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Zagcom >> Links>> Electronic Circuits >>Audio circuits >> Measuring

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

Measuring ( 38 ) :

  • VU meters

    • -30dBm to +30dBm Audio Level Meter - circuit with balanced input and adjustable gain to drive needle type VU meter, uses special amplifier module from   
    • Audio LED VU meter - built around discrete components   
    • Audio Millivoltmeter   
    • Audio Output Level Meter - This unit is designed for monitoring the audio output level across a loudspeaker when carrying out alignment of radios.   
    • High-resolution volume-unit meter simplifies CD recording - CD digital-recording decks typically have peak-reading-only volume-level meters. This feature is adequate to prevent clipping but does a poor job of reading the average volume, or loudness, level. A high-resolution, average- (not peak-) reading volume-unit meter produces an accurate reading of loudness.   
    • LED Audio VU Meter - logarithmic scale with 3 dB steps, based in LM3915 IC   
    • LM3916N bar graph driver - datasheet in pdf format, drives a 10 LED bar graph with VU proportions (3dB/step)   
    • Peak Reading Audio Level Meter - indicates peak audio response on an analogue meter, similar to a tape recorder recording level meter   
    • Simple circuit forms peak/clipping indicator - This simple peak detector is the result of a need for a single-5V-supply, level/clipping indicator for a multimedia-PC sound system. The design is unique in that it detects both stereo channels on a single peak-hold capacitor. All the adjustments in the circuit simultaneously apply to both left and right stereo inputs. The output is suitable for driving a bar-graph display or for analog-to-digital conversion and display with a microprocessor. The circuit operates as a dual positive-peak-detector circuit.   
    • Sound Level Meter - one chip replacement for the standard analog meters, based on LM3915 audio level IC   
    • Stereo VU Meter - A simple, low cost stereo VU meter that uses two LM3915 dot/bar display driver ICs to drive 2 rows of 10 LEDs moving bar display, pdf file   
    • The Allen & Heath GL2 - in anger - The desk was great but the metering -YUCK, so what to do about it. Obviously the metering system needed expanding but how? Ten meters were required in all and a suitable power supply would have to be constructed. This describes how to built those LED VU meters (-21..+6dB range using 10 LEDs).   
    • Three-Level Audio Power Indicator - Battery-operated 3 LED display that connect it to loudspeaker output   
    • Understanding Peak-Reading Meters - includes one example circuit diagram   
    • VU And PPM Audio Metering - circuits using analogue needle meters   
    • VU Meter - 5 led VU meter, in pdf format, includes circuit board, text in Finnish   
    • VU Meter Amplifier   
    • VU Stereo Meter - will indicate the volume level of the audio going to your speakers by lighting up LEDs, based on LM3915 IC   

  • Other measuring circuits and notes

    • 1 kHz Audio Oscillator - This circuit consists of a CMOS square wave oscillator on a frequency of approximately 1 kHz. The RC filter, which has a roll-off frequency of 500 Hz, filters the harmonics, providing a sine-wave output. The oscillator has many uses, sidetone circuits in transmitters and signal injectors for audio tests are just two.   
    • 3 Channel Spectrum Analyzer - This 3 channel 15 LED spectrum analyzer can be used as an addition to any audio amp project. It produces fantastic displays on three LED bars that can be individually adjusted for any particular frequency range.   
    • DIY Speaker Testing Microphone Preamp   
    • Measuring Input and Output Impedance - input or output impedance of any two terminal network or electronic equipment can be determined by measuring the small signal ac currents and voltages   
    • Simplified Measurement of Output Impedance - suitable for measuring audio circuits   
    • Spectrum Analyzer and Equalizer Designs - for audio frequencies, article first appeared in the February 1982 issue of Recording-engineer/producer magazine   

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