While I was visiting Syntax last month, he checked the speed stability of his machine. The laser from the Timeline was spot-on and did not waiver...his well-tuned Micro Seiki RX-5000/RY-5500 was simply steady and consistent.
Albert, you may have already mentioned the reason, if so, I apologize for bringingtip the question again...why do you think that the NVS was not up to task? Since you are not having issues with your fabulously-modified Technics Mk 3, great; why do think you maybe having instability with the NVS? It appears that is not an issue with the quality of the mains being presented to the motor controller; otherwise, I guess that Technics Mk
3 would also have an issue...what do you think could be the issue with the NVS?
Cheers!
Alan |
Albert - excellent, thoughtful response. You may now don your asbestos suit! ; - )
I think you make a couple of excellent points; namely that speed precision AND accuracy are both important. IME, individuals vary in their sensitivity to one versus the other. I also agree that while speed parameters are obviously important to turntable performance, other characteristics contribute to the overall turntable quality including immunity from internally and externally generated noise/vibration. |
Albert, Thanks for the specifics on the TimeLine tests. That Mk 3 must be something and perhaps "best of DD breed". I'd love to hear it someday. Pity it's no longer made.
I witnessed a TimeLine demo on a DD table last weekend. The owner held an envelope 12" from the laser and yes, the spot did not move during the 30 second test. When I asked him what the result would be if he let the laser hit the wall six feet behind the table, he admitted it would not maintain its fixed position. Now that table does have speed adjustments for fine tuning, and I presume better results could be attained, though we did not spend the time. I appreciate and respect the thoroughness with which you seem to be doing your evaluations.
The remainder of your post is thorough and well reasoned, it seems to me. Thank you for summarizing the issues to clearly. It's very helpful. |
Dear Henry, I guess I have been too lazy to check the Kenwood L07D with Timeline so far. However, my neighbor's Timeline is still sitting around my listening room, and I will do it today, sans LP and sans stylus drag. If there is a consistent error up or down, that would not concern me, because speed is adjustable within the outboard PS. (The L07D does not provide user accessible fine tuning, as does the Technics Mk3 and the Denon DP80,) I had two L07D's until recently and was using one heavily whilst the other was being "refreshed" by Howard Stearn (the L07D guru who is also an orthopedic surgeon, not the shock jock on radio). Howard did a fabulous job on my first one, so I trust him to have done similar work on my second. (I bought the second so as to get the original Kenwood accessory record weight and platter ring that go with the L07D and because it was in mint condition.) Anyway, I sold the first one and have not yet got the arm mounted on the second one, because I want to re-wire it. This is why I am in between L07Ds. With the Lenco and the Mk3 in full service, I hardly feel the screaming need for a 3rd table. The L07D was far and away my favorite table before I had the Mk3 up and running.
Albert, EMI picked up by the cartridge from the L07D motor was rumored to be an issue. It seemed improbable to me, because the platter and mat constitute two solid slabs of stainless steel which ought to afford some decent shielding. Nevertheless, I made an LP-size shield out of "TI Shield" (Texas Instruments), the best shield around for a combo of EMI and RFI, and I inserted it over the spindle and in between the platter and platter mat. This actually did result in a noticeable but small increase in transparency even though I heard no "noise" per se prior to installing it. The Mk3 ought not to have any issues in this area, because its thick brass and SS platter is an even better natural shield than is that of the L07D. |
Was invited to have a listen to 2 audio systems and did bring the Timeline with me just to see how other tables faired. The first was a modified Technics SP10 MKII (I believe) with the plinth from Albert Porter and the Timeline did not waiver one bit. The other was an SME10 and here the Timeline showed the table running fast, unfortunatelty we the SME does not have pots to adjust the speed. Could we hear this effect on the SME? There were 4 of us listening and to be honest no but it would have been nice if we could have adjusted the speed to be dead on and then hear what we thought.
