[RFI] RFI Clean Audio Amplifiers For Amateur Use?

[Bob Turner]

I use this one with the supplied wall wart.  

https://www.parts-express.com/dayton-audio-dta-1-class-d-ac-dc-battery-powered-mini-amplifier-15-wpc--300-380

I feed spkr audio to line-in on a mixer, then mixer out to the amp which drives two small Optimus speakers.   Amp is behind mixer in my qrz pic.  Its about 99% interference free from my own TX signals.  There was a particular freq which I can't remember now that might have been getting into my audio distribution system.  Part of my HF loop antenna with up to 500w used is about 15 feet above the shack/amp.  I operate HF with up to 700w, and VHF+ with up to 200w.

7 3  Bob
N2SCJ

-----Original Message-----
From: RFI [mailto:rfi-bounces+n2scj-lists=outlook.com at contesting.com] On Behalf Of KD7JYK DM09
Sent: Monday, October 5, 2020 12:37 PM
To: Tony <73guddx at gmail.com>; Rfi List <rfi at contesting.com>
Subject: Re: [RFI] RFI Clean Audio Amplifiers For Amateur Use?

> 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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