[hpsdr] TAPR Hermes - Noise on Audio Out

[David McQuate]

Ron,
   The fact that Hermes works perfectly when you're using a different 
desktop computer surely indicates that the problem is not with Hermes, 
but instead is certainly with the computer and OS issues.  No need for 
any mods to Hermes.

73,
Dave
WA8YWQ

On 11/22/2012 11:37 PM, Ron Nelson wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Thanks to all for comments and suggestions.
>
> On a different desktop computer, Hermes works fine with no extraneous 
> audio noise. I tried with both PowerSDR 2.2.3 (10/27/12) and cuSDR. 
> Works great!
>
> On my "problem" desktop PC the audio output noise continues to be 
> completely reproducible. More tests:
>
> I updated from PowerSDR 2.2.3 (10/07/12) to (10/27/12) - made no 
> difference in the noise. So I am using the latest software now.
>
> The noise is completely independent of the audio settings, volume, 
> sample rate, sample size, etc. It is on both the headphone and speaker 
> outputs. Everything points to oscillation of the audio output stage. 
> The ADC and FPGA are working fine - the RF spectrum and signals are as 
> expected. I can receive stations, but it is very annoying to listen 
> with the constant  loud noise, and forget about listening to weak 
> stations.
>
> With PowerSDR in the "Off" state there is no audio output, as 
> expected. With the ethernet cable disconnected the audio output also 
> turns off, as expected.
>
> The noise is there whether I use headphones or speakers.
>
> I tried different ethernet cables (direct to PC) with no change.
>
> Because I have such a good testbed for tracking down the problem ;->, 
> I am willing to try some mods. Adding capacitance to the audio outputs 
> or power for the D-A converter has been suggested. I may try this 
> after a good nights sleep. Or I may try adding a different ethernet 
> port to the PC to see if that makes a difference.
>
> 73
> Ron
> NR5ON
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at openhpsdr.org
> Subscription help: 
> http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
> HPSDR web page: http://openhpsdr.org
> Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/
>
>

-- 
Clear Stream Technologies


 1353691325.0