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Decibel Meter  Circuits
 

Last Updated: June 02, 2021 01:44 PM

Circuits Designed by Dave Johnson, P.E.

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8 Stage LED VU Meter -  The circuit below uses two quad voltage comparators   (LM339) to illuminate a series of 8 LEDs indicating volume level.  Each of the 8 comparators is biased at increasing voltages set by the voltage divider so that the lower right LED comes on first when the input is about 400 millivolts or about 22 milliwatts peak in an 8 ohm system.  The divider voltages are set so that each LED __ Designed by Bill Bowden

Analog LED Bar VU Meter -  The circuit was designed to work with an audio power amplifier which operated off +18v-0v-18v power rails.  The actual voltage used is not too critical except that the feedback is referred to the LED chain which itself is anchored to a +12v rail, hence the separate stabilizer __ Designed by Richard Torrens

Audio Power Meter -  This simple circuit indicates the amount of power that goes to a loudspeaker.  The dual-color LED shows green at an applied power level of about 1 watt.  At 1.5 watts it glows orange and above 3 watts it is bright red.  The circuit is connected in parallel with the loudspeaker connections and is powered from __

Audio VU Meter -  A VU meter with 20 LED's.  The input source can be a line input or a microphone __ Contact: P. Townshend EduTek Ltd

Audio VU Meter -  LM324, This circuit uses two quad op-amps to form an eight LED audio level meter.  The op-amp used in this particular circuit is the LM324 __ Designed by Matthew Hewson

Audio VU meter 9 LEDs -  5 LED VU Meter kit is based on LB1409 IC from SANYO, which will indicates the volume level of the audio signal it senses __ Contact: IQ Technologies

Decibel Meter -  The circuit below responds to sound pressure levels from about 60 to 70 dB.  The sound is picked up by an 8 ohm speaker, amplified by a transistor stage and one LM324 op-amp section.  You can also use a dynamic microphone but I found the speaker was more sensitive.  The remaining 3 sections of the LM324 quad op-amp are used as __ Designed by Bill Bowden

Digital volume control -  The Tiny Audio Amplifier kit is a good choice for battery operation.  It is based on LM386 IC. __

Digital Volume Control -  The heart of this digital volume controller DVC circuit is IC2 4067, 16-channel analog multiplexer.  Because the 1kΩ has been connected between every input and output, the multiplexer can act like a potentiometer.  The total resistance is 15kΩ.  You can use different values for the resistor to obtain a different characteristic.   __ Designed by Popescu Marian

Digital volume control -  Circuit of a digital volume control using six discrete ICs, including a 5V regulator, is presented.  IC1 (555) is configured to function as astable flip-flop.  Its frequency or period may be adjusted by proper choice of resistors R44, R45 and capacitor C6 combination.  Here it is for 0.3 second period __ Contact: IQ Technologies

Digital Volume Control -  This circuit could be used for replacing your manual volume control in a stereo amplifier.  In this circuit, push-to-on switch S1 controls the forward (volume increase) operation of both channels while a similar switch S2 controls __ Contact: IQ Technologies

Digital volume control has log taper -  04/11/02 EDN-Design Ideas Digital potentiometers provide a compact and convenient way to attenuate audio-amplifier signals.  However, most such potentiometers suffer from at least one flaw  a nonlogarithmic step increment.  To avoid this problem, a user must usually step the potentiometer in a nonlinear sequence to simulate a logarithmic taper__ Circuit Design by Doug Farrar, Los Altos, CA

Digital Volume Control using DS1669 Digital Pot IC -  This digital volume control has no pot to wear out and introduces almost no noise in the circuit.  Instead, the volume is controlled by pressing UP and DOWN buttons.  This simple circuit would be a great touch to any home audio project.   __ Designed by Aaron Cake

High-resolution volume-unit meter simplifies CD recording -  EDN-Design Ideas 06/21/01    Digitally recorded music on CDs offers superior quality to that recorded on vinyl records or tape, but most prerecorded CDs have an annoying characteristic: The average volume levels of the recorded signal can vary by as much as 14 dB from disk to disk.  Significant variances, such as 4 dB, can occur from track to track on a single CD.__ Circuit Design by Chester Simpson, National Semiconductor, Santa Clara, CA

LED Audio UV Monitor -  The circuit is completely conventional, and is based on the App Note  From National Semiconductor.  The circuit is shown in Figure 1 and as you can see it uses a single IC and a few discrete components.  The extra diode (D3) is included to ensure that the DC to the LEDs is almost unfiltered __ Designed by Rod Elliott  ESP

LED Decibel Meter -  The circuit below responds to sound pressure levels from about 60 to 70 dB.  The sound is picked up by an 8 ohm speaker, amplified by a transistor stage and one LM324 op-amp section.  You can also use a dynamic microphone but I found the speaker was more sensitive.  The remaining 3 sections of the LM324 quad op-amp are used as __ Designed by Bill Bowden

