[Elecraft] K3 LINE Out mixes KRX3 and main output?

[Joe Subich, W4TV]

> For the device in question, Griffin iMic, this doesn't seem to be the 
> case. It does not separate enumerations for independently setting left 
> and right input gain. It does support stereo input, just not two 
> mic/line gain controls.

I don't know about the iMic - Chen would though.  We've been using 
TI and Micronas USB sound devices that are directly supported by the 
native "Windows Audio."  The TI devices do not have an input mixer - 
sounds a lot like the iMic - but they still provide two channels of 
receive audio and an application can hook either channel or force 
the driver into mixed mono.  

I've used both the TI and Micronas based devices in stereo (separate 
left/right) for dual receive or right only (sub RX only) with MMTY, 
MMVARI, and MixW.  Unfortunately, I see the issue with FLdigi ... it 
uses mixed mono with either the TI or Micronas CODECs.  I can handle 
that by turning down the input level to the CODECS (manual gain 
controls) but that still does not permit dual receive.   Interestingly, 
DM780 handles both the TS and Micronas in left channel (Main RX) only. 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: Leigh L. Klotz, Jr WA5ZNU [mailto:Leigh at WA5ZNU.org] 
> Sent: Saturday, January 31, 2009 7:51 PM
> To: lists at subich.com
> Cc: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 LINE Out mixes KRX3 and main output?
> 
> 
> Joe Subich, W4TV wrote:
> >> It doubles the data transfer to capture both sound channels
> >> and discard one. 
> >>     
> >
> > Why would you bother to capture both?  Your software should
> > be able to select left, right or mixed input from the soundcard. 
> >   
> 
> Hmmm...I'm looking at the multi-platform PortAudio v19 API here:
> http://www.portaudio.com/docs/v19-doxydocs/structPaStreamParam
eters.html

Currently, we're using PaStreamParameters::channelCount=1, which doesn't 
offer the opportunity to specify a left or right.
With channelCount=2, we could of course get two channels and discard 
one, as I mentioned.

PulseAudio, which is Linux only, doesn't seem to support it either, but 
I believe ALSA and OSS do.

So, if we use a Linux only solution it's possible to specify 
single-channel capture without discarding one channel, but for the 
cross-platform APIs, it doesn't seem possible. I know you know more 
about sound device manufacture than I do, so maybe you can point us at 
something we've overlooked in PortAudio, so at least we could get 
portable sound capture support for single-channel input.
> Even relatively basic USB sound codecs provide control over the
> input configuration. 
>   
For the device in question, Griffin iMic, this doesn't seem to be the 
case. It does not separate enumerations for independently setting left 
and right input gain. It does support stereo input, just not two 
mic/line gain controls. This seems to be the case on Linux (see 
http://seehuhn.de/pages/imic ) as well as Vista. On Vista, it's even 
worse, and won't capture in stereo at all.

Leigh/WA5ZNU