[Elecraft] headphone impedance

[Steve Ellington]

No problem...Just grossly out of specs.
Whatever happens....happens
73

Steve N4LQ

On Mon, Dec 28, 2015 at 2:53 PM, W2RU - Bud Hippisley <W2RU at frontiernet.net>
wrote:

> What am I missing?
>
> I use 600-ohm stereo headphones plugged directly into the front panel jack
> of my K3S.
>
> I run the Audio Gain control at 9 o’clock — roughly a 25% rotation toward
> full volume.
>
> I have more than enough audio for my elderly ears, and when I pull the
> headphone plug out of the jack, my speaker audio is at a comparable level.
>
> What is the non-problem with high-impedance phones that you guys are
> trying to solve?
>
> Bud, W2RU
>
> > On Dec 28, 2015, at 1:59 09PM, Steve Ellington <steven4lq at gmail.com>
> wrote:
> >
> > 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
> >
>
>