AC, DC Motor Noise

[analog2analog]

Hi,

I wish to know more about motor noise from AC or DC motors. Previously I have used an SME 20/2 and its motor was very quiet . I visited a friend to check out his AirForce III and although the air bearing was silent the motor was not as silent as SME 20/2.

I want to know the level of normal motor noise from different turntables. If you put you ear to the your turntable's motor, is it dead silent or do you hear the some noise?

Thanks

 

[Lagonda]

Savvas, did you start a new profile ?

 

[Lagonda]

Some of the best sounding motors i have heard are the old Pabst capstan AC motors. They where made to run inside a closed in R2R environment and are a little noisy when used more freely . Some Hurst AC motors are very silent, but sound like shit. Most motors have a little bearing noise if you listen very close to them. Modern Pabst DC motors have a little bearing noise too, and they are widely used for TT's.

 

[Vienna]

by nature BLDC and DC motors are quieter and smoother than AC synchronous ones.
SME is using BLDC motor and Techdas AF3 AC synchronous.
Both are audible when you will place your ear next to them, SME is quieter but with less speed accuracy and stability compared to the AFIII.

Brinkmann Sinus motor is totally silent even with the ear placed very close to the motor.

By far the most noisy motor I have ever tried was the Dereneville (with Papst BLDC ) followed by the VPI (with Hurst AC synchronous motor)

 

[analog2analog]

Savvas, did you start a new profile ?

I suspect you are confusing me with some other member; I just joined and this is my first questions.

 

[analog2analog]

by nature BLDC and DC motors are quieter and smoother than AC synchronous ones.
SME is using BLDC motor and Techdas AF3 AC synchronous.
Both are audible when you will place your ear next to them, SME is quieter but with less speed accuracy and stability compared to the AFIII.

Brinkmann Sinus motor is totally silent even with the ear placed very close to the motor.

By far the most noisy motor I have ever tried was the Dereneville (with Papst BLDC ) followed by the VPI (with Hurst AC synchronous motor)

Thanks for post. Am I correct to assume that the direct drive motor technology is different than the motors used on belt driven turntables. I have seen a Technics turntable and it was extremely silent.

 

[analog2analog]

Some of the best sounding motors i have heard are the old Pabst capstan AC motors. They where made to run inside a closed in R2R environment and are a little noisy when used more freely . Some Hurst AC motors are very silent, but sound like shit. Most motors have a little bearing noise if you listen very close to them. Modern Pabst DC motors have a little bearing noise too, and they are widely used for TT's.

From the TechDas Airforce Zero news somewhere I read that its Pabst motor has air bearing. Shouldn't the air bearing motors then completely silent?

 

[Lagonda]

I suspect you are confusing me with some other member; I just joined and this is my first questions.

Just a inside joke, sorry ! Welcome !

 

[Lagonda]

From the TechDas Airforce Zero news somewhere I read that its Pabst motor has air bearing. Shouldn't the air bearing motors then completely silent?

I think the TechDas Zero uses a air bearing under both platter and motor. The motor is a excellent old capstan Pabst motor that ddk also uses on his AS 2000 TT, my favorite TT I think the way TechDas uses it, is with a large flywheel that is coupled to the motor casing with a air- bearing, the motor itself still has 2 sintered bronze bearings and a steel ball in the bottom, it also has a propeller type ventilation system as part of the outside rotor, the Germans call it a " ausenlauffer" motor, a "outsiderunner" the bearings and the ventilation system make a little wooshing sound, but these motors are very durable even in closed circumstances with bad ventilation. I am listening to one running my TT right now, it was made in 1969 and spent many decades inside a R2R but still runs perfectly !

 

[mtemur]

By far the most noisy motor I have ever tried was the Dereneville (with Papst BLDC ) followed by the VPI (with Hurst AC synchronous motor)

I have seen both a dead silent sme 30/12 and just a little bit noisy one.
all the airforce turntables I have seen were quiet enough.
by far the noisiest turntables that I have ever come across are Kronos models.
on the other hand I have seen a 35 year old papst ac motor on a Transrotor running almost silent.

 

[Yeti]

I run an Artemis SA-1 which has a brushed DC motor with sintered, impregnated bearings and it was audible from close up since I got the deck (ex demo) until the speed stability went haywire a few month ago. By then the motor noise had got louder. I managed to source some suitable oil and ran about 100?l down the shaft into the motor bearing where it’s stayed, the motor is now hardly audible and the speed is once again constant. There’s never been a hint of the motor noise breaking through to the cartridge via the drive tape as judged from a blank groove.

 

[analog2analog]

Thank you all for participation.
Turntables' prices are touching the sky and even then I am amazed that the motors for belt driven platters are not as quiet as the direct drive mechanisms are. I wonder if someone has tried to use a Technics direct drive mechanism to belt drive a platter to get the best of the both world.

 

[tima]

I want to know the level of normal motor noise from different turntables. If you put you ear to the your turntable's motor, is it dead silent or do you hear the some noise

Use a stethoscope. I suspect there are no dead silent turntables, but some are definately quieter than others. You may also be hearing plinth resonance. I don't know how to listen for platter resonance with the 'table spinning. ;->

 

[YNWaN]

There are quiet AC Synchronous and noisy ones, the same with DC. In addition, how they are implemented makes a difference. In my own deck I use an AC synchronous and no noise at all can be heard even with your head close to the motor. Similarly, if a stethoscope is used on the chassis, armboard or platter there is absolutely no audible motor (or bearing) noise. It’s very difficult to draw conclusions about individual elements of a turntable as one part has so much impact on another.

 

[Addicted to hifi]

Slight noise should not be any problem.

 

[TLi]

Every bearing makes a sound. Basically it is two surfaces rubbing each other which causes vibration and sound.

So all motors are noisy, even for Air Force Zero which has air bearing for everything, the motor still has solid bearing. What TechDAS does is to buffer the motor with a flywheel on air bearing before driving the platter. It is like a small Air Force mini turntable on the motor side and connect it to the main platter with a belt. What’s why the tension of any belt drive turntable should be as light as possible. Tighter belt tends to be more effective in transmitting the motor sound to the platter.

One may think the slight noise doesn’t matter but everything matters in analog reproduction. Everything adds up to the final sound.

 

[Lagonda]

Every bearing makes a sound. Basically it is two surfaces rubbing each other which causes vibration and sound.

So all motors are noisy, even for Air Force Zero which has air bearing for everything, the motor still has solid bearing. What TechDAS does is to buffer the motor with a flywheel on air bearing before driving the platter. It is like a small Air Force mini turntable on the motor side and connect it to the main platter with a belt. What’s why the tension of any belt drive turntable should be as light as possible. Tighter belt tends to be more effective in transmitting the motor sound to the platter.

One may think the slight noise doesn’t matter but everything matters in analog reproduction. Everything adds up to the final sound.

Yes it looks like they have replaced the bottom ball-bearing with a air -bearing, supporting the extra weight added as a flywheel on the bottom of the outside rotor. Smart ! I will try something like that on one of my 24 pole Studer motors that already have a large flywheel added as outside rotors.

 

[YNWaN]

Actually, I have an industrial air bearing where the attached motor shares the main air bearing and doesn’t have any metal to metal (or synthetic liner) contact. I’m not sure what this bearing was originally manufactured for - possibly the production of hard discs for computer drives. Unfortunately I’ve never actually had it running as it requires an air supply (that’s not the problem) and some complex electronics to control it - which is the problem.