On Tue, Oct 12, 2004 at 02:42:59PM -0700, Mark Knecht wrote: > Much of the 'consumer' equipment out there uses high resistance output > drivers since they are less expensive to build. Pro equipment will > almost always use low impedance outputs. I'd expect most consumer equipment to use op-amp based gain blocks which are cheap enough and have very low output impedance. Usually the output has a resistor (100 ohm or so) in series for protection against instability. [snip explanation of impedance mismatching] > 1V amp PP output -> 1000 Ohm output <---cable----> 100 Ohm input 100 ohms is very unlikely for an input. Even a low-z mic input has an impedance of over 1k, and a consumer line level input is likely to be 10k. The actual voltage levels used by consumer equipment do vary, though. There is a semi-professional standard of -10dBu for RCA connectors, but domestic equipment does not necessarily follow that. You often see that in a stereo 'separates' system where you routinely have to adjust the volume when switching between tuner/CD player/tape etc. I suspect this may actually not be too much of a problem. 25% of the way up a VU meter (VU meters are linear) means 12 dB below full scale, and a 16 bit digitized signal will actually be 14 bits. So boost the gain electronically (e.g. with normalize, or I'm sure sox or ecasound can do it too) after it's in the computer. There will in theory be some loss of signal-noise ratio, but as the original poster was using a Sound Blaster, we're not talking about professional audio here. A professional-grade sound input device would either have variable analogue gain to match the input level precisely, or acccurately specified input level requirements so the user knew exactly what to expect. -- Anahata anahata@xxxxxxxxxxxxxx Tel: 01638 720444 http://www.treewind.co.uk Mob: 07976 263827
