Following on from the thread about VTF and Gauges (@Richard.Dane that Technics SH-50P1 gauge is a joy to use), I have acquired a USB Microscope (time-limited offer on the river, so a sub £20 outlay) with the intention of measuring and setting SRA.
Micheal Fremer of Analog Planet/Stereophile, has some articles published, How to Use a USB Digital Microscope to set 92 Degree Stylus Rake Angle (SRA) | Analog Planet and links to an article from the '70s when profile where much simpler https://www.analogplanet.com/images/512MFVTA_article.pdf
This approach has been pioneered by Wally Malewicz of WallyTools, in terms of measuring the actual SRA against the profile.
The USB Microscope used by Mr Fremer is one costing a few hundreds and Mr Malewicz uses an optical microscope with Digital camera to obtain the images - so I was interested where something similar could be obtained with a cheaper/low-cost USB Microscope, the software it comes with and a Laptop.
My cartridge is a Lyra Skala mounted in an SME V on my Michell Orbe, so I have a level of investment I want to ensure is maximized and optimised.
Before I get flamed, yes SRA can be set by ear, and tune into the cartridge’s sweet-spot, but with VTF I would like to understand what this is, and apply some empirical measurement as well as listening.
So the type of image I was able to obtain with the Microscope was
From these images I was able to measure the left and right angles (as per Mr Fremer’s instructions & a related video) and calculate the SRA.
My initial value, set by the SME V height scale, headshell bubble level and by ear, was in the range of 86.7325 to 88.677
So with some adjustment of arm height and re-measurement, I saw small changes, took it up to 95.154 and back to 85.5565 while seeing what range of change was required. Finally got it into the 92.253 - 92.424 range.
Then a full alignment check, as the arm pillar had been loosened to adjust the height.
And VTF check incase the revised height had affected anything.
Interesting time and not totally straightforward, trying to keep the stylus on the edge of the upside CD, the Microscope in the same position and in focus at this resolution. At times, quite frustrating, and you do realise you are down in the audiophile rabbit hole!
However, 1st record on after the process (Joan Armatrading/Joan Armatrading on Nimbus Supercut) and yes, there is a difference - subtle but an improvement on sound stage, instrument presentation and positioning.