The importance of VTA, SRA and Azimuth - pics

[ack]

So what Dino-Lite scopes are people using now?

 

[J.R. Boisclair]

Dunno about the Dinolites but consider this Supereyes package

Microscope with Z axis adjustment holder: https://www.supereyes-store.com/col...s-handheld-digital-microscope-loupe-magnifier

XY stage (must have): https://www.supereyes-store.com/col...and-for-digital-microscope-endoscope-otoscope

You may not need this but it works nicely - a zoom lens (allows greater magnification AND long operating distance): https://www.supereyes-store.com/col...s-microscope-lens-for-digital-microscope-b011

 

[tima]

I have the perfect tool for what you're asking for:

Dino-Lite Digital Microscope
Dino-lite makes a stand that firmly holds the microscope and provides finely adjustable control in the 3 dimensions you're looking for. You'll need to get the RK-10 , the RK-10-PX, and one other part (which escapes me now) to hold the microscope so that it's pointing horizontally.

Thanks for that squasher. This looks like a newer device from Dinolite than when I was experimenting and appears to have a finer degree of control. I'd appreciate it if you could identify the 'other part' that you mention.

 

[tima]

15. To Tima at #210. Your photo is taken too high relative to the stylus platform. Get that camera down so that the platform edge is taking up the bottom 1/3 to 1/2 of the photo frame and you see very, very little to none of the top surface of the platform. You can use the edge of the platform as a more reliable level reference for your angle measurements. Do this and your SRA reading will change.

Thanks for the tip JR. Any suggestions for getting the lens perpendicular to the stylus?

I haven't studied your responses in detail yet, but with the XY Stage you mention it seems like you are examining a cartridge off of its tonearm. Is that the case?

When I was attempting to use a USB microscope I always examined the cart/cantilever/stylus on a tonearm. thinking that I would take an initial picture/measurement then adjust the arm height accordingly then measure again to learn how close I got degree-wise with the adjustment. Is that approach advisable ... or?

 

[ianm0]

Hello ianm0,

Everything is calculable when you have the right dimensions and compliance. For dynamic conditions you'll need the coefficient of friction as well.

You are correct that on most tonearms (those that are not neutral balanced) a change in tonearm height will also cause a change in VTF, which causes a change in SRA (it changes azimuth too, but that's another matter). The degree to which this change is effected depends upon the distance between the horizontal bearing and the center of gravity of the tonearm and the compliance of the cartridge. The 4mm height change causing a 1 degree SRA change is a good rule of thumb. Is it perfect? NO! However, if we worried about ALL the variables that are impacted on our multivariate analog transcription devices, we'd never get any time in for listening to music! At some point in engineering, you have to choose what is significant enough to worry about what determine what is "noise". If you play only conical styli - or even some elliptical styli, you'll do well to think that pretty much all I care about in analog playback is noise - and that's just fine!

The 4mm (actually, it's 4.2mm but who's counting?!) per 1 degree SRA on a 9" tonearm is useful and MOSTLY accurate. Here is some more useful information (the "Tonearm Ð Change" can be read as "Tonearm arm wand angular change":

Effective Length	Offset Angle (IEC standard)	Tonearm Ð Change = 1° SRA Change	Tonearm Height Change = 1° SRA Change	Impact to Azimuth Angle	Impact to Azimuth Angle	Tonearm Ð Change = 1° SRA Change	Offset Angle (IEC standard)	Tonearm Height Change = 1° SRA Change
220	25.1°	1.1°	4.2mm	0.5°	0.469174	1.104593	25.1	5.327067​
230	24°	1.09°	4.4mm	0.4°	0.444632	1.094394	24.0	5.471105​
240	22.9°	1.09°	4.5mm	0.4°	0.42271	1.085672	22.9	5.619028​
250	21.9°	1.08°	4.7mm	0.4°	0.402989	1.078146	21.9	5.770135​
260	21.1°	1.07°	4.9mm	0.4°	0.385137	1.071602	21.1	5.923885​
270	20.2°	1.07°	5mm	0.4°	0.368889	1.06587	20.2	6.079853​
280	19.5°	1.06°	5.2mm	0.4°	0.354028	1.060819	19.5	6.237701​
290	18.8°	1.06°	5.3mm	0.3°	0.340378	1.056341	18.8	6.397157​
300	18.1°	1.05°	5.5mm	0.3°	0.327789	1.052353	18.1	6.557998​
310	17.5°	1.24°	6.7mm	0.2°	0.316139	1.048782	17.5	6.720042​

Heading of Column 4 same as that of rightmost column, but the figures are so different. Why?

