So you might go back to tying the emitter to gnd, and use a 10K in series with the 220 uF cap on the base.
Well, actually, not "quite" a Class A design. Class A is intended to bias the transistor into its linear region of operation, but you'll never get that with the ckt as shown.It looks like the person who designed it had the intent of Class A, but you would needa resistor in the emitter lead, so the 100Ks on the base have something to bias ina stable fashion. As it is, they simply turn on the transistor, and whether or not thecollector sits at Vcc/2 is strictly a factor of the hFE [beta] dc current-gain of the transistor.Advice - throw this ckt away, use something better.
This is the speaker. I am quite happy with them.http://www.mpja.com/4-Ohm-Mini-Speaker/productinfo/14618%20SP/
By a coincidence I got these in the mail today from eBay:2 Channels 3W PAM8403 Class D Audio Amplifier Board 5V$US 2.84 each.Wired one up to my iPhone and those old speakers. Quite nice sound out of it.
Quote from: oric_dan on Apr 02, 2013, 05:50 amSo you might go back to tying the emitter to gnd, and use a 10K in series with the 220 uF cap on the base.Nah, that just killed the sound altogether (the 10K resistor).
And, given the choice of Class A, Class AB, Class B, Class C or Class D, what would YOU call it? The emitter resistor isn't really needed because the bias-stabilizing negative feedback comes from the fact that the top base resistor is connected to the COLLECTOR and not to VCC.