Electronic tuner

• US 4,120,229 A
• Filed: 12/22/1975
• Issued: 10/17/1978
• Est. Priority Date: 12/30/1974
• Status: Expired due to Term

• Current Assignee: KEIO Giken Kogyo Kabushiki Kaisha
• Original Assignee: KEIO Giken Kogyo Kabushiki Kaisha
• Inventors: Ota, Kyozo
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Miska, Vit W.
• Application Number:
  US05/643,054
• Time in Patent Office: 1,030 Days
• Field of Search: 84/454, 84/1.01, 324/78 R, 324/78 Z, 324/78 J, 324/78 N, 324/79 R, 324/79 D, 324/83 R, 324/83 A
• US Class Current: 84/454
• CPC Class Codes: G10G 7/02 Tuning forks or like devices
• CPC Class Codes: G10H 1/44 Tuning means

Abstract

An electronic tuner for musical instruments is disclosed which has built therein a voltage-controlled reference oscillator having its oscillation frequency controlled by a control signal and in which the oscillation signal of the reference oscillator and an input musical sound signal from a microphone are phase compared by a phase comparator and the oscillator is controlled by the phase compared output so that its oscillation frequency is synchronized with the frequency of the input musical sound signal. A control voltage, which is obtained when the oscillation frequency of the reference oscillator is synchronized with the frequency of the input musical sound signal, is applied to an indicator to indicate the ratio between the two frequencies.

Claims

1. An electronic tuner for musical instruments comprising:

an amplifier for amplifying an input musical signal, said amplifier including means operative to shape said input musical signal into a square wave;

a reference oscillator of the type adapted to have its oscillation frequency controlled by a control voltage to produce a reference oscillation signal of controlled frequency;

a phase comparator coupled to said oscillator and to said amplifier for comparing the amplified musical sound signal in phase with said reference oscillation signal;

a waveform shaping circuit for shaping the oscillation signal from said reference oscillator into a square wave, said waveform shaping circuit comprising a plurality of frequency dividers connected in cascade and supplied with said reference oscillation signal to frequency divide said reference oscillation signal, and an AND gate for obtaining the logical product of the outputs from the frequency dividers and for supplying the phase comparator with said logical product in the form of a signal containing a higher harmonic;

said phase comparator comprising a multiplier for multiplying the square wave musical signal from the amplifier by the output from the waveform shaping circuit;

a low-pass filter for extracting the low-frequency component from the output of said phase comparator and applying it as the control voltage to said reference oscillator; and

an indicator connected to the output of said low-pass filter and responsive to said control voltage for providing a direct visual indication of the ratio between said reference oscillation signal and the frequency of said input musical signal.

2. An electronic tuner for musical instruments according to claim 1 wherein said indicator includes a movable pointer, means for deviating said reference oscillation frequency from a correct scale frequency in a manner operative to derive at the output of the phase comparator a voltage which causes said pointer to register with one end of its deflection range in the absence of the input musical signal and to register with the median of its deflection range when the input musical signal is inputted at a correct frequency.

3. An electronic tuner for musical instruments according to claim 1, including means for selectively changing the oscillation frequency of said reference oscillator, a fixed frequency oscillator stably generating a signal of a correct frequency of a certain scale, and a changeover switch for supplying said multiplier with the output from said fixed frequency oscillator in place of said musical signal, said indicator including a graduated scale for indicating the oscillation frequency of the reference oscillator based on the oscillation frequency of the fixed frequency oscillator and the output voltage from the multiplier supplied with the oscillation output from the reference oscillator.

