I don’t know if one can. Win Tinson’s design did not have any rumble that I could detect for being an idler, nor Thomas Schick’s design. Modern lenco and Thorens fans replace the idler wheels with those whose “tire” is precision ground. To what extent any rumble or vibration still gets transmitted or if that is even noticeable given stylus noise, is beyond my knowledge.
Turntable Theory on the Optimal Turntable
- Thread starter MrC.
- Start date
You can't or I should say One can't. And please add direct drives to the list. With those drive types one's listening to motor noise and rumble. Sorry I jumped in.
You're describing exactly Kondo Ginga. I listened 3 different Gingas over time. That's a very nice sounding turntable. I don't agree with you on rim/idler/direct drive.
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What music and records do you use to evaluate analog? Based on your signature your system is MBL 111 with Atmasphere amps? The OTL drive the MBL with the auto formers?
I don’t know if one can. Win Tinson’s design did not have any rumble that I could detect for being an idler, nor Thomas Schick’s design. Modern lenco and Thorens fans replace the idler wheels with those whose “tire” is precision ground. To what extent any rumble or vibration still gets transmitted or if that is even noticeable given stylus noiseis beyond my knowledge.
Yes, the 111s work surprisingly well with the autoformers in the chain. My amps see a minimum of 11 ohms as a result and work beautifully. I use records that have a lot of dynamics. I like Alejandro Jodorovsky's soundtrack from the Holy Mountain. Slade Alive is a good album to evaluate spacial clues. I listen to rock albums that I am familiar with like Yes Fragile and vocals from Yves Montand and Bing Crosby.
Idler drive is an interesting beast, a friend of mine once brought over a modified Lenco with slate plinth, nothing exotic! While the background noise cannot be compared to highend direct and belt / string drive, the leading edge and explosive transient seemed to bettered even the high torque Technics SP10 MK3! I don’t know why, but when I auditioned that Lenco for the first time, it just startled me a bit when those explosive passages hit!
One interesting point is while the older Japanese direct drive used high torque motors, some modern direct drive, such as Brinkmann, prefer using lower torque motors!
One of my engineer friends plan on experimenting using a Technics SP10 MK2 motor for belt / string drive. That would probably be interesting!
One interesting point is while the older Japanese direct drive used high torque motors, some modern direct drive, such as Brinkmann, prefer using lower torque motors!
One of my engineer friends plan on experimenting using a Technics SP10 MK2 motor for belt / string drive. That would probably be interesting!
And Ked is out !
I suspected the music taste because of the preference for direct drive and not liking belts
Pt. 7 - The Drive cont.
An interesting question is whether to run a turntable on AC vs DC and to use a synchronous as opposed to asynchronous motor. A synchronous motor will run at a fixed speed based on the frequency of the AC current coming in with voltage variations affecting torque but not speed. In an asynchronous motor voltage will effect speed.
If a synchronous motor encounters friction its current draw to maintain speed will be instantaneous. It is, therefore, self correcting and needs no computer to measure and correct speed while the motor is in use. So long as the frequency is constant so will the speed be constant, at least in theory. In actuality the friction will cause a lag causing the motor to draw more current to catch up to the frequency. The speed at which this occurs is based on the maximum torque of the motor the poles and the inertia of the system including the flywheel and the windings. The oscillation near the frequency speed based on a changing load is called “hunting”.
An asynchronous motor will not be bound by the AC frequency and can be varied with input voltage. The speed can easily be changed without the need for different pulleys or differently sized idler wheels. If a DJ wants to match speed between songs it can easily be done with a knob on an asynchronous motor but brakes of felt or magnets must be employed to trim the speed of a synchronous motor all of which will load the motor and cause heating. Asynchronous motors are cheaper, generally smaller and do not require custom machining of a belt wheel or idler wheel to reach a specific speed. If you want two or even three speeds of your turntable you will require two or three wheels to match the speed you require, as the synchronous motor will only spin at one speed for a given frequency. Because of the windings needed and additional windings to start the motor to get to speed, synchronous motors are heavy, more likely to give off vibrations especially when giving off more torque due to instantaneous power demands.
