All DC motors for TTs will have by necessity some form of feedback to control their speed. If a TT has a DC motor it will come with a dedicated speed controller. AC motors "synchronise" with the frequency as has been dicussed. That is not the only reason for a controller. In an ideal world all loads would be purely resistive and the AC waveform would not be distorted. With compact flouresce lights and AC motors and other reactive loads adding distortion, throw on top of that the typical PSs that draw most of their current at the AC peaks which tends to flatten the peaks, the AC waveform coming from the wall is hardly a pure sine wave. This will effect the sound of a AC driven TT. Even if your TT ran dead accurate, there is still a case for an outboard controller. |
The 20 years old classical book The Art of Electronics by Paul Horowitz and Winfield Hill fully described a high quality variable sinusoidal power supply that could be easily built with a full cost of less than 50 usd in parts. I can not understand how any one can think of connecting a synchronous turntable motor to a dirty mains plug! |
With all these aspects effecting turntable's speed and no practical universal way to correct it, I say every hi-end turntable SHOULD have a speed controler so the user can at least have their table run at the correct speed for a few hours listening duration.
Experienced all this, I would never buy another hi-end table if it does not offer a way to fine tune speed. Save me a lot of headache. |
I keep track of the frequency and voltage coming from the wall outlet, and very few times I get to see 120v @ 60Hz. This varies from different utility companies though.
Best,
iSanchez
|
"The power generated in the US is supposed to be 60 Hz by specification."
That can be out of spec in certain places inside this country from time to time. |
The power generated in the US is supposed to be 60 Hz by specification. Granted there is a lot of variables to this rule. However, I have been told from several sources that turntable platter speed motors are built to run off of this specification. Therefore, if that is true, then at 60 hz, theoretically speaking, the platter speed should be right on at 33 1/3 rpms. That isn't the case here, however. So I guess what I am getting at is: Isn't it possible that the motor which came with my turntable is out of spec from the get go since at 60 hz it runs at approx 34 rpms? |
"A $500 Technics SL1200 mkII will keep speed as accurately as a belt drive turntable costing thousands of dollars."
Maybe it will be more accurate than many turntables out there, but it isn't the end all answer to proper speed control. The reason is because it creates a sort of analog jitter in the process of maintaining the desired speed. So, if you think about it, it isn't accurate at all because both detail and dynamics suffer. A better solution is to generate perfectly tailored power to a superior motor. That can be done a variety of ways with any drive system, but you don't really fix power after the fact. A correct fix is made before it is created. |
In many instances, the power that comes from the electrical outlet is unstable. This instability tends to affect the speed of many turntable motors. So it is quite possible that electrical power is one of the main causes for your turntable to run faster.
As mentioned in previous posts, there are other variables that also affect the speed of a turntable. The leveling of the bearing will affect the speed of a turntable in many cases. In this scenario, the weight of the platter plays a more active role. In my particular case, I set a calibrated PRO 3600 digital protractor on top of an Avid 45 adapter to level the platter bearing. The PRO 3600 has accuracy of 1/100 degrees. When my platter is perfectly leveled, speed accuracy of 33 1/3 is dead on. The platter will play at this speed for as long as the turntable is absolutely leveled.
If a turntable uses a bearing well with oil, as the oil dries out, one should expect the speed to slow down with it. Also, Many oils will change viscosity as their temperature changes. Since the bearing friction will increase the temperature to some extent, one can expect the turntable to go through some speed changes.
The Synchro is a power re-generator, so it will output whatever frequency you set it up to, regardless of the input frequency from the electrical outlet. What you're experiencing with the Synchro is normal.
Best,
iSanchez
|
Yesterday, I borrowed a Clearaudio Synchro and installed it in my system. Using the Clearaudio readout in hertz mode, to get my 'table to run at 33 1/3 rpm, the hertz indicated on the screen is 57.2. Setting the Clearaudio to 60 Hz makes my 'table run too fast, about 34 rpms which is the speed I was getting before I had the speed controller in the system (see original post). All along everyone I talk to about my speed problem has been telling me that my electrical power is the cause. I have one question: To me, these results do not appear the substantiate that claim. Am I all wrong here? |
I can't help weighing in here that speed consistency was solved economically over 30 years ago with the quartz-regulated direct drive turntables. A $500 Technics SL1200 mkII will keep speed as accurately as a belt drive turntable costing thousands of dollars. There are currently armboards that enable you to upgrade the Technics to a tonearm from SME or any Rega-compatible tonearm, including the entire line from Origin Live.
