|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
118.148.169.228
In Reply to: RE: Feickert Azimuth Adjust software - can I use a software Spectrum Analyzer instead? posted by John Elison on February 09, 2016 at 09:26:33
" I have never heard any advantage to setting azimuth at the point of minimal crosstalk."
This is what I have found as well (in terms of using the test discs). The potential mismatch in coil inductances will tend to make it unlikely to ever be able to achieve zero difference between the channels.
I personally prefer to use the physical tip alignment as the reference and accept the difference in channel separation measurements for L and R relative to the specification. My observations with a tip azimuth error are a slightly smeared soundstage and subtle loss of detail. On silent grooves, one can hear that the rumble isn't "centred". Of course this assumes that the antiskate is also optimally set!
As a slight diversion, I discovered a more reliable way of verifying the optimum antiskate level relative to the calibrated value since different tip profiles would have subtly different drag coefficients depending on polish etc. I know that Line Contact designs would have a higher required value (which is also modulation amplitude dependent), but they are less than elliptical.
I believe that this can be determined more reliably using high level vertical modulation tones (rather than simply using the high level lateral tones which tend to give a higher than necessary value) combined with the usual analysis of the distortion components. A minimum level of 50um is very revealing. I used this to subtly adjust the antiskate for my OC9ML/II over the weekend by +10% relative to the calibrated value and the distortion components for the vertical modulation became the same for both channels as expected and the soundstage became rock much more focussed and smooth. In the R channel there was a collection of components around 5 kHz which completely disappeared after optimising the antiskate.
Prior to this I noted that the LF resonance values were not quite the same for each channel. After the adjustment, they came back in line. Since the LF resonance modulates higher frequency components, any mismatch would straight away give differences in the channel characteristics which would translate to a subtle difference in the perceived soundstage. In the same way VTA mismatch also contributes to additional distortion around 4 to 5kHz.
For me, the lateral "equal buzzing" is a little less precise when doing it by ear as I found when using fluid damping that any slight eccentricity of the disc would alter the buzzing amplitude in a particular channel. Sometimes on a marginal test, you would get a clean tone and then a slight buzz as the centre amplitude error increasd to maximum.
Anyway, just thought this might be of interest to you given you would have the suitable test tones at your disposal on your test discs.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Follow Ups:
"The potential mismatch in coil inductances will tend to make it unlikely to ever be able to achieve zero difference between the channels."
True I'm assuming there is not much that can be done by the end user about things like channel to channel inductance tolerance, or incorrect orientation of the coils with respect to each other without rebuilding the cartridge. Though I am potentially putting this into another class, ie problems which can be addressed by setup changes intended to be adjusted by the end user. The difference John Ellison saw seems really significant to me. I don't know that I'd worry about it for normal listening but I might for archival work. What are the theoretical downsides to this approach assuming one can trust their test disc signal that is, ie minimizing crosstalk via azimuth adjustment?
> What are the theoretical downsides to this approach assuming one can trust their test disc signal that is, ie minimizing crosstalk via azimuth adjustment?
The downside is the very high probability that your test record has absolutely no relationship to any of your other records with respect to azimuth. I concluded this from the fact that of eleven different test records I own, only two exhibited the same azimuth requirements.
Best regards,
John Elison
2 records out of 16 is definitely not a strong trend. Thanks for your comments.
Realistically 2 to 3 degrees is quite possible with a given cartridge. If we take MC cartridges, then the Feikert method will help optimise electrical azimuth i.e coil relationship to groove wall. However, depending on quality control the stylus tip may not be mounted perpendicular to the cantilever. So if the cantilever is correctly mounted with respect to the coil orientation, but the tip is not, you will end up with what I personally find to be a slightly smeared presentation with a definite loss of focus and susceptibility to sibilance.
The more extreme the stylus cut (i.e large bearing radius), the more critical tip azimuth needs to be since the stylus physically won't sit in the groove correctly past a certain angle of rotation. Elliptical and spherical are more tolerant in the sense you can rotate them further without issues with touching the correct portions of the wall. However, the pear shape contact area basically means you have different effective tracing radii on each wall and my experience is that you get really bad sibilance.
Consequently, I prefer to sacrifice the electrical azimuth specification and ensure the tip is perpendicular to the groove. In extreme situations, the channel imbalance can be very large, but you have less tracing distortion (as with elliptical) or you contact the grooves in the ideal segment thus avoiding the portions close to the shoulder which may be damaged.
For MM, I have some *superb* examples of Stanton/Pickering styli where I had cantilever rotations of 8 degrees and in one case 10 degrees. That's what happens when you buy NOS I guess....Anyway, the spec of the cartridge is typically 35dB for the 681, 881 etc. Well when the tip is correctly sitting in the groove, a 10 degree rotation gives you a very out of spec channel imbalance (can't remember specifics but something like 4 dB) and channel separation of 20dB or less. I can accept this better than sibilance! FWIW, those styli just sit unused.....they were Stereohedron styli too!
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Going to need to digest this for a bit I think. Thank you for your words. Very much appreciated.
This image may help in the understanding. The image is of a Soundsmith OLC seen from the front. It is not quite as sharp as I would like, but there appears the camera focus plane on the Zeiss microscope I was using is not the same as the optical focus plane as I had it pin sharp in the eyepiece!It appears to be similar to if not actually a Fritz Gyger tip. You will notice how large the internal angle is between the scanning surfaces - it is very wide in order to extend the length of the scanning surface. An elliptical or spherical is only about 55 degrees IIRC.
If you have a tip azimuth error past a certain level, the stylus simply won't fit in the groove properly.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Ah. Rereading when I had more time also made a difference. Thanks for explaining. It does make more sense after I've thought about it now. Best regards.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: