Mic preamp

258

04:19:44

A mic preamp for a condenser mic. For a dynamic mic remove the 3.3k resistor. For a carbon amp some readjustments must be made so ill leave that behind. Its designed so that it would supply a power amp with line level of around 1V/pk-pk (around 330mV RMS). The amp is designed to amplify signals within the 300Hz-3400Hz range because thats where human voice lies.

published 11 years ago

rbrtkurtz

11 years ago

1Vrms = 1.414V amplitude (aka Vmax). 707mVrms = 1V amplitude. 330mVrms = 467mV amplitude. 233mVrms = 330mV amplitude. Your amp is putting out about 330mVmax, which is 233mVrms. I looks like you're trying to use the formula Vrms=0.3535·Vpp. Remember, Vmax (or amplitude) is half the wave. From 0 to the peak. Vpp (peak to peak) is literally the measurement from one peak to the other. An amplitude of 1V has a Vpp of 2V (+1V to -1V). So, you have an amplitude to 330mV. Peak to peak is 660mV. Vrms=0.3535·660mV. Vrms=233mV. Personally, I think that method is silly. Just multiply your amplitude by 0.707 to get rms. 330mV·0.707=233mVrms. If you're looking for an output of 1Vrms, you need an amplitude of 1.414V.

hurz

11 years ago

Vpp for me is Vpeak-to-peak and 1Vpp is 1V/2*0.707= ~350mVrms, right?

thebugger

11 years ago

I know the formulas. Vmax=1/2 Vpk-pk whereas Veff (Vrms)=Vmax*0.707 its just that I made readjustments after posting the description.

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