[Elecraft] KX3 with external speaker

[Joe Subich, W4TV]

A very similar amplifier (same amp IC, similar layout) here:

  <https://www.amazon.com/HiLetgo-TDA7297-Version-Amplifier-Dual-Channel/dp/B00LOG51EE/135-0623238-9759344>

73,

    ... Joe, W4TV


On 2026-02-17 1:44 AM, Walter Underwood via Elecraft wrote:
> A while ago, I added a 12 V audio amp to my setup and wrote it up on my blog. I don’t think that particular amp is available now, but I’m sure there are similar ones.
> 
> https://observer.wunderwood.org/2017/03/04/speakers-for-my-elecraft-kx3/
> 
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
> 
>> On Feb 16, 2026, at 4:30 PM, Walter Underwood via Elecraft <elecraft at mailman.qth.net> wrote:
>>
>> The KX3 “PHONES” jack is for headphones. It produces 100 mW. —wunder, K6WRU
>>
>>> On Feb 16, 2026, at 3:44 PM, Jim Brown via Elecraft <elecraft at mailman.qth.net> wrote:
>>>
>>> On 2/16/2026 3:15 PM, Phil Hystad via Elecraft wrote:
>>>> Can someone give pointers on this?
>>>
>>> The K3, K3S, and K4 have separate audio power amplifiers for headphones and speakers, each with their own individual output jacks. I haven't studied the schematic, but I suspect that the KX3 has only the amplifiers for headphones. Speakers require considerably more power.
>>>
>>> The headphone output could probably drive a powered speaker (that is, one with its own built-in amplifier), but powered speakers are notoriously bad for RFI, both generating noise and being susceptible to nearby transmitters, so are unlikely to be a solution.
>>>
>>> 73, Jim K9YC