As they are heavy, expensive, are more likely to vibrate and only run at one speed, why, you may ask, would anyone use a synchronous motor? The answer is simplicity as once the motor and pulley or idler are properly designed the speed will be consistent despite momentary voltage changes or lags. If one were to build an outside frequency generator you could control the speed electronically rather than needing a different set of wheels. Because the torque reaction to load is instantaneous the explosive transients that are recognized from a properly implemented synchronous motor is hard to match. Implement a system where a motor is intentionally run too fast and braked down to speed by a constant load and you also reduce hunting as the entire system will be less reactive to the small stylus load while it deals with a heavy eddy brake, felt brake and/or grease bearing. A constant application of torque to the entire system will make it less sensitive to stylus drag the way your windshield insensitive to mosquito drag at highway speeds.
An asynchronous motor can be run on a dc power supply that is filtered and voltage regulated to lock in its speed. A brushless motor if low vibration can be implemented with a low mass and easy mounting. What is best is generally a question of implementation rather than dogma. I am only aware that older idler types like Thorens, EMT and Garrard used synchronous motors. More modern belt drives like Micro Seiki used asynchronous motors. I’m not sure if any direct drives use a synchronous motor with a frequency generator, or simply depend on a voltage controller with measuring servo on the platter and a feedback loop. Information by those who know the drive systems of different turntables would be welcome.
An interesting question is whether to run a turntable on AC vs DC and to use a synchronous as opposed to asynchronous motor. A synchronous motor will run at a fixed speed based on the frequency of the AC current coming in with voltage variations affecting torque but not speed. In an asynchronous motor voltage will effect speed.
If a synchronous motor encounters friction its current draw to maintain speed will be instantaneous. It is, therefore, self correcting and needs no computer to measure and correct speed while the motor is in use. So long as the frequency is constant so will the speed be constant, at least in theory. In actuality the friction will cause a lag causing the motor to draw more current to catch up to the frequency. The speed at which this occurs is based on the maximum torque of the motor the poles and the inertia of the system including the flywheel and the windings. The oscillation near the frequency speed based on a changing load is called “hunting”.
An asynchronous motor will not be bound by the AC frequency and can be varied with input voltage. The speed can easily be changed without the need for different pulleys or differently sized idler wheels. If a DJ wants to match speed between songs it can easily be done with a knob on an asynchronous motor but brakes of felt or magnets must be employed to trim the speed of a synchronous motor all of which will load the motor and cause heating. Asynchronous motors are cheaper, generally smaller and do not require custom machining of a belt wheel or idler wheel to reach a specific speed. If you want two or even three speeds of your turntable you will require two or three wheels to match the speed you require, as the synchronous motor will only spin at one speed for a given frequency. Because of the windings needed and additional windings to start the motor to get to speed, synchronous motors are heavy, more likely to give off vibrations especially when giving off more torque due to instantaneous power demands.
As they are heavy, expensive, are more likely to vibrate and only run at one speed, why, you may ask, would anyone use a synchronous motor? The answer is simplicity as once the motor and pulley or idler are properly designed the speed will be consistent despite momentary voltage changes or lags. If one were to build an outside frequency generator you could control the speed electronically rather than needing a different set of wheels. Because the torque reaction to load is instantaneous the explosive transients that are recognized from a properly implemented synchronous motor is hard to match. Implement a system where a motor is intentionally run too fast and braked down to speed by a constant load and you also reduce hunting as the entire system will be less reactive to the small stylus load while it deals with a heavy eddy brake, felt brake and/or grease bearing. A constant application of torque to the entire system will make it less sensitive to stylus drag the way your windshield insensitive to mosquito drag at highway speeds.
An asynchronous motor can be run on a dc power supply that is filtered and voltage regulated to lock in its speed. A brushless motor if low vibration can be implemented with a low mass and easy mounting. What is best is generally a question of implementation rather than dogma. I am only aware that older idler types like Thorens, EMT and Garrard used synchronous motors. More modern belt drives like Micro Seiki used asynchronous motors. I’m not sure if any direct drives use a synchronous motor with a frequency generator, or simply depend on a voltage controller with measuring servo on the platter and a feedback loop. Information by those who know the drive systems of different turntables would be welcome.
