VPI 2nd Pivot for 3D
Dear Stringreen, I think what Raul may be referring to is the eccentricity as the uni transcends a warp. If you videoed it then played it back in slow motion you'd see the cart wobble from side to side. My guess is that the effect might be worse with line contact and low compliance but the fact is that folk have been using regular unis for years and are unconcerned by rumours of eccentric behaviour. It goes without saying that in the general sense increased noise (for example) during the warp is often expected. Gimballed arm users needn't feel too smug because warps seldom remain in the same lateral plane as the cartridge but there is no active compensation other than via the cart's suspension or the cantilever. ;) If there is a contest between the SL1200G & the Prime, this modification ups the stakes. Happy listening! |
Clearthink, You realise you've just given Lew a brainstorm... :D :D Like the Krell knowledge base, it'll take him years to decipher that ;) :D https://www.youtube.com/watch?v=3GSd92zgqAs |
Dear Raul, The report you published is the first I’ve seen that confirms my long-held belief that diamonds “burn” more than they “wear”. Many thanks for that! :)
The importance of the “message” rather than the messenger is the main thing. People may differ on what they regard as the perfect analogue medium or how to achieve it but it is gratifying that vinyl records are still being celebrated today regardless of those differences.
Diverse solutions are also something to celebrate. It shows that we’re still alive and thinking even if there are downsides and compromises. :) Best regards, Bill |
Indeed Raul, there's no substitute for a satisfied user endorsement :) It would be interesting to see a list of all designs that included a measure of compensation. VPI have now joined this club and you mentioned the Graham series. I believe Frank Schroeder has also had a try at defeating the "Achilles heel". Interestingly MF is no longer using a Cobra on his Continuum. Those duties are now shared between a 4-Point and the Swedish "SAT" tonearm ($28K - see here) : https://www.stereophile.com/content/swedish-analog-technologies-tonearm ....which must make it a contender for the most expensive on the market? Happy listening, Bill. |
Dear Raul, Perhaps the moderator should step in at this point... ;) Yes, I've only heard the SAT tone arm via 320kbps needle drops versus CDs etc but it presents a persuasive argument even if unattainable for the many. If there are hidden distortions in there I like them! ;) :) BTW before I took early retirement, our thermal engineers constantly used thermal imaging cameras to analyse circuit boards and develop thermal maps. It's probably what VDH used to get an approximation of the stylus interface? They could be quite handy for troubleshooting too. I recall an EMI chemist commenting on one forum that the melting point of some vinyl formulations was as low as 112C (I know, a bit nerve wracking for the steam cleaning brigade;) Best regards, Bill |
Hi Raul, I agree it is confusing. I recall looking up the data at the time and the "248C" figure was known to me. I was somewhat surprised back then but given how easily vinyl warps next to central heating radiators I dismissed 248C as one possible value depending on composition and state i.e temperature at which it becomes fully liquid as opposed to becoming "soft"? Clearly it does need to be a lower figure than 248C in order for the melting/reforming thesis to work? Now you've got me wondering again. :) I'll try to find the reference for you ;) Best regards, Bill |
Dear Raul, VDHs measurements of his own stylus seem to be defying the "natural order" of things by lowering the junction temperature to 60C. If true, one wonders if instead of vinyl reacting in a malleable way the stylus dislodges chunks which then fall into the groove causing further problems ;) Of course 60C must presume perfect azimuth of his line contact(?) stylus. One would assume that misalignment would undoubtedly push the temp even higher than a perfectly aligned conical stylus's 140C, leaving the user in the same state as he was before :) If VDH is successful with his low temp approach, the unit price of Last is going to rocket :D Best regards Bill |
I suspect what we may have witnessed in the video is an example of the "filmmaker's art". Just because Daniel Craig appears to jump off a bridge in 007 movie doesn't mean it is actually him doing the jumping! ;) They may have inserted stock footage of a unipivot in action? People more familiar than I with the product range might be able to identify what's going on here more accurately? |
My guess is the artistic director decided on substituting with a unipivot because it looked less boring than a gimballed one ;^) Is it possible though, Raul, that even gimballed arms aren’t entirely "torsionally stable"? The movements may be small but real due to a necessary amount of bearing "play". I remember, decades ago, Syrinx used offset bearings to try to improve this and resonance behaviour. In fact I used to own a Syrinx PU2... ;^) Not surprisingly the LF performance really was something to write home about :) |
Hi Raul, I agree with your earlier statement that there will always be trade-offs.