Just some more data points for all to think about. |
Unoear ask: why do you think that the NVS was not up to task? ... It appears that is not an issue with the quality of the mains being presented to the motor controller; otherwise, I guess that Technics Mk3 would also have an issue...what do you think could be the issue with the NVS? So far no turntable has passed the test as I conducted it, except the MK3. The NVS was up to the task as the rest. Have you checked your DD Rockport? I have a huge bias in favor of that table. I wish to know if it's as rock solid as I imagine it to be. |
Lewm posted: Albert, EMI picked up by the cartridge from the L07D motor was rumored to be an issue. It seemed improbable to me, because the platter and mat constitute two solid slabs of stainless steel which ought to afford some decent shielding. Nevertheless, I made an LP-size shield out of "TI Shield" (Texas Instruments), the best shield around for a combo of EMI and RFI, and I inserted it over the spindle and in between the platter and platter mat. This actually did result in a noticeable but small increase in transparency even though I heard no "noise" per se prior to installing it. The Mk3 ought not to have any issues in this area, because its thick brass and SS platter is an even better natural shield than is that of the L07D. I use the TI FerriShield too, although it had no affect in tests with the MK3. With the MK2 the results were astounding, I imagine the holes in the aluminum MK2 platter looked like a strobe light to the phono cartridge. When I say FerriShield was effective with MK2, this assumes the stock rubber mat, the Funk Firm mat, Boston Carbon Fiber or other mat that offers no blocking from RF and EMI. Looking back I now realize some of the amazement of the Micro Seiki Cu-180 was the hard surface and superior design, but also the total blocking it provided, equal to the Texas Instruments in my tests. My current mat is the TTM from Japan and is the highest performance mat so far on my MK3. I suspect it's mass is too much for the MK2 but the MK2 does well with the Micro Seiki Cu-180 and negates the need for FerriShield. I have not gotten into this much in forums, but the center weight or clamp, plus mat is almost as much affect on sound as tonearm cable (and in some cases) the cartridge itself. Maybe I'll make up a list of combinations of mats and clamps and what I heard. I sometime wonder if this variable plays a role in cartridge preference among members. If any of you have tested same, I would love to read your results. I've been doing this for several years, it's a tedious process since one must be VERY careful to insure VTA and other variables are not more result than the parts in play. |
Hi Albert,
Yes, the string-driven Big Micro Syntax machine was up to the task and, as I mentioned, spot-on; the Seiki was consistent, rotation after rotation, as represented by hole burning in the wall.
No, I did not get a chance to try a Timeline with Rockport Sirius lll while it was here last year. However; Tim Sheridan, was here late last year for a visit before I shipped the Rockport to its new home...where it joined a few other Rockport TT siblings in the UK. As you may know, Tim is the designer of the motor controller (MDA) for the Sirius lll. He tweaked the MDA to bring the speed accuracy of the Sirius lll back to his standards along with preparing the mains change and a few other items.
Cheers!
Alan |
Perhaps the key to the accuracy and consistency of many DD turntables.....is their inbuilt ability to monitor the platter speed against a quartz crystal timing device......and make instant corrections for any deviations?
I don't know of any belt-driven turntables able to do this?.....nor for that matter....any idler decks either?
My experience with belt-driven turntables and the Timeline.....is that one can set the speed controller to be fairly stable with no cartridge playing OR with a cartridge tracking the groove.....but they are two different settings?
The 'stylus drag' slows the actual platter speed.....but as the motor controller does not know this (it is only putting out a constant signal)......there is no compensation?
Alan, have you tested your own Micro Seiki SX-8000 with the Timeline and when you say that Syntax's RX-5000 kept constant accurate speed......did you see this with and without a cartridge in the groove whilst not adjusting the motor controller? |
Halcro: "Perhaps the key to the accuracy and consistency of many DD turntables.....is their inbuilt ability to monitor the platter speed against a quartz crystal timing device......and make instant corrections for any deviations." While I am a fan of direct-drive but I am not sure that's a good thing about servo making "instant corrections for any deviations." Any error has to be detected first before making correction so it's after the fact and sometimes if treating it with an iron fist approach it can cause unnecessary jitters and possibly that sterile sound we associate with DD tables. I think the key to good sound in DD, other than motor quality, is how the designer approaches this servo or corrective system in a sensible way. If the outside disturbance of the speed is too large, I see no need to correct it and just let it be. For example, if I were to tap the platter rim with my palm while spinning and I don't see the need for the platter trying to hold speed. It comes down to how smooth the correction is. I don't think servo response time have to be so quick. A gentle approach is probably more pleasing to the ear than a brute force one. I can be wrong and there are probably good sounding DD tables (TT-101?) out there using the quick fix approach. I understand stylus drag is not a constant resistive force, neither is music. Perhaps the torque should be set just high enough to plow through the most demanding musical passages (1812, anyone?) and leave it at that so the servo does not have to do tap-dancing all the time? Of course, it's impossible to do instant servo on belt-drive of course due to the elasticity and time delay of the belt but its gentleness probably offers a pleasing sound. ______ |
Hiho, Well said. The L07D is among those that use the servo feedback sparingly or gently, whichever term fits best. But since I cannot understand any of the feedback circuits without a tutor, it is hearsay evidence coming from me. I am reporting what is implied in the owners manual for lay persons to read.
