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

Joe Subich, W4TV lists at subich.com
Thu Jul 30 11:09:22 EDT 2015


On 2015-07-30 10:23 AM, Jim W7RY wrote:
 > Did you watch the entire video Joe?

Yes, I watched the entire video.

 > Nowhere is the K3 even mentioned in this issue.

Kenwood and Icom are and the K3S uses the same PCM290x series codec
as do many other amateur interfaces beside Signalink.

 > Please elaborate on the oscilloscope pattern and the hard limiting.

The hard limiting is simply because the the slider is at 100% or
30 dB of gain.

 > Also, please explain why the level drops dramatically when the
 > default format is changed.

*That* is because of a bug in the Windows 7 and prior drivers.  The
CODEC identifies the endoint (input) as a microphone but when the
user selects a 2 channel format, Windows 7 changes to a Line
configuration *without properly adjusting the user interface*.

73,

    ... Joe, W4TV


On 2015-07-30 10:23 AM, Jim W7RY wrote:
> Did you watch the entire video Joe? Nowhere is the K3 even mentioned in
> this issue. Please stick to the facts and the hardware that is addressed
> in the video.
>
> Please elaborate on the oscilloscope pattern and the hard limiting.
> Also, please explain why the level drops dramatically when the
> default format is changed.
>
> 73
> Jim W7RY
>
>
>
>
> -----Original Message----- From: Joe Subich, W4TV
> Sent: Thursday, July 30, 2015 6:43 AM
> To: N1MMLogger-Digital at yahoogroups.com ; N1MMLogger at yahoogroups.com ; RTTY
> Subject: Re: [RTTY] Reddit Article Showing Windows 7 and certain USB
> Audio Chipbug
>
>
> 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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