Issues With Stereo Audio(Pi3+PAM8403+ Kedei HDMI)

[DeRock89]

I think you are the first to use pi 3 and HDMI.
did you try the config.txt example to see if it helps with the power problem?

I read somewhere in this forum that composite screen draws 430mA, which would means the HDMI screen draws much more. In your case you need to source a more powerful power boost.

Maybe this will do the job? https://www.aliexpress.com/item/5V1A-2A ... 0.0.yfQF0d

The AMP can be supplied with 3.3V, you might want to try that too.

I tested the screens draw with a multimeter and it appears to draw 380-400mA. The amp by itself was drawing 500-700mA by itself, possibly more, I was nervous about turning it up too loud...

I've done some experimenting with resistors in various places and it seems I can reduce the draw by placing resistors in line between the amp and audio jack on the screen. I don't know what the safe level I should aim for though... it seems to be loud enough at max volume with a high enough resistor value in this location to reduce the currant to about 60mA. I got a ton of resistor 1/4 watt resistors with 1% value in the mail the other day to try and find the right values and locations for them. I have no idea if what I'm doing is actually a good idea or not...

Also I'm wondering if it would be a good idea to put the resistors in this location and in line between the amp and speakers.

I really find it hard to believe that you have a major power issue, and that you haven't been able to sort it out yet....

the setup you've got is pretty much identical to the 1UP HD Game Boy kits



now your issue might actually be the powerboost, but i personally wouldnt start getting power supplies that havent been tried and tested in builds....

i would try the generic/banggod psu, and if you havent already done so connect a battery to the setup (having a battery hooked up can also make a difference)


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Yeah Im going to order a bangood PSU when I get paid... it sucks because I already have a safe Shutdown for a powerboost, and With the way I've done my build, it will be a major pain to change to a differnet PSU...

Based on my limited knowledge, I personally think it's because I'm trying to use two speakers with 4 ohm impedance now that I've been mulling over it and going through it with you guys. I'm also into collecting vinyl records and vintage audio equipment. I know from dabbling in that that if I use 4 ohm speakers with a stereo setup, it almost doubles the watts pulled on a receiver/amp versus using 8 ohm speakers.

You remember when we tried just directly hooking the speakers to the screen jack? It resulted in barely audible sound, yet with the resistors in line before the signal reaches the amp, it's reducing the amperage the amp is drawing and it's still pretty loud. Granted, I'm using a separate PSU with the amp during these tests.

I wonder if next I try using the resistors to reduce the amperage on the amp and then try and connect it to the builds PSU with everything else and the problem still persists, then it's an absolute confirmation that it's an issue with the powerboost.

[VeteranGamer]

Yeah Im going to order a bangood PSU when I get paid... it sucks because I already have a safe Shutdown for a powerboost, and With the way I've done my build, it will be a major pain to change to a differnet PSU...

Based on my limited knowledge, I personally think it's because I'm trying to use two speakers with 4 ohm impedance now that I've been mulling over it and going through it with you guys. I'm also into collecting vinyl records and vintage audio equipment. I know from dabbling in that that if I use 4 ohm speakers with a stereo setup, it almost doubles the watts pulled on a receiver/amp versus using 8 ohm speakers.

You remember when we tried just directly hooking the speakers to the screen jack? It resulted in barely audible sound, yet with the resistors in line before the signal reaches the amp, it's reducing the amperage the amp is drawing and it's still pretty loud. Granted, I'm using a separate PSU with the amp during these tests.

I wonder if next I try using the resistors to reduce the amperage on the amp and then try and connect it to the builds PSU with everything else and the problem still persists, then it's an absolute confirmation that it's an issue with the powerboost.

i only use 4ohm speaker, I've had them in all my builds (there normally internal laptop speaker off eBay)
there better quality than buying off the shelf small 8ohm speakers, and have never let me down.....

the Generic/Banggood psu may be a better fit
have you actually got a battery hooked up as well.....


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[vnman]

@Derock89 -I have a few spare Banggood Power boost, PM me and I'll send you two...
But why change the power boost when the amp is the problem? (I know that I said change the power boost to the one that capable of outputing more ampere).

What is the amp that 1UP uses in his build? Is it stereo or mono?

[DeRock89]

@Derock89 -I have a few spare Banggood Power boost, PM me and I'll send you two...
But why change the power boost when the amp is the problem? (I know that I said change the power boost to the one that capable of outputing more ampere).

What is the amp that 1UP uses in his build? Is it stereo or mono?

Sorry, life has gotten super busy. I'm not sure what amp he uses, but from the pictures, it doesn't look anything like a pam8403. I don't see any ICs with the right amount of pins in the pictures to be a 8403.

I think the amp is just too much for the build with it having an HDMI screen and a pi3 too(im planning on using a fan too...) I haven't had the opportunity to fully test but I think making the amp " smaller" so to speak with resistors seems very promising. I've tested many combinations of resistors on the input and I'm able to dial down how many miliamps the amp draws at max volume. I feel I just need to get the overall currant down under what's within acceptable limits. I just haven't figured out the rest.

I've did notice there are big peaks in currant draw when there are things such as explosions played back in the audio. It may be nothing to worry about at all, it's more of a pondering for educational purposes. I've been doing tons of reading about capacitors and I'm wondering if I could also use caps in parallel with the amp power supply to manage transient peaks in current. For instance with the audio I've been testing with, I found that 72k ohm resistors has a good volume and it reduces the amp currant at max volume to 40-60mA on average but there are occasional peaks of 100 or more mA when there is a lound noise(like the wooden boxes breaking in crash bandicoot). Sometimes with more complex audio, the miliamps jump all over the place and I can't even pick a value to write down in my notes.

I'm wondering if caps could be used to smooth the draw to smaller fluctuations. It's not because it's necessary, but I simply want to know if it's possible and how to do it for the sake of knowledge if nothing else. I don't know how to determine how many uF the cap needs if it's possible too.
I know there's probably more simple solutions, but I'm doing this to learn too.

[DeRock89]

@vnman
@VeteranGamer
We have pretty much solved it! The screen is no longer going on and off! The only issue now is there is an occasional lightening bolt symbol in the corner. The battery is installed. There's not lightening bolt at all if the battery is installed and it's also plugged into a power supply. The audio is still VERY loud...

I installed a 10uF 50V cap on the power rail. I have a 75k ohm resistors for each input coming from the screen. I decided to use a single 3W speaker. On the output of the amp, I bridged the positives with two 10ohm resistors(did not bridge the ground. I read this is bad)

I reduced the system volume to 80% and the lightning bolt symbol only appears when exiting a game. Any lower then 80% and the volume isn't adequate to me at max volume on the pot. The retroarch menu still freezes sometimes and I think this is also related to a power demand issue.

I used the PAM8403 with the volume pot installed on it and screw terminals for the speakers when I was testing and didn't have a lightening bolt symbol at all when using that one. After I installed the small coin sized PAM8403 with the through holes, it became much louder at max volume and the lightening bolt symbol started appearing sometimes. I wonder if the final solution to solve everything would be to try super caps...

[salami738]

Hi, you can reduce the energy usage of the display if you can solder SMD.
If you do the things in: viewtopic.php?f=44&t=4242#p51445 you can reduce the energy consumption by 25%.
Maybe this is enough to solve your power issues.