[Elecraft] headphone impedance

[W2RU - Bud Hippisley]

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
>