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+--- Thread: Speaker Noise On Start Up - After Market Amp (/thread-2123.html)
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Speaker Noise On Start Up - After Market Amp - robinInTheHood12 - 10-18-2020
Hi,
So when I installed OAP in my car, I opted to remove the stock head unit and install the Raspberry Pi in it's place. Doing so removed the amp for the car speakers. To remedy this, I got a new amp, put it under the driver's seat, and ran a 3.5mm jack adapter to the USB sound card on the Pi. This works great and I get sounds through the car speakers, but there is all kinds of noise and popping through the speakers before OAP has booted. Once the unit is up, the noise stops and speakers function normally. I'm guessing it's just random electrical noise on the sound card before the unit has initialized. My question is, is there a work around for this? Can I run some kind of script that disables the sound card until OAP has fully booted? Or is there some kind of hardware related fix? I would like to not have to listen to hissing and low concussive booms on the car speakers when I'm waiting for OAP to come up. Thanks in advance.
RE: Speaker Noise On Start Up - After Market Amp - Justindu - 11-02-2020
I'm surprised there isn't more on this topic. - I also replaced my head unit with the Raspberry PI with USB Audio card. In my case a UGREEN card. My Alpine Amp (in the trunk) has a v4 line level input option. My old head unit could supply this, and the sound quality was perfect.
I needed to turn the amp back to a "normal" line level input 2v? in order to get a normal volume level out of OAP. Unfortunately, the amp is picking up noise with the engine running setup this way. I suspect the pre-amp line level from the UGREEN USB Audio card is so low its mixing in with the ambient line noise.
I'm wondering if others have resolved this by adding a line level gain booster close to the USB sound card?
Justin
RE: Speaker Noise On Start Up - After Market Amp - BlueWave - 11-02-2020
Please have a look at the papers regarding ground loop issue. There are several solutions to fix it.
RE: Speaker Noise On Start Up - After Market Amp - Chrisfromwa - 11-02-2020
My install is about the same as yours, I've replaced the headunit with the PI and have aftermarket amps.
I don't have any engine noise in my system.
Couple things you can check
Make sure your amp grounds are good, make sure they are as short as possible, and also make sure they are connected to a clean piece of metal on the car.
Also make sure you're using a good quality RCAs and avoid having them routed right next to your main power wire.
RE: Speaker Noise On Start Up - After Market Amp - Justindu - 11-05-2020
(11-02-2020, 08:19 PM)BlueWave Wrote: Please have a look at the papers regarding ground loop issue. There are several solutions to fix it.
I looked there, but am thinking the ground is not my issue. My noise is introduced with the engine running. I'm going to look at adding a simple noise filter on the + voltage power supply to Pi. This is harmless at worst.
https://www.amazon.com/dp/B015RAZTIA
Or something more aggressive:
![[Image: 123318822_369663774279844_76109989169419...e=5FC8C728]](https://scontent-sjc3-1.xx.fbcdn.net/v/t1.15752-9/123318822_369663774279844_7610998916941924239_n.png?_nc_cat=101&ccb=2&_nc_sid=ae9488&_nc_ohc=jCSuWgYpstgAX_WBBmn&_nc_ht=scontent-sjc3-1.xx&oh=033befa833b7a5b8300dcb7cd8e33e31&oe=5FC8C728)
Where L = a 2.4" Ferrite core wrapped with 25ft of 14 gauge wire, and C = 4700uF capacitor.
https://www.ebay.com/itm/FT-240-43-Ferrite-toroid-core-2-4-inch-diameter-43-Material/262867309093?hash=item3d341cd225%3Ag%3A8JUAAOSwtfhYr0ML&fbclid=IwAR2Wauz4nBw5QEoI65vwN-2gUTgdQM5-HndwksAw5_wY4EXXKpYOo-xx5DE
https://l.facebook.com/l.php?u=https%3A%2F%2Fwww.taydaelectronics.com%2Fcapacitors%2Felectrolytic-capacitors%2F4700uf-25v-105c-jrb-radial-electrolytic-capacitor-5x11mm.html%3Ffbclid%3DIwAR1wRx_SFJAIWHedFmsaNPP-a6vDZkzjuNXvnWnBGYw9XXcg59ChUWMjOWQ&h=AT2lmcKaNCV2ziWvGBjzJGoIVWlVP7s7ZnprZKN_3E3xb0PypFhP7w_5UxwsO_p-HeVYS8J-4UfcNwFtBJIt4_N6d2iNzijb3wWz8-S36IWbwKt8uUzHlkY1RB3w_SsN7JRuccRcEA
RE: Speaker Noise On Start Up - After Market Amp - Chrisfromwa - 11-05-2020
You have what's commonly called as engine whine.
check your main amp ground, it needs to be as short as possible and connected to a clean piece of metal on the car.
