Question [U-AMP] quiet left headphone channel

[elpax]

I have a self-assembled U-AMP. Everything works fine except the left headphone. The sound is too quiet.
Judging by the oscilloscope and my modest skills in using it, the left (400 mV) headphone plays half as quietly as the right (800 mV) one.
I tried listening to the main theme of "Shadow of the Colossus" and a few songs through the "Simple Media System" app.
The only mention of the same problem I found was in Bozer's post.
I use I2S audio. The speakers work fine and play at the same volume.

Does anyone have any suggestions ?

 

[cy]

I don't have any suggestions, but I will say that I have a similar problem with the headphone jack in a Louii I built. From what I remember, the sound effects are only audible on one side, and the music is only audible on the other side. Changing the audio mode to Mono made it behave similarly to what you described here.

I was assuming my problems were the result of a repair I needed to do to my U-Amp. But seeing how I'm not the only person who's having this issue, I'm starting to think otherwise. I'm sure this isn't too helpful, but it can help knowing you're not the only one having this type of problem.

 

[fluffypenguin]

I have been experiencing the exact same thing with an unmodified U-Amp from 4layertech in a Wii portable. For me, the music is on the right, and the sound effects are on the left. I haven't tested mono audio, but I'm guessing that it would be the same situation with the right being twice as loud.

I know this also doesn't help much, but it is interesting to see other people had this problem, as I thought it was just my headphones.

 

[PurpleSkyz]

Hi! I have a very similar issue. Speakers sound fine, or at least they seem to be, as the quality is so low I am unsure (minus crackling at high volume, tried soldering them directly and using shielded wire but to no avail, anyway I digress).

However using rvl-amp, on headphones, I get music on both sides but sound effect is halved in volume on the left headphone. very strange.

Glad others have similar issues.

Q

 

[fluffypenguin]

Someone in the 4LayerTech Discord server found a fix, and it has worked for me.

The pinout for the headphone jack was slightly off on the U-Amp/RVL-Amp and the Ashida interface board, with the HR and GND pins being swapped. Changing those pins makes the audio equal in both sides.

 

[cy]

Interesting, I should open my Louii back up and see if doing this fixes it. I'll also send @Gman a message letting him know about this.

 

[PurpleSkyz]

Someone in the 4LayerTech Discord server found a fix, and it has worked for me.

The pinout for the headphone jack was slightly off on the U-Amp/RVL-Amp and the Ashida interface board, with the HR and GND pins being swapped. Changing those pins makes the audio equal in both sides.
View attachment 40274

Thank you!

1 year later, finally fixed. Spent a good 3 hours removing it and applying the fix. But it solved the issue.

 

[elpax]

Well, it's nice that someone noticed a bug in the Ashida interface board. But it's strange that the fix worked. After all, before the fix, wouldn't there only be a mono output?
Also, in my case I have a custom pcb (based on u-amp github) and I'm pretty sure I have the right pins because I wired it relative to the lm49450 datasheet. So I don't quite understand how we can have the same problem.

 

[PurpleSkyz]

Well, it's nice that someone noticed a bug in the Ashida interface board. But it's strange that the fix worked. After all, before the fix, wouldn't there only be a mono output?
Also, in my case I have a custom pcb (based on u-amp github) and I'm pretty sure I have the right pins because I wired it relative to the lm49450 datasheet. So I don't quite understand how we can have the same problem.

I mean it was weird to begin with that I had music on both sides, but only sound effects reduced 50% on left, It's also strange that all out issues seems related yet different.

I would say just give it a go and see.