Developing A List Of Tonearm Candidates For A SOTA Turntable

After 42 years working in R&D I only pursue and fix real problems.

Are you saying that incorrect VTA is not a real problem.

If you believe that I would suggest your optimum cartridge would be something with a conical or spherical stylus.

@dover No, as I think you know, I did not make that statement.  

I was responding to the point made by the persons I quoted (who were I think a little fatigued with the to and fro on methods) that the reason I had explained my method in detail was because I wanted to find a setting that would satisfy me as the "good enough" setting and on my system "good enough" sounds better than systems I have heard at several manufacturers R&D facilities.  But also notwithstanding the issues of show set ups.  Close to systems with the same level of source I have but that have 3-5 times more expensive speakers at the Ascot HiFi show (such as Wilson Chronos) where I am fortunate to be able to go on press / VIP day and listen in relatively quiet rooms.

But since you brought it up, what you seem to either not be appreciating, or perhaps you are just not voicing in your thoughts, because it contradicts the 'spot on VTA for each record'. The point I made regarding 'fixing' was regarding the magnitude of and the full range of factors influencing the "incorrectness"  / the proportion of this that can actually be corrected through adjustment of VTA in order to set SRA and consequently the potential for that to impact the deviance this would have from 'total' enjoyment of the individual record. 

Because you are noting VTA (fundamentally SRA) in isolation would actually need to combine this with the other factors that alter the 0.004 degree SRA accuracy requirement you noted to be significant to you. But there are other factors you typically cannot control (and certainly not through the VTA) that vary the resultant SRA you have set by orders of magnitude 10 to 20 (+/- 5 to 10) times. What is more that variation is going on throughout the record.

What I sought was to establish was whether, to my ears, the adjustment from "one position" set to work with the majority of vinyl thickness that I play to what would be the true optimal for transducing the signal as close to the input signal. Not just true to the cutting head but removing that angular variation, etc, of different production processes to achieve the "original" in every case.

I explained my process, but for your 0.004 degree accurate SRA, what I haven't heard is whether you set this for the low, middle or high of the dynamic range of the track?  Because whichever it is will make a difference (as a function combined with  tracking force and whether we are talking 33 1/3 or 45) to the variation in contact angle due to the upward force component of quiet and loud passages. I did take this into account with my "one" setting as I tried a variety of quiet ballards to dynamic rock.  But for your 1/1000" do you listen to the whole track adjusting as you go?, pick a particular passage? If so high, low or medium?   

Then we have warped records.  You may have none, but as the typically quoted standard for 'warp' is that there must be "no interruption to continuous play" and for example eccentricity tolerance is 0.2mm.  Lets take half that 0.1mm because I certainly know I have records that play with no discernable issue that have variation above that.

A 0.1mm adjustment to the 'opposite' of the triangle makes a comparative variation of 0.023 degrees for a 9.5" / 241mm arm.  That is 3.93 times the amount of SRA / VTA variation of the 1/1000" / 0.004 degrees you hear.

In fact to get to a warp variation equivalent to the 0.1 degree resolution specification that the cartridge manufacturers quote would mean just under a +/- 0.25mm variation from a nominal neutral surface. The 0.5mm range giving a angle variation of 0.11 degrees. So given I know I also have records with a 0.25mm deviation. Which means even if I set them to the exact spec angle or chose that by ear for a noticeable characteristic. Over the record that SRA , , that is almost 20 times the variation in SRA you can hear.

So even on your records with less than +/-0.05mm variation from neutral surface, you are setting by ear, so you cannot be sure to be adjusting for the nominal.  That said of course the measurement you 'desire' being the measurement you set by is you taking that 4 to 20 times the SRA variation that you stated you are setting to when you "on balance" decide that is the best setting for that record.

So are you doing that on a particular tonal or dynamic characteristic of a section of that record?  If you do, then do you set the SRA to the same the next time you put that record on?  Or do you do the adjustment again?

Because not only does your record have surface variation, so does your platter. So if you have 0.1mm variation on the platter and 0.1mm variation on the record in one orientation these may cancel, in another they could double.   So my point is, when you think you are listening to a SRA/VTA that is set to your quote of your audibly discernable 0.004 degrees.  You are likely to be listening to something that is typically varying per revolution by 4 to 10 times the accuracy to which you believe you are setting it.