Halcro, I tried to test the L07D with the Timeline today. It's the first time I had this unit up and running. But sadly the test could not be done, because the Timeline will not fit over the L07D spindle. Apparently, L07D has a "fat" spindle like my Lenco. The L07D ran spot on with the KAB strobe, however and for whatever that is worth. Sutherland should make some sort of adapter to accommodate each of the 3 possible spindle diameters. it would not be difficult. |
Have been following and reading all the posts since I posted back in November.
Here is my follow up.
Since my post I have made it a ritual to use my Verdier and Timeline every time I start to listen to vinyl.
Experimented with various different threads and settled on the J&J unwaxed dental floss.
My ritual is to place a record on my Platine, turn on the air for the tonearm, place the Timeline at the speed of the LP's rpm and then turn on the Verdier motor.
When I start tracking the speed with the Timeline on the wall behind the table I can clearly see if it is running slightly fast or slow. Have a piece of grid paper taped against the wall with blue painters tape. The grid paper has black ink lines drawn every 1/4 inch vertically.
The laser dash on the wall is approximately 1 1/4 inch long. My Verdier spindle is 18 inches away from the spindle and 16.5 inches from the timeline.
I adjust the speed in order for my "laser dash" to stay constant. After about 2 minutes of staying put " good dog spot" had to throw that in..... It is then that I start playing my music.
After playing numerous Lps and it time to get things wrapped up for my listening session I then check to see if the Verdier is still holding speed.
Timeline strobe light not drifting.
Now it gets interesting.
When I have my next LP listening session, I go through the same ritual and sometimes I have to adjust the speed on the Verdier.
Ever so little about a 1/16" to 1/8" of inch" of adjustment on the dial is all that is required so that the timeline doesn't drift.
What is causing this ? Don't know. Line voltage, slippage, stretching ? Time for the battery set up for the Verdier.
When I play LPs on my Denon DP 6500 the speed does not drift while playing LPs with or without tonearm engaged.
Just for S&G decided to play the Denon with the Timeline but with no tonearm engaged. Left this playing for one hour (iPhone timer) the timeline laser dash was still in the exact same spot.
I did not stay there for the whole hour but was there for the first 20 minutes, son did the next watch for 10 minutes, I returned and finished up the last 30 minutes. This is such a fun hobby starring at a red line ............
Speed stability the DD DP 6500 first place, tread drive Verdier second place.
Sound comparison and conclusion.
The Kuzma tonearm stays on the Verdier. The FR64 can be inter changed between the Denon and Verdier and the set up takes about 30 minutes for an "equal" comparison. The protractor used is Dertonarm's.
Which table brings me more emotion and gestalt ?
Result is still the same. Even with the extra steps required The Verdier is the table that I go to 99.9% of the time.
Knowing that it needs to be tuned to be accurate is not a biggy for me. Effort is worth the result. Curious how a heavy platter DD would sound.
IMO my ritual with my Verdier is like my days of tuning multiple Webers on a car. Anyone remember those days?
Get it right and you are rewarded with the glory of the exhaust note and the response of a fine tuned engine.
Music to my ears. My other passion.
Take care all, |
> Lewm: "The L07D is among those that use the servo feedback sparingly or gently, whichever term fits best." I don't know enough of electronics to decipher servo circuits but I do know one DIYer in another forum tinkered with the servo on a heavily modded unit of a stock Technics SL-Q3 turntable with the following: "I modified the negative feedback loop network to make the whole thing under-damped. As it is from the factory, it is over-damped and after doing some A/B test by switching instantly between the factory network and the new one, it is obvious the change in sound. The modded version is much more relaxed and clear and all the distortion (similar to jitter in digital) in mids and highs is gone." Now, I wish I can do that to my Technics table... > Lewm: "But sadly the test could not be done, because the Timeline will not fit over the L07D spindle. Apparently, L07D has a "fat" spindle like my Lenco." Maybe you can raise the Timeline above the spindle with, say, a piece of styrofoam or a roll of electrical tape, center it and hold it with double-side tape? It's a little mickey mouse but it can be done...... that is, if you have the time and energy to entertain us. :-) _______ |
Unoear: No, I did not get a chance to try a Timeline with Rockport Sirius lll while it was here last year. However; Tim Sheridan, was here late last year for a visit before I shipped the Rockport to its new home...where it joined a few other Rockport TT siblings in the UK. I can hardly believe after all the work and effort you put into obtaining the Rockport you sold it. Your post is the first I've heard about that. |
For $400, the timeline needs to be built with an internal clamp so that it will fit any spindle. |
Hi Albert,
Yes, having the Rockport Sirius lll here last year was really some enlightening audio fun. It is now with Mik in the UK...he is a mad about Rockports; three lll's, and two ll's. He is also a big fan of stonebody Koetsu cartridges and the Goldfinger cartridge.
