Looking at VTA from a different angle, I already mentioned the Dr Feickert test disc.
Below you first see three sets of images, where in each image the HTA was changes in steps of 0.5 degrees from -2 degrees to +2 degrees.
The top of the image shows the phase relation between L and R.
The bottom shows the crosstalk L - R and R - L.
The difference between the three image sets is the VTA setting.
In the left image set the Cart is tilting a bit backwards towards the arms pivot point.
The image in the middle has the arm raised by 3mm, or ca. only 0.8 VTA degrees upwards.
The image at the right has the arm raised by another 1mm or ca. 0.3 VTA degrees.
Now there are two things to watch: first is at what HTA do the two lines cross, answer is at +0.5 degrees, so this is the HTA setting to be used.
Second important point is that this crossing point should be at 90 degrees on the vertical axis. This crossing point lies resp. at 60, 80 and 90 degrees from the left to right image set.
So raising the arm only by 1mm, meaning a VTA adjustment of only 0.3 degrees makes a noticeable difference !
Next to these three images I have enclosed the results of adjusting my tone arm.
Obviously HTA has to be zero in my case and crossing is at 90 degrees so VTA is correct just after many attempts adjusting the height of the arm.
To conclude, I do not know what mechanism is behind this adjustment procedure, but it works perfectly and is very sensitive to the smallest adjustments.
Hans
Below you first see three sets of images, where in each image the HTA was changes in steps of 0.5 degrees from -2 degrees to +2 degrees.
The top of the image shows the phase relation between L and R.
The bottom shows the crosstalk L - R and R - L.
The difference between the three image sets is the VTA setting.
In the left image set the Cart is tilting a bit backwards towards the arms pivot point.
The image in the middle has the arm raised by 3mm, or ca. only 0.8 VTA degrees upwards.
The image at the right has the arm raised by another 1mm or ca. 0.3 VTA degrees.
Now there are two things to watch: first is at what HTA do the two lines cross, answer is at +0.5 degrees, so this is the HTA setting to be used.
Second important point is that this crossing point should be at 90 degrees on the vertical axis. This crossing point lies resp. at 60, 80 and 90 degrees from the left to right image set.
So raising the arm only by 1mm, meaning a VTA adjustment of only 0.3 degrees makes a noticeable difference !
Next to these three images I have enclosed the results of adjusting my tone arm.
Obviously HTA has to be zero in my case and crossing is at 90 degrees so VTA is correct just after many attempts adjusting the height of the arm.
To conclude, I do not know what mechanism is behind this adjustment procedure, but it works perfectly and is very sensitive to the smallest adjustments.
Hans
Attachments
Just an ordinary elliptical (Grado Black) so together with my relatively low end table I would not jump to any conclusions just yet.
Hans, we were just trying to duplicate the RCA patent's results I'm sure there are other ways to do this.
You are on the verge of having trouble with VTA. Stay low budget for piece of mind
What's the number of the RCA patent?
George
Can it be that simple ?
At the crossing point where the phase is the same for L and R, how can Adjust+ determine that Phase Angle at that very point is 30, 90 or whatever number of degrees.
Where is the reference to which this phase angle is measured or calculated ?
Shouldn't you have at least 2 frequencies playing at the same time ?
Could it then be that the algorithm has some part of the RCA patent in it ?
You are correct, there are not enough degrees of freedom with a single tone. I should have been more clear web comments claim that and I doubt it is true. In the past I have used simple 1K tones to do the alignment tangent to the groove. Certainly for pure vertical motion the cartridge height alone can't affect the channel to channel phase. We have time to figure this out, it would be nice to see some data from more sophisticated setups.
Last edited:
Have you checked it from your tones? As far as I can tell it's perfect at 400 Hz and within a single sample at 4K. An X/Y plot does open a little on the higher tones, but I can't see any offset looking sample per sample, the left and right peaks line right up. I'm not sure how you could do better, but maybe a little tweak while monitoring a >3K tone on X/Y. Maybe
It's very likely via stylus-groove friction, Hans. Being potentially very sensitive to alignment, and having potential for profound effect on tracing performance (stylus riding up one wall).
There's no purely geometric explanation that makes sense under scrutiny, AFAIK.
LD
Last edited:
Had a quick look at Scott's files, and crudely adapted the SW FM demodulator to examine 400Hz FM modulation of the 4kHz carrier, across the VTA angles recorded.
Good news is it's all there and appears to correlate as expected. Bad news is the FM detector needs work to produce results good enough to calibrate, so will take a few days.
LD
Good news is it's all there and appears to correlate as expected. Bad news is the FM detector needs work to produce results good enough to calibrate, so will take a few days.