So when I say "I only pursue and fix real problems" first I don't want to adjust it every time to believe I am correcting an error that even if I used one increment on the VTA 'dial' which on mine is 30 degrees vs approx 10 degrees rotation for 1/1000" on a 1 mm pitch thread. Then I (or anybody else) would still be adjusting for something where there is at least 1 to 5 times that amount of variation in the warp of the record and what I know to be a 0.07mm variation (+0.4/-0.3 to the mean) in the surface of my platter.

Those amounts combined are approaching 50% of the variation due to the min to max thickness of most of what I play. So whilst of course these variations exist as an additional stacked tolerance to the variation in warp and platter etc,.  But if I set individual SRA via VTA to an aural characteristic, to be repeatable I would also have to note a reference of label orientation to a reference mark on the platter so as not to alter the relative peaks and troughs of the setting that I considered "the one". 

Even then the record and platter tolerances will not be varying by less 5 to 10 times of your quoted 1/1000th / 0.004 degree hearing capability. 

So adjusting VTA is only removing part of the 'problem' and to fix what I could I would (and have) attempting to remove / minimise the 'constant' variation in the platter which I note somebody who has undertaken around 30 years more experimentation in this area than I have and whom I trust to make £50k turntables and £35k+ arms tells me 0.25mm clocked platter makes no difference. The surface variation in the record cannot be adjusted (without a 'flatter' copy and only by referencing rotational position to the platter can it be said to be deviating but in a repeatable manner.

Consequently, both for this hypothesis and the empirical results that (once I had removed the 'extremes' of the problem through the method previously noted) I heard little improvement on adjustment for the majority of what I listen to, for the simple reason that the other factors are altering SRA to multiples of the degree that you consider to be the 1/1000th 'increment' threshold for VTA.   

Thus I have one setting and if I were to every move from that it would be to have one for 'thicker' and one for 'thinner' because for the actual system variations above I cannot constrain SRA to hold within 0.004 of a degree. 

Note that in my profession, apart from dealing with some of the best hifi source manufacturers in the world, I also deal both with systems that have up to 12 billion, billion setup permutations. But also analysis of manufacturing systems where the accuracy requirement of the manufacturing end effector must achieve a better than 4 nanometre accuracy. Which to achieve requires a manufacturing facility with foundations that for a single storey building have twice the steel reinforced concrete of the Burj Khalifa, [which I also did some analysis for]. When considering this, one has to take into account EVERY factor impacting positional and vibrational contributors to the FMEA in magnitude importance.  Just as I do in addressing the real problems in the factors impacting my hobbies.   

With regard to your last point. Thanks for your "advice" but I am extremely happy with the cartridge and I am more than capable of making my own calculations, analysis and decisions on them. When I do replace or refurb, my analysis will again take into account and prioritise scientifically all the factors that actually impact its performance. 

Dear @audio_rd_uk  :  I have not your knowlege levels and skills, I'm a mere "mortal ".

" to be repeatable I would also have to note a reference of label orientation to a reference mark on the platter so as not to alter the relative peaks and troughs of the setting that I considered "the one".  "

I did it in my comparison tests whole proccess with the LP tracks choosedfor those tests/comparisons and I did it only with those LPs and I did it many years ago when a gentleman in Agon commented about and I did it and made comparisons by listening changing the LP label positions and certainly we can aware of the sounds changes.

Yes,all is through my ears and today I need to revamp about because it makes an audible differences.. Thank's to posted.

R.

Would anyone be able to offer an informed opinion on whether the Fidelity Research FR-64S arm would work on a SOTA Star Sapphire?

@rauliruegas   No 'immortals' here, simply applying engineering rigour in consideration to all the contributing factors, especially when there are those that outweigh direct VTA/SRA adjustment in their quantum.

I had just incorporated it into my consideration because when I get a turntable I have a laser test and then if required a dial test for quantum. But I am unsurprised to find that others had already considered the warp / platter peak to trough orientation and found it made, as one would expect a difference being close to / higher in quantum than the resolution of the cartridge manufacturers specification.   

My follow up question would be, given you heard differences in those you tested.  Did the quantum of the variation persuade you to expand your test set and incorporate the "record to patter warp matching" in your daily playing alongside SRA if you adjust.   Or do you have a 'compromise' optimum for your normal range as I do?