K3 uses the. LM4811 Headphone Amplifier
Texas Instruments Specs for output Z RL = 16Ω 105 mW RL = 32Ω 70 mW At 60 ohms the output power drops to 20 mw. Per their graphs. 300 ohms is not even considered. Amplifier gain control is done digitally within the chip. With such a high Z load, gain would likely need increasing. The results of doing so are unknown. Consider pop, click, white noise etc. Also consider what happens when switching from headphones to speaker when the AF Gain control is turned up high. Blasting? I suggest sticking within the 16 to 32 ohm range. Steve N4LQ On Mon, Dec 28, 2015 at 1:16 PM, Jim Brown <j...@audiosystemsgroup.com> wrote: > On Mon,12/28/2015 10:08 AM, Barry N1EU wrote: > >> I believe this also means that the K3 headphone output circuit will >> deliver 10X power (with fixed V, P~1/R) into a 30-ohm headphone as a >> 300-ohm headphone, so at some point the amp might clip as you raise >> the headphone impedance? >> > > Only if you crank the headphone output too high. My 1V example is simply > the maximum sine wave output at clip, and that value is typical. When you > turn down the headphone gain, you reduce that voltage. I don't recall the > spec for the K3. In your 30 ohm headphone example, you would probably not > need to crank the gain nearly as high, so the output voltage would stay > below clip. The exception might be if the operator has significant hearing > loss, so was driving the headphones very hard. > > 73, Jim K9YC > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to steven...@gmail.com > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