The one remaining problem is isolating the plinth from the room, and draining in-base vibrations out. I wish the audiophile industry had spent more time and research lowering the noise level of direct drive instead of starting over with garden-variety AC motors and a rubber band. The best of them have wound up with a Rube Goldbergian complexity of mechanisms to keep the bearing on-center (since a belt pulls it sideways) and on-speed, or a bearing-grindingly high mass-loaded platter.
I'm not dissing any turntables or anyone's gear; I just think that if the British cottage turntable industry of the '70s had embraced the Japanese quartz-regulated direct drive mechanism, they could have turned their attention to NHV control and tonearms, because speed accuracy with them is not a problem. |
To VPI's credit, they do give you the ability to (slightly) adjust speed even without a motor controller-the motor pulley on their decks is 'stepped' from a larger to smaller diameter, thus allowing you to move the belt to the pulley diameter that corresponds to attaining the correct platter speed. Credit where due, etc. |
Frepec,
I totally agree with you. It seems that we, as audio equipment consumers, have grown complacent with the idea that it is not so relevant for analogue playback to have speed control with a turntable. The fact that there are so many turntables in the market without any sort of speed control is really puzzling to me. This is one of the main reasons why I sold my previous turntable and got the Acoustic Signature Mambo. I think most of the AS turntables come with the same power supply/motor controller.
There seems to be a new generation of turntables that take the notion of speed control a step further. There is the new Clearaudio Innovation turntable that reads the speed of the platter via a sensor and corrects it accordingly. Another turntable with its own speed correction technology is the Grand Prix Audio Monaco. To the best of my knowledge, both of these turntables are in the 20K neighborhood. It think it is a matter of time before these technologies drip down to more affordable turntables.
I think in some cases a turntable may not come with a motor controller in order to trim down the cost, but the manufacturer should warn the consumer that the motor controller is a necessity for the serious listener, which is the target consumer for the high-end turntables.
Best,
iSanchez
|
Dan-ed-
You're right of course-I should have emphasized the theoretical nature of that thought process (-:
Still, with the correct circuitry designed for a specific motor and application, you'd think they could get it right.
To take it a little further, those same DC- motored decks should, if anything, rotate *slower* with the effects of age, wear, dirt, belt slippage, etc., not, as is the case with the OP, faster. Which perhaps gives even more credence to the 'faster by design' theory, especially if the OP's deck is maintaining an always and constant (too high) speed. All theoretical, of course.
Maybe someone who knows a lot more than I about designing run circuitry for DC motors will join in-where's Mark Kelly or Chris Brady when you need 'em? I'm guessing, though, that a manufacturer could pretty easily add speed adjustment to their basic DC circuitry for Very Little Money-that is, if they didn't have an optional Motor Control ready to sell you. |
I'm beginning to get the idea, now. I did some checking and it does seem to be that most high end turntable manufacturers also have speed controllers as part of their product line. I think that johnbrown has it right. AC motors are not reliably accurate and thus require speed controllers to get them dialed in. It does seem like a marketing ploy. Let the buyer discover he has a speed problem and then sell him a speed controller. It's beginning to become evident to me that speed problems are the nature of the business and that there is most likely nothing wrong with my equipment. I just think that with all the technological advances that have been made in the home audio field, that making an accurate platter drive motor should not be that big a deal. Not being an electrical engineer, I could be way off base with that statement. |
A DC motor, though, should be able to run at the exact speed required every time it's turned on-so with the correct pulley and platter size, and belt thickness, 33 1/3 rpm should be easily maintained, minus the effects of wear, dirt, belt slippage, etc. If that were the case we'd all be using DC motors and none of us would be concerned with speed. ;-) Unfortunately, it doesn't seem to work that way. |
AC synchronous motors are dependent on the line frequency for correct speed (such as the aforementioned Scout) so I imagine that VPI offering the SDS as an aftermarket accessory (though in reality it's a necessity, since frequency can vary, thus changing the motor speed) is simply a marketing decision to keep initial tt pricing down.
