Yes. The VTF range is there because the compliance may vary from one cartridge to another. But even more problematic is the varying VTA/SRA angle due to warps.
Thus. Set the arm parallel to the record at the nominal VTF. Check the SRA with a microscope. If between 92-95 degrees it is ok.
You are tallking about severe warping here. I am talking about warps that alll LPs have. If you have a ring clamp + a center clamp, vacuum platter or raise the resonance frequency to 10-15 Hz you will reduce but not eliminare warp noise. See link to measurements that I posted in the crosstalk/azimuth thread regarding tone arm mass. You have other effects that influence VTA/SR, eg variable drag and friction.
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If you take an example of SRA and different thickness of records.
If you have set the SRA to 92.0° using a standard LP you will get around 91.8° using a ticker LP (+0.8 mm) if you have an arm length of 220 mm.
Even if you could set the SRA to a precision of 92.0 degrees during static situation, you will have at least +/-0.5 mm warping in a majority of of LPs that will affect this angle 91.87-92.13°. This not only cause different angling but also slight variation of VTF that in turn will alter the SRA/VTA. Also you will have drag issues that act on the suspension dynamically and effectively change the SRA.
Finally, the SRA of the specific record is not exactly 92.0 degrees. The standard is wider than that, and it probably varies along each record itself depending on the frequencies.
So conclusion. Set the arm parallell to the record at nominal VTF, check static SRA if needed with a good (USB) microscope. If between 91-94° you are good to go.
If you have set the SRA to 92.0° using a standard LP you will get around 91.8° using a ticker LP (+0.8 mm) if you have an arm length of 220 mm.
Even if you could set the SRA to a precision of 92.0 degrees during static situation, you will have at least +/-0.5 mm warping in a majority of of LPs that will affect this angle 91.87-92.13°. This not only cause different angling but also slight variation of VTF that in turn will alter the SRA/VTA. Also you will have drag issues that act on the suspension dynamically and effectively change the SRA.
Finally, the SRA of the specific record is not exactly 92.0 degrees. The standard is wider than that, and it probably varies along each record itself depending on the frequencies.
So conclusion. Set the arm parallell to the record at nominal VTF, check static SRA if needed with a good (USB) microscope. If between 91-94° you are good to go.
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Below is a link to my OM40 Fritz Gyger II SRA. Arm parallell to record surface at 1.5 g VTF.
Dropbox - SRA OM40.pdf
Dropbox - SRA OM40.pdf
Nice Pic Thomas, you are better at the photography than I am!
Having only read Josh's pages on this 3 times I am still confused over whether VTA actually makes a blind bit of difference. I know it used to be around 15degrees, then moved to 20 and now we just don't know (but most cartridges are in the 20-24 range). I have not read of anyone keeping an old ortofon SL-15 just for pre-75 recordings so I tend to think it's lost in the noise of all the other distortion mechanisms on vinyl replay.
Having only read Josh's pages on this 3 times I am still confused over whether VTA actually makes a blind bit of difference. I know it used to be around 15degrees, then moved to 20 and now we just don't know (but most cartridges are in the 20-24 range). I have not read of anyone keeping an old ortofon SL-15 just for pre-75 recordings so I tend to think it's lost in the noise of all the other distortion mechanisms on vinyl replay.
My 2p worth is that SRA matters far more for fine radius styli, such as FG, because stylus presentation angle to the groove surface affects surface friction/drag more than for, say, spherical stylii. The principal performance issue isn't a geometry thing, it's about tribology IMO.
Only when tribology is right can geometric benefits of fine radius styli be properly harvested, IMO. And when it all comes together, very good it is too
LD
Only when tribology is right can geometric benefits of fine radius styli be properly harvested, IMO. And when it all comes together, very good it is too
LD
Referring to post #67. Such charts generally grossly exaggerate groove angle and curvature to demonstrate the effect. As is the case here.
Most grooves for normal programme material have gentle angles and curves, only at peak levels do things get interesting, and the same is true for pinch effect. Nevertheless, harmonic distortion at normal programme levels is audibly lower for fine radius styli. But the benefit is mostly from improved traceability because the stylus does not need to be accelerated downward in a hurry to recover from pinch effect, which is always tricky. At least not to the same extent as for, say, sphericals.
Just my 2p worth.
LD
Thanks,
In principle VTA has a profound impact on vertical IMD. If not matched you have similar problem as improper LTA.
I think if you by a cartridge with a 15 degree VTA and play records with 20 VMA/vertical modulation angle, you have to live with the distortion component that comes with it. It is not clear to that there is a big difference is with 15 or 20°. However below shows harmonic distortion and not IMD, where the figures appear larger.
I am not 100 % sure about the 15 degree angle of the V15. It should be 15 degrees according to the original statement, but the actual measurements of VTA may be different, the Josh page refers to 23° measured on the V15-II.
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I have been trying to find corroboration for the V15 actually being 15degrees and have come across this interesting snippet http://www.bostonaudiosociety.org/pdf/bass/BASS-08-04-8001b.pdf on page 30 with some measurements from Tom Holman which suggest the V15 was 28 degrees or more. He also has some numbers on the effects of wrong playback VTA and is not convinced of audibility. BAS clearly used to have a lot of fun .
.I have been trying to find corroboration for the V15 actually being 15degrees and have come across this interesting snippet http://www.bostonaudiosociety.org/pdf/bass/BASS-08-04-8001b.pdf on page 30 with some measurements from Tom Holman which suggest the V15 was 28 degrees or more. He also has some numbers on the effects of wrong playback VTA and is not convinced of audibility. BAS clearly used to have a lot of fun
Interesting...
I looked at John Elisons pictures of the AT-OC9/II and Shure V15VxMR using the CBS STR112 record and vertical IMD signals. The IMD of the AT was around 35-36 % and double for the Shure. The lateral IMD distortion was significantly less around 3 %. I get similar lateral IMD with the Ultimate analogue test LP, but unfortunately none of my test records have vertical IMD test signals.
It's due to the fussy nature of tribology, not geometry, and rig specific IMO.
Measured THD for pure vertical modulation includes mistracing, which is as tricky as it gets and varies with stylus-groove friction so potentially SRA. It's tough to separate mistracing from geometric causes in this case, both are a bit of a theoretical disaster zone at high programme level.
Edit: If VTA doesn't match, then there's also a programme level dependent mismatch in presentation angle between stylus and groove. For small signals the error is small. Not so for large signals. It's a toughie but try to think 3D.
LD
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@gigigirl
30 years ago I recall playing through the LP collection and finding the one that sounded "utterly fantastic" Then we would put a micrometer on it for a reference measurement.
This then made it a simple task, using the Well Tempered tonearm, to make an adjustment using block and automotive feeler gauges between the the damping cup and table to quickly adjust each LP for "utterly fantastic-ness"
I'm still finding LP's in my collection with a sticker on the back cover stating the measured thickness...lol
YouTube
30 years ago I recall playing through the LP collection and finding the one that sounded "utterly fantastic" Then we would put a micrometer on it for a reference measurement.
This then made it a simple task, using the Well Tempered tonearm, to make an adjustment using block and automotive feeler gauges between the the damping cup and table to quickly adjust each LP for "utterly fantastic-ness"
I'm still finding LP's in my collection with a sticker on the back cover stating the measured thickness...lol
YouTube
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That bit I get as it's easy to visualise the arc of the needle rather than a straight up and down motion. It's just the scale of it (and apparant ignorance of it in 21st century vinyl playback) I have not grasped.
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