Jim, I think it would be great if you would clarify your comment to Steve. I've looked at the data sheet and everything Steve said seems correct to me???
And I'm not sure I'm willing to totally buy (per Joe) that there's necessarily a proportional relationship between headphone impedance and efficiency that makes up for the inverse relationship between output power and load impedance. I just don't observe this efficiency rule consistently in my collection of headphones with varying impedance. Headphone efficiency clearly has other dependencies than impedance. 73, Barry N1EU On Tue, Dec 29, 2015 at 6:46 AM, Jim Brown <[email protected]> wrote: > You clearly don't understand what you're reading on that data sheet, nor the > design of audio output stages. I refer you to my earlier posts, and to those > by W4TV, W2RU, and W3FPR. > > Those numbers you quote are NOT the output impedance, they are the minimum > LOAD impedance that the output device is designed to work into. Modern > output stages are essentially constant voltage sources. That's what Bud is > telling you with his discussion about damping factor -- the output Z (source > Z) is typically 50-100 times the load Z. > > With headphone amplifiers, a good designer will add some small value of > resistance in series with the output to prevent the output stage from > failing if a short is connected to its output (which could occur when a plug > is being inserted, or with an improperly wired plug). Line level outputs use > a series output resistor to prevent the output stage from seeing the > CAPACITANCE of a long cable, which could, by interaction with the feedback > network, cause the output stage to oscillate. > > Executive summary -- simply buy good quality headphones, and don't worry > about impedance. > > 73, Jim K9YC > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
