WO1981002957A1 - Audio echo circuits - Google Patents

Audio echo circuits Download PDF

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Publication number
WO1981002957A1
WO1981002957A1 PCT/AU1981/000041 AU8100041W WO8102957A1 WO 1981002957 A1 WO1981002957 A1 WO 1981002957A1 AU 8100041 W AU8100041 W AU 8100041W WO 8102957 A1 WO8102957 A1 WO 8102957A1
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WO
WIPO (PCT)
Prior art keywords
april
signal
pure
circuit according
echo
Prior art date
Application number
PCT/AU1981/000041
Other languages
French (fr)
Inventor
R Lawson
Original Assignee
R Lawson
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by R Lawson filed Critical R Lawson
Publication of WO1981002957A1 publication Critical patent/WO1981002957A1/en

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H1/00—Details of electrophonic musical instruments
    • G10H1/02—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/08—Arrangements for producing a reverberation or echo sound
    • G10K15/12—Arrangements for producing a reverberation or echo sound using electronic time-delay networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/26—Time-delay networks

Definitions

  • the invention relates to audio echo circuits.
  • the object of the invention is to recreate in an echo circuit the same phase relationships between the undelayed output and the echoes as exist in the case ofnatural echo phenomena in the atmosphere.
  • the velocity of sound in air is the same for all frequencies, therefore the difference between the times of arrival of the original sound and. the echoes is the same for all frequencies. Reflection reverses the phase of a sound wave if the direction of travel is reversed.
  • phase shift applies if different frequencies are displaced by different durations. When there is a phase shift, such as when a signal passes through a capacitor, different frequencies may be delayed by the same phase angle, therefore they are delayed by different times.
  • a signal path may be specified in terms of pure time delay, phase shift and phase inversion.
  • an echo circuit is designed so that the difference between the times of arrival of the undelayed output signal and each delayed output signal is the same for all frequencies.
  • Switching is also provided so that the phase of each echo signal may be reversed relative to the phase of the undelayed output signal.
  • a method is provided whereby different channels, having different time delays, are matched in terms of their phase shift characteristics.
  • the simplest and most economical method of doing this is usually by duplicating the phase shift components in each channel.
  • Matching between channels may be effected using different components such as by using the phase advance of an inductor to compensate for the phase lag of a capacitor.
  • Zero phase shift channels may also be designed.
  • the phase shift of the time delay stage may be compensated by the phase shift of the feedback stage, so that where the delayed signal is mixed back into the input signal, the difference between their times of arrival is the same for all frequencies.
  • the feedback loop imposes a pure time delay.
  • the phase of the feedback signal may be reversed relative to the phase of the input signal at the point of mixing.
  • a single time delay device may be matched with an active stage in terms of phase shift characteristics.
  • the method requires that if the time delay path comprises an input coupling capacitor and a time delay device which delays all frequencies by the same duration and an output coupling capacitor, then the nondelaying path must be designed to also comprise an input coupling capacitor, and active stage (such as a transistor stage) which delays all frequencies by the same (zero) duration, and an output coupling capacitor.
  • the double tracking or close echo effect is produced if the difference between the times of arrival of the echo signal and the undelayed output signal is between 25 ms. and 100 ms.
  • differential double tracking is produced by subtracting the two differently delayed versions of the signal from each other instead of adding them to each other at the place of mixing.
  • the phases of the odd numbered echoes may be reversed relative to the phases of the undelayed signal and the even numbered echoes.
  • a double tracking circuit may be used as a variable pitch harmoniser which gives an output signal comprising an undelayed version of the signal mixed with a delayed and pitch altered version of the signal. This is achieved by modulating the clock oscillator frequency with a ramp signal.
  • an improved variable pitch harmoniser is realised by ramp modulating the clock oscillator frequency of a pure double tracking circuit or of a pure differential double tracking circuit.
  • the duration control of a pure double tracking circuit or a pure differential double tracking circuit is controlled by a proximity detector or a proximity expression pedal.
  • Figure 1 shows a pure differential double tracking circuit. Part A is the input. Parts B and C are low pass filters. Part D is a single transistor stage. Part E is a variable time delay device. Part F is the output mixer. Part G is the output. Figure 2 shows a circuit for producing two echoes, the first one being reversed in phase.
  • Part A is the input.
  • Parts B and C are low pass filters.
  • Parts D and E are single transistor stages.
  • Part F is an inverting single transistor stage.
  • Parts G and H are time delay devices.
  • Part I is the output.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Electrophonic Musical Instruments (AREA)