 

[J.R. Boisclair]

Heading of Column 4 same as that of rightmost column, but the figures are so different. Why?

Because those figures were really for my own consumption and that was the first time I shared them with anybody so I got sloppy with my descriptions. However, I’m glad you asked because the answers support your point, ianm0. Column four should be labeled “apparent change in tonearm height = 1° SRA change“ and the last column should read “REAL change in tonearm height = 1° SRA change“

summary: 4.2 mm arm height change doesn’t deliver a full degree of SRA change on a 9” arm. Due to the offset angle some of it gets translated to azimuth. To truly impact a full 1° change in SRA you need to raise the alarm by the amounts in the right hand column.

 

[J.R. Boisclair]

Thanks for the tip JR. Any suggestions for getting the lens perpendicular to the stylus?

I haven't studied your responses in detail yet, but with the XY Stage you mention it seems like you are examining a cartridge off of its tonearm. Is that the case?

When I was attempting to use a USB microscope I always examined the cart/cantilever/stylus on a tonearm. thinking that I would take an initial picture/measurement then adjust the arm height accordingly then measure again to learn how close I got degree-wise with the adjustment. Is that approach advisable ... or?

I do not have any suggestions for you to confirm perpendicularity of cantilever/camera when the cartridge is mounted to the tonearm.

The XYZ stage is meant to support the holder of the microscope (which itself offers the Z axis freedom). The holder must be able to orient the camera horizontally. The XY stage allows you to move it closer/further and left/right from the subject.

just be sure that you are not aligning the camera in relation to the subject in order to FIND the results you’re looking for – because you will find it and it won’t be accurate. The emphasis has to be on proper set up first and then taking your images. You’ll see on my cartridge analysis report that I use nine different images to find the SRA but I never move the camera, other than focus, to take those nine photographs. I play with illumination, magnification, focus, polarization and focus stacking to get the various images.

 

[J.R. Boisclair]

Thanks for that squasher. This looks like a newer device from Dinolite than when I was experimenting and appears to have a finer degree of control. I'd appreciate it if you could identify the 'other part' that you mention.

Part MSA2T

 

[squasher]

I, too, am interested in what microscopes people are using and at what magnification.

The Dino-lite that I have is accurately spec'd at 140X and has a long focal length. That means that I don't have to be a fraction of an inch away to get a good look. However, it is not a high enough magnification to allow me to see the facets on the stylus so I can see where the contact line is (which is the only part critical for measuring SRA).

Frankly, I don't trust the large advertised magnification numbers on the bulk of the cheap USB microscopes for sale..

 

[ianm0]

Because those figures were really for my own consumption and that was the first time I shared them with anybody so I got sloppy with my descriptions. However, I’m glad you asked because the answers support your point, ianm0. Column four should be labeled “apparent change in tonearm height = 1° SRA change“ and the last column should read “REAL change in tonearm height = 1° SRA change“

summary: 4.2 mm arm height change doesn’t deliver a full degree of SRA change on a 9” arm. Due to the offset angle some of it gets translated to azimuth. To truly impact a full 1° change in SRA you need to raise the alarm by the amounts in the right hand column.

Thanks again J.R. You clarified my lingering doubt quantitatively that 4 mm is not quite equivalent to 1 deg and how much it is off for the cartridge on which your figures are based. I assume the figures in the rightmost column are from calculations for particular values of compliance, cantilever length, VTF. If so, I have a hunch that stylus profile, which should be another significant contributor, also plays a part. What do you think?

 

[J.R. Boisclair]

I, too, am interested in what microscopes people are using and at what magnification.

The Dino-lite that I have is accurately spec'd at 140X and has a long focal length. That means that I don't have to be a fraction of an inch away to get a good look. However, it is not a high enough magnification to allow me to see the facets on the stylus so I can see where the contact line is (which is the only part critical for measuring SRA).

Frankly, I don't trust the large advertised magnification numbers on the bulk of the cheap USB microscopes for sale..

Good not to trust them as magnification on a digital camera is fraught with conditions and "yeah, but..." As a general rule of thumb, aim for at least 250x but you'll have to have at least 400x if you have a Shibata or Soundsmith OLC stylus. There is a "work around" for the Soundsmith if you don't have that magnification but I'm not 100% sold on it.

