• Item: Turntable  
  • Type: Belt driven self adjustable  
  • Posted: 31 August 2016  
  • Builder: Hornsolutions  
  • Country: Germany  
  • Comments: 2  

Hornsolutions Turntable

Motor:
To get a constant speed from the driving motor, we use a quartz- driven PLL. To explain this: A quartz gives a stable and constant frequency, accurate to 0,0001%. In the motor we have a hall-generator, which gives 200 pulses per revolution. Now the frequency of the quartz is divided, till it´s also 200 impulses for the given time of one revolution. Then both pulses are compared and the speed of the motor is regulated, so there is no difference. Execution of such a PLL not easy, because the reaction time is critical, so there is no cough or low frequency speed variation.

We use a very slow turning multi pole motor with sintered bearings. The motor has very high torque. To drive the platter, we use a belt or Kevlar-string. There is a small sonic difference between belt drive and string drive. The customer can try, which signature is preferred. We recommend the string-drive.

In comparison to other manufacturers, we have chosen a much bigger diameter of the pulley. While normal pulleys have a diameter of 1 cm to 3 cm we have a pulley of 16cm diameter.
This big pulley has some advantages:
Platter speeds are 33 1/3 or 45 revolutions per minute. This equals a frequency of: 0,55 Hz (33 1/3rpm) 0r 0,75 Hz (45rpm). In case the pulley has a diameter of 1,5 cm, like commonly used, so we got a frequency of the pulley of 11,1 Hz (33 1/3rpm) or 15 Hz (45rpm) Whatever rotates makes some noise and also the related harmonics of the fundamental frequency. For 33 1/3 platter speed, the 2nd to 10th harmonic are in the area of 22,2 Hz to 111 Hz, which is well in the audible area.
Our Pulley has a diameter of 16cm. By this diameter results a frequency of the pulley of 1,1 Hz (33 1/3rpm) or 1,5 Hz (45rpm) . All the harmonics up to the 10th are well below the audible area. 
Our Pulley has a weight of 1,6 kg. So the pulley also operates in the way of a fly-wheel. By the inertia, the drive of the platter has much less variations, than one with a smaller pulley.
The bigger diameter of our pulley also has another advantage: A standard pulley of 1,5 cm diameter only has a contact area between pulley and belt of about 1,6 cm, while with our pulley the contact area is 16,75 cm. This much bigger area of contact means much less slippage of the belt equals higher torque. We accomplish torque-values of an idler drive turntable, without the disadvantages of an idler drive (noise). By having so much contact area and torque, we don´t need a high tension of the driving belt, which results in less disturbances from the motor transmitted and also less horizontal force on the bearing.
All parts of the pulley and motor housing are optimized for minimum resonance and high internal damping. The motor is fed by an external DC power supply. 

Platter bearing:
We use an air bearing, normally used in highest precision laser applications.
The concentricity is 0.1 micron. The camp takes both horizontally and vertically. Thus, no running noise by the rotational movement can be expected. Also the air bearing is maintenance free and has no wear.
The air bearing is designed to hold a load of 160 kg. a force horizontally to the axis of 25 kg is allowed. The tension of our string is less than 1 kg. So the air bearing is intentionally oversized about 10 times.

If we now simply would mount this air bearing, the platter could rotate perfectly and without noises and friction. However, would we have the vibration energy generated by tracking the grooves in the platter without any way to be dissipated. This would affect the quality of the play back in a very negative way.

For this reason, we have constructed an axis with a very low adjustable ground pressure over a ceramic ball and a Teflon mirror which can lead the generated  vibrations to the tripod and sub chassis.
The overall design of this is a world first in this form.
 
Platter:
The platter created by us consists of two components: the support platter to which the air bearing is secured and which is driven by the belt. This support plate is made of aluminum and other metals to gain the necessary weight and inertia. That compound platter is optimized to be free of any resonances and reflections.

On this support plate is, decoupled with spikes the playback platter made of POM, which has been proven for its good sound characteristics already widely. The spikes, made of brass and additional weights, also made of brass help to avoid any resonances.

In "normal" drives the bearing axis is usually also the pin on which the record is fixed. This way any noise from the bearing then is transferred directly to the record !
By the division of the platter, we have this problem completely eliminated.

Also another problem is eliminated: A heavy platter is needed for high inertia, to keep the speed of rotation constant. But in a heavy platter, a lot of energy generated by the vibrations of play back can be stored. This energy is also partly and without control reflected to the record. This effect is frequently heard as a loss of dynamics.
Light weight platters, as used in direct drive turntables or idler drive turntables have a widely spread reputation for sounding more dynamic, cause the lighter platters store less energy.
By our construction we gained the advantages of both principles without the disadvantages of them!

Tone arm base:
This component is usually constructed with conventional products exclusively according to visual criteria. It is this component that is really significant for perfect reproduction. It is crucial that the base fixes the arm completely locally stable relative to the turntable. But to avoid vibrations from motor and bearing to reach the tone arm there also should be some way of decoupling .In addition, the vibration energy generated by the reproduction process must still be discharged in a single and exactly defined way via tone arm and tone arm base.

To meet these requirements, we have designed a new tone arm base: The tone arm itself is fixed on a brass plate with eccentric bore in order to adjust the effective length accurately. (Brass plates for tone arms 9-12 inches in length are custom designed). More than 12 inches bases on request.

This brass plate is suspended on three Kevlar strings in the tube-shaped tone arm base In addition, below the brass plate a substantial counterweight is attached to keep the tone arm in a balanced horizontal position.

In principle, this suspension acts as spikes normally used to work in a horizontal direction: from the tone arm vibration energy can flow through the brass mounting plate and Kevlar strings to the sub-chassis. Interference from the sub-chassis may be transferred only very slightly to the mounting plate.

The complete tone arm base can be exchanged quickly for change of tone arms. All adjustment parameters are not affected by the change. A structure with two tone arms is not possible, since this would contradict the concept of a well-defined single path energy flow. Change of the tone arm can be done in one minute, without changing any adjustment parameters. Thus, a set arm is replaced by another in no time.

Subchassis:
Our sub-chassis consists of two parts: Once the tripod: On this the platter bearing and the tone arm base is mounted. The plate which supports these two components is made of different metals, which attenuate each other in their resonance frequencies. The other two arms are made of POM and carbon to ensure a secure footing. Only under the metallic support plate is a brass spike mounted, in order to guarantee a defined energy transfer path. The other two spikes are made of POM and thus acoustically insulating.

This tripod stands on a massive 6-pointed star, which is decoupled with air bearings and pillars of the installation area.

Overall, all parts are made as small as possible in order to provide a low impact surface for airborne sound.


The sub chassis is equipped with a purely mechanical self-adjustment. In this type of building an absolutely unique achievement in building turntables.

Comments

  • vintageaxeman
  • 10 September 2016 at 10:30AM
  • Unbelievable. Well done!

Leave a Comment