A DC motor, though, should be able to run at the exact speed required every time it's turned on-so with the correct pulley and platter size, and belt thickness, 33 1/3 rpm should be easily maintained, minus the effects of wear, dirt, belt slippage, etc.
Which leads to the possibility that some manufacturers purposely build their tt's to run slightly fast, in order to give a false sense of excitement, and PRaT, to the sound.
This is just a guess-AFAIK, no proof exists-though Rega has long been rumored to employ this technique. |
"Keeping it accurate is an ongoing process. "
There are, however, several steps that can be taken to ameliorate having to tinker continuously. Make sure the belt and belt path are scrupulously clean; be certain the table's bearing is clean and properly lubricated; be certain the table is level (this is a must); try to maintain a constant ambient temperature in your listening space - believe it or not, the viscosity of both the bearing and motor lubrication change considerably over a relatively small temperature range. I'm sure there are others I am neglecting.... Good listening,
-Richard |
I also don't see how any turntable could be accurate without a speed controller. I check my speed every day and often have to make minor adjustments with the SDS to get right on 33 1/3. I'm sure a multitude of factors work together to change speed slightly from day to day. Keeping it accurate is an ongoing process. |
The Origin Live controller is designed for DC motors and is, AFAIK, the only commercial aftermarket controller solely for DC motors.
-Richard |
If the Transrotor motor is indeed a DC type, as you suggest above, I don't think that a typical after-market motor controller (e.g., the Walker Audio PMC or the VPI SDS) will help your problem. The ones I know about are made to control AC synchonous motors, where the frequency of the AC input voltage will affect motor speed. You should check this out with a Transrotor representative. However, I do believe Transrotor make an optional outboard DC supply which might solve your problem. By all means, don't spend your money until you are sure you are buying a cure for your problem. |
I think you are correct and I would agree that a speed controller is an indispensable part of a high performance analog setup.
But I still think that 33 1/3, if not perfectly stable, should be achievable without a speed controller. If I couldn't get 33 1/3, even briefly, without my speed controller, I would take the table back to the dealer and let them prove to me that the table lives up to it's high-end reputation. Because, to me, this is job #1 for a turntable.
Cheers.
Tom |
Tom:
Thanks for responding. My 'table is in my house so temperature is not an issue, but since the bearing is oil lubricated, I do let it "warm up" by letting it run for a few minutes before I play anything. All speed measurements were taken under warmed up conditions. Also, I am aware that changing the distance between the motor and the plinth will effect platter speed. I have played with this on several occasions. In order to get the platter speed close to 33 1/3, my motor has to be so close to the plinth that the belt sags and speed consistency suffers. I even bought two new belts and that made no difference.
When you say "If you cannot get 33 1/3 from a table without a speed controller, something is wrong," I agree totally. But from what I am hearing and from over a year of on and off investigating, that doesn't appear to be the reality. I seems that most turntable owners are using some kind of speed controller just to get correct platter speed. This exercise on Audiogon,is just the latest in a series of investigations I have made into this subject. I could be totally off base here, but I am becoming more and more convinced that accurate platter speed is not a given when one buys a turntable, unless it comes equipped with a speed controller, as is the case with more expensive 'tables. A review of the replies in this thread seems to substantiate this conclusion. |
Hello,
I think the speed of the turntable is a product of correct setup, and maybe manufactures have no choice but to claim that their tables operate correctly at 33 1/3 rpm under proper operating conditions when properly set up.
To explain further, I own a VPI Super Scoutmaster. My equipment rack is in a separate room (a 3-season room, if any of you know that term) from my listening room. The 3-season room is so called because it's small and has windows on 3 of the 4 sides. It also has french doors to close it off from the next room.
What does all this mean? In winter (the 4th season) in Chicago, this room gets VERY cold. If the french doors are kept closed, when I get home tonight the temperature in that room will be about 40. (It's about 20 outside right now).
If I go home and immediately turn on my turntable, my speed will probably be 28 rpm. I can use the SDS to get the speed back to 33 1/3, but as the room and the motor warms up, the speed will work its way back up. So I really have to let the room warm up first, or I'll be re-adjusting the speed after every album side.