Like yourself, I do like to hear and make decisions based on what is going on in our systems.
I believe that in my case with the Rockport along with your case with the NVS, we both decided that we were not able to replicate what was presented. So, mine has found a new happy home; similarly, you are trying to find a new home for your NVS and Talea.
Albert, I have fondly followed your posts and do appreciate your desire to find the differences that work.
Cheers!
Alan |
Lew and others with "the big spindle" issue. Could you stack enough metal washers on the spindle to leave only the top exposed, then use that to center the Timeline? If the top of your respective spindle is slightly rounded this might work. If your spindle is machined flat across the top then I suppose you could only "approximate" centering. |
Alberporter: Intuitively, I would think that what a dd turntable sits on would have a big effect on its sound. Maybe you've addressed this with plinths, but I would still think what that sits on should be discussed much more than it is, and wonder why it is not. Is that because the plinth lessens the need for proper sitting(A little bit off the subject, but what the heck.)? |
Mmakshak,
The plinth is important in that it provides a solid platform for the powerful DD motor to operate without vibration or oscillation. I had one direct drive table here that was so light it almost sounded digital.
You are correct that what a DD table sits on could be discussed more. Truth is all turntables react radically to outside forces and the stand, platform, spring base or whatever plays a huge role.
For me it's most important to isolate my table from foot falls and effect of my powerful sub woofers. I choose Vibraplane and I am totally satisfied with what it provides.
I was so moved by the performance upgrade from Vibraplane I bought a second one for my Studer tape machine. Surprisingly it provided almost as much upgrade there as the DD table.
I think we still have quite a lot to learn about isolation. I wish I had more money and time to experiment. Seems an endless task with all the variables. |
Guys, Yes, I thought of offsetting the Timeline so it rests essentially above the spindle or so that the spindle can enter it just enough to center it. However, my fear then is that if the Timeline is even very slightly off center, it will make the TT appear to be off speed. This is because the Timeline seems SOOO sensitive to slight speed variations. It seems to me that it would not be difficult to provide 3 different adapters with the Timeline so as to fit each of the 3 possible standard spindle diameters snugly. Errors due to off-center positioning of the Timeline could be quite misleading. (Or maybe not; I have to think about that.)
Hiho, I think the L07D servo was designed to be "underdamped" as well. Whoever the guy was who modified his own Technics, he either has developed a good understanding of how its servo works or... not. The very idea of playing around with the servo is a whole new can of worms. |
Lewm
Do you think that adding mass to the platter of an existing dd turntable( assuming the spindle bearing is up to the task) could also achieve the same effect as "loosening" the servo response.
Perhaps the periphery clamp of the LO7D helps to achieve this. |
Here is my vid of me touching the side to test pulsed speed stability... it is a hung suspended table so you may see it move alittle actually its just the suspension moving laterally
http://www.youtube.com/watch?v=PB2TaN2FPRU&feature=youtu.bey... no movement on the strobe! |
Lharasim
Which turntable are you using for the demo in your video ?
Watched it but do not recognize it.
Thanks for sharing. |
While I agree with Albert on the importance of the mass and the material composition of the plinth as a determinant of dd performance, you should know that there is a whole "school" of thought on the other side of the question, that holds that "no plinth" sounds best. Those guys place the naked DD chassis on nothing but a set of isolating feet, like for example the old AT feet. Then they mount the tonearm on an outboard pod. To me, this is a violation of many different "rules". But I think it may indicate that a bad plinth can be worse than no plinth at all.
