D I Y page

2 X 3.5 Watt Audio Current Amplifiers

The fundamental error in most audio amplifiers intended to drive 'voice coil' or 'Ribbon' speakers is the use of voltage feedback.

The movement of the cone or ribbon is proportional to the current passing through it. But due to the variations of  impedance over the audio frequency range this current is not proportional to the voltage applied.

An attempt is then made to correct for the worst of these variation, the low end roll off, by designing speaker boxes with tuned ports to boost the bass.

This simple true current drive amplifier with true current feedback, (not the false current feedback), design eliminates this roll off and gives surprising audio quality even with a 4 inch speaker; and is incredible with two 8 inch speakers and a ribbon tweeter. (sorry that is my professional speakers).

Connect your speakers and audio source and your ready to listen to live audio.

Love the new project case from Jaycar part number HB5556 or RS part number 754-5985.

Amplifier Circuit Diagram

In this circuit the DC feedback components are R5, R7, C1 and C3.

And the AC feedback components are R2, and C1.

The current Gain is set by R2.

Bode Plot

Second Harmonic Distortion Graph

Third Harmonic Distortion Graph


click on image to download protel 2.8 .pcb file.

Printed circuit board

Front panel layout.

Front Panel

Amplifier Layout