[Wayner]

I have made a small error. I laid out my stick-figure drawing with the pivot at the same level as the stylus and it should have been elevated. I'm going to adjust that tomorrow (I'm really tired tonight to do any more). What this means is that the rate of change will increase at a faster rate, so the 2° amount may be more. Stay tuned.

[SteveRB]

A 2° change on my 12" arm requires me to raise it 11mm.

[neobop]

Neo you're ranting again about personal attacks,you have shown disrespect to a fellow vinyl person,we're a community of vinyl people here,we shouldn't behave like you did,have i ever disrespected you or commented bad at you before,no!!!,kind regards...

You're the one ranting.  Again, your comments are non-specific.

[Letitroll98]

A 2° change on my 12" arm requires me to raise it 11mm.

Is that right?  The 2 degree change on a 9" arm is .1524 mm according to Wayne's numbers, big difference.  Which leads me to my question, I wonder what the numbers are for a 10" arm?  It would be interesting to see if there's a significant difference, or advantage, to longer arms.

[SteveRB]

Is that right?  The 2 degree change on a 9" arm is .1524 mm according to Wayne's numbers, big difference.  Which leads me to my question, I wonder what the numbers are for a 10" arm?  It would be interesting to see if there's a significant difference, or advantage, to longer arms.

Here's my simple drawing. To move the vertical line (diamond) 2° the back end is raised 11mm for an effective length of 307mm...  This is how it works, non?

[neobop]

A 2° change on my 12" arm requires me to raise it 11mm.

On a couple of other forums there used to be a poster called Luckydog.  He is a physicist and was a major contributor on technical matters on VE.  Some of his posts are there under LD name.  Apparently he was kicked out of VE and posted a bit on Karma.  We were discussing effective mass/MOI (moment of inertia) among other things, and he said something surprising.  Due to a quirk in the math, eff mass does not increase due to length between 9 to 12".

Eff mass is the same as MOI and both weight and distance  are factors.  So, this states that the only increase in arm eff mass in this case is due to the increase in material weight due to extra length.  If weight is kept the same like a thinner arm tube, then no eff mass increase. 

If you're not bubbling over with excitement I don't blame you.  Maybe Wayner will find it interesting when he sees it.
neo

[Wayner]

Is that right?  The 2 degree change on a 9" arm is .1524 mm according to Wayne's numbers, big difference.  Which leads me to my question, I wonder what the numbers are for a 10" arm?  It would be interesting to see if there's a significant difference, or advantage, to longer arms.

Steve was talking about how much he had to raise the back of the arm to get the 92° rake angle.

I'm discussing how much the stylus moves out of alignment by such rake angle adjustments.....

'ner

[Wayner]

OK, the hinge point of my Technics tonearm is actually about 5/8" higher then the stylus. This has now changed the stylus offset distances by a considerable amount. Here are the results in 1/4° increments:

.25° = .003
.50° = .006
.75° = .009
1°    = .012
1.25° = .016
1.50° = .020
1.75° = .023
2°    = .027 (which is almost 1/32")

In conclusion if the amount of vertical change is only a couple of millimeters, the alignment will still be in an acceptable position. However, drastic amounts of VTA, like 2° will throw the alignment way off.

'ner

[undertow]

[neobop]

If the height of the pivot is taken into account and not the height of the cart, I think it will tend to alter results.

The arm is roughly parallel when playing.   This is not a simple triangle.  That's why I said it gets complex.  I don't think there's disagreement with your general conclusion.
neo

[SteveRB]

Well, I continue to find ways to keep this hobby interesting. I decided to anti-up and see how I can get a workable 92°. I spent several hours last night balancing: SRA, VTA and VTF... The above image is my result. Once I got close, I re-set the image and measurements 3 times to make sure I was not getting bad alignments -- you really are splitting hairs with camera angles and CADD.

I achieved this with with my 12" arm raised up about 1.1° (5mm) and dropped the tracking weight 0.3 grams. The cart tracked just fine and the results are pleasant. Is it any better?! Time will tell; I find it hard to make value judgements in one evening.

Note: Dropping the tracking force changes the SRA much more drastically than raising the VTA.

Please feel free to critique my image or methods.

[undertow]

Obviously compressing the suspension via VTF variations will of course force your SRA to adjust... But then again we can argue so will a 180 gram record vs. standard thickness as well.

The way I suggest is getting the VTF as close as possible to the best optimal weight suggested, then work from there using the arm to compensate. Because even if its tracking fine, its still tracking "Light" which will likely affect some of the frequency balance more than worrying whether the SRA is dead on 92.

