Main problem is finding good test records , on AM some tracks were alright but others were not so it's best to use few test records and compare the readings.
That is / was my biggest concern. Test records are notoriously non-standard even across batches, so having a (rather expensive) piece of software rely on a possibly faulty test record makes the point of "correctness" moot.
Basic test is azimuth/channel balance measurement , use 1kHz left and right mono tracks ,
for tracking- VTF 315Hz and 7 or 10kHz tracks and measure THD,
VTA you need to test IMD on 2 tone test tracks same with a zenith and most likely you will find zenith adjustment to make quite a difference .
Obviously it is a good to run frequency sweep to give some sort of idea about linearity of your setup.
This is all excellent information, thank you - we are already at a point where a very usable guide can be compiled. I have to say though I have had limited success with zenith adjustment owing to the fact almost all of my cartridges are variants with integrated headshells - nigh impossible (for me) to rotate the cartridge in the headshell to establish proper zenith.
I’d add to that, somewhat controversially, to avoid test records with trackability tests etc as they invariably encourage setting for the worst case scenario when it comes to VTF and antiskate, which just isn’t what sounds best with 98.5% of records.
I must admit to being guilty of that, but for a very different reason. Years ago, during a research driven by my contributions on a local (to me) forum, I devised a methodology around the use of the 300Hz +15dB tracks on the Hi-Fi News Test LP, but mostly due to the fact that it was the only record I could find that had the same tone on three positions of the record (beginning, middle and end).
It yielded interesting results which help me calculate the proper range of antiskate even without a test record, and it also confirmed a number of hypothesis already established about skating force (including works published by the Boston Audio Society in 1978 and Klaus Rampelmann in 2009).
The research, including all the audio samples, calculations, methodologies, and a somewhat crude translation of the paper I prepared for the local forum all available here:
A series of methodologies, measurements and analyses on turntable skating force. - stojnev/dwr-skating
github.com
That done listen very carefully to bolt torque as ‘tight’ is seldom if ever what sounds best to my ears. Especially when it comes to mounting arms on armboards, armboards to turntables etc.
Seconded ("thirded?").
Although I did this by accident I must say. I designed and built a SME compatible base that allows for repeatable and measured changes to the height of the tonearm mount. Knowing what I know now, I hesitate to call it "a VTA-on-the-fly" mechanism, but it does repeatedly and precisely set the height of the tonearm in reference to the playing surface.
It relies on using springs to maintain horizontality, and said springs can have varying compression rates set with screws. The entire armboard is then connected to the turntable base using POM (Delrin) fasteners of a sufficiently large diameter to facilitate minute changes to the fastening torque.
Details (and machining drawings) of the SME compatible base can be found here:
A mechanical device to provide easy VTA / SRA changes on tonearms requiring a SME cutout. - stojnev/dwr-vta
github.com
I did get a cheap USB microscope, and it certainly looked like many expensive carts were "out" by several degrees.....but without a really good setup its possible that was just bad tools and a small angle of the scope magnifying and exaggerating the image
These USB microscopes, even very cheap ones, can be very effective as long as you provide sufficient lighting. They do not replace a proper microscope, but a proper microscope warrants the removal of the cartridge from the tonearm. One alternative to this is the
WallyScope, but at $1,500 + shipping + duty + tax, I think I can do somewhat better.
I currently use an Andonstar AD407 (~$200), but converted for horizontal movement,
as suggested by this video.
for one of my 3d printed arm bases I actually had a sprung base
Not replied on this earlier, apologies - but your arm looks very interesting, especially if it outperforms an established standard like the SME V. I must admit I have not seen a pivoted tonearm with the tonearm wand extending that much past the pivot point in the back - it goes against accepted wisdom that the majority of the balancing weight should be as close to the pivot as possible.
I have seen such setups in manually driven linear tonearms, but not a pivoted one - would be very interested to see how it affects effective tonearm mass.