Is this VPI's fault? Of course not. When the equipment temperature stabilizes the speed is dead solid 33 1/3.
Also, ignoring the temperature factor, the distance from the motor assembly to the plinth determines the belt tension. You can adjust the speed by moving the motor closer to or farther away from the plinth. Belt wear becomes yet another factor. The power supply to the TT motor is yet another variable.
So, I think I can summarize by saying that you SHOULD be able to get 33 1/3 rpm on a table if set up properly, paying attention to all these variables. A speed controller, in my opinion, should not be necessary just to ACHIEVE 33 1/3. It should provide a much more STABLE 33 1/3 compared to the wall power. It is also a very handy item to compensate for all those variables and irregularites, and my VPI SDS was worth every penny. If you cannot get 33 1/3 from a table without a speed controller, something is wrong. The speed controller just makes it a lot easier.
Cheers.
Tom
Addendum: With the VPI rim drive, the SDS frequency needs to be lowered considerably below 60hz. I once remarked to VPI that they should make it clear in their documentation or on their website that the SDS is NOT optional for rim drive users. |
Thanks to all who have taken the time to respond to my questions. I would like to clarify something which may not have been apparent from my post. That is, I like the Atlante. I like the sound I get and I like the "fit 'n finish" of the product and I like the way it looks. In no way was I implying that Transrotor turntables were less than quality products and I really have no desire to replace mine. That said, I am getting the idea that platter speed is a problem for owners of other brands as well and like Jaytea, have lots more expensive 'tables than I do. It also appears that an outboard speed controller is my only option at this point. That's OK, I just wanted to know for sure.
It still is and probably will remain a mystery to me why we as consumers are obviously not getting all that we are paying for, and yet, we are still willing to pay for products that require us to invest in more outboard products to get the original product to work correctly.
Thanks again for replies. One more reply. To Thsalmon: I did use a strobe with a stylus groove. |
You should measure the speed using a strobe that allows you to do the measurement with your stylus in the groove of a record. I'd bet you'll be very close to 33 1/3 when the drag of the stylus is taken into account. |
I totally agree with 0thd. I owned a very highly regarded Avid Acutus (Stereophile Class A) before, and despite the fact that I really liked its sound, I decided to sell it (well..traded it in towards my SME 20/2) just because I could not stand the fact that a $11,000 hi-end turntable lacked a speed controller. Before buying it, i assumed that the speed would be accurate and rock solid for this expensive turntable but it proved me wrong.
I think you should either sell it and get something with a speed controller, or buy a controller for it. Otherwise it will drive you mad! |
For the kind of money high end turntables command the speed should be dead on, no matter what the incoming voltage, within reason. Or it should be adjustable.
Speed is just as important as stability of speed.
I like to play guitar to a lot of music and if the speed is not accurate the guitar is out of tune with the music and that is frustrating.
I've got a Transrotor Fat Bob S. I was fortunate because it came with the a speed controller that included fine adjustment for 33 1/3 and 45.
I'm not sure I agree that any cheap controller will do the job though.
If it's not rock solid that will drive you just as crazy. |
I believe that this is also a problem more specific to Transrotor. I have a Sirius that also runs a bit fast and in researching the issue found a lot of Transrotor owners had similar problems. Since the unit is not in use, I haven't pursued a solution. I suspect that there are reasonably priced 3rd party speed controllers out there and I'll pursue one if I put the Sirius back to work.
Good Luck
Marty |
Frepec,
Your speed issues are not uncommon with turntables without a speed controller. I found myself in your same situation when I had a Wilson Benesch turntable and ended up buying a speed controller for it. I went for the Clearaudio Synchro since it also cleans the power fed to the motor, besides controlling the speed.
It is possible that the speed is faster because of voltage/frequency you're getting from the wall outlet.
I totally agree with you in that all turntables should come with some sort of speed controller if you spent more some serious cash on it, since accurate speed cannot be guaranteed by the manufacturer.
Pro-Ject makes some affordable speed controllers, if you're interested in not spending much. I think the cheapest speed controller will be better than no controller at all. It's puzzling to me that Pro-Ject can come up with a very affordable speed controller, but the higher-end companies can't.
All the best,
iSanchez
|
