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Thread: APX 7000 & 8000 digital audio input

  1. #1
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    Default APX 7000 & 8000 digital audio input

    I've tried searching the forum and reading through the APX forum, but still no answer. Hopefully I'm not asking to be spoon-fed here.

    I'm not a tech, I'm a user, but I'm trying to help out with an issue we're having. We have an audio accessory that digitizes your voice and when used with P25 it results in double vocoding and poor/unusable audio quality. My question is this: if we can get the audio accessory manufacturer to update firmware and output digital audio, is there any way to configure the APX Portables to input digital audio? I know the accessory pinout has data input and external mic, but I'm not sure if it can be configured for digital audio input.

    If it can, what format or standard of digital audio does it support? Obviously this whole topic is best left to the tech guys, but in this instance at least they're scratching their heads.

    Thanks,
    -Dan


  2. #2
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    You cannot just put digital audio into the radio. The APX has no direct modulator input. Also you would have to create a codeplug dedicated to your use.

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    What specific audio accessory are you trying to interface? Almost everything made by a third party requires tweaking of the audio profile settings to get it to sound right.
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    Bad_karma (Apr 16, 2019)

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    It is a well known in-ear hearing protection headset that appears to use DSP to reduce background noise. I'm not sure I can further specify the exact hardware or agency due to NDAs. So far no luck with audio settings, but I'm not sure yet exactly what they've tried. I'm sorry, I know that isn't much to go on, but I appreciate your willingness to help anyway.

    The setup works with portable to portable (likely only tested at very short range) but is unintelligible on repeated systems, leading me to believe there is a double vocoding issue.

    Does anyone have any specific audio setting suggestions for the APX series that would minimize the distortion when used in such a system?

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    You need to do some more research into what DSP and noise cancellation the device performs. It sounds like the issue isn't double vocoding but double DSPing, which will definitely produce bad audio.

    If it were me... before I went screwing around with settings I'd establish a baseline for audio performance using the internal microphone and a non-XE/XP Motorola OEM lapel mic, then compare that to the accessory and figure out where it deviates. After I had the deviation from standard nailed down I'd start tweaking EQ or noise reduction/DSP settings. If the accessory performs internal DSP and noise reduction, those need to be disabled in the audio profile that will be used with that accessory... and you also need to strap that audio profile to any channel the accessory will be used on in the zone/channel assignment. There should be zero difference in P25 audio quality between simplex and repeated/trunked, and if there is it's a system issue, not a subscriber issue.
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    fake edit: You asked about general audio settings... I typically start at -3/+12 for DSP on P25 and no DSP with +3 fixed gain for analog, and Aggressive/Normal for the background and wind noise reduction settings.
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    Thank you very much, this sounds like a great place to start.

    -Dan