Windows bug causes decoding performance with certain Soundcard Interfaces.

Discussion in 'Amateur Radio News' started by NT1K, Jul 29, 2015.

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  1. NT1K

    NT1K Ham Member QRZ Page

    Because TI has since came out with revisions of the chip (Now at Rev E).
    With vista or later, Windows recognize that the chip doesn't have an input volume so windows automatically assign a value that happens to treat the input as a microphone instead of a "Line In" device giving an extra 60db of "gain".
    Makes for a distorted signal. Simply turning down the volume in the sound settings will not help since you are just attenuating an already distorted signal.

    Will M$ fix it? Most likely not. There are new revisions of chips that do work with vista and up. The new Elecraft K3S uses a new rev PCM2XXX
  2. W5LMM

    W5LMM Platinum Subscriber Platinum Subscriber QRZ Page

    Is there a newer solder-in chip for Signalinks?
  3. W0EA

    W0EA Ham Member QRZ Page

    No, unfortunately the newer chips are not drop in replacements
  4. K7JGM

    K7JGM Premium Subscriber QRZ Page

    Thank you!!!
  5. KK4SUH

    KK4SUH Ham Member QRZ Page

    Never knew about this, thanks for sharing.
  6. W0PV

    W0PV Ham Member QRZ Page

    This is a great bug catch !! Kudos for blowing the whistle. I would bet there is quite a number of those early TI chips already in the installed base. While it may be understandable for MS to not revise current versions, I would hope they would fix it for Windows 10.
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    I am not sure it is a Windows Bug. It is a Windows design.

    It is just the results of what happened to the Windows Audio Mixer, when they decided to hose it and make it PNP for you.

    Enjoy the new contacts.
  8. W0PV

    W0PV Ham Member QRZ Page

    FYI - see below as copied from the N1MM Yahoo Group. It seems Joe Subich, W4TV, has a different take and more info on this issue. And allegedly a software upgrade to a later version of Windows is a solution. 73 de John WØPV

    Re: [RTTY] Reddit Article Showing Windows 7 and certain USB Audio Chipbug
    • Joe Subich, W4TV
      Today at 9:43 AM

      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!


      ... Joe, W4TV
  9. NT1K

    NT1K Ham Member QRZ Page

    Then how come many people with Windows 8.X and that have the PCI29XX with the old rev are experiencing the same issue in the video?

    He says KD9DAL is wrong but then he acknowledges that there is a bug so KD9DAL is technically not wrong. I can't comment on the suggested settings that the author suggested but it's better than trying to decode a distorted signal. I am sure many of us were unware of the issue since the majority of us don't go collecting the white papers for each IC in our equipment. The TI white sheet for the revs of chips don't list Win7 as a supported OS. We just assume it would work. It might have worked with XP but times have changed and now it doesn't work but by looking at the comments on here, reddit and youtube, it appears many people were unaware.

    So at least it's brought to your attention. You can decided to check it out, ignore it or try something out. Worst case is that you have to redo your audio settings. It won't brick it.
    Last edited: Jul 30, 2015
    AI6AS likes this.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    That is a bit of a stretch.

    Why mess up a good OS when a small tweak or different mixer can fix it ?

    Windows 8.1 or Windows 10 does not protect from operator error.
    KF5RRF likes this.

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