My main reservations about gimballed bearings are “brinneling” & stiction. 40 years ago when I was making my earliest forays into “serious” hifi, “Flat-Earthers” would talk of how low output, low compliance cartridges (such as those popularly from Linn) could “wreck” the bearings of lesser tonearms i.e. those with poor(er) quality, loose bearings such as the old Rega “S” shape. For this reason one could never use such an MC in such an “inadequate” arm. And so the era of the so-called “Super Arms” began (Zeta, Ittok, PU2, etc). I owned several of them. I am no longer a “Flat Earther” but brinneling hasn’t died, more “ignored”(optimistically) these days, especially when buying a S/H example 30 yrs old... The Linn arms in particular tended to be run “dry” i.e. no bearing lubricant. This probably wouldn’t help very much, so, if poor reaction to warps is the (simple)Unipivot’s Achilles Heel, then brinneling could be defined as the gimballed tonearm’s Achilles Heel #1. Achilles Heel #2 is probably, amongst other things, the result of the engineered solution to brinneling : forms of increased friction.
https://en.wikipedia.org/wiki/Brinelling
To me, Stiction sounds like an invented word rather than a real one but gimballed arms often have it. There can be moments when an arms ability to travel in either axis is hindered by a reluctance to move under light impulse. It was one of the reasons I switched to unipivots, because I could actually see it for myself in bearing tests. This can be attributable to long term bearing damage, deformation of the housing, contamination, drying out of lubricant (if applicable)etc. When you have a situation where the LP is drilled off centre, the tonearm is suddenly presented with the problem of tracing/weaving from side-to-side in addition to handling the warp. Given the possible presence of stiction and the enormous forces mentioned in your article this will be compounded by inertia and, in some cases, fluid damping. The end result will be that, often, the arm doesn’t respond fast enough and the pressure on the groove lining is ramped up, multiplied to even higher levels as the locus of the arm switches from pressurising one groove wall to the other? Surprisingly, our ears seem to be fairly immune to such effects, just as they can be with the forementioned bearing wobble. In fact, purists may pick up more on pitch errors due to non-concentricity than they might SQ differences resulting from variable pressure? Forgot to mention what may be categorised as Achilles Heel #3. When a warp occurs it usually emanates as a (lateral) angular undulation orientated from the LP centre to the outer rim which diminishes as we reach the inner groove. During this time a gimballed doesn't even operate in the same plane/angle as the warp, so it has lost its precise relationship and alignment with the groove. It's stable(!) but that's it! (Note : this behaviour would include the arm that I currently use despite it being a unipivot)
In conclusion, Unipivots can offer more “certainty”, even if some of them do have an “Achilles heel”. I’m always acutely aware of the need to avoid damaging gimballed arm bearings so wouldn’t even tighten a cartridge screw without stripping the arm completely from the T/T first (and if it possesses a captive cable, that too!) :^( Despite doing it countless times in pursuit of perfection, whenever removing a gimballed tonearm I still resemble a munitions man defusing a bomb! :^D Others may find it less nerve jangling but I don’t (not when I “paid an arm & a leg” for those bearings! ;^)
There is no question that many unipivots are much more facilitating and user-friendly in this respect. (Of course if one has interchangeable headshells then easier swapping but small prices to be paid on resonance & rigidity). Finally I stress that I LIKE certain gimballed arms, I like certain gimballed arms with interchangeable headshells and I like certain unipivots. I also like some hybrid arms that don’t fall into these exact categories. I guess the upshot of all this is that there are no easy answers, just compromises, as you said. Best regards & happy listening. Bill. |
Hi Raul, Thanks for your thoughts on the widespread use of ABEC9. Of great interest is the fact that that there are buyers who wish to supersede the Technics tonearm (excellent quality) on the new SL1200 with {insert as applicable} tonearm? Vandalism! :) Sometimes, with gimballed, it came down to bearing quality and alignment. (Remember the Breuer arm?) http://www.adventuresinhifiaudio.com/03/12/2013/the-breuer-dynamic-type-5a-pickup-arm/ Moving on, it’s very common to see Forum questions such as, “Is Product A Better Than Product B?”. On this thread I’ve argued both merits and demerits of both sets of products/methods. Examples of the above question could include “Is MM Better Than MC?” or “Is Direct Drive Better Than Belt Drive?” or “Should MCs Be Damped or Undamped?”. In each case there is no outright winner or global resolution, much though everyone would appreciate that to be the case. Life would be simple if it were. I can understand that those engaged in the above topics sometimes misguidedly expect a “winner”, as indeed they might do in this thread, but as you have seen in the past it is not happening. The result is what we politely and affectionately refer to as “debate”. ;^)
Gimballed tonearms have been in manufacture a long time to the extent that they might be seen as the truer “soft option”. To me, folk suggesting unipivot design/manufacture is “easier” than gimballed is rather like saying that designing a pushbike is harder than designing a gimballed tonearm because the pushbike has both gimballed bearings and gears(!) ;^) It’s meaningless because those concerned are trying to find their own unique solution to a set of design problems. In fact, many manufacturers will sub-contract the bearing design and manufacture to an agency (Japanese companies are historically good at this, as you indicated) after which it becomes an item on an assembly “tick list”. Who needs to pre-load and align bearings when you can get someone better at it to do it for you? (to balance things up, Unipivot bearing manufacturers can also get help if they need it.)
Being a Devil’s Advocate is hard work. ;^) Best regards, Bill |
