[Elecraft] K3S SSB TX monitor - feature request

[Richard Lamont]

On 08/04/17 18:11, Joe Subich, W4TV wrote:
> 
>> On 4/8/2017 2:24 AM, Richard Lamont wrote:
>>> The firmware, however, does not appear to support what seems a simple
>>> and common-sense requirement.
> 
> It is *not* the firmware - it is the *hardware* that does not support
> what you call a "simple and common-sense requirement" and what others
> call stupidity.  Perhaps you should study the schematic - at least of
> the K3 which is published.   Notice on the sheets K3 DSP: CODECS and K3
> DSP:DAC AUDIO the headphone/speaker amplifiers are fed *IN PARALLEL*.
> LHPOUT/RHPOUT of U7 (the DC) goes through the audio lowpass filter to
> U1 (speaker amplifier) and U2 (headphone amplifier) *IN PARALLEL*.
> *THERE IS NO POSSIBLE WAY* to send monitor audio *to only* the
> *headphone amplifier* (or for that matter *only* to the speaker).

I studied the K3 schematics a few days ago. I've just studied them
again. Thanks for the reminder.

On receive, the rig is capable of muting the speakers when the
headphones are plugged in. This is quite normal. This happens despite
the two audio amplifiers having parallel inputs.

There are switch contacts on the front panel headphone jack that enable
the rig to 'know', firmware permitting, whether there's a jack plug in
the socket. There is also a line labelled MUTE1 connected to the pin 2
of the speaker amplifier U1.

So the hardware exists to enable the firmware (a) to know whether
headphones are plugged in, and (b) to mute the speaker amplifier. This
hardware is, AFAICS, used on receive. All I'm asking for as an option to
do the same thing on transmit, if a particular set of circumstances is true:

Is the rig on a voice mode?
Is the audio input set to mic (not line in)?
Is the rig transmitting?
Is there nothing plugged into the front panel headphone socket?

If these four conditions are all true, then mute the speaker amplifier.


73,
Richard G4DYA