Help with interference and hissing problem on speakers and amplifier for Bartop project

Rion

Rankie HDMI to VGA Adapter with 3.5mm Audio Port - Black

rbaker

@rogerdodger I had this problem. The amplifier that you show actually amplified my issue as I had a similar one and sent it back. I decided to build an amplifier. Same issue. After a bit of searching, I came across this resource. What worked for me was a combination of adding disable_audio_dither=1 to /boot/config.txt and not having the volume set too high in the retropie setup, say around 60%. I then hacked apart a set of old speakers that had reasonable quality electronics inside and used that to amplify the sound. I ended up tweaking the volume setting in Retropie whilst experimenting with the volume control on the speakers and managed to get virtually no hiss. I think that the HDMI to 3.5" converter is a good idea too but I have not tried it.

stoney66

@rogerdodger This is what I bought a couple years ago, I use the 3.5 jack and I don't have any sound issues. Your mileage may vary though.

https://www.amazon.com/gp/product/B003XRGY8Y/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B00K2ESJZ2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

cyperghost

@rogerdodger Let's go digital with I2S amps

rogerdodger

Thanks very much for all the useful help and suggestions.

I'll let you know how I get on.

Lolonois

@rogerdodger Welcome to Retropieforum :-) and welcome to the world of RPi audio annoyances :-/

For USB-Audio Devices with 3.5mm jack almost any (c-media compatible) will work.
Any I did test had a better S/N than the on-board 3.5mm jack, e.g.:

ID 0d8c:000c C-Media Electronics, Inc. Audio Adapter
ID 040d:340a VIA Technologies, Inc.
ID 1b3f:2008 Generalplus Technology Inc.

From another project (no Arcade) I know that the HiFiBerry DAC+ standard provides even better sound.

I had very good experiences (read: precise, noiseless audio) in both projects with Sure Electronics amps.

You can build a dedicated, external volume knob by using a dual potentiometer (50k Ohm, logarithmic) in between the Rpi out and the amp in.

Some troubleshooting hints:
I assume -without knowing the real schematic- the 5v from Pi and the 12v/18v/24v from the amp share the same ground. Have you tried feeding them with two separate supplies - one for the pi and one for the amp?

Are you using LED stripes in the arcade or nearby to the arcade? They may induce audio noise if they switch a a high rate (impossible to perceive with the human eye - LED stripe makers may use this trick (POV) to save energy and to prolong the LED lifetime).

If you use LED stripes inside the arcade and drive them via PWM, this may also induce noise. Some possible solutions are sketched here or here.

Last but not least, double insulating audio wires may have some benefits.

HTH

rogerdodger

I've managed to fix the problem.

As many of you have suggested it is all down to the dreaded 3.5mm audio jack.

As per the suggestions @Lolonois and @lostless I now hav emy amplifier and speakers connected to the Pi via a usb sound card and everything is blissfully noise free.

I do still have one minor problem in that I'm getting the error:

lv10: VolumeControl::init() Failed to find mixer elements

I wondering if this is part of the reason why sound doesn't work in my splash screen video's when the device boots?

mitu

@rogerdodger said in Help with interference and hissing problem on speakers and amplifier for Bartop project:

I wondering if this is part of the reason why sound doesn't work in my splash screen video's when the device boots?

May be - try to make the USB card the default soundcard, either by disabling the onboard sound or changing the order of cards.
https://retropie.org.uk/docs/Sound-Issues/

rogerdodger

@mitu Brilliant, looks like all the information I need is in there.

I'll let you know how I get on.

rogerdodger

Right I've solved the problem and now have everything working correctly.

Many thanks for everybody's help with this.

I thought it might be useful for future reference to close with a summary of the issue and how it was resolved.

Problem Summary

3.5mm audio output on Rasperry Pi causing hiss and interference from RetroPie sound output.

System info

Rasperry Pi Model: Raspberry Pi 3 Model B+
Distro: Rasperian 9 (Stretch)
RetroPie Version: 4.3

Solution

Disabling the on board 3.5mm audio jack and using a USB sound card (https://www.amazon.co.uk/gp/product/B07MNRRT84/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) to connect the amplifier and speakers.

USB sound card installation steps

Disable the on board 3.5mm audio jack in /boot/config.txt:
Change the line:
```
dtparam=audio=on
```
to:
```
dtparam=audio=off
```
Under Sound Settings within Emulation Station select:
```
Audio Device: Speaker
```
```
OMX Player Audio Device: Local
```
Note, you may also wish to turn up the system volume however this is down to personal preference.

Optional step to enable sound in Splash screen videos

Update the script:

/opt/retropie/supplementary/splashscreen/asplashscreen.sh

change the line:

omxplayer -o <option> -b --layer 10000 "$line"

to read:

omxplayer -o alsa -b --layer 10000 "$line"

flatmax

One solution to noise and ground loops is to use an isolated sound card for the Pi.

If the sound card is magnetically isolated, then noise and hum (ground loops) from the Pi can't get to the acoustic pathway.

Matt