 

[J.R. Boisclair]

Thanks again J.R. You clarified my lingering doubt quantitatively that 4 mm is not quite equivalent to 1 deg and how much it is off for the cartridge on which your figures are based. I assume the figures in the rightmost column are from calculations for particular values of compliance, cantilever length, VTF. If so, I have a hunch that stylus profile, which should be another significant contributor, also plays a part. What do you think?

My numbers assume no impact at the cantilever pivot point. In my opinion, in MOST situations the impact of the compliance, tonearm COG, etc. isn't an important enough impact to compensate for. Put a high compliance cartridge on the Kuzma 4Point and then it certainly does! I don't have a rule of thumb for you, but with all of the research I have been doing and all I have planned I imagine I will one day into the future.

 

[DasguteOhr]

You need to know what LP you play with modern Cart 20-23° old LPs are in 15°.

1957 - 1967: Teldec 45/45 cutting heads in connection with half-speed mastering
1968 - 1973: Neumann SX-68 cutting heads (15 degrees according to DIN)
1974 - ??: Neumann SX-74 (18 degrees as a compromise between DIN and IEC recommendation).
It is even likely that Decca used the SX-74 head until the end of the 1970s (after that Philips pressed for Decca, but in the early 1980s Decca still mastered and also cut the foils themselves, from 1981 with a Neumann VMS-80 cutting machine who also uses the 18 degree SX-74 heads).
Literature tip about microphones, tape and cutting machines from Decca: e.g. Michael Gray, "The golden age: the birth of Decca / London stereo"

With modern pickups 23 it can come to sibilants in the voice when playing old LPs. so choose your pickup well.
that's why an EMT called TSD 15 first version 15 °new carts are 20-23°

 

[ack]

You need to know what LP you play with modern Cart 20-23° old LPs are in 15°.

1957 - 1967: Teldec 45/45 cutting heads in connection with half-speed mastering
1968 - 1973: Neumann SX-68 cutting heads (15 degrees according to DIN)
1974 - ??: Neumann SX-74 (18 degrees as a compromise between DIN and IEC recommendation).
It is even likely that Decca used the SX-74 head until the end of the 1970s (after that Philips pressed for Decca, but in the early 1980s Decca still mastered and also cut the foils themselves, from 1981 with a Neumann VMS-80 cutting machine who also uses the 18 degree SX-74 heads).
Literature tip about microphones, tape and cutting machines from Decca: e.g. Michael Gray, "The golden age: the birth of Decca / London stereo"

With modern pickups 23 it can come to sibilants in the voice when playing old LPs. so choose your pickup well.
that's why an EMT called TSD 15 first version 15 °new carts are 20-23°

Thank you for this

 

[DasguteOhr]

Here is something really interesting to read. A tip I use a
Denon 103 (16 °) for old records, sounds much better than with modern records.

VTA

 

[ack]

Here is something really interesting to read. A tip I use a
Denon 103 (16 °) for old records, sounds much better than with modern records.

VTA

I wonder if our playing such old records with 20-23 VTA is really why they sound so awful?

 

[DasguteOhr]

sra is 92 °diamond , the needle carrier is 20-23 degrees from the new pickup, the old Lp is sra 92 ° cutting stylus but 15 ° from the angle, which can be 5 to 8 degrees less.
with some pickups is not so noticeable, and some terrible. In any case, it will never sound like it should with modern pickups.


P.S Arche Headshell can be SRA correct it, I'm not sure of my opinion

 

[ack]

cutting stylus but 15 ° from the angle, which can be 5 to 8 degrees less.

Exactly; which why I am thinking that VTA may be more important than SRA. not sure...

 

[J.R. Boisclair]

Exactly; which why I am thinking that VTA may be more important than SRA. not sure...

Just as we use the horizontal alignment of the cantilever to determine perfect tangency to the groove, so VTA is used to align the cantilever's angular relationship to the grooves. BOTH approaches are proxies for what really matters to optimal playback: zenith angle and stylus rake angle. Within some VTA angular limits that cause wasted energy being transferred to the coils, VTA is irrelevant on its own. What matters is the relationship between the VTA (which we can see) and the SRA (that is very difficult to see). Unfortunately, you need microscopy to identify your ideal SRA and you need REALLY GOOD microscopy to determine your zenith angle. See HERE for more on our relationship by proxy to the stylus via the cantilever.

 

[ack]

What matters is the relationship between the VTA (which we can see) and the SRA (that is very difficult to see).

Yes I can see that