Amplifier Circuit 2W

Amplifier description:

     This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc, iPod and CD players, computers and similar devices fitted with line or headphone output. Of course, in most cases you will have to make two boxes to obtain stereo. The circuit was deliberately designed using no ICs and in a rather old-fashioned manner in order to obtain good harmonic distortion behavior and to avoid hard to find components. The amplifier(s) can be conveniently supplied by a 12V wall plug-in adapter.Closing SW1 a bass-boost is provided but, at the same time, volume control must be increased to compensate for power loss at higher frequencies. In use, R9 should be carefully adjusted to provide minimal audible signal cross-over distortion consistent with minimal measured quiescent current consumption; a good compromise is to set the quiescent current at about 10-15 mA. To measure this current, wire a DC current meter temporarily in series with the collector of Q3.

Amplifier circuit diagram:

Amplifier circuit partlist:

P1----------10K

R1----------33K

R2----------33K

R3----------33R

R4----------15K

R5----------1K

R6----------1K

R7----------680R

R8----------120R-1/2W

R9----------100R-1/2W Trimmer Cermet

C1 ----------10µF-63V

C2 ----------10µF-63V

C3-----------100µF-25V

C4-----------470µF-25V

C5-----------47pF-63V

C7-----------470µF-25V

C6-----------220nF-63V

C8-----------1000µF-25V

D1-----------1N4148

Q1-----------BC560C

Q2-----------BC337

Q3-----------TIP31A

Q4-----------TIP32A

SW1---------SPST switch

SPKR--------3-5 Watt Loudspeaker