08-02-09: Axelwahl
PS: by the way, I just like how SME tts go about it, a belt drive with dynamics! -- that's why I got one :-) For a long time the SMEs were the only belt drives I'd heard that don't mute transients and artificially "relax" the musc. Fortunately, now the Ayre/DPS turntable creates the same sensation for significantly less money. I'm not saying it's as "good" as a $30K SME, but if that's the sound you like and can't spring for a SME, look into the Ayre. |
Buconero117,
>>>... the cat will keep chasing its tail <<<
And so the cat is having some entertainment, what's wrong with this?
Cheers,
PS: by the way, I just like how SME tts go about it, a belt drive with dynamics! -- that's why I got one :-) |
All the comments remind me of the endless discussion of speaker drivers and the material science that relates to it. As many have suggested, whatever sounds best to you, is the best. That goes for all the links in the chain. In the meantime, the cat will keep chasing its tail. |
I cannot speak generally to the question, but Chris Brady did a demo at RMAF, one year, comparing his rim drive to his belt drive on the same table and system. I'm sure everyone in the room could clearly hear the difference as it was not subtle. The rim drive had a blacker background and seemed to bring out more detail...kind of a veil-lifting effect. |
Hiho :-)
y.s.: >> Enough with wimpy toy motors already! <<
I guess you are fully aware that this type of wimpy motor is supposed to do the same thing as a soft (and long?) belt already. 'Mellow out' any kind of speed variation that's occurring. It screws the dynamics but it sure will be 'smooth'.
Greetings, |
The "whatever sounds good" opinion is a consumer attitude and there's nothing wrong with that but can never work as and apply to science nor truth seeking. I certainly hope people who do manufacturing has done more research than just "whatever sounds good" and came up with more educated decisions. Therefore I completely support the kind of work Mr. Mark Kelly has done and appreciate the time he spent in experimenting and, even more importantly, sharing his findings in print with us. Thank you Mr. Kelly.
I have experience with all three drive systems and they all can sound good but, right now, I completely reject using a soft rubber belt. If a turntable has to use something that soft to filter vibration and masking speed irregularities then it needs a better motor, period. In the last decade in belt-drive manufacturing, much has been belabored on fancy platter, thick and shiny, and bearing, thick and shiny, but little has been focused on the actual motor. Enough with wimpy toy motors already! |
In my opinion theory doesnÂ’t really matter because we can debate it forever and never come up with a consensus. All that really matters is what sounds best to the listener. |
We will always have different opinions about what platter drive is the "best" because we see here -again - different "schools".
I - again - just want to mention the fascinating idea first proposed by japanese audio engineers about using the string on heavy platter and working with a WANTED and precisely tuned "slip".
This works just great with a precise platter of considerable weight and inertia.
The string with minimal grip and minimal tension does indeed minimize any speed alternations, transmitted vibrations and just have to prevent the platter from loosing speed.
The (only...) trade-off is a long time till constant speed is obtained (1-2 minutes).
On the other hand we have the minimal possible influence from transmission, motor etc towards the platter.
Its the basic principle behind the big Micro Seiki, Melco and Epic turntables.
Add to this the concept of putting the bearing free from horizontal force (counter-bearing) and you have a smooth TT principle which just needs a considerable amount of space, weight, precision tooling (these 3 = money....) and care.
But - as in most other audio "fields" - different "schools" will favor different concepts and "models". |
The flaws in the way most vinyl was mastered will far out weight what 'perfection' that you chase in the TT design. Once you arrive at the 'perfection' design, it will be time to move on to a base that is no less than a $10K electron microscope table. Then on to other parts of the chain. Please, just enjoy the music. |
Hi,
having read further through this thread one thing comes to mind: The actual length and shear thickness, mostly width of the belt in use.
Some say that this is of quite some importance and actually kept the belt VERY short (pulley under the platter) and beefy, (not thin, round or square) like the flat belts e.g. SME and Linn use.
Then there is the motor controllers, ‘done over’ a number of times by Linn, and at least once by SME.
Listening to a thin (square) belt of a top Pro-ject table and thin (round) on TransRotor Z3 (sans controller) and then a short (flat) belt with controller on SME gives a pretty clear indication of the difference in transience/attack.
So much so, that on VERY dynamic vinyl the LP seems to 'slip' on the platter (rather then the belt) in the case of the SME -- if the LP is not fixed with the clamp provided.
This raises the question of 'slippage' of the vinyl on the platter in the case high torque direct OR belt drive, and if no platter clamp is used or even available.
Lastly, if the drive is THAT tightly coupled, then the motor controller's performance comes a LOT more to the fore. With the hole drive line becoming so much more unforgiving with next to no measurable 'slip' it is now unable 'paint over' some dynamic ‘problem passages'.
