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 Post subject: Dexter audio quality
PostPosted: Tue Feb 13, 2018 5:48 am 
DAPHNE Team
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Hello folks,

I wanted to share the resolution for some audio issues I've been having with Dexter. As far as I know, no one else has complained about this, so either I'm being a picky little jerk or everyone else has their Dexters installed in cabs in noisy arcades so they don't care. If you're perfectly fine with the audio output by the Raspberry Pi with your Dexter, stop right here.... you don't need to do anything.

To make a long story short, I was experiencing two separate audio noise problems with all 3 of my Dexters. The audio sounded like there was a bunch of electrical interference plus some intermittent hiss. I was able to reproduce this behavior outside of my cabs. My cabs are not in noisy arcades, so the static and hiss coming through the speakers was really annoying to me. Based on all my testing, I believe anyone would have this same problem.... but I am only speaking based on my own experience here.

Here's what I did to resolve this audio noise issue:

1. Make sure you have a Dexter that had the ground fix. (Dexters that have the ground fix are rev 3f and above. Most people should already have this... I believe only 20 or so early revs were made that didn't have the ground fix.)

2. Get a DC Barrel Jack to Micro-USB B Male Connector Adapter
https://www.amazon.com/JacobsParts-Barrel-Micro-USB-Connector-Adapter/dp/B019CXCHNS/ref=sr_1_3?ie=UTF8&qid=1518496772&sr=8-3&keywords=DC+Barrel+Jack+to+Micro+USB+adapter

And plug it into the Raspberry Pi power port on your Dexter and plug your Dexter power supply into that. No need to connect power to the Dexter.

At this point, you will notice that the audio is wayyyy cleaner now. But we're not quite done yet. You'll notice that when the video seeks, stops, or the audio is just generally quiet, a very audible hissing sound can be heard. This is a result of the Raspberry Pi's dithering "feature."

To disable audio dithering:

3. Take the SD Card out of the Raspberry Pi and put it in a card reader on your PC. Edit the config.txt file with Notepad++ or similar. Add the following line to the bottom:
Code:
disable_audio_dither=1



Put the SD Card back into your Raspberry Pi and start the game.

That's it.... you will have some far cleaner audio now!

I hope this helps someone else out. It took me awhile to finally come up with a solution for this.


Last edited by Brad O. on Sun Feb 18, 2018 2:16 am, edited 1 time in total.

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 Post subject: Re: Dexter audio quality
PostPosted: Fri Feb 16, 2018 3:37 am 
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Wow, thanks for the detailed information! Can you tell me how to check my Dexters to see if they have the ground fix you mentioned in #1?


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 Post subject: Re: Dexter audio quality
PostPosted: Fri Feb 16, 2018 8:25 am 
DAPHNE Team
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Bumblebrow wrote:
Wow, thanks for the detailed information! Can you tell me how to check my Dexters to see if they have the ground fix you mentioned in #1?


That's a very good question. I'd say the easiest way to tell is if you buy that power adapter, plug power into the Pi and it doesn't eliminate the electrical interference static. I don't know if there's a rev number on the board that identifies them... Matt Ownby would know better regarding that.

Thanks,

Brad O.


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 Post subject: Re: Dexter audio quality
PostPosted: Fri Feb 16, 2018 9:11 pm 
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Bumblebrow wrote:
Wow, thanks for the detailed information! Can you tell me how to check my Dexters to see if they have the ground fix you mentioned in #1?


Almost everyone has a Dexter rev 3f which has the ground fix. The revision is printed on the bottom PCB near the reset button, underneath the raspberry pi.

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 Post subject: Re: Dexter audio quality
PostPosted: Sat Feb 17, 2018 11:31 pm 
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Brad,
Thanks for this info.I have a prototype that was noisy and using the pi power input took care of most of the noise. I would like to use the edit in the config file. I looked at the file and noticed at the botom the last comand is ### End Custom Settings. Do you enter the audio comand above that line or below it. I just want to be sure before I edit and save.


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 Post subject: Re: Dexter audio quality
PostPosted: Sun Feb 18, 2018 2:10 am 
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ginazz wrote:
Brad,
Thanks for this info.I have a prototype that was noisy and using the pi power input took care of most of the noise. I would like to use the edit in the config file. I looked at the file and noticed at the botom the last comand is ### End Custom Settings. Do you enter the audio comand above that line or below it. I just want to be sure before I edit and save.


You can just put the audio command right after the ### End Custom Settings. It can be the very last line in the file.


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 Post subject: Re: Dexter audio quality
PostPosted: Sun Feb 18, 2018 3:11 am 
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Brad,
Thank you for the reply. Nice work on this issue much appreciated. :D


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