[Elecraft] K3+microKeyer+MM: Realtek AC'97 feedback

[Lyle Johnson]

Hello Eric!

>    I'm seeking advice on a feedback problem.
> 
>    Scenario:
> PC line out -> microKeyer -> K3 mic in (Note 5)
> PC line in <- K3 line out.  (Note 1)
>    Note 1:  microKeyer is bypassed so that stereo gets delivered to the 
> computer for archival recordings.
>    Note 2:  K3 CONFIG: LIN OUT can be either "nor 001" or "=phones" 
> without changing the problem.
>    Note 3:  To simplify and isolate the problem, MM is not running.
>    Note 4:  More details about the PC and K3 firmware listed below.
>    Note 5:  Can connect direct to K3 Line In (bypassing the microKeyer), 
> changing MENU MIC SEL accordingly, without affecting the problem.
> 
>    When I put the radio into TX (short the footswitch input on the 
> microKeyer), and play an audio file out the PC, a feedback loop exists.  
> The severity of the loop depends on the K3 MON setting: low setting 
> (<<10) means no echo chamber.
> 
>    The only possibilities are the K3 is making the loop, or the computer 
> is making the loop.  I'm not sure how to isolate this.

I suspect (but do not know) that it is the PC mixer configuration.

If the K3 is outputting MON audio, then what appears at the K3 LINE IN 
will re-appeer at K3 LINE OUT with some delay and +/- gain. If the PC's 
mixer is active so that the PC LINE IN is mixed with whatever source you 
are playing back, then you'll probably get feedback.

One way to tell is to remove the K3 and just loop the PC output back to 
its input.  You might want to listen on an amplified speaker using Y 
cable - or not, depending on how much you value your hearing :-)

73,

Lyle KK7P