma]

HI Don,
What exactly were you measuring and what was your instrumentation? Yours is a very interesting experiment.

Sparky

[DonH50]

Thinking back it may have been crosstalk, not IMD... In any event, the test record had two-tone signals in each channel plus single tones in each channel (the better to tack vertical/horizontal modulation). Test equipment was a 'scope and audio analyzer to measure THD/IMD/SNR and a spectrum analyzer (HP, I think). With a slightly different tone in each channel we looked for the "wrong" tone in the other channel. We also did two-tone tests in each channel and both to check IMD.