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

[Joe Subich, W4TV]

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

I agree with Lyle ... the computer is almost certainly echoing Line 
In to Line Out.  Right click on the task bar speaker Icon and 
select "open Volume Control."  Select options | Properties | Playback 
and the miser device for the soundcard to which microKEYER/K3 is 
connected.  Look to see if Line In is one of the "Volume controls" 
options ... enable it and click "OK."  Now, make sure the Line IN 
level is all the way down and that channel is muted (note Line IN 
may be identified by the color of its jack).  Update Router's presets 
so the Line In is always muted on the playback side. 

microKEYER does not have any ability to connect Line In to Line Out. 

73, 

   ... Joe, W4TV 
 




> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Lyle Johnson
> Sent: Tuesday, March 03, 2009 6:26 PM
> To: eric at k3na.org
> Cc: Joe Subich W4TV; Elecraft mailing list; N1MM Logger; 
> support at elecraft.com; Elecraft K3 mailing list
> Subject: Re: [Elecraft] K3+microKeyer+MM: Realtek AC'97 feedback
> 
> 
> 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 
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