Fix one thing, and it will reveal the next issue for sure.
‘Too much’ platter weight (never mind just the main bearing implications) in such a 'tight coupled' scenario may just 'over-load' the motor/controller, running behind torque demand and its reverse, producing delay and over-shoot if the platter's inertia is out of tune with the motor's torque delivery and the controllers feedback loop speed.
All this can explain why a more 'benign' coupling might sound better or more natural, even if slightly less 'dynamic'.
Greetings, |
Hifitime
y.s.: >>>...the motor bearing was destroyed from the junk tight rubber band belt the dealer used<<<
Now what 'table would that have been, I ask?
To get a belt THAT tight, the motor if it was out-board would simply fall over, or?
BUT, if not out-board --- well that's another story. So before I go on, can we hear about this tt by any chance.
Thanks, |
I'm not an engineer,but more mass seems like it would sound better on all drive systems as long as its done right.That will put more load on the bearing too.The softer the rubber used for the idler or drive belt will probably make it more quiet also resulting in a nicer table.One thing we must keep in mind is good maintenance.About 35 years ago,I had a nice turntable that was pricey for me. The belt got loose from age,so I took it to a mid to high end dealer to let them change it.I thought I was hearing something that wasn't right.By the time I looked into it,the motor bearing was destroyed from the junk tight rubber band belt the dealer used.Try to learn about your table to keep an eye on things. |
I was thinking about the SL1200 series - the SP10s used push pull pairs on a dual rail power supply. Since there is no coupling capacitor it can't be the problem but it is still the case that the amplifier will be sensitive to the quality of its power supply. |
Albert that's not strange at all when you look at the way Technics implemented their servo drives.
They drive the motor coils with single ended amplifiers using capacitive coupling to block the inevitable DC offset. Any such amplifier is very sensitive to the quality of the coupling cap used because it is in series with the motor coil. If the impedance of the cap increases, as it inevitably will with age, the drive available to the motor drops which will in turn reduce the forward slew rate.
I agree that there are a lot of things going on with the various drive mechanisms. Where we might disagree is with your implication that this means they cannot be adequately analysed. The reason I was dismissive of the parts per million difference due to belt stretch is that the belt creep is around 1000 times larger, so there's no point in worrying about belt stretch - by the time you fix the creep problem the stretch problem is gone as well.
Mark Kelly
|
Albert,
I may get into trouble here, but I am increasingly convinced that the micro-dynamics of analog playback, in particular, hinge partly on things we have yet to measure. I thought I had built a great turntable, but somehow I inadvertently improved the dynamics of it without trying by implementing a change to make assembly easier. We may have figured out a lot about audio, but I really believe there are still volumes left out there for us to discover. I suppose the goal should be not to know everything, but to not know as little as the competition...assuming it is about competition, and I'm not so sure that that should be the end goal. Me? I'll settle for good sounding no matter where it originates. :) |
Quiddity The direct effect which you postulate is reduced by the second order low pass filter formed by the belt / platter combination. The maximal velocity variation for a given length change is the product of the radial displacement produced by the length change and the corner frequency of the filter system expressed in radians per second. The numbers come out in the parts per million range. You want to hear a really strange story? I have two identical Technics SP10 MK3 turntables. One was sent to a tech who is considered to be one of the best in the USA. He replaced all the caps, diodes and rectifiers and upon return (even though it tested the same) it KILLED the table with no upgrades. There has to be a lot of complicated things going on with "drive" and "speed" of these various tables because the start, stop, accuracy and drive can be drastically improved by things like this upgrade and I don't know if those are even in the parts per million. |
Mosin That said, he owns idlers including the Garrard 301, Commonwealth and others, and he can fix the speed on pretty much anything. Basically, he may be saying that the Garrard needs a good speed control. ;) The Garrard I heard was running on European settings with the Loricraft motor controller. Sounded very good, with strong drive and energy to plow through difficult passages. Quiddity I have designed a belt drive which has a very, very low level of creep. It is in the process of being built and will be on show at RMAF in the Galibier room if we get it finished in time. I do not expect it to sound like an idler table, I expect it to sound like a belt drive with the belt creep problems removed. I can't speak about technology that has not yet been created, I can't even speak about every turntable made as I have not heard them all. I have heard tens of dozens of belt drives and all the things discussed here at Audiogon matter (suspension, belt, arm, cartridge, isolation, etc). but there remains one overall character and that is lack of drive. You have to live with each for awhile to understand. I'm not saying all rim drives are perfect nor all belt drives faulty, I'm saying they tend to exhibit qualities or personality, much like we attribute to tubes versus transistors. |
Johnny
The net effect of the belt stretch is that it causes creep over the drive pulley, so we are talking about the same thing.