4. An electronic tuner for musical instruments comprising:

an amplifier for amplifying an input musical signal;

a reference oscillator of the type adapted to have its oscillation frequency controlled by a control voltage to produce a reference oscillation signal of controlled frequency;

a waveform shaping circuit comprising a plurality of frequency dividers connected in cascade to frequency divide said reference oscillation signal;

a phase comparator coupled to said oscillator and said amplifier for comparing the amplified musical signal in phase with said reference oscillation signal, said phase comparator comprising a multiplier for multiplying the signal from the amplifier by the output from said waveform shaping circuit;

an octave changeover switch for selectively picking up the output from each frequency divider and the output from the reference oscillator, and so arranged that the output from the octave changeover switch is applied to the first-stage of said cascade connected frequency dividers;

an AND gate for obtaining the logical product of the outputs from the frequency dividers and supplying said logical product to said phase comparator in the form of a signal containing a higher harmonic;

a low-pass filter for extracting the low-frequency component from the output of said phase comparator and applying it as the control voltage to said reference oscillator; and

an indicator connected to the output of said low-pass filter and responsive to said control voltage for providing a direct visual indication of the ratio between the frequency of said reference oscillation signal and the frequency of said input musical signal.

5. An electronic tuner for musical instruments according to claim 4 including means for switching the cut-off frequency of said low-pass filter in ganged relation to said octave changeover switch.

6. An electronic tuner for musical instruments comprising:

an amplifier for amplifying an input musical signal;

a reference oscillator of the type adapted to have its oscillation frequency controlled by a control voltage to produce a reference oscillation signal of controlled frequency;

a frequency divider for frequency dividing said reference oscillation signal into a plurality of signals of difference frequencies;

a plurality of phase comparators which are respectively supplied with said different frequency signals and with said amplified input musical signal for comparing the frequency-divided outputs from the frequency divider in phase with said input musical signal;

a plurality of low-pass filters for individually filtering the outputs from the plurality of phase comparators and for applying the low frequency components in the phase comparator outputs as the control voltage to said reference oscillator; and

an indicator connected to the outputs of said low-pass filters and responsive to said control voltage for providing a direct visual indication of the ratios between the frequency of said frequency-divided outputs and the frequency of said input musical signal.

7. An electronic tuner for musical instruments comprising:

an amplifier for amplifying an input musical signal;

a reference oscillator of the type adapted to have its oscillation frequency controlled by a control voltage to produce a reference oscillation signal of controlled frequency;

a phase comparator coupled to said oscillator and to said amplifier for comparing the amplified input musical signal in phase with said reference oscillation signal;

a low-pass filter for extracting the low-frequency component from the output of said phase comparator and applying it as the control voltage to said reference oscillator;

an indicator connected to the output of said low-pass filter and responsive to said control voltage for providing a direct visual indication of the ratio between the frequency of said reference oscillation and the frequency of said input musical signal;

a variable frequency oscillator adapted to have its oscillation frequency controlled by a control voltage, said variable frequency oscillator being identical in construction to said reference oscillator;

a relatively stable fixed frequency oscillator;

a second phase comparator for comparing the phases of oscillation signals of the variable frequency oscillator and of the fixed frequency oscillator in phase with each other; and

a second low-pass filter supplied with the compared output from the second phase comparator and applying it to a control terminal of the variable frequency oscillator, the filtered output from the second low-pass filter also being applied to the reference oscillator as a control signal to compensate for frequency fluctuation of the reference oscillator.

8. An electronic tuner for musical instruments comprising:

an amplifier for amplifying an input musical signal;

a reference oscillator of the type adapted to have its oscillation frequency controlled by a control voltage to produce a reference oscillation signal of controlled frequency;

a phase comparator coupled to said oscillator and to said amplifier for comparing the amplified input musical signal in phase with said reference oscillation signal;

a low-pass filter for extracting the low-frequency component from the output of said phase comparator and applying it as the control voltage to said reference oscillator;

an indicator connected to the output of said low-pass filter and responsive to said control voltage for indicating the ratio between the frequency of said reference oscillation signal and the frequency of the input musical signal;

a voltage-frequency converter for converting the output voltage from the low-pass filter into a signal having a frequency related to the magnitude of said output voltage;

a counter coupled to said converter for counting the number of cycles of the output signal from said voltage-frequency converter for each unit time; and

a plurality of light emitting elements spaced in an array corresponding to scale graduations and selectively lighted by the output from said counter to indicate the ratio between the frequency of said reference oscillation and the frequency of said input musical signal.