Azimuth adjustment is important in line contact styli, the longer the contact the more critical it is. Conical does not matter and Elliptical not so critical.
My Stanton 880s runs a Fritz Gyger Signature diamond 5x120um channel separation measures 39dB +- 0.5dB each channel. It's currently in my EPA100, being a removable headshell there is a very small amount of play in the collet, if the headshell is held CCW before tightening I get a 15dB difference between channels in separation.
If the arm has no azimuth adjustment shimming is tedious but pays dividends.
Great to see you guys contributing for us new to the sport on here. Thankyou!
It is only after reading your thoughts that i started measuring things and have some measurements to back up the subjective findings and to guide developments.
Concerning azimuth, i started out without azimuth adjustment and without knowing it had channel separation >10Db unbalanced. I now get it within 1 or 2 Db easily with a simple adjustment like that shown, so definitely worthwhile.
I measure starting resistance and rolling resistance of the carriage on the rails. in my experiments, starting resistance is always higher than rolling resistance, normally by 25-50%. Many rails are around 300mm long and have level adjustment. i started using a bubble level but the run of a (good) cart on its rails is far more sensitive than that, and in my experience can be judged as follows. if raising one end of the arm 1.5mm doesn't consistently start the cart rolling the starting resistance is too high to achieve reasonable performance. Good performance (low resistance) starts at less than 1.25mm and it starts to be excellent at 1mm. i never got below 1.5 with BB's on rails, hence non recirculating balls. Others have calculated the coefficients from this.
I make things more complicated by trying to ensure that in the vertical motion the cartridge also remains parallel to the disc, and this means a different mechanism to the simple pivots others are employing. this concept came from studying little Casey.
When i have got this to the point i consider as good as i can i would be very interested to see comparisons with the simple pivot alternative. Maybe the result will not justify that effort.
Its an interesting thought that pre-echo is a good indicator, i get that on a proportion of discs, on some its more irritating than others!