Dr.EM said:
Hi. I dont know too much about impedance, but I was basically wondering, what are the implications of using say a 3kohm device with perhaps a 600ohm input. Other than degraded sound quality, are there any more serious issues involved with this?
You need to be more specific, there are two totally different methods of impedance matching used:
1) Power transfer - this requires both input and output impedance to be identical, and gives the maximum power transfer (by simple ohms law and watts calculations). Used for the output in RF transmitters - by definition the output dissipates the same amount of power as the load receives.
2) Signal transfer - this requires a low output impedance, and a high input impedance - this gives maximum signal transfer, but not maximum power. Used for general audio connections (or most signals?), for example the output impedance of an audio amplifier is probably under 0.1 ohms, and the speaker load 8 ohms. This provides high power in the load, and low dissipation in the amplifier.
As you mention 600 ohms, presumably you're talking about microphone inputs?.
The first thing you need to think about is what the actual impedances are?, a 600 ohm microphone input is not likely to be 600 ohms, most likely it will be higher?. Likewise, your 3K output impedance may well be lower than that?.
You only need simple ohms law to work out that the two together form a potential divider, with 3K at the top, and 600 ohms at the bottom - giving considerable attenuation to the signal. But as a low impedance input has more gain, it won't be as low as you might first imagine.
Best idea is to try it and see what happens, if you're trying to feed a high level signal (out of a CD player or preamp for example) into a 600 ohm input, you should add a series resistor - which will provide a better imedance match, and attenuate the signal down to the correct sort of level.
Many years ago the first Philips cassette recorders only had microphone inputs, to make a line input lead you added a 1.5MOhm resistor in series inside the DIN plug.