I have a 12" arm that allows you to not only adjust height at the arm mount, but all the way at the headshell it will also pivot directly above the cartridge to let you make a much easier fine adjustment from there. Most arms will not do this obviously so without literally attempting to set this perfect condition for every single record, or re-checking the variables consistently I would not go crazy over this. Get it close, but cartridge weight being in the proper range is more important. Remember 10 years ago SRA was not even possible, or rarely discussed on 99.9% of arms, and vinyl still existed!

Good Luck

[SteveRB]

Obviously compressing the suspension via VTF variations will of course force your SRA to adjust... But then again we can argue so will a 180 gram record vs. standard thickness as well.

The way I suggest is getting the VTF as close as possible to the best optimal weight suggested, then work from there using the arm to compensate. Because even if its tracking fine, its still tracking "Light" which will likely affect some of the frequency balance more than worrying whether the SRA is dead on 92.

Yes, I am still in the range for VTF, so I still feel confident that I'm working the cart as designed. I found it interesting that a couple tenths of a gram can change the angle more than a couple degrees. I have absolutely no interest in adjusting this for different LPs. But I like the idea of having the three numbers I can use as a repeatable control and adjust to suit.

[Wayner]

Well, I continue to find ways to keep this hobby interesting. I decided to anti-up and see how I can get a workable 92°. I spent several hours last night balancing: SRA, VTA and VTF... The above image is my result. Once I got close, I re-set the image and measurements 3 times to make sure I was not getting bad alignments -- you really are splitting hairs with camera angles and CADD.

I achieved this with with my 12" arm raised up about 1.1° (5mm) and dropped the tracking weight 0.3 grams. The cart tracked just fine and the results are pleasant. Is it any better?! Time will tell; I find it hard to make value judgements in one evening.

Note: Dropping the tracking force changes the SRA much more drastically than raising the VTA.

Please feel free to critique my image or methods.

Wait 'till you encounter records of vastly different thicknesses. Case in point, Supertramp-Brother, Where you Bound? is at 1.54mm, Genesis-And then there were Three is at 2.20mm.
That is .66mm difference.............

'ner

[SteveRB]

yup.

But we gotta start somewhere... after 4-5 drinks I'm not too worried about those 0.1mm

[Wayner]

I guess the point I was trying to make is if we are all concerned about maintaining a 92° SRA, then we have to be concerned about the record thickness, or its kind of all for nothing. Go thru all that work and ignore the medium you're trying to conquer.

[undertow]

Well if you read above I already mentioned that. Because between a 180 gram and standard LP even you will have variations, not to mention the fact the suspension is exactly that... Suspension! It will continue to vary and bounce along the surface at different rates with every LP you drop on the table, you will get 92 degree for about 2 seconds every 10 minuets anyway. That is really not the point, fact is trying to get it locked in as close as possible to all parameters and you will do well. Perfection is not possible, nor are any of the recordings being played back.

If you are truly not happy with performance or overall sound on an LP the LP should be replaced, or forgotten all together in many cases. As for the rest of it, tone, musicality, frequency balance, are all better adjusted using a different cartridge or phono amp over all else because only so many VTF changes, or arm adjustments will net much result in overall consistent playback.

[SteveRB]

I guess the point I was trying to make is if we are all concerned about maintaining a 92° SRA, then we have to be concerned about the record thickness, or its kind of all for nothing. Go thru all that work and ignore the medium you're trying to conquer.

i agree, and with a consistent set of tools we can set a repeatable baseline. Each of us will have to come to terms with what we accept as +/- tolerances.

[GentleBender]

Wait 'till you encounter records of vastly different thicknesses. Case in point, Supertramp-Brother, Where you Bound? is at 1.54mm, Genesis-And then there were Three is at 2.20mm.
That is .66mm difference.............

'ner

That is why I have 10 turntables, each set for a specific set of records.  All kidding aside, all this information is good to make informed decisions. We can choose how far down the rabbit hole we want to go. I've got a lot to learn so thanks for sharing.

Enjoy the music or tinkering with your setup, whatever makes you happy.

[undertow]

That is why I have 10 turntables, each set for a specific set of records.  All kidding aside, all this information is good to make informed decisions. We can choose how far down the rabbit hole we want to go. I've got a lot to learn so thanks for sharing.

Enjoy the music or tinkering with your setup, whatever makes you happy.

Well see that's your mistake right there... You don't need 10 different turntables, just one well isolated table, and then 10 different arm pods with arms each set to the varying degrees stored in a drawer marked with each album color coded to the measurements in order to have fast retrieval between albums! Welcome to the 21st century. Not sure what all that digital nonsense was people were going on about 25 years ago either.