After turn on the musical instrument, the user must tune the oscillators.
The tuning work is a little bit difficult for the first time. Firstly user have to understand the construction of the Theremin itself.

  • The system has 2 oscillator pairs in different working style, fixed and variable.
  • The 2 antennas connected to the oscillators are working in variable frequency.
  • The antenna sens the magnetic field drifting by hands.
  • The demodulator outputs the beat made from the difference of the frequency of the oscillators by running in the variable/fixed frequency.
  • The up-edges between the waveform of the beat is measured the time by the counter in the micro controller and converted to the pitch/volume values.
  • The oscillators must be tuned to almost the same frequency.
  • There are 2 tuning methods, changing the frequency on the hardware or add- ing the offset value by software.
  • Firstly, the user has to search for the best tuning point by the trim pot. The user can hear the demodulated sound of the oscillator on the pitch side while pushing the Volume LED switch over 1 second. Then, the user finds out where the beat appears and can check the direction of appearing in the difference.
  • Tune the oscillators where the pitch turns higer while moving a hand toward the antenna.
  • The upper knob color turns in RED when the frequency of the pitch oscillator has been tuned to the lower limit. Tune the frequency just above the knob color turns in GREEN .
  • The tuning method for the volume side is almost the same (push the switch again over 1 second), but the setting is in the different manner. The user has to find out the best position for getting the widest working area while the left hand is moving toward near by the volume antenna.
  • Pushing the switch again over 1 second, then tuning mode is moved to the frequency tuner of the root note for the sequencer.
  • Finishing the tuning mode with short pushing the Volume LED switch.
  • Selecting the upper knob in GREEN, then tune the offset of the pitch side. And pushing the upper knob over 1 second for memory the offset value to the EEPROM. After recording, user do not have to do this step again.
  • Selecting the upper knob in BLUE, then tune the offset of the volume side. And pushing the upper knob over 1 second for memory the offset value to the EEPROM. After recording, user do not have to do this step again.

________ Spectrum 01 ________

The picture shows the spectrum waveforms of the oscillator pair.

The user should set the distance of the frequencies between the oscillators about 5 to 6 kHz.

________ Spectrum 02 ________

The frequency of the oscillator drifts to the lower side by the moving hand toward the antenna.

The distance (between the output frequencies) decrease, the pitch of the de-modulated tone would be down.

When the frequencies turns almost the same, the beat sound would be stopped.

_____ Demodulator outputs _____

The difference of the frequencies are converted to the beat by the demodulator.

The microcontroller measures the time between the up-edges of the beat.

  

BACK TO TOP