Rap 'n Tap
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From: Jim Wood, Brea, CA
Date: 9/2/99
Time: 10:52:47 PM
Remote Name: 152.175.181.219
< Jim White offers an explanation of the 'primitive detector' I'd never heard before; that electrons prefer exiting a point in deference to a flat metallic surface. I would have guessed that such a phenomenon would not be polarity-sensitive. I'd always figured that rectification took place because of some oxide layer on the razor blade. < Also, though tuned circuits in a table radio do not differ materially from those in a crystal set, doesn't the table radio have the advantage of a restricted IF passband to help its selectivity?
Jim
From:
Date: 3/16/99
Time: 9:32:43 PM
Remote Name: 209.109.233.90
Garry, Forget about all the center tap stuff. A good transformer to order from Mouser is 42TU013 which is 1k to 8 ohms, or 42TU003 which is 1.2k to 8 ohms. (The Radio Shack XFMR too.) They both work good into the walkman phones. They are about 1" cube. They give good low freq response on strong stations. If you want a smaller one, (size) they will work too, but I have found the Bass response a bit lower (Naurally). For starters, don't wire the center tap, just the ends. Later, try different wiring configurations. If you like to experiment, go ahead and hook to the center tap, and see what happens.
A higher impedance ratio is not necessarily better. The XFMRs have more turns of finer wire in them, and thus have more power loss into walkman earbuds. Too high an impedance ratio also leads to other more subtle types of mismatch problems at the detector too. If you want to experiment with higher impedance ratios later, go ahead. I have tried 1k to 8 ohm and 2k to 8 ohm. Results are pretty much the same. Only a slight change where the best place is to tap the detector diode.