How to set SRA after determining true vertical?


Here is a picture of a stylus with zero rake angle:

http://members.cox.net/nsgarch/SRA@%200.0%20deg.jpg

Since all modern styli are symmetrical in the x and y plane about the verical z axis, the tapered stylus and its reflection will make a perfect "X" when vertical (z axis perpendicular to the groove) and viewed from the side.

This condition is established by raising or lowering the tonearm pivot post. Once you find this point, and assuming you have a typical 9" tonearm (about 230 mm from pivot to stylus) then each 4 mm you raise the post from the zero
SRA point will apply one degrewe of SRA to the stylus.

A test setup is shown in these two pics:

http://members.cox.net/nsgarch/SRA%20setup1.jpg
http://members.cox.net/nsgarch/SRA%20setup2.jpg

Equipment includes:

a mini Mag-Lite flashlite,
a first surface mirror from old SLR cameras -- easy to find at photo repair shop)
a 50X pocket microscope
bean bags

Don't forget to first remove antiskate and set VTF.

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128x128nsgarch
Andrew, don't be skeptical. There is absolutely no mystery here. It's all physics and simple geometry. The most important thing to remember when approaching the matter of setting correct SRA, is to have all the other settings perfect beforehand. IMO, the proper order for setting up TT/TA/cart. is as follows:

1.) Level the platter, and then cross-check to make sure the headshell is level (across, not front to back) -- especially important if the headshell is not adjustable (like an SME V!)

2.) Install the cartridge and adjust the stylus overhang at the spindle.

3.) Adjust the cartridge yaw (rotation as seen from above) to reduce tracking error at two points across the record using one of the many cartidge alignment gauges available.

4.) Set the VTF -- at the top of its range if it's a new cartridge, less if already broken-in. Use a digital stylus gauge that reads to 1/100 gram (two decimal places.) Do not apply antiskate yet. You'll need it off to check the stylus vertical position.

5.) Then set the arm parallel to the platter. By eye is good enough. I sometimes use one of those little round bubble levels. They weigh only .15 gm, so you can put it right on top of the headshell before setting the stylus on the record, without fear of cartridge damage.

6.) Now you can begin the SRA setup process. First find where the stylus is vertical as I explained earlier -- and which was the reason for this thread ;-)) -- and then raise the tonearm post 4 or 5 mm.

7.) Now you can set the antiskate. I do it visually if I can (meaning if I have a high compliance cart. which lets me see the cantilever shift with the application of AS force) Otherwise set it by the numbers. Using a test record can also be helpful.

8.) NOW you are ready to begin listening and moving the tonearm post sligntly up or down from the +4 mm setting.

I cringe when people make absolute pronouncements, but honestly, you must follow this process exactly if you expect meaningful results.
Nsgarch,

Good points. I pretty much followed your process, however I began with setting VTF on the low range. I'll begin experimenting with higher VTF's and resume the SRA testing.

Thanks.

Andrew
Doug,

I knew exactly what the shrugs, nods, etc., meant. And interpretting those indicators is what made it so much fun to watch. I hope we can all get together again before too long. I will have another pre-amp by then and quite possibly another phono stage as well. I'll bring more jazz next time so as not to put Paul off so much! :) I believe I also heard some disparagement towards Nashville so I'll leave the Pickin' music behind as well. ;) Seriously, that was very "eye-opening" to hear how much difference there is between recordings of different musical genres.

SirSpeedy, I guess we'll just have to watch as someone else makes the money. Again! BTW, you once warned me about listening to other's systems and how it can lead to a certain amount of displeasure with your own. Well, it's happened to me. But I do think it is a good thing in the end since what most of us are after is to build our systems as good as we can get them. I also agree with you about different music. I'm fortunate to have a friend who is a very highly trained jazz trombonist. He's taught me a lot about jazz over the last two years so I'm beginning to gain an appreciation for it. Classical is going to take me a while longer but I do have many fairly good recordings both on vinyl and cd.
Andrew, I only mentioned the business about setting new carts' VTF at the high end of the range because it is necessary to do that in order to get the cantilever/coil assembly to "line up" squarely in the magnetic flux field (maximum output).

Later on, after about 100 hours of being compressed under record playing conditions, when the rubber suspension "limbers up", a somewhat lighter VTF will be sufficient to achieve that same proper mechanical alignment of the coils in the flux field.

Again, there is no magic involved here. In fact, as far as I'm concerned (here we go!!) the only criteria for the correct VTF setting is this alignment of coils in the magnetic flux. If you have that right, and the SRA and AS are on the nose, there should be no tracking problems (the most common reason for fiddling with the VTF).

If for some (other) reason your cartridge still won't track, look elsewhere, especially for possible compliance vs. eff. mass mismatch with the tonearm.
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.