How to set SRA after determining true vertical?

If all the cutting engineers had been that meticulous, we could almost set and forget!

Nsgarch,

Great geometry refresher, thanks! And yes, it was a compliment. As we probably all know, cutting engineers allowed a wide range of SRA's when cutting lacquers. If they'd all taken such care it would make accurate playback much simpler. Tonearm height adjustments could exactly = record thickness changes. That would be nice.

A naked-eye method for (fairly) precise SRA setting has been posted in the VA FAQ's for many years:

http://www.audioasylum.com/audio/vinyl/messages/1240.html

Jon Risch, the author, offers excellent technical explanations. After studying many different cutting lathes, he recommended that a good compromise SRA for "set and forget" rigs would be 2 degrees forward of vertical, ie, top of sylus pointed away from the tonearm pivot.

Before getting the TriPlanar I used Risch's method when setting up a new cartridge. It was an effective way to settle on a baseline arm height position. Now I'm spoiled. It's easier and more fun to twiddle while listening than to fuss with maglites and magnifiers.

Regards,
Doug

Actually, it's a right theory carried to a ridiculous extreme.

A simpler solution is a tonearm with adjustable height. Then you can use any cartridge you like and play any record you like, while matching SRA.

Great pix!

If we imagine a line contact stylus trying to trace those modulations, if SRA is off then one end of the contact line will encounter each modulation before the other end. The stylus will shave across the modulation instead of tracing it precisely.

Mechanically (sonically) this will:
1) reduce stylus deflections (reduced micro-dynamics),
2) lengthen the time the contact line sees each modulation (temporal bloat),
3) alter the timing of when the stylus encounters multiple frequencies (loss of temporal focus and timbre) and,
4) alter the frequencies the stylus actually plays (FM distortion).

I hear #s 2 and 3 most easily. Paul is very sensitive to #1. He was able to adjust SRA on Cello's rig just by feeling the pressure waves coming off the woofers, without actually listening at all. Raul says he adjusts by listening to bass, so his sensitivity may be similar to Paul's.

P.S. Those records could use a good cleaning!

Raul,

Exactly right, "our best is only an approach". That is true of everything in audio of course. All the expertise, good will, time and money in the world will not turn a pile of wires and silicon into a violin.

But we keep trying, because it sounds so good when we take another little step closer...

Well, based on the answers I got from you guys, I guess this theory is false.

That's wasn't my answer or Nsgarch's. I said the theory was true but that attempting to apply it would be ridiculous. Nsgarch elaborated by explaining why matching VTA between individual cutting lathes and cartridges would require too many cartridges and would be virtually inaudible anyway.

Gregadd,
Put a stick of soft butter flat on a plate.
Hold a sharp, pointed knife straight vertical, with the edges of the blade oriented across the stick.
Lower the point into the butter and drag it the length of the stick, moving it left and right as you go.

Now rotate the butter to put a fresh side on top.
Hold the knife edges across the stick as before, but angle the point sharply either point-forward or point-back.
Cut a modulated groove as before.

Compare the two grooves. They are clearly different. The modulations cut with the vertical knife have straight vertical sides. The modulations cut with the angled knife have angled sides. The only way to accurately re-trace either groove is to use a blade with the same size and shape and hold it at the same angle (SRA). Any other angle will cause the blade to slur past parts of each modulation, creating playback timing errors.

We adjust arm height for each LP. The changes we hear are consistent with SRA-matching theory. Some people do not hear the differences as readily as others. That's normal, but it doesn't change the shape of the butter!

Andrew,

I don't know if Dan_Ed noticed when he visited us a few weeks ago, but our armtube is not level either. It really doesn't matter that much. I rarely hear any sonic effect that I would attribute to armtube angle. What we do hear is best explained by the SRA-matching Nsgarch and Jon Risch described.

Glad to learn you're achieving great results! The more you play around with it the easier it gets to hear. When you start putting little yellow stickies on each LP jacket to record arm height settings, we'll know you've gone over edge - like me! ;-)

Gregadd,

SRA actually IS the position of the stylus in the groove. That's what Stylus Rake Angle means. I think we're both saying the same thing, just in different terms.

Dan,

You're right, our arm is low at the pivot. But that makes the cartridge level, at least on this rig. IME ZYX's like to be level.

I'd hadn't thought about it, but I suppose fiddling with the arm during play on a suspended table could be more exciting than you'd like. It's a non-issue on tables like these, as you saw. I can jump up and down and it won't skip, despite the suspended wood floor.

Paul developed his acute sensitivity to SRA soon after we got our first Teres/OL Silver/Shelter rig. On familiar records he can reliably tell me, "too high" or "too low" from the den, two rooms away. It's a bit nuts, but with exposure and an improving system I find my acuity increasing too. Once you start down that path...

BTW, Paul thinks all rock listeners are headbangers! He apparently grew up hoping the British invasion meant those hooligans were all leaving his native country for good. ;-) If I want the house to myself all I have to do is spin one of my (three) rock LP's. Of course for their own safety I do have to hide them.

Seriously, those shrugs were just us acknowledging that it's harder to hear arm height changes with rock than classical. Amplified instruments often become slightly bloated. Many tube guitar amps are tuned for a bit of roundness of course. That bloat masks the nano-timing cues of small SRA changes. Acoustic instruments with quick rise and decay times respond more audibly. Obviously that is both a blessing and a curse.

Thanks again for coming down. It was great getting together with you guys.

I will have another pre-amp by then and quite possibly another phono stage as well.

Dan,
I don't know how well you liked ours, but if an Alaap interests you at all let me know. I'll put you in touch with Nick and - crucially - tell him you're an okay guy!

I'll bring more jazz next time so as not to put Paul off so much! :)

Nonsense! It'll do him good.

I do agree with SirSpeedy and his buddy Sid however. Nothing reveals what a system or component can (or cannot) do better than challenging classical. We didn't subject you guys to opera or large scale choral music, but they are the acid test. I have a few records that were comparatively unlistenable until Nick's components showed up. Our old c-j stuff just couldn't cope.

My Nashville crack was only that of course, and pretty d@mn funny if I may say so! Michael introduced us to 'Trio' by Dolly, Emmy Lou and Linda. We enjoy that LP so much it's never found its way into the record library upstairs. It lives in one of those I-may-want-to-play-you-again-soon baskets in the living room. There's a song on side one I still can't listen to without tears, since it reminds me of Lugnut.