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.

.
128x128nsgarch
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.
Doug's post reminded me that this word "level" is getting tossed around quite a lot. Just so it gets mentioned, the first thing to "level" is the platter. And if you have a suspended table, that means with a clamp and record in place on the platter. (Keep the tonearm in its rest, it won't make any significant difference to "level" in its rest as opposed to sitting on the middle track of the record!)

After that, the position of the tonearm relative to the platter (either parallel or nose-down) will be determined by setting it to provide the proper SRA for the stylus.
Whoops! I've said all this before. I keep getting sucked in. Any way vdh's advice sort of proves my point. Think about it. He also had to make the call. If the cantilever is sort of a spring it will deflect under different loads (vtf). Thus if the range is 1.5 -2.2 grams. Then in setting the SRA he had to pick the load producing his optimum sra for that load and arm geometry.

I "believe" that all your are doing is "relocating" that point based on your different load and arm geometry and not duplicating the original SRA of each record. Of course it changes from record to record because record thickness again alters the arm geometry.

Perhaps Doug is right and we are approaching the same solution from a different direction.
Dan,take a look at the Acoustic Sounds latest advertising.They're selling our little(well,mine)digital guage(95 bucks on Audiogon)for 185 dollars!MAN,we could have bought them all up,and made enough to buy a Blue Pearl!Well maybe a platter mat,for it.

This business of manufacturers making the cartridge bodies to line up one way or another is kinda cute.You have to be careful here,because I can guarantee that plenty of our little cantilever angles are NOT all exact,from model to model.Whomever the mfgr is!The EAR is the only viable way to discern this.But you all knew this anyway.I just wanted some post time.-:)Heh,heh.

PAUL--"To shrug,or NOT to shrug".That question is inarguable to me,as if we want to really hear/know what our favorite "great" cartridges can do,especially the cream of the crop,it seems to be a no brainer to use something like well recorded classical lp's.Or something of that ilk.
I mean to listen for something like the breath being blown,gently through a flute or oboe(for example)trumps an electric guitar being broken over some "groupie's" head!No?Yet that acoustic guitar/singer song writer disc that Cello played for me,really blew me away.No heavy metal,but heavy duty ambiance and gorgeous tonal shadings.I can only imagine how great Larry's set-up must sound by now.

I kinda smile when some audio maven(reviewer) lists the criteria that makes a particular cartridge(or any component)great,and then goes on to list almost all music listed,as hard rock.Oh yeah,you'll notice they throw in one or two classical war horses,to seem interested in that stuff.
Don't get me wrong.I love rock,and have no boundaries in my musical appetite,but when you want to define the sublimeness of a great transducer,nothing compares to listening to the tonal shadings,and harmonic beauty of the instruments of an orchestra.Get that right,and everything else falls into place!Sid always tells me that though something gets a rave,it is meaningless to him,because he has no concept of what that person values in the LP's he listens to.Or what that particular person values in music reproduction.We all seem to skew a bit,in what type of system presentation we favor.It's called individual taste.
Hear that Raul!Enough with the love affair with Heavy Metal!Jan Allaerts SURELY did NOT design his "magic beauties" with the thought of "hooligans banging heads"!-:)
A little humor,if you will,so please no bombs from south of the border.You know you're still the cartridge kin

Sorry for going on so long.It's been three months that my set-up is down.I have nothing else to do!Hey,Mr amp manufacturer,please hurry up.I've got all my other stuff done already.Enough with the hiking cross country!

Best!

Nsgarch,

I found this to be true as well. Raising the arm at the pivot point by 6-8mm improved the sound dramatically. Better bass extension and tautness (very punchy) combined with more detailed highs.

I tried this compared to a level arm tube postion and sligthly lower height of the arm from true parallel. I found that a lower than parallel arm tube position seemed to bloat and diminish the detail of the bass and soften the highs.

Maybe the "right" SRA of the tip in the grooves compared to the original cut is irrelevant. Maybe all we're really doing by determining our preferred SRA or VTA settings is taming the particular sonic signatures of certain tonearm and cartridge combinations.