I'm looking for an RFI-free audio amplifier that I can use to power the
external speakers on my SDR transceiver. The PC speakers I've tried were
very noisy, especially the USB powered speakers from China.
Almost anything from a thrift shop made in the past thirty plus years,
that runs on a wall-wart from 6 to 12 volts. Use a battery, linear
transformer (about a quarter), or clean SMPSU (25 to fifty cents, same
thrift stores...). So long as your local shop isn't in a high rent
district, expect to pay no more than a buck or two for a pair of
speakers, or five to ten for a fancy surround sound system with a
sub-woofer, although the sub-woofer will require AC to drive it, if the
rest of the speakers are nice, re-donate it.
I don't know if that's been been mentioned here before, but the
portable, and QRP boys have been doing this since the early 90's when
super awesome free-to-cheap RFI-less PC speakers began flooding the
stores, yardsales, and hamfests. Best of all, most are through-hole, so
easy to interface.
Kurt
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