Dear Lespier, Good point. adding mass to the platter definitely has an effect on the servo, but I have to think whether that would reduce the damping effect or enhance it, i.e. under- vs overdamped. If I start with the idea of no platter, the servo mechanism is rapidly hunting for correct speed, so maybe that is the condition of underdamped. Ergo, adding mass to the platter, e.g., via a heavy platter mat as is done by many, would tend to overdamp the servo response, I think.
The L07D has a secondary switch on the PS chassis that one engages only when using the accessory peripheral ring weight. This switch alters the servo response so as to account for the added weight. I checked my L07D using the KAB strobe both with and without the ring. The speed was accurate both ways. |
Lewm: "If I start with the idea of no platter, the servo mechanism is rapidly hunting for correct speed, so maybe that is the condition of underdamped. Ergo, adding mass to the platter, e.g., via a heavy platter mat as is done by many, would tend to overdamp the servo response, I think." I don't think the damping factor of a servo circuit is determined purely by mass, that is, higher mass = overdamped or lower mass = underdamped. It is probably preset by the electronics how responsive or how quick the response time to the load or mass deviation, I supposed there's a "reference" load much like a zener diode in a regulated power supply, which is a form of feedback. Some turntables have very "loose" or gentle response to mass deviation, that is, even without the platter it can still rotate smoothly. I think it is predetermined by the electronics in the over all design. I think sometimes by adding mass to the platter can sound "smoother" is to purposely overwhelm the servo to allow more platter inertia to do the job so it's actually underdamped (less hunting, perhaps?). I guess it's a balance between letting the mass or letting the motor/servo/electronics do the work. It really comes down to engineering decisions. Back to the same idiom that there are many ways to skin a cat, I guess? _______ |
Hiho, The point is that if you don't know enough about the circuit to fiddle with the servo at the level of its electronics (which includes me), you can at least affect damping by changing the rotating mass of the platter, which is a parameter built into the servo system. Easiest way to do that is to alter the mass of the platter mat. Adding mass does not "overwhelm" the servo; it adds damping to the system as a whole, if you take the "no platter" condition as "undamped". I think in engineering terms this is the correct way to think of it, but I am more than willing to be corrected by an engineer.
But I agree with the sense of what you wrote, mostly. The L07D and perhaps the aforementioned TT101 may be examples of servos that don't attempt to control speed as tightly as does, for example, the Technics system. The engineers that worked for Denon, Kenwood, Victor, Technics, Pioneer, etc, each had a go at deciding upon the optimum way to achieve the same goal, and they came up with different answers. |
Doesn't this discussion on DD servos highlight the question, does a very high mass platter, with very high inertia, driven by a high torque motor with a belt, thread or fluid drive with built in slippage, such that the platter mass will drive through any load fluctuations sound better than a DD with its constant speed correction.
Correct me if I'm wrong, but isn't the need for servos because DC motors inherently do not respond in of themselves to changes in loads.
For those that are keen to experiment - here are a couple of decks worth trying :
Rossner and Sohn - latest special custom-made turntable is called The Mott (The Mother of Turntable). The rotating platter itself weighs 232 kg. Choice of air or oil bearing.
Sati - 50kg platter, interesting comments on motors on their website. |
I believe the Brinkmann Bardo and Oasis use the gentler servo speed control. Here's what they wrote in their white-paper; it's a little long but it's a good read: PROBLEM WITH DIRECT-DRIVE
Studios (radio stations in particular) demand quick start-up times turntables typically have to reach their correct speed within half a revolution. For LPs this means 0-33 1/3 rpm within 0.9 seconds. Such acceleration figures can only be achieved through use of high-torque motors and correspondingly tight coupling between the drive and platter. It isnt a surprise then that for decades idler wheel drive designs were the defacto standard in studio applications. But idler wheel turntables also had seriously high maintenance costs in order to be up and running 24/7 and to avoid rumble and other sound degrading issues caused by worn out idler wheels to affect the sound negatively. Thus out of necessity, in the late 1960s manufacturers of studio turntables began to look for low(er) cost maintenance alternatives. They came up with direct drive, whereby the platter was placed directly on the motors shaft, ie the stator was mounted around the bushing and the shaft was used as the rotor and voila, the goal was achieved; at least in theory.