LD
I think we keep forgetting that your take on this is an extension of past practice. The geometry problem is tricky but it has been solved and the test tracks out there exploit the traditional solutions. I did notice at least, as Pano noted, my channel balance is pretty good as is.
EDIT - Someone kindly sent me the track listing of Dr. Feickert's LP, and it has a 0dB 1kHz tone with a "pilottone" as the azimuth track so we are probably working along the same lines just need to fiddle the maths.
Last edited:
Actually, it was solved by Keppler c 1601, that's about 300 years before the phonograph......as referenced and used verbatim by Baerwald ! Planetary orbit geometry is effectively the same problem. It's not that tricky.....
Exactly.........
On the other hand, one shouldn't neglect the effect stylus attitude can have on performance parameters. And when apparently geometrically impossible results are obtained by small changes in alignment, eg hd or L-R phase with pure tones, the roots likely lie in stylus-groove interface friction, IME. If that's what you mean by 'past practice', it might be mine but sure isn't that of decades of the industry
LD
If that's what you mean by 'past practice', it might be mine but sure isn't that of decades of the industry
LD
Maybe clumsy wording, I meant using a fancy protractor and USB microscope to nitpick the geometry thing is possibly not the whole story. Another thing I thought of this morning, I'm not sure what came first the CBS LP or their patent. It's possible those tracks were fortuitously around already and as you said there might be a better track now to do this.
Last edited:
I may have discovered the secret behind the Adjust+ VTA test.
There is definitely no second frequency involved, the test sequence is :
stereo - left - right - pilot - left - right - stereo.
Everything 1KHz@0dB except for a 315Hz pilot stereo tone in between.
LD, if friction were to be the determining factor to find the correct VTA setting, this parameter should either be measured directly or indirectly.
Since a direct measurement is not available, it could only be an indirect measurement.
But then Adjust+ should know a lot more, like element make plus type, needle in use and tracking force causing every element to have a different friction.
That a correct HTA causes L and R to produce the best channel balance for a stereo signal is easy to understand.
Adjust+ however can tell with just one single fresh measurement performed with the correct HTA, that the tracking angle is 90 degrees, needed for an optimal VTA setting or else whatever less optimal figure between zero and 180 degrees.
This can only mean that the SW does not have to build up a data table from different VTA settings, needed for calculating an optimum.
So the Friction option does not seem to apply here.
What I can see however, is that in my case the crosstalk signals L-R and R-L are both phase shifted by resp. 45 and 135 degrees with their main signal, giving exactly the 90 degrees in between for an optimal VTA setting.
That is why I think that Adjust+ measures just the phase angle between the main L or R signal and their crosstalk product in the opposite channel.
For some reason, they found out that the correct VTA setting is producing resp 45 and 135 degrees phase shift between the main and their crosstalk products, giving a final difference of 90 degrees between the two crosstalk products.
The RCA Patent that I was hoping for, is definitely not at work here.
Hans
There is definitely no second frequency involved, the test sequence is :
stereo - left - right - pilot - left - right - stereo.
Everything 1KHz@0dB except for a 315Hz pilot stereo tone in between.
LD, if friction were to be the determining factor to find the correct VTA setting, this parameter should either be measured directly or indirectly.
Since a direct measurement is not available, it could only be an indirect measurement.
But then Adjust+ should know a lot more, like element make plus type, needle in use and tracking force causing every element to have a different friction.
That a correct HTA causes L and R to produce the best channel balance for a stereo signal is easy to understand.
Adjust+ however can tell with just one single fresh measurement performed with the correct HTA, that the tracking angle is 90 degrees, needed for an optimal VTA setting or else whatever less optimal figure between zero and 180 degrees.
This can only mean that the SW does not have to build up a data table from different VTA settings, needed for calculating an optimum.
So the Friction option does not seem to apply here.
What I can see however, is that in my case the crosstalk signals L-R and R-L are both phase shifted by resp. 45 and 135 degrees with their main signal, giving exactly the 90 degrees in between for an optimal VTA setting.
That is why I think that Adjust+ measures just the phase angle between the main L or R signal and their crosstalk product in the opposite channel.
For some reason, they found out that the correct VTA setting is producing resp 45 and 135 degrees phase shift between the main and their crosstalk products, giving a final difference of 90 degrees between the two crosstalk products.
The RCA Patent that I was hoping for, is definitely not at work here.
Hans
So there is no attempt to get the correct SRA as well? Technically every time you raise or lower the arm you should adjust the overhang, this is too much fussing for me BTW. So in the end a change in VTA by raising or lowering the arm has a corresponding change in HTA and without a two tone test the third degree of freedom comes out where it may by the tracking force and design of the cartridge?
Our idea of the spiral signal that smoothly goes from left only all the way to right only would probably yield all the same information as above.
Last edited: