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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.
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.
Precision Audio MilliVoltmeter - Measures10mV to50Volt RMS in eight
ranges Simply connect to your Avo-meter set @50µA range.
Room Noise Detector - One LED monitors three levels: 50, 70 & 85
dB. Useful to detect too noisy environments.
Sound Level Meter - One chip replacement for the standard analog
meters, based on LM3915 audio level IC.… [Aaron Cake's design] |