How are you getting the signal from the the PI to the amp? RCAs?
Keep your amp power wire away from your RCAs.
If it still persists, let us know how you have everything wired up.
Some other tips
https://www.caraudiocentral.net/forums/advance-theory-/11876-pursuit-noise-free-system-ten-commandments-noise-prevention.html?highlight=whine
RE: Speaker Noise On Start Up - After Market Amp - Justindu - 11-05-2020
(11-05-2020, 04:50 PM)Chrisfromwa Wrote: You have what's commonly called as engine whine.
check your main amp ground, it needs to be as short as possible and connected to a clean piece of metal on the car.
How are you getting the signal from the the PI to the amp? RCAs?
Keep your amp power wire away from your RCAs.
If it still persists, let us know how you have everything wired up.
Some other tips
https://www.caraudiocentral.net/forums/advance-theory-/11876-pursuit-noise-free-system-ten-commandments-noise-prevention.html?highlight=whine
Good reading. Bear with me here - Since everything was good before the head unit swap - I'm focusing my efforts at the source.
RE: Speaker Noise On Start Up - After Market Amp - Justindu - 11-05-2020
(11-05-2020, 05:38 PM)Justindu Wrote:(11-05-2020, 04:50 PM)Chrisfromwa Wrote: You have what's commonly called as engine whine.
check your main amp ground, it needs to be as short as possible and connected to a clean piece of metal on the car.
How are you getting the signal from the the PI to the amp? RCAs?
Keep your amp power wire away from your RCAs.
If it still persists, let us know how you have everything wired up.
Some other tips
https://www.caraudiocentral.net/forums/advance-theory-/11876-pursuit-noise-free-system-ten-commandments-noise-prevention.html?highlight=whine
Good reading. Bear with me here - Since everything was good before the head unit swap - I'm focusing my efforts at the source.
Here is some diagnostics results:
1. Disconnecting the RCA cables from the sound card, leaving the RCA cables connected to the amp - loose ends hanging in the air, I could hear no noise in the speakers - with or without the engine running.
2. Connecting the sound card to Headphones, with and without the engine running - no detectable noise.
I think this tends to eliminate the power supply on the Pi as a source of the noise?
So - noise only when engine running with the RCA from Pi connected to the AMP. hmmm, but same setup with a decent head unit no noise.
(scratching head)
RE: Speaker Noise On Start Up - After Market Amp - Justindu - 11-07-2020
(11-05-2020, 11:01 PM)Justindu Wrote:(11-05-2020, 05:38 PM)Justindu Wrote:(11-05-2020, 04:50 PM)Chrisfromwa Wrote: You have what's commonly called as engine whine.
check your main amp ground, it needs to be as short as possible and connected to a clean piece of metal on the car.
How are you getting the signal from the the PI to the amp? RCAs?
Keep your amp power wire away from your RCAs.
If it still persists, let us know how you have everything wired up.
Some other tips
https://www.caraudiocentral.net/forums/advance-theory-/11876-pursuit-noise-free-system-ten-commandments-noise-prevention.html?highlight=whine
Good reading. Bear with me here - Since everything was good before the head unit swap - I'm focusing my efforts at the source.
Here is some diagnostics results:
1. Disconnecting the RCA cables from the sound card, leaving the RCA cables connected to the amp - loose ends hanging in the air, I could hear no noise in the speakers - with or without the engine running.
2. Connecting the sound card to Headphones, with and without the engine running - no detectable noise.
I think this tends to eliminate the power supply on the Pi as a source of the noise?
So - noise only when engine running with the RCA from Pi connected to the AMP. hmmm, but same setup with a decent head unit no noise.
(scratching head)
Anyways, I updated existing 2 section RCA with a new continuous twisted pair - Its not terrible. You have to put your ear near the tweeter to pick up on it - but its there, A high pitch bizzzz sound.
Wish I had a scope for this...
I think going to give a line level booster with various grounding options a try. It would address one or both ways to improve signal.
RE: Speaker Noise On Start Up - After Market Amp - Chrisfromwa - 11-07-2020
How do you have your PI grounded?
What type of power supply are you using for it?
The testing you've done rules out everything after the PI. So I would now look into the grounding of the PI, and then next the power supply you're using. If the noise is coming from the PI itself (source), a pre-amp I have a feeling might amplify the noise too.