[RTTY] Reddit Article Showing Windows 7 and certain USB Audio Chipbug

John Merrill jlmerrill at outlook.com
Thu Jul 30 10:18:26 EDT 2015


Thanks, Joe. I can confirm my 590SG has no problem with Win 8.1 or 10.

73, John N1JM


> On Jul 30, 2015, at 6:43 AM, Joe Subich, W4TV <lists at subich.com> wrote:
> 
> 
> The "bug report" is highly inaccurate and the instruction to
> set the "microphone" level to 100% is completely *wrong*.
> 
> Right click on the microphone slider and set the display for
> *decibels*.  In Windows 7 the microphone slider scale will range
> from -196.0 dB at 0 to +30 dB at 100% while in Windows 8.1
> the scale will be -96.0 dB to +30.0 dB.
> 
> Negative gain levels represent attenuation between the input of the
> CODEC and the analog to digital converter while positive gain levels
> represent excess gain.  Sands is completely *wrong* when he says any
> value below 100% represents attenuation.  In fact, any value above
> 0.0 dB represents *GAIN* in the CODEC.
> 
> There is one "bug" in Windows 7 and prior - the USB Audio Class
> driver will reset the gain of the endpoint (input) on any CODEC
> that has a *single input identified as "microphone"* every time
> the CODEC is opened.  This means Windows sets some members of the
> TI PCM29xx family to +30 dB on each use.  *THIS BUG HAS BEEN FIXED*
> in Windows 8 and later.
> 
> The best recommendation for setting USB levels for any "microphone"
> input supported by the Windows "USB Audio Class" driver is:
> 
> - start the program that uses the sound card in question
> - go to Control Panel | Sound | Recording tab, double click on
>  Microphone - USB Audio Codec device
> - on the Levels tab, right click on the microphone slider and
>  set the units to *dB*
> - adjust the slider for 0.0 dB +/- 0.5 dB - this will typically
>  be 3% in Windows 7 and 54% in Windows 8.1
> - tune to strong carrier (S9+)
> - watch VU meter on Recording tab and adjust output level from the
>  radio (typically the RX pot on the interface - "Line Out" in the
>  K3/K3S) to 2 bars below full scale. If it not possible to reach
>  2 bars below full scale (the K3/K3S has plenty of excess drive)
>  increase the level slider slightly until signal is no more than
>  2 bars below full scale.
> 
> I no longer have working XP or Vista systems and do not recommend
> the use of obsolete operating systems.  However, the same procedure
> (adjust for 0.0 +/- 0.5 dB) should also work with XP and Vista to
> prevent overdrive and clipping there.
> 
> In any operating system, a 0 dB input gain setting will provide the
> best balance of dynamic range and sensitivity in a sound card with
> properly designed audio input circuits.  Audio from the transceiver
> should be set so the no-signal "sky noise" is about 15 dB above the
> noise floor of the CODEC and the strongest signals no more than "2
> bars" below the top of the "VU Meter" to prevent clipping.
> 
> It may be more difficult to properly adjust levels in some Icom
> transceivers that offer no hardware control of the audio levels
> into the PCM29xx family than in external interfaces or the Kenwood
> (and Elecraft K3S) transceivers that *do* provide control over the
> audio level to the CODEC.
> 
> This "bug" *IS* a compelling reason to upgrade to Windows 8.1 or
> Windows 10!
> 
> 73,
> 
>   ... Joe, W4TV
> 
> 
> 
> On 2015-07-30 1:08 AM, 'Jim' jimw7ry at gmail.com [N1MMLogger-Digital] wrote:
>> This was from the RTTY reflector. I though it would be appropriate for here too.  Both my IC7600 and new IC7410 have this issue.
>> 
>> 73
>> Jim W7RY
>> 
>> 
>> 
>> Found this article on Reddit tonight.  Apparently this gentleman has
>> discovered through some testing that certain TI chipsets used in some
>> popular rigs and a popular USB interface may be causing serious errors in
>> digital decoding.  There's a link to the Youtube video showing the bug, and
>> how he's found a work around for it.  Apparently there's a possible issue
>> with some Icom rigs with built in USB audio, as well as the Kenwood TS590
>> series, and the Signalink USB Interface.
>> 
>> 
>> https://www.reddit.com/r/amateurradio/comments/3eytah/huge_windows_bug_ruining_your_receive_performance/
>> 
>> 
>> 
>> 
>> 
>> Charlie
>> 
>> N5WE
>> 
>> 
>> 
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