Paul, W9AC, wrote: Also, anyone contemplating the use of the D-104 with the stock Astatic amp should consider an alternative buffer amp. The input Z to Astatic's 2-stage
preamp calculates to 470K-ohm -- way too low for a crystal cartridge. The crystal cartridge should see a termination of no less than 5 megohm, and preferably greater than 10 megohm in order to preserve reasonable low-end response. --------------------------- The Astatic D-104 was designed as a *communications* microphone with a carefully shaped frequency response for speech and not for extreme high or low frequency response. The graph of the audio response published by Astatic, using the built in amplifier, shows 0 dB at 1 kHz. Below 1 kHz the output drops off smoothly to -5 dB at about 200 Hz, then more steeply down to -10 dB at 100 Hz where the published curve ends. That roll-off is important since excessive low frequency response robs a signal of intelligibility and "punch" since the bulk of the energy, but virtually none of the modulation in the spoken voice is down in those ranges. Above 1kHz, the output rises smoothly to a peak a bit above +10 dB at 3 kHz, the smoothly drops off to almost - 20 dB at 10 kHz. That rising characteristic to a peak in the roughly middle point of the speech audio spectrum is what made it so effective in communications and made it so popular. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
