I only need a very very basic speaker, powered maybe by AA batteries,
that amplifies the 3.5mm audio output from the iPod Touch.
Is this going to be cheap?
Could I just connect a small buzzer to it?
Don't use a buzzer.
This sounds to me like a job for an entry-level DIY-er trying to work
with actual electronics to work with:
An LM386, specifically LM386N-1 IIRC, a "cheap-and-dirty" hobbyist
audio power amplifier in low power range and good for 6V and 9V use, 12V
with some care.
Use any 8-ohm loudspeaker at least 2 inches in diameter with 5V to 9V
power supply, such as USB power, a 5V regulated power supply, 4 AA cells
or a 9V battery. Even if you push things very loud, the LM386 tends to
survive and even the crappiest loudspeakers won't completely die quickly,
and most won't get damaged at all.
LM386N-1 is the version that Radio Shack sold, and fair chance still
sells. Radio Shack catalog number 276-1731, may not be available in all
stores. Other parts needed withy it may not be available in all stores.
I recommend looking for Radio Shack stores with 4 sets of drawers of small
parts, as opposed to 2 or some other smaller number.
The lead-free version is available at Digi-Key, get to that here:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=LM386N-1-ND
(Minimum order or falling-short-of-minimum-fee and shipping charges
apply.)
Datasheet for National Semiconductor LM386 is here:
http://www.national.com/ds/LM/LM386.pdf
Pinout (viewed from above) of LM386 is in the lower-right corner of the
1st page of this PDF.
The schematic of my favorite way to use this (simplest) is in the
upper-left corner of Page 5 of this PDF.
The capacitor mentioned as 250 uF can be larger, though I see little need
to use more than 1000 uF.
The capacitor mentioned as .05 uF can be the more-common .047 uF. I
have successfully used .1 uF, but I recommend staying in the range of
nominally .047-.1 uF.
===============================================
If you want a loudspeaker to use with the LM386 that I especially like:
Radio Shack 40-1909. May not be easy to get now, may be obsolete. It's
very much an all-purpose lower-power 5" fullrange loudspeaker with fairly
decent efficiency and some capability of impressive bass response.
Put it in a box of about shoebox size and made of wood at least 1/2
inch thick - amazing even without a port. Bass response is rather decent
in a .23 cubic inch box against a wall, with -3 dB at 108-110 Hz. It even
works well in a .125 cubic foot box - -3 dB is at about 120 Hz. In a .1
cubic foot box, its -3 dB bass point is about 126-127 Hz.
In a .63 cubic foot box with port tuning of 62 Hz, the bass -3dB point
is 53 Hz. That is good bass response for a box that size with 91 dB @
1W, 1m with a fullrange or woofer of any size.
Details including box and port dimensions at:
http://donklipstein.com/1909.html