But start-up times of less than 1 second necessitated high torque motors, which designers achieved by using motors with 32 and more poles. The penalty they paid were heavy cogging effects accompanied by high wow & flutter numbers. The cure was found in quartz locked motors and phase locked regulators; which corrected for any deviations from their preset with an iron fist. On paper at least, these corrected direct drive turntables boasted hitherto unimaginable low wow & flutter numbers down to 0.001%. But the rigorous iron fist regulation prevented the platter from spinning smoothly; instead, the regulation caused the platter to oscillate continuously between speeding up and slowing down. These start/stop motions translated into an unpleasantly rough and hard sound; odd as wow & flutter numbers in the 0.001% range are deemed inaudible.
Once the direct drive technology had gained a foothold in pro audio applications, the benefits of mass production (ie. trickle down effect) made sure that very soon even $100 turntables were equipped with direct drive and advertised as having less than 0.01% wow & flutter. This is precisely where direct drive got its bad rap sheet. Under closer scrutiny however, this assumption were based on some misunderstandings. For one, in home audio application use, turntables are not really required to reach 33 1/3 rpm in less than a second, thus 32 pole motors and phase locked regulators are not really necessary either.
THE BRINKMANN SOLUTION
Having decided to utilize a direct-drive mechanism for our new turntable, we began searching for the appropriate motor. Sadly (or luckily, as it should later prove) and despite much effort we were unable to find a motor that was up to our stringent quality requirements. We therefore decided to design and build the motor in-housewhich had the nice side effect that we did not have to cut any corners and instead were in the fortunate position of defining all relevant parameters ourselves. The motors stator consists of four specially designed field coils, which are mounted concentrically with high precision around the platter bearing. Based on listening and tuning sessions, we decided to forgo the typical 90-degree mounting angle in favour of a non-standard 22.5-degree raster, which, due to the magnetic fields overlapping, further reduced cogging. The motors rotor also acts as the sub-platter and carries a magnetic ring with 8 poles on its underside.
The drive mechanism, based around Hall sensors and an encoder disk, is designed in such a way that there is just enough power to bring the 10 kg heavy platter up to 33rpm in about 12 seconds. Conversely, only a minimal amount of energy is actually necessary to keep the rotational speed at a constant. While the drive mechanism is indeed direct, power
is actually transferred without any contact. This soft coupling via a low power magnetic field translates into a silent drive, which reduces cogging further. One of the main attributes behind the sound quality of the Oasis has to do with our proprietary motor control. It works proportionally, i.e. it transfers just enough energy to the motor for it to remain at constant speed. Conversely, due to our ultra low-friction bearing, only a small amount of energy is actually necessary to keep the motor at constant speed. Previously available regulators typically work disproportional and rather abruptly: they speed up and slow down the motor very rapidly when necessary.
During the development phase of the Oasis turntable, we spent many long hours auditioning several different regulator designs; it became quite evident that utilizing our concept of proportional regulation always resulted in better sound: typical harder motor control concepts produced a sound significantly lower in quality, with less color and drive. I suspect their decision "to forgo the typical 90-degree mounting angle in favor of a non-standard 22.5-degree raster" is influenced by Dual's design of the EDS-1000 motor, which also has the same coil arrangement... _______ |
Dear Dover, You wrote, "Correct me if I'm wrong, but isn't the need for servos because DC motors inherently do not respond in of themselves to changes in loads." OK. You are wrong. First you are wrong because your statement carries the assumption that all DD motors are DC motors. I am not sure you meant to say that or perhaps you meant to type "DD" and out came "DC". In fact, a major fraction of DD motors are 3-phase AC synchronous types. DC motors are also used in some pretty fancy and expensive belt-drive turntables. Second, you have failed to define what you mean by "load"; I assume you refer to variations in forces due to stylus drag, etc, that occur during the course of playing an LP. Third, you are wrong because your statement carries also an assumption that all DD turntables use servo feedback. Some of the new ones don't, e.g., The Beat. In any case, I think that the adoption of servo mechanisms has to do with the fact that a DD turntable motor has to turn constantly at the relatively slow speed of 33 rpm, and using servo feedback is one way to reach that goal. As we have been saying, there are many many different ways to apply servo feedback. Belt-drive motors run much faster and for some the belt itself is used to smooth over small changes in speed. Also, it's cheaper not to use any feedback. But major point is that in principle DD motors qua motors (thank you, Nandric) are no more and no less inherently speed constant than are belt-drive motors. I do not think it is possible to argue from generalities that one way is better than another. |
Lewm, I meant DC motors. As far as I know the following DD's use DC motors - EMT948, Technics SP10mk2&3, Sony PSX9, Kenwood Lo7D, Exclusive P3. The Denon DP100 uses an AC motor.
