[RFI] RFI Clean Audio Amplifiers For Amateur Use?

[KD7JYK DM09]

> 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