I would love to hear his experience of using a SP-10 motor for belt/string drive. If you post about it maybe suggest he try belts of different elasticity, ie, in addition to a rubber belt, trying a silk and or Kevlar belt which, if slightly tensioned, won’t have any mor stretch in them. Kuzma uses a “rigid” plastic belt, whatever that means. The Naia by Rega uses a triple belt coupling. Please let us know his experiences and your perceptions if you get to listen in.
If the plinth, platter and arm are rigidly coupled together, vibration in common cannot be transduced by the pickup; the arm is moving in the same plane as the platter so no motion is detected.
This is why its so important to avoid arm pods or armboards that are separate or use materials (like damping materials) dissimilar to that of the plinth. For example if the arm is mounted to a damped armboard, its stillness will now allow vibration in the platter to be transduced. If the plinth isn't rigid (and damped) then airborne vibration can cause the system to exhibit coloration.
So you can see that a very stiff and dead plinth is essential, as well as a damped platter. The plinth couples the platter to the base of the arm; any decoupling will allow coloration.
I understand this in principle Ralph. I’m having a little bit of difficulty understanding how a platter can be rigidly coupled to the plinth when it is moving. Doesn’t a thrust pad or any kind of bearing interrupt the rigid connection?
The other aspect that confuses me is that even if everything is made out of the same material, the platter and arm board and plinth are different dimensions so they should resonate at different frequencies.
Resonance is different than speed of vibration propagation through a material. Two different lengths of aluminum or steel will resonate at a different frequency, which is how a xylophone is made. Each steel bar, however, will transmit a vibration from one end to the other at the same speed. Coupling different materials that have different propagation speeds can cause interference in the new laminate’s ability to vibrate. This is damping. Couple two pieces of the same material and you may move the resonance point but won’t stop the vibration. With all things connected to the same plinth the forces or vibrations making the plinth move side to side will also move the bearing and arm board attached to it to move side to side at the same speed, meaning that from the bearing’s or arm board’s point of view, the plinth is not moving at all.
No. In order for the platter to be rigidly coupled to the plinth and thus the base of the arm, it must have a well-machined bearing which exhibits no runout, endfloat or the like, IOW no slop.
That is why I am careful to use the word 'rigid'. The more rigid the coupling can be from the platter bearing to the arm, the better. It must also be 'dead' which is to say 'damped'. Typically the more massive the harder it is to get the whole thing moving. IOW, do your best to eliminate resonance!
We made a turntable we called the model 208, since it started life as a modified Empire 208. We designed a new plinth more the machine but used its excellent bearing and platter, the latter of which we machined and damped. The original Empire plinth was made of cast aluminum, which got to about 1/4" thick in places except around the edge where it was a little thicker. We designed a plinth that looked just like it when assembled but was machined out of solid aluminum, with the least amount of machining to accommodate the turntable parts. The resulting machine was quite dead; you could thwock the platter while playing and not hear it in the speaker nor hear a speed variation.
So it had fairly heavy, rigid plinth that did its job exceptionally well. But to really top things off I always felt it needed an additional part made of steel that was a machined ring about 1" thick with a machined bar acting as a beam between the base of the bearing (which the ring surrounded) to the base of the arm. Being of dissimilar materials when bolted to the plinth the result would be increased coupling between the two locations as well as additional damping, since the coupling of the two materials would rob energy from each other.
But the Technics SL1200G came along and feeling that was an excellent example of what I've been talking about here, we discontinued the 208 instead; the steel brace was never built.
Both the 208 and the Technics SL1200G benefit from a robust drive which is essential for any good turntable. If you look at the vintage machines that have acquired a following, nearly all of them have a fairly robust drive: Garrard 301, Empire machines, Lenco, Thorens TD124, Technics SP10s.
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