DC motors react to variable loads quite differently to AC motors. Seems to me there is potentially as big a difference generated by DC/AC motor choice and implementation as there is by drive type.
Actually, I believe I'm right with regard to DC motors - DC motors do not self correct when speed fluctuates, hence the need for servos or speed sensors at the very least. Question is as Brinkmann suggests there is a trade off on sound "quality" between fast recovery and soft recovery type servos. Too fast and you get overshoot and more correction.
Platter mass also factors into the equation as well in that it can dampen the servo action in a DD TT.
There was no argument or generality suggested, but a question posed if you reread the post. |
Servo design in a DD 'table certainly includes the expected mass of the platter. If that changes significantly it sill alter the response of the servo; likely to the underdamped side of things. Many cheaper DD tables have a platter that can be removed and the motor can be operated without it- in this case the cogging effects are often quite visible. This an extreme example of course, but illustrates an under-damped condition.
So you probably can decrease the electrical damping by increasing the mass, but you should also not be surprised if overall speed stability is also compromised. Servos often have to operate within some fairly tight parameters. |
Hiho, Lets keep in mind that what you quote from the Brinkmann website is a commercial, full of blather with a sprinkling of fact. Like many politicians, they set up a "straw man" controversy in order to show how their product "solves" the problem that may or may not be a problem in reality.
What I especially found questionable was the part about 32-pole motors causing increased cogging. More poles should mean less cogging, if done right. Anyway, I am sure the Bardo is a nice product in spite of their blarney. The design brief resembles that of the L07D in many ways, including the copying of the Dual coreless motor with the odd raster. What's a "raster"? |
Dover, I think my response to you was too harsh. I apologize. Denon DP80 uses a 3-phase AC synchronous motor and also uses a quartz-referenced servo. Speed is monitored via a tapehead that "reads" the inner rim of the platter as it rotates. Knowing this, I was a bit confused when I read about The Beat turntable, which also uses a 3-phase AC synchronous motor that is claimed to self-correct by virtue of being so. (I think with The Beat there is a small amount of constant drag on the bearing, and the motor works against that.) Suffice to say that we need a motor expert here to straighten this out. I do think that the motor technology has not changed at all since the late 70s and that the designers of the tables you list used motors that they felt were best suited to the task. There are many high-dollar belt-drive turntables that use DC motors and no servo, as you know. |
Lewm, no worries. I think there is a lack of real info as DD manufacturers and vendors placed more focus in their advertising on the fact that it is DD. I know the SP10mk3 and Lo7D well and agree with your descriptions of the difference in sonic signature. The Denon DP100 looks very interesting. |
Travis has a DP100. But where is Travis (aka T_bone)? |
Lewm: "Lets keep in mind that what you quote from the Brinkmann website is a commercial" Yeah, I know. It's full of their own propaganda but I was too lazy to edit the pertinent parts so I just posted the entire section on drive system.... didn't mean to impose their bias on anyone. But it's still a good read for me and for the most part I agree with them about having a gentler servo system instead of a iron-fisted one and it resembles my own experience, granted there's always exception out there. I think this is a great thread as it allows people to focus on one of the most important and underrated aspect of a turntable: speed accuracy. It's been fun. P.S. Yeah, where is Travis or T_bone? I miss him. ______ |
I sent him a private email about 10 days ago but have had no response. He recently moved from Tokyo to Hong Kong, but he was communicating with me even during the packing and moving phase. He should be stabilized by now in HK.
It may be overly simplistic to think of a particular servo mechanism as "tight-fisted" vs "gentle". From speaking to Bill Thalmann, I gather that these circuits are quite complex, and the real differences in how the different ones operate may be accordingly complex as well. One is nevertheless free to choose a favorite based on listening. |
Lewm,
Are you in contact with Bill regarding the modifications on MK3? |
Albert, Will talk to Bill this week on that subject, I hope.