Abstract

Audio echo circuits in which the difference between the times of arrival at the place of mixing (F) of the undelayed signal and each delayed signal is the same for all frequences. Different channels having different time delays are matched in their phase shift characteristics. The phase of selected echoes may be reversed. Double tracing circuits, i. e. echo circuits with 25-100 ms delay difference, and differential double tracking circuits, i.e. circuits involving subtraction of differently delayed signal versions, and the duration control thereof by a ramp control signal or a proximity detector or an expression pedal having proximity control.

Description

AUDIO ECHO CIRCUITS
The invention relates to audio echo circuits. The object of the invention is to recreate in an echo circuit the same phase relationships between the undelayed output and the echoes as exist in the case ofnatural echo phenomena in the atmosphere.
The velocity of sound in air is the same for all frequencies, therefore the difference between the times of arrival of the original sound and. the echoes is the same for all frequencies. Reflection reverses the phase of a sound wave if the direction of travel is reversed.
In this specification the word "echo" applies only if the time delay is greater than 25 ms. The word "pure" rs used to describe a time delay in which all frequencies are delayed by the same duration. The expression "phase shift" applies if different frequencies are displaced by different durations. When there is a phase shift, such as when a signal passes through a capacitor, different frequencies may be delayed by the same phase angle, therefore they are delayed by different times. A signal path may be specified in terms of pure time delay, phase shift and phase inversion.
According to the invention a method is provided whereby an echo circuit is designed so that the difference between the times of arrival of the undelayed output signal and each delayed output signal is the same for all frequencies. Switching is also provided so that the phase of each echo signal may be reversed relative to the phase of the undelayed output signal.
A method is provided whereby different channels, having different time delays, are matched in terms of their phase shift characteristics. The simplest and most economical method of doing this is usually by duplicating the phase shift components in each channel. Matching between channels may be effected using different components such as by using the phase advance of an inductor to compensate for the phase lag of a capacitor. Zero phase shift channels may also be designed.
In the case of a feedback echo circuit, the phase shift of the time delay stage may be compensated by the phase shift of the feedback stage, so that where the delayed signal is mixed back into the input signal, the difference between their times of arrival is the same for all frequencies. This means that the feedback loop imposes a pure time delay. According to the invention, the phase of the feedback signal may be reversed relative to the phase of the input signal at the point of mixing.
If only one echo is required, a single time delay device may be matched with an active stage in terms of phase shift characteristics. The method requires that if the time delay path comprises an input coupling capacitor and a time delay device which delays all frequencies by the same duration and an output coupling capacitor, then the nondelaying path must be designed to also comprise an input coupling capacitor, and active stage (such as a transistor stage) which delays all frequencies by the same (zero) duration, and an output coupling capacitor.
The double tracking or close echo effect is produced if the difference between the times of arrival of the echo signal and the undelayed output signal is between 25 ms. and 100 ms.
According to the invention, differential double tracking is produced by subtracting the two differently delayed versions of the signal from each other instead of adding them to each other at the place of mixing.
According to the invention the phases of the odd numbered echoes may be reversed relative to the phases of the undelayed signal and the even numbered echoes.
A double tracking circuit may be used as a variable pitch harmoniser which gives an output signal comprising an undelayed version of the signal mixed with a delayed and pitch altered version of the signal. This is achieved by modulating the clock oscillator frequency with a ramp signal. According to the invention an improved variable pitch harmoniser is realised by ramp modulating the clock oscillator frequency of a pure double tracking circuit or of a pure differential double tracking circuit.
According to the invention the duration control of a pure double tracking circuit or a pure differential double tracking circuit is controlled by a proximity detector or a proximity expression pedal.
Figure 1 shows a pure differential double tracking circuit. Part A is the input. Parts B and C are low pass filters. Part D is a single transistor stage. Part E is a variable time delay device. Part F is the output mixer. Part G is the output. Figure 2 shows a circuit for producing two echoes, the first one being reversed in phase.
Part A is the input. Parts B and C are low pass filters. Parts D and E are single transistor stages. Part F is an inverting single transistor stage. Parts G and H are time delay devices. Part I is the output.

