Audio circuit diagrams

Vinyl Pre-Amplifier

For those who might wish to 'save' to their computer hard-drive a digital copy of their own vinyl record collection, I have redrawn my 1975 vinyl pre-amplifier circuit. It remains capable of optimising disc playback and offers features still not repeated today.

Doorphone Intercom

A simple Intercom made with a single transistor and low power audio amplifier LM386. The circui uses 8 ohm speakers, which also double as a microphone.

Loudness Control

When listening to music at low volume levels, bass and treble frequencies are attenuated more than mid frequencies. This loudness control alters the frequency response curve to correspond roughly with the equal loudness characteristic of the ear. The circuit shown, is for a single channel, so for a stereo system, two such units should be built. This circuit has a boost of 13dB at 20Hz and approximately 9dB at 20kHz.

Guitar Amplifier

10W Old-Style ultra-compact Combo. Two inputs - Overdrive - Treble-enhancement

TDA2030 8w Amplifier

An 8 watt amplifier made with the TDA2030 IC. Built two such units for a stereo amplifier.

60W Bass Amplifier

Low-cut and Bass controls. Output power: 40W into 8 Ohm and 60W into 4 Ohm loads

Audio Notch Filter

A variable notch filter with both high and low pass filters.

Sound Modifier

Four shape-controls portable unit. Wide variety of output waveforms

3 Band Equalizer

A tone control circuit made with a single op-amp and having three ranges, bass, middle and treble controls.

150W MP3 Car Amplifier

LF353 Wide Bandwidth Dual JFET Input Operational Amplifier