Hi Ralph, Belt drive turntables differ from one other in belt compliance and platter moment of inertia, so their oscillation wow patterns differ. That explains in part why belt drive turntables sound so different from one another in pace and rhythm, in steadiness of pitch, and in solidity of bass (bass notes last longer, so they require a longer sustain of turntable pitch accuracy to sound straight and massively impactive, rather than warbly, wobbly, and weak).
Can the belt drive designer reduce or damp the unwanted oscillations between platter and belt? In principle yes, but in practice it's tricky to execute. In principle, what's required is simply the addition of some resistive damping. This would damp the reactive LC tank circuit of belt and platter so it would no longer oscillate.
A common form of resistive damping is friction. Thus, if a knowledgeable turntable designer wants better speed constancy, he might well consider intentionally adding some friction to his rotating platter. It's worth noting that some Swiss and German engineers are so justifiably proud of their ability to produce nearly frictionless bearings that they cannot bring themselves to make turntables with high friction. As a result, the Thorens turntables exhibit some of the most spectacularly low friction bearings on the planet, and will spin seemingly forever (with the belt removed); but, at the same time they also exhibit some of the worst audible wow, in part because there is, as a matter of engineering pride, almost no resistive damping for the oscillating reactive tank circuit.
What might be useful ways to introduce friction? The fit and/or finish between platter spindle and well could be made poor, instead of smooth and polished. But this would be causing friction via crude irregularities, like two meshing mountain ranges, rubbing each other. The crude irregularities of these two mountain ranges rubbing together would cause unwanted speed irregularities (snags and letting gos), as well as unwanted vibrational rumble (the earthquake rumble of each letting go after each snag). So that tactic is out.
One useable tactic is to introduce a viscous fluid in the bearing, which provides friction in a liquid hence smooth form. This can be especially effective if the spindle is made in a larger than normal diameter, so that the viscous fluid has a larger moment arm (more leverage) with which to work its resistive magic (as in the Linn Sondek). The use of viscous fluid for resistively damping platter rotation can also be enhanced by various helical screw kinds of arrangements, which force the fluid to do extra work in opposing the rotation of the platter (as in the turntables from Max Townshend). It's no accident that these two brands have the best reputation among belt drive turntables for pace and rhythm, solid bass, and master-tape-like clarity. It's because both these designs recognize that belt drive, far from being a simple Hail Mary solution, brings with it new problems that must be addressed, and that overcoming the problem of speed constancy requires at least the addition of a fourth element, resistive damping, to the three usual elements of a belt drive turntable. That's a quote from Peter Moncrief's incisive article about turntable speed control. As also described in his article....is the fact that a 'stretchy' rubber belt can iron out the 'pulses' of a poled motor whereas if a non-compliant tight thread were employed........we're back to transferring that cogging into the platter? |
Same model as yours which was also too fast ironically, the other table was a 30/2 and was too slow but when we put it on 45 too fast.
Owners were not very happy! specially when they thought it was set up correctly.
What do you do if you have no adjustments or worse the adjustments still don't allow you to get it accurate?
Not one table that I have tried has been spot on including my own with both speeds initially, some were really bad, mine wasn't but I learned that most could not be corrected either, mine was so I was lucky.
This TimeLine tool has assisted providing information that using other tools to set-up really to me are misleading but worse that manufactures are not paying close enough attention building their products.
So mine being off slightly, once I got it spot on I really could not hear nor feel the difference but on others I most defiantly could hear improvements if they were off badly so this is a postive tool to use and will be used in the future by me.
I recently went into a store whom I know the owner but will not mention the name and has some mighty exspensive tables and not one was spot on, he basically dismissed the use of the TimeLine saying they have all been set-up properly blah! blah!
I asked him if he did not mind to allow me to get one set-up using the TimeLine and then have a listen afterwards, it's not hard to do if there is a fairly accurate fine speed adjustment allowing such but the table also must be capable of doing such and this table was pretty darn close in the end but originally off pretty bad and this room we are talking big dollars.
I was told the rep was by the week prior and saying how sweet things sounded, humm!
When we were in the room he was tapping his foot and I said straight up are you for real, sorry but I'm not feeling it and this is a pce when I play at home my whole body gets into it and I just want to get up and boogie.
No way would it have me opening up my wallet but after using the TimeLine the sound was now locked in, the focus was way better, all arround just sounded different in a positive manner and just felt better if you know what I mean in a good way.
He came into the room and without even sitting down said he was already experiencing the difference so guess who will be getting a TimeLine to use.
Still did not leave me feeling the way I expressed above listening in my own place.
Personally I feel acurate table speed should be the basics of a table design, the foundation and then you go from there. If you can't get this right well ... I feel something is just wrong. |
Hi Lewm,
but using a mylar belt has it's own issues. Static, dust attracts to it, they only last so long before slippage occurs. You have to spend some time makeing them up all the time etc.
Sorry but I just want to listen to music and not be dealing with that.
I also tried on a Lenco, won't mention the seller but it was also off. I inquired about this and basically got back a answer that it's fairly close. hummm
I tried it on a "DD" SP10 MK2 and it was off, no way to correct like the MK3 offers speed adjustments so the owner has to send it in.
Albert I had asked you about your NVS, I'm sure you have checked it.
Can you tell us the results. |
Unfortunately bringing the motor closer to the platter also brings it closer to the cartridge as well. Which on the TT's I have had with that arrangement caused hum on most of my cartrides. There may be some TT's that sheild the motor well enough to pull it off. |
The comment about using viscous drag or friction to dampen platter oscillations on bd tt's struck me. I do my own maintenance on my Sota tt. It is easy enough to disassemble the platter, clean and relube the spindle and bearing. I let it go for a few years and then about two years ago, I got around to pulling it apart and relubing it. I noted then that the tt sounded better, but I didn't really understand why. So now I clean and relube it every year. Some other Sota owners have also mentioned they found some synthetic lubes make it sound better than other lubes. I tried some synthetic lube last Fall and didn't notice a big difference in sound myself. The synthetic lube is very tacky and definitely added drag to the spindle compared to the lithium grease that I was using. Since my speed is pretty rock solid, I guess the drag is not too high. |