The direct effect which you postulate is reduced by the second order low pass filter formed by the belt / platter combination. The maximal velocity variation for a given length change is the product of the radial displacement produced by the length change and the corner frequency of the filter system expressed in radians per second. The numbers come out in the parts per million range. |
08-01-09: Quiddity
...the torque numbers by themselves prove ... that the argument over motor torque does not provide a key to the sound of an idler table vs belt drive.
That variable being eliminated, we can now ask "what other characteristics of these tables may result in the sound we hear?"
I nominate two for discussion: the very small degree of mechanical creep in the idler transmission and the very high reflected inertia of the typical idler motor. Which is more important? I don't know. Yet. I nominate a third: how the drive system reacts to stylus drag. A drive with an elastic belt could stretch and recover when it encounters greater stylus drag from transients, where an idler drive or quartz-regulated DD might power right through them. After all, there are belt drive enthusiasts who replace their stretchy belts with mylar tape or dental floss. And VPI offers a rim drive. Reviews I've read consistently praise it for more realistic presentation of transients and rhythm. |
Albert
I measured those results in my lab on a Garrard motor I know is in good working order. I have also measured several other motors used in idlers and found very similar results. Since the results accord with the theoretical results expected from these designs I have no reason to suspect that they are anything but typical.
You are correct in saying that the torque numbers by themselves prove nothing, with one exception: they prove that the argument over motor torque does not provide a key to the sound of an idler table vs belt drive.
That variable being eliminated, we can now ask "what other characteristics of these tables may result in the sound we hear?"
I nominate two for discussion: the very small degree of mechanical creep in the idler transmission and the very high reflected inertia of the typical idler motor. Which is more important? I don't know. Yet.
I have designed a belt drive which has a very, very low level of creep. It is in the process of being built and will be on show at RMAF in the Galibier room if we get it finished in time. I do not expect it to sound like an idler table, I expect it to sound like a belt drive with the belt creep problems removed.
The drive design allows for the addition of a high speed inertial system. I expect that if this system were added the sound would change; it remains to be seen exactly what this change is and whether it is seen as a benefit. The inertial system is still on the drawing board, it will not be at RMAF.
One of the problems is that the "donor table" has inevitably been designed to perform with a different drive system. Accordingly I've asked Thom to audition the drive on his lowest model table on the grounds that this has had the least attention given to optimising the synergy between the drive and the other mechanicals.
Mark Kelly
|
Albert,
Mark makes the controller for my Saskia idler drive, and I can say firsthand that he looks at things from a critically analytical viewpoint. That said, he owns idlers including the Garrard 301, Commonwealth and others, and he can fix the speed on pretty much anything. Basically, he may be saying that the Garrard needs a good speed control. ;)
Best,
Win |
All this technical discussion reminds me of the numbers war in electronics in the 1980s. If we are to believe any of those specifications the Yamaha receiver is a much better performer than a Lamm.
I began with rim drive over 40 years ago and was talked into a belt drive, assured of it's superiority by the Thorens rep himself.
I owned tens of dozens of belt drives and each sounded different but not until I returned to rim drive / direct drive did I get the immediacy and impact that had been missing all these years.
I clump rim drive and (good) direct drive into the same category as both provide similar sound.
Quiddity, I don't know where you heard a Garrard or other rim drive that had such poor speed results, but in a side by side test against three of the finest belt drive tables on earth the Garrard was top or very near. |
Oops
I looked at the wrong motor on the Hurst table, the actual motor used by VPI is the lower torque model so the figures are 16mNm at the shaft and 290mNm at the platter respectively.
This would seem to favour the Garrard but only if you find a 10% speed reduction acceptable. If you want the Garrard to slow by a lesser amount (say 1%) the useable torque drops almost proportionally - at 1% the torque is about 1mNm at the shaft, say 50 mNm at the platter.
Mark Kelly
|
The first thing to deal with is the torque issue. The thing about high torque idler motors versus low torque belt motors is largely a furphy.
The output torque at the shaft of the Garrard motor is a little under 10 mNm. The output torque at the shaft of the 3W Hurst motor used by VPI is 26 mNm.
The reflected torque at the platter is the shaft torque times the gearing ratio. For the Garrard the gearing ratio is about 48 to 1 so the final torque at the platter is about 440 mNm. For the Hurst motor the gearing ratio is 18 to 1 so the final torque at the platter is 470 mNm.
The "low torque" Hurst thus has more torque than the "high torque" Garrard.
To add insult to injury, the Garrard motor slows by 10% when delivering that torque where the Hurst motor does not slow at all.
Mark Kelly
|
The primary hurdle to jump with belt driven turntables is their inherent belt creep.
It is best described here...
http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=694178&highlight=belt+creep&r= |
