I was wondering the same. If the 'polishing the diamond' is true, that matches the fokelore about ortofon DJ sphericals where they claim you need to run them in for 6-12 hours on a locked groove before use. Also there is another bit of fokelore around Denon broadcast sphericals having better polish than normal which is why they lasted well despite tracking with a pile of coins on the headshell! Like all fokelore there may be a grain of truth.
I think this is fair use given the book has been out of print over 50 years. Rescanning will incur delay as not in the office much at the moment AND these are very detailed photos. One attached as example, which is one of the more interesting ones. Does anyone have software to resample a pdf as I have 2 which are over 1MB?
Those pictures are amazing. Any pictures of very high frequency modulations. Because thats where the maximum damage would occure I suppose. You can use Sendspace to upload and give link here in the forum.
Thanks everyone for the effort.
https://www.sendspace.com/
regards.
Thanks everyone for the effort.
https://www.sendspace.com/
regards.
Thanks, Bill and George.
I'm smelling a rat concerning the SEMs and optical images of damage arising from what's stated to be a single play, and association with 3mg tip mass......
The damage apparently is in the wrong locations on the groove shape to be associated with high acceleration/curvature, and on the opposite groove wall there's a deep uniform channel that appears to be carved without corresponding variation one would expect..........
And, even with a tip mass of 3mg, stylus tracing force in a groove of that modulation wouldn't be significant compared to VTF........
If I had to guess, I'd say the grooves showing damage had been played at excessively high VTF perhaps with a cartridge having a non compliant suspension, or damaged stylus? I think this might be close to the source of common misunderstanding/ mythology, which is interesting in itself if we can make sense of it.
Does the text explain what exactly is meant by 'tip mass' and how that was measured/derived, Bill?
LD
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Right I should have scanned the page before I now realise as some of the photos are composites. So for example on plate 5, the upper half (where the unmodulated groove is on the test record) shows the actual path taken by the stylus, but the text doesn't explain how they worked that out, other than saying Dr. Chippindale did it and the images are by permission of Decca. This was a 3mgm tip at 2g VTF, but he does not that tip mass should include the effects of resonance. I suspect a trawl of all the references is needed to get to the very bottom of it.
Given my current spare time issues, It might be beneficial if I post you the book to allow you to fully digest?
Given my current spare time issues, It might be beneficial if I post you the book to allow you to fully digest?
I have the Decca SXL2057 test record.
The 10kHz track is near the outer radius, and as you say level works out physically about 5cm/s rms. Modulation amplitude is about 1um peak, curvature radius about 63um peak. Acceleration is about 434G peak which is fairly hot, but even at 3mg tip mass works out as a force of about 1.2g peak which is modest in the context of 3g VTF downforce.
LD
PS: posts crossed, will reply separately thanks
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Thanks for this Bill.
Of course being a greedy sod, I'll probably ask if someone will scan the rest of the book
Also to highlight Walton's achievement pre 1965,
V15-I was 1.2mg 1964 and also the Ortofon SL15 & SL15E.
It was only until the 1966 V15-II that other makers beat Walton's 0.5mg. "effective tip mass"
... and he achieved this via bendy cantilevers so lucky must approve
see John Jones' stuff from https://linearaudio.net/downloads 18apr17
V15-I was 1.2mg 1964 and also the Ortofon SL15 & SL15E.
It was only until the 1966 V15-II that other makers beat Walton's 0.5mg. "effective tip mass"
... and he achieved this via bendy cantilevers so lucky must approve
see John Jones' stuff from https://linearaudio.net/downloads 18apr17