LEDs Indicate Sound Level -  08/25/11  EDN-Design Ideas Build a battery-operated portable meter to measure sound-pressure levels.   This Design Idea describes a battery-operated, portable soundlevel meter (Figure 1).  Its portability makes it useful for detecting the source of noise in automotive engines and power trains, factory machinery, and residential HVAC (heating/ventilation/air-conditioning) systems__ Circuit Design by Stephen Kamichik, Ile Bizard, PQ, Canada

Noise-Level Alarm -  Noise is a serious environmental problem that affects us in our daily life.  There is scientific evidence supporting that noise exposure can cause hearing loss, hypertension, heart disease, annoyance, sleep disturbance...___ Electronics Projects for You

Precision Audio MilliVoltmeter -  Measures10mV to 50Volt RMS in eight ranges Simply connect to your Avo-meter setAT 50µA range __ Contact: Flavio Dellepiane, fladello @ tin.it

Room Noise Detector -  One LED monitors three levels: 50, 70 & 85 dB; Useful to detect too noisy environments __ Contact: Flavio Dellepiane, fladello @ tin.it

Simple Stereo VU Meter -  I like to see lights move to music.  This project will indicate the volume level of the audio going to your speakers by lighting up LEDS.  The LEDS can be any color so mix them up and really make it look good.  The input of the circuit is connected to the speaker output of your __

Sound Level Meter -  One chip replacement for the standard analog meters, based on LM3915 audio level IC.   __ Designed by Aaron Cake

Sound Level Meter -  This sound level meter circuit can be used to control the intensity of a sound recording or in a disco.  It has 5 measurement domains between 70 and 120 dB; reading accuracy is 0.5 dB.  Microphone M1 is used to receive the acoustic signal and is coupled to C1, C2, R1 and R2.  This components, together with the microphone’s __ Designed by Popescu Marian

Sound Pressure Level Meter -  This SPL meter will allow for a broad range of Sound Intensitity Tests.   The 4 Transistors near the middle of the schematic, Basically make an Integrated Circuit, Op-Amp.   I Specifically built it this way, as it really isn't much bigger an IC and these are very common transistors. __ Designed by G.L. Chemelec

Stereo LED VU meter using discrete components BC547 transistors -  This is it.  It's a STEREO LED LEVEL METER.  It's the cheapest and best bar graph display available and best of all, it uses readily available components.
You only need a handful of LEDs, 22 transistors, some resistors, diodes and a set of electrosit doesn't require any chips __ Designed by Collin Mitchell

Stereo-VU-Meter -  Dieses Stereo-VU-Meter ist sehr simpel aufgebaut und lässt sich einfach an ein Line Audio-Signal hängen.  Dann zeigt es den Signalpegel mit 10 Leuchtdioden pro Kanal an.  Diese Schaltung hat keinen Verstärker vorgeschaltet, weshalb der __ Designed by Text in German

Volume Control -  This digital volume control has no pot to wear out and introduces almost no noise in the circuit.  Instead, the volume is controlled by pressing UP and DOWN buttons.  This simple circuit would be a great touch to any home audio project.   __ Designed by Aaron Cake

Volume Control has Log Taper -  04/11/02 EDN-Design Ideas Digital potentiometers provide a compact and convenient way to attenuate audio-amplifier signals.  However, most such potentiometers suffer from at least one flaw  a nonlogarithmic step increment.  To avoid this problem, a user must usually step the potentiometer in a nonlinear sequence to simulate a logarithmic taper__ Circuit Design by Doug Farrar, Los Altos, CA

VU & PPM Audio Metering -  A versatile and useful VU meter circuit, can also operate as a Peak Program Meter  __ Designed by Rod Elliott  ESP

VU Meter -  This simple VU Meter may be used in variety of projects.  Since real electro magnetic type VU Meters are no longer available or too expensive, I decided to make this one using LM3914 and 10 LEDs, which I can use in my other projects __ Designed by Nina Gajjar

VU Meter -  5 led VU meter, in PDF format, includes circuit board, text in Finnish __

VU Meter -  A very simple circuit of indication of level, with 10 Led.  Is used the circuit of half-wave rectification of precision round the IC2, with gain one.  With switch S1, we can select the indication of Led.  The level of entry is 60 mV-1.25 V __

VU meter  -  Dieses Stereo-VU-Meter ist sehr simpel aufgebaut und lässt sich einfach an ein Line Audio-Signal hängen.  Dann zeigt es den Signalpegel mit 10 Leuchtdioden pro Kanal an.  Diese Schaltung hat keinen Verstärker vorgeschaltet, weshalb der __


Decibel Meter  Circuits


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