Gentlemen,
Say I hook a dynamic mic up to a voltage amplifier of 1M+ Zin. The amp provides a gain of around 650. Could I reasonably expect to hear some (albeit very low level) output if I tap the mic with my finger whilst listening for an output signal with xtal earpiece? Thanks.
Pull my finger.
Output of an SM58 is about -56dBV at 1 Pa, and tapping on a mic easily exceeds 1 Pa. You should see at least 1V out of the amplifier.
CDsay S fuckoff, troll.
I was just trying a 'quick and dirty' approach with the mic and earpiece, to be honest. Very unscientific. It's the amp I'm testing; just wanted to see if it worked *at all* but probably the best thing to do is replace the mic with an audio signal generator and scope the output properly. I'd have thought given the very high impedance of a crystal earpiece I'd have heard something without need for a buffer, but that method is so crude and it's unable to confirm the expected Vgain so I'll start from scratch and do it properly I think. I have about 14 oscilloscopes so there's really no excuse.
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