I need to add an out put to the SA-21 I've just modified because the built in output bypasses a couple of teh bends. I checked the tips page and it's got that handy diagram, the only problem is I can't figure out which wire from teh speaker is the ground and I'm too new at this to know if it matters.
I've only really noticed a porblem with polarity, when you have a stereo speaker set up.
Essentially - when one speaker, in a stereo system is wired wrong (+ to - not + to +) you get what's known as a 'phase' problem. Which means that as one of the speakers is pushing the air, the other one is moving backwards - kind of sucking, really. The overall volume gets reduced, and (in the magic world of theory) could cancel each other out ( perfect anti-phase)
So - I wouldn't worry about it really.
However!
What I would recommend - is put some small resistor (preferably one of those ones that can be adjusted with a small screwdriver) on the new output, to ensure that it's not too 'hot' (loud basically).
And if you do use one of those small screw-driver adjustable variable pots - you can then 'zero' it - so that the output volume of the speaker, and the output volume of the jack output are fairly simmilar in volume.
I think the + is the blue speaker wire judging from the picture you posted on the other SA-21 thread, at least on every one of the small toy speakers i have in a box that i can't bear to throw away, the + is on that side. In fact i wouldn't be surprised if you take a very close look at the white bit on the speaker where the wires solder on you might find some tiny + and - markings.
Had a closer look and it was just as you said, little '+' and '-' signs. Turned into something of a mission in the end but it's in there. Now all I need to do is add a switch to selct between output and speakers.
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