NAD T757 clipping?

Polkies...

I recently hooked up my cable box to a NAD T757 AVR to watch tv in surround. I also hooked up an amp to power the two front towers. While it sounds great watching a channel it occasionally give a nasty clipping sound through the speaker(s) when I change channels. The occasional clipping only happens when changing channels. I am guesstimating it has to do with the sound format changing. On the AVR display I see it change from PCM to Dolby Surround and Dolby Surround+.

Any help is greatly appreciated!

TIA

Comments

  • msg
    msg Posts: 6,448
    Does it sound like a really loud, harsh, quick click/pop?
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  • msg
    msg Posts: 6,448
    edited December 2020
    I've had a similar thing happen sometimes with a Roku player when starting up or shutting down an older TV. My AVRs are older with no HDMI, so all HDMI goes through the TV, and TOSLINK out to the AVR.

    The hookup from your cable box to the AVR - is that HDMI or TOSLINK?

    Maybe HDMI handshake?
    Tried a different cable?

    Only thing I can think of is firmware updates on both the TV and AVR. Probably not a lot you can do with the cable box.

    Are you able to replicate this issue on demand?
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  • Kex
    Kex Posts: 4,418
    Yeah... this does not sound like the common definition of “clipping”, as in overdriving speakers so as to damage the tweeter (which is very difficult to do with a NAD - I’ve never even come close, and with an amp on the front two channels, I’d think that it would be next to impossible).

    Sounds more like loud popping. If this were my setup, I would try removing the amp entirely (as a test), and see if you still get the popping when changing channels.

    By changing channels, you mean changing channels on the TV?

    I’ve been using the same AVR for years, BTW. Never experienced a popping sound.
    Alea jacta est!
  • Kex
    Kex Posts: 4,418
    This could also be something to do with the settings on the T-757.

    PCM is Pulse Code Modulation, but it can be configured in settings to play back in Dolby Surround or other formats. If [None] is selected, then the source should play back in its native format. I would expect that [None] would not trigger popping.

    You could also try to reproduce the popping sound forcibly by using the remote or front panel to switch the listening mode, and see if that triggers the popping.
    Alea jacta est!
  • Kex
    Kex Posts: 4,418
    One other thing is to determine whether the popping is coming from the speakers, or the subwoofer. It sounds a lot like a signal auto-detection pop from what you describe (and those can be quite unpleasant).
    Alea jacta est!
  • acmf74
    acmf74 Posts: 919
    Hi and Thank you for all the replies. In Settings/Listening Mode I selected all the choices to NONE. This helped quite a bit in solving the issue but now its an occasional pop when changing channel's from the cable box. Maybe I need to update the software on it.
  • Kex
    Kex Posts: 4,418
    If the popping occurs when changing channels on your cable box, then the problem is likely not from the the NAD (no change in inputs on the AVR involved). No HDMI input switching involved - which never generates any popping for me anyway.

    Does the front display show “Direct” on the NAD when you are using cable, or something else? Is the cable box connected to the NAD through HDMI, or something else? So video gets fed from cable box —> T-757 —> TV ?

    It may be possible to update the firmware on your cable box. I would have thought that was OTA, and automatic, but maybe not (haven’t had a cable box in years).

    I’m not aware of a procedure to update the firmware on the T-757. If one were available, it would involve a visit to a service center.
    Alea jacta est!
  • acmf74
    acmf74 Posts: 919
    I have it connected by cable box —> T-757 —> TV and also have it set to DIRECT. I am guessing it may need a firmware update but need a specific cable to connect from my PC to avr.
  • Kex
    Kex Posts: 4,418
    edited December 2020
    I’m still not convinced an update the 757 will change anything, since the AVR is not “switching” when the cable box changes channels.

    In any case, I do not think the 757 is intended to be updated by the end user, so NAD Electronics will not provide an update file for that.

    You can try a Factory Reset, as outlined in the procedure HERE. You will lose all settings, including the Audyssey setup, and input/output settings.

    Otherwise, contact Customer Serivce. I haven’t done that in a while. They used to be quite good, but I don’t know if they still respond directly to customers. The main link is HERE.
    Alea jacta est!
  • acmf74
    acmf74 Posts: 919
    Thanks again... NAD did reply and sent me the file to update the software which I wont do my own. I will find a NAD center to see what they say.
  • acmf74
    acmf74 Posts: 919
    So for the closure I had a technical rep from Verizon help me diagnose the issue. He walked me through on how to get into the diagnostics of the box and did a HDMI reset. We changed the Surround sound code from AUTO (surround) to LPCM and this remedied the issue! :)
  • Kex
    Kex Posts: 4,418
    Excellent news! 👍

    Well done. Well worth persevering! Those cable/satellite/fiber boxes frequently have hidden settings that they don’t disclose to the end user.

    Thanks for updating the thread — if another NAD user finds themselves in a similar predicament in the future, they’ll know where to start their investigation.
    Alea jacta est!
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