[hpsdr] TAPR Hermes - Noise on Audio Out

[Jim Sanford]

I agree with Phil.  I had a similar problem using an external high-end 
sound card and a laptopto move my reel-to-reel recordings to CD.  Turned 
out, it was a windows problem, which went away, when windows got 
re-installed (for other reasons).

Good luck!
73,
Jim
wb4gcs at amsat.org

On 11/23/2012 6:47 AM, Phil Harman wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Ron,
>
> You may want to run a  Deferred Procedure Call (DPC) check on the PC 
> that has the noise on the Audio out.
>
> See Appendix B in the Hermes User Guide for information relating to 
> this test.
>
> 73 Phil...VK6APH
>
>
>
> -----Original Message----- From: Ron Nelson
> Sent: Friday, November 23, 2012 3:37 PM
> To: hpsdr at lists.openhpsdr.org
> Subject: Re: [hpsdr] TAPR Hermes - Noise on Audio Out
>
> ***** 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
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