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Turntable Speed

I own a Transrotor "Atlante" turntable. I purchased it about 2 years ago with all the available upgrades (platter and tonearm). This unit was $4500.00 without cartridge. It is a belt driven product with an outboard power supply which lowers the incoming voltage to the 18 volts the motor requires. My problem is turntable speed. My 'table speed is about 34 rpms. I could be more accurate if I had better measuring equipment. Anyway, that's about 2% over the correct speed and you can definitely tell the difference in sound quality between 34 and 33 1/3 rpm!. I was a little upset with this revelation and called my dealer about it. I also talked with the dealer's supplier. I received several reasons from these people as to why the speed was not accurate among which was that my power was "out of tolerance." But when all was said and done, none of the given reasons held water and I am now being advised that really there is nothing that can be done. That there is no defect in the equipment and if the speed problem continues to bother me, I should invest $1700.00 in a Transrotor speed controller. As I think over this, I wonder why platter speed is never mentioned or measured and reported on in the reviews for turntables in the major audio mags. (This could be because there isn't any problem, except for my 'table, or there is and no one is admitting it). To my way of thinking, platter speed has to be one of the primary functions of a turntable and that manufacturers would be making sure that their products' platter speeds were within strict specifications. At least better than 2% margin of error as is the case with my turntable.

My question is: Is platter speed error a given in this industry or is my 'table actually in need of repair? And, if platter speed is an industry problem, why are we as consumers paying thousands for equipment which actually doesn't work up to expectations?

frepec
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isanchez
276 posts
 
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
mosin
410 posts
 
"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.
frepec OP
17 posts
 
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?
mosin
410 posts
 
"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.
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isanchez
276 posts
 

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
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