OK, let's see... (it's been a lot of years so take this with a grain of salt):

1. I don't think this is going to be sufficiently powerful to drive a speaker, at least not with any noticeable volume. The transistor is a low power one, rated for well under a watt. Looks like more of a preamp stage than a speOther limits for the 2N3904 are 200mA current and 625mW power, so let's see...aker amp.

2. The transistor is rated for ~40V max, so that is the absolute highest, but this seems more like a circuit that would run on 12V or less to me.

3. R1 seems to be in an odd place, normally input resistors like that are connected to ground not to a power rail.

EDIT - might have found the original source, or at least another instance of it. In the following link the author is using a 3v cell, which seems reasonable.

http://hackaweek.com/hacks/?p=327

In this article r1 is there because the circuit is being used as a microphone preamp. The author mentions an electret microphone but I didn't think electrets needed a bias voltage from the preamp. Oh well...

Hope this helps. Good luck...

Last edited by bridgman; 09/08/16 12:27 AM.
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