using a digital usb microscope to measure vta

[oceanobsession]

Just seen this for measuring vta , using a cadenza bronze which I think has weak suspension , has anyone done this ,


( https://www.analogplanet.com/content...usb-microscope )

phil.

[Ammonite Audio]

This all seems quite logical until you actually try it and for a while I thought it was great! It is a useful tool to have at hand, but actually getting the USB microscope to focus clearly on the tip is far from easy, and you do of course need to understand what you're looking at. I would make the following points:

1. When you look at a stylus tip through a microscope do you know what you're looking at? In practice, the almost invisible business end of a stylus (the tiny bit that sits in the groove) often has a different alignment to the bulk of the stylus which is readily seen. To use a visual SRA/VTA alignment method you have to know how your stylus body and tip are shaped, otherwise you can end up with horrendous SRA errors. An example of a stylus that, when correctly seated, looks badly misaligned is the Ortofon Replicant, but there are many other examples. So, do understand how the playing part of the tip corresponds to the overall shape of the visible tip before making any assumptions that they are the same.

2. Michael Fremer says to use a static reflective surface, which is obviously good for looking at the tip and its reflection. But, when a tip is following a moving LP groove, friction between the tip and groove does in practice pull the cantilever upwards and that changes SRA compared to the static position. It's quite difficult to focus on a stylus while it's actually playing a record. To make things more vague, the degree of cantilever deflection does depend on the cartridge's suspension compliance, itself somewhat dependent on ambient temperature, and indeed the type and shape of the tip, so it's not really possible to come up with a notional 'guess' on SRA angle compared to the static position.

3. A number of commentators have pointed out that different LPs may have been cut with slightly different cutter head angles, so the magic 92 degrees is not an absolute figure. I suspect that most LPs were cut at 92 degrees but it's another variable factor that complicates things.

Setting VTA/SRA accurately can be a bit painstaking but I now recommend setting up the cartridge (initially) according to the manufacturer's specifications and level when sitting on a representative LP. If a cartridge has been correctly and accurately manufactured, that should result in the angle between the cantilever and record surface (VTA) being close to the stated specifications. That angle is a great deal easier to evaluate than tip angle, but the method assumes that the cartridge does adhere to its specs and for re-built cartridges that may not be the case. So, perhaps another flawed method!

So, how to set VTA/SRA accurately? Well, if you don't have access to a measurement system like I do (Analog Magik) then use your ears, adjusting arm height from its 'level' position up or down until things sound 'right'. Potentially laborious but ultimately accurate enough.

One way out of potential neurosis with this is to use cartridges with spherical/conical tips which are naturally somewhat forgiving about SRA errors, compared to more exotic line contact tips etc. I used to scoff at the idea of spherical tips but hearing the Ortofon SPU Wood A rather changed my mind!

[oceanobsession]

Thanks for your reply , ive used a normal microscope and that's not easy to focus in on the needle , its ok to see if its clean but as you say to work out wear and angle much harder , thanks again phil.

[Barry]

I think people can get obsessed over this. Whilst the use of a USB microscope might seem attractive, to examine stylus wear you need at least x200 magnification, and at that level of magnification the depth of field is so shallow it is very difficult to maintain focus in order to assess wear.

Secondly the correct SRA will depend on the VTA (which is the angle between a line running between the point where the stylus contacts the groove and the cantilever pivot point (itself poorly defined) and the horizontal. The VTA in turn depends on the compliance (which also varies to some extent with temperature), the thickness of the disc and the VTF.

I would do what Hugo suggests: set the arm up so it is horizontal with the manufacturer's recommended VTF. Make small changes to the VTF so the cartridge plays securely (don't worry too much if it can't track the most difficult track on the test record; those levels of modulation velocity are very rare on most LPs), reset the arm to be horizontal, then make small changes to the height by ear. Some stylus profiles are fussier than others in this regard.

Once set up, leave well alone and don't worry about different record thicknesses - otherwise "that way madness lays".

[oceanobsession]

Update , ive got a compliance issue by the looks of things it would seem the cadenza bronze is not suited to the technoarm , after spending 1k on the
cartridge and then buying a technoarm with audio origami mods fitted to a mk1 xerxes , my audionote dac sig 2.1 sounded better , so to be honest ive
not used the turntable , but since replacing the tv ive had more space on the rack so out comes the turntable and ive started playing again and what I
found was the turntable had more punch and speed but lacks the natural sound also a bit dry compared to the dac , lacking in treble also , I was thinking my amps were lacking a bit or the speakers were to hard to drive for ming da 805 monoblocks , today ive placed 5 g onto the head shell and re adjusted the 2.5g cartridge weight and wow things have really improved , don't get my wrong dull vinyl still sounds dull but playing colour of spring talk talk rock solid punchy bass with speed , also Johnny come home fine young cannibals it beats the dac for sure , now im thinking about having the cartridge checked by expert stylus £47 and maybe then replacing the tonearm with something more suited don't know what yet they have all gone up a bit , thanks for your help phil.

[Ammonite Audio]

Update , ive got a compliance issue by the looks of things it would seem the cadenza bronze is not suited to the technoarm , after spending 1k on the
cartridge and then buying a technoarm with audio origami mods fitted to a mk1 xerxes , my audionote dac sig 2.1 sounded better , so to be honest ive
not used the turntable , but since replacing the tv ive had more space on the rack so out comes the turntable and ive started playing again and what I
found was the turntable had more punch and speed but lacks the natural sound also a bit dry compared to the dac , lacking in treble also , I was thinking my amps were lacking a bit or the speakers were to hard to drive for ming da 805 monoblocks , today ive placed 5 g onto the head shell and re adjusted the 2.5g cartridge weight and wow things have really improved , don't get my wrong dull vinyl still sounds dull but playing colour of spring talk talk rock solid punchy bass with speed , also Johnny come home fine young cannibals it beats the dac for sure , now im thinking about having the cartridge checked by expert stylus £47 and maybe then replacing the tonearm with something more suited don't know what yet they have all gone up a bit , thanks for your help phil.

That rather reflects my own experience some years ago with a Kontrapunkt B in a Technoarm A. Not a good combination but I failed to learn my lesson and bought another (new) Technoarm A before I realised that, for me, there are much better matched arms to be had!