I guess there is not much juice left in this topic. Here's a tidbit. I noticed someone on Vinyl Asylum out up a URL for a new line of turntables, made by a company called "George Warren". It's really one belt-drive model that comes in several finishes. They use a Maxon motor, which is a high quality DC motor. Platter speed is monitored much like what Denon and Sony did 30 years ago, by a sensor at the platter. Then corrective information is fed back to the motor via the controller. No mention of quartz referencing, but the concept fits in with what we have been talking about, DD technology used to stabilize speed of a BD turntable. Like someone else pointed out, using a DC motor, which needs it. |
ΟΚ, but we have to decide about the correlation between motor's torque and platter's inertia, the amount of belt's grip or slippage, the speed, the distance and diameter of the pulley in correlation with the desired circumferance of contact around the platter, a magnetic, hydraulic or pneumatic preloaded break ... So many things to consider and we have to know precisely the correct values in order to cooperate and fulfill the purpose of correction at the time the platter asks for. As the motor commands the correction and the drug varies continuously, the transitional stages of the driveline must be zeroed, it seems that it is a critical point in every part that meets the criteria. A golden ratio for everything. |
No argument here. It does use fishing line for a drive belt, which would have little elasticity, at least. |
Albert, I know the engineer well who designed the mods for the SP10mk3.
Will be very interested to see your feedback. One point to consider, you may be better to get the bearing mod and review the impact before the electronics mods, or you will be unable to discern what has done what. You wont know whether the bearing or electronics mod is a positive or negative unless you do one step at a time. |
Dover,
Considering the shipping risk and time needed to get in line at Music Technology I don't have that luxury. Should I be worried about the electronics mods?
The oil and paper is the only change since my MK3 has already had every possible electronic part and adjustment performed long ago and I'm completely familiar with the sound of that.
I'm skipping the lead block mod on the bearing well. I'm nervous about the sound of lead plus I have my version of that as damping rod and block on my Panzerholz plinth.
That leaves only the oil and paper mods I think. Bill says they are harmless electrically and only provide damping. Do you have any listening experience with these mods? |
Hi Albert - no that sounds fine. The engineers modus operandi is that he overbuilds everything, which is great. I have heard the SP10 mk3 but unfortunately in a system, which although I have followed the evolution, I don't know what is doing what. That's why I'm interested in your feedback. Your bearing mod makes sense to me, wicking the energy away. There may be advantages to your solution in that if the energy is higher up the frequency scale a harder conduit ie the rod into the lead may be more effective than just sinking the bearing directly to a lead block. Unless we AB it we'll never now. The electronics should be fine if Bill is OK. Good luck. |
Thank you Dover.
Bill says the mods should make the transformer, motor and sense coils more reliable (longer life) so even if there is no appreciable performance upgrade it's still a worthwhile venture.
If it sounds better I'll be doing the victory dance. |
Hi Henry -
Have finally managed to try the Sutherland Timeline on the Final Audio TT ( heavy mass - platter 19kg, string drive ( single silk thread ), AC motor driven by oscillator preamp( reconstructed sine/cosine waves) and power amp.
Testing with and without the record playing I have to adjust for stylus drag.
Both the KAB and the Timeline show the stylus drag. The net movement of the laser with stylus drag is about 2mm on the wall per rotation.
If I correct for stylus drag with the KAB then recheck with the Timeline it is spot on.
With record playing the Timeline is spot on as per the KAB.
Conclusions are I can sleep at night, and the KAB, or at least my one, is as accurate as theTimeline.
|
Hi Dover,
Congratulations. Good to hear :-) |
"2 mm on the wall" is meaningless, unless you tell us the distance from spindle to wall surface, but in any case it sounds like the effect of stylus drag is very tiny, probably not audible and probably not worth worrying about. Unless I misremember some of the earlier posts, it sounds like the Final Audio, as you have equipped it, is among the best of the belt-drives in terms of resisting stylus drag. |
I picked up a Timeline as I was interested in how our Scully Lathe was doing while cutting lacquers.
The Scully uses a 1/8 horsepower Bodine AC synchronous motor, driving a transmission that then drives the platter via a drive shaft.
With the cutterhead cutting on the plate, the laser does not move- over the entire side you can't see the change even when you use a micrometer. Not bad for being built in the 1940s :) |
Atmasphere - think of all the "wear and tear" of all the drive train over 70 odd years. I think whilst we have gained in technology, we have probably lost ground in metallurgy, it's the age of junk metals ( PC & non toxic manufacturing processes required ). I still marvel at the lack of main bearing wear in the Final TT which is now over 30 years old.
Love to hear playback via a lathe and good old Mcintosh MI200's that I lusted after years ago.
Lewm - distance from wall is 400mm if you want to do the maths.
Henry - just to say thanks for the inspiration - your video challenge has really upped the game for die hard analogue folk. |
