MagicQuartz, the Computing True Sine Turntable Speedbox


MagicQuartz prototype 3

What is MagicQuartz?

MagicQuartz is a turntable speed box / power supply that adds true quartz precision to your turntable – without having to modify anything on your turntable! It contains a sophisticated power transformer and is capaple of delivering high-quality, quartz-stable true-sine power with a variable voltage and AC frequency. It is controlled by a modern mikrocontroller, and MagicQuartz can measure the current platter speed with a small optical sensor and change the platter speed accordingly. It precisely fine-tunes your turntable’s speed! MagicQuartz is much more than just a turntable speed box!

MagicQuartz allows you to do “incredible” things:

  • Manually alter the RPM or supply frequency with a precision of 1/10.000’s RPM/Hertz, MagicQuartz automatically calculates the other value accordingly. It employs an advanced microcontroller programming technique that allows it to operate at this high precision.
  • Live quartz mode: Let MagicQuartz measure the current speed and let it correct it (precision: about 0,001 RPM at 33 RPM in the long run).
  • For musicians: transpose your music to any half-tone.
  • Use 220 Volts / 50 Hz units in countries with 110 Volts / 60 Hz mains and vice versa.
  • Play 78 and 16 RPM records on turntables which were not construced to do this.
  • Keep track of stylus wear. MagicQuartz not only counts the total time of operation, but also the time of playback (when the platter is rotating).
  • Do nerdy things: For example, shift the noise level (rumble) into a different frequency spectrum: e.g. set the physical turntable speed to 78 RPM and let MagicQuartz calibrate the motor to play at 33 RPM.


Main Functions

The main screen allows you to change various speed settings for your turntable and acts as the entry point to all other functions (e.g. the live quartz mode). It is cursor-controlled: Use the left and right buttons to move the curser below the digits representing values (e.g. 33.3333 or 50.0000) or characters representing menus or functions (e.g. M, which enters the setup menu). Then use the up and down buttons to change the values or to enter the menu or function.


  • Physical platter speed: Set this to match the physical speed setting of your turntable. “Physical” means the belt or idler wheel setting on your turntable: if the turntable is set to play at 45 RPM, set this to parameter 45. Use the up and down button to switch between 16, 33, 45 and 78 RPM.
  • Transpose: Use the up and down buttons to transpose the playback in half tones.
  • Target platter speed: Move the curser under the desired digit, then use the up and down buttons to increase or decrease the RPM. The unit automatically calculates the corresponding supply frequency.
  • Switch 16/45/45/78 RPM: Move the curser below RPM and use the up and down buttons to switch between the standard RPM settings. This directly changes the target platter speed and the supply frequency is changed accordingly.
  • Motor status: This displays if the motor is running, or not. An R is displayed if it’s running, otherwise an – is displayed. If nothing is shown, the unit was not able to detect the current motor status.
  • Switch back to default supply frequency: Move the curser below Hz and use the up or down button to switch back to the default supply frequency (typically 50 or 60 Hertz). Note: This deletes the current (static) quartz calibration.
  • Supply frequency: Move the curser under the desired digit. Then use the up and down buttons to increase or decrease the supply frequency (in Hertz). The unit automatically calculates the corresponding target platter speed.
  • Quartz: Enter live quartz mode.
  • Sensor calibration: Enter sensor calibration mode.
  • Menu: Enter setup menu.

This is taken out of the documentation. You can download the documentation on the Download page.

Why use MagicQuartz?

Are you a true vintage HiFi fan? I am. And I know that audio equipment from the 60ies and 70ies is the very best in regards of build quality. Speaking of turntables, the units from this time feature platters made of heavy cast metal, driven with a powerful AC motor over either an idler wheel or belt. On the best units, the arm bearings were constructed with four needle bearings to dramatically reduce friction. Fully automatic control, pitch change and spring-controlled anti-skating were standard at this time (beginning in mid-class units). Today, even most expensive units normally do not contain the features mentioned above. Don’t get me started about the “new” platters made from fiber sheets! There are many good reasons to operate high-quality turntables such as the Dual 1019, 1219, 1229, Perpetuum Ebner 2020 and the like. The 60ies and 70ies were the stronghold of the turntable industry!

For such units, the motors were typically asynchronous motors, running directly from mains power (110 or 220 Volts). The platter speed therefore is coupled to the mains frequency. In theory, the platter speed should be extraodinary stable. In fact it is in fact pretty stable, but it’s not perfect. The mains frequency always fluctuates to a certain degree (see for Germany’s 50 Hertz mains). Another problem is the warm-up of the mechanics after the turntable has been turned on. During this phase, the platter steadily increases its speed. Even more, the needle’s friction decreases while the tone arm is moving towards the center, thereby increasing the playback speed. Admittedly, these speed changes are very small, but they are measureable and disturb the perfect playback of your precious recods!

When and how will MagicQuartz be available?

The hardware is finished, as is the software. However, both components are currently undergoing heavy testing, to ensure that MagicQuartz operates as expected. It will probably be finished in spring 2016. Please keep in mind that this is (currently) only a hobby project next to a full-time job. And I really want to deliver a quality product, so there’s no reason for me to get this onto the market in a hurry.

MagicQuartz will be available as a DIY kit. I try to keep the kit costs as low as possible, to make it affordable for everyone. The hardware components will probably be sold near to their prime costs, but I will do ask for some money for the software, as it was a big challenge to develop the software. I aim to keep the price of the kit similar to a cheap true-sine car power inverter, which can be obtained for around 80-100 Euros.