{"id":1625,"date":"2018-06-19T09:35:00","date_gmt":"2018-06-18T23:35:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2018\/06\/19\/digital-pot\/"},"modified":"2025-07-21T11:51:44","modified_gmt":"2025-07-21T01:51:44","slug":"digital-pot","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2018\/06\/19\/digital-pot\/","title":{"rendered":"Digital Pot"},"content":{"rendered":"
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No, this is not some on-line mail order thing. <\/b><\/i><\/span>Bruce KC1FSZ has done something that I find both amazing and horrifying: he using a “digital potentiometer” as the AF gain control in his BITX. Remember when pots were simple and pure, when they were just a metal wiper that ran across a crescent of carbon of increasing resistance? Well, those happy days are apparently behind us my friends. What now? Will we have endless discussions about where to find the driver for the 10k pot? Will Facebook or Amazon or Microsoft secretly seize control of the data on our AF gain, perhaps to sell us hearing aids? But enough of my ludism. Good going Bruce. AGC beckons. <\/b><\/i><\/p>\n

Hi:<\/span>

I’ve built a few BITX rigs from scratch now and I’m starting to move to a modular approach using fabricated PCBs to make it easier\/faster to build\/mix\/match the stages. My audio amplifier module is based on the LM386. I know others have moved away from this chip, but it still works for me.<\/span>

I’ve added one feature to my audio amp stage that opens up some good possibilities. Instead of the traditional potentiometer between the AF preamp and the LM386, I’ve inserted a digital potentiometer (MCP4131-103) that is controlled by three extra pins on the microcontroller. The digital pot lists for $0.81 on Mouser so it’s no more expensive than a physical pot and it’s way more versatile.<\/span>

Why do this?<\/span><\/b> <\/p>\n