Claims

The claims defining the invention are as follows:
Claim 1. A double tracking circuit in which the difference between the times of arrival of the undelayed version and the delayed version of the signal at the place of mixing is the same for all frequencies. 11th April, 1980.
Claim 2. A pure double tracking circuit according to claim 1 in which the undelayed version and the delayed version of the signal are mixed differentially. 11th April, 1980
Claim 3. Any echo circuit in which the difference between the times of arrival of the undelayed version and each delayed version of the signal at the place of mixing is the same for all frequencies. 11th April, 1980
Claim 4. A pure echo circuit according to claim 3 in which the phase of each echo may be reversed.
11th April, 1980
Claim 5. An echo circuit in which the phase of the odd numbered echoes are reversed relative to the phases of the undelayed signal and the even numbered echoes. 10th April, 1981
Claim 6. A pure echo circuit according to claim 3 in which the phases of the odd numbered echoes are reversed relative to the phases of the undelayed signal and the even numbered echoes.
10th April, 1981
Claim 7. A feedback echo circuit in which the difference between the times of arrival at the input of the input signal and the feedback signal is the same for all frequencies. 10th April, 1981
Claim 8. A feedback echo circuit in which the phase of the feedback signal is reversed relative to the phase of the original signal at the place of mixing. 10th April, 1981
Claim 9. The combination of a pure feedback echo circuit according to claim 7 with the differential feedback mixing of claim 8. 10th April, 1981
Claim 10. Modulation of the controlling means of a pure double tracking circuit according to claim 1 by a ramp control signal. 10th April, 1981
Claim 11. Modulation of the controlling means of a pure differential double tracking circuit according to claim 2 by a ramp control signal.
10th April, 1981
Claim 12. A pure double tracking circuit according to claim 1 in which the duration control is controlled by a proximity detector.
11th April, 1980
Claim 13. A pure differential double tracking circuit according to claim 2 in which the duration control is controlled by a proximity detector.
10th April, 1981
Claim 14. A pure double tracking circuit according to claim 1 in which the duration control is controlled by a proximity expression pedal.
11th April, 1980
Claim 15. A pure differential double tracking circuit according to claim 2 in which the duration control is controlled by a proximity expression pedal.
11th April, 1980 Dated this tenth day of april 1981.
RICHARD LAWSON
PCT/AU1981/000041 1980-04-11 1981-04-10 Audio echo circuits WO1981002957A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPE308780 1980-04-11
AU3087/80 1980-04-11

Publications (1)

Publication Number Publication Date
WO1981002957A1 true WO1981002957A1 (en) 1981-10-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1981/000041 WO1981002957A1 (en) 1980-04-11 1981-04-10 Audio echo circuits

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WO (1) WO1981002957A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0209380A2 (en) 1985-07-17 1987-01-21 Sony Corporation Recording and/or reproducing apparatus
ITPD20090009A1 (en) * 2009-01-15 2010-07-16 Eleven Electrix Di Marino Basso FILTER DEVICE FOR ELECTRICAL MUSICAL INSTRUMENTS

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1947621A (en) * 1932-06-14 1934-02-20 American Telephone & Telegraph Reverberation circuit
US2433863A (en) * 1943-05-13 1948-01-06 Bell Telephone Labor Inc Pulse generation circuit
AU4615579A (en) * 1978-04-19 1979-10-25 Richard Lawson Pure musical phase circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1947621A (en) * 1932-06-14 1934-02-20 American Telephone & Telegraph Reverberation circuit
US2433863A (en) * 1943-05-13 1948-01-06 Bell Telephone Labor Inc Pulse generation circuit
AU4615579A (en) * 1978-04-19 1979-10-25 Richard Lawson Pure musical phase circuit

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0209380A2 (en) 1985-07-17 1987-01-21 Sony Corporation Recording and/or reproducing apparatus
EP0209380A3 (en) * 1985-07-17 1988-11-23 Sony Corporation Recording and/or reproducing apparatus
US5191487A (en) * 1985-07-17 1993-03-02 Sony Corporation Helical-scan-type VTR with echo effect playback
ITPD20090009A1 (en) * 2009-01-15 2010-07-16 Eleven Electrix Di Marino Basso FILTER DEVICE FOR ELECTRICAL MUSICAL INSTRUMENTS
WO2010082178A3 (en) * 2009-01-15 2010-09-23 Eleven Electrix Di Marino Basso Filter device for electrical musical instruments

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