bbbenji
Posts: 2
Joined: Fri Oct 04, 2013 10:33 pm

RPi to 4 channel audio amplifier

Fri Oct 04, 2013 10:34 pm

Hello,
I'm here with a question.

My latest project is a RPi headunit/car computer. I've worked out all the details expect for a way to connect my RPi, with decent audio quality, to my speaker system. My car has 4 speakers, 1 subwoofer and a 600w amplifier which currently only drives the sub bridged. I would like to completely remove the current crappy noname radio and replace it with the RPi and touchscreen.

So my question is, what is the best way of doing this?

Below I have posted my idea, but I may be way off on my thinking:
Here is a diagram of what I envision.
Here you can find the input side of my exact amplifier.
Here you can find the output side of my exact amplifier.
Here is a similar sound card as the one I'm looking at. (I would probably end up replacing the 3.5mm jack ports with RCA, or just buy 3.5mm to RCA adapters.)

I should add that I am not an audiophile, all my music is in mp3 form so the highest of quality is not important. Though that doesn't mean I want to listen to shit music either.

Thanks!

Edit:
Cost is important to me as well. I don't have much to spend and this is going to end up being a long term project anyway.

Or perhaps I should use a USB DAC, like this, and split the left and right into 2 so i can have front and rear connections on my amp? It seems like a lot less trouble, but the price is a little higher.

User avatar
cyrano
Posts: 714
Joined: Wed Dec 05, 2012 11:48 pm
Location: Belgium

Re: RPi to 4 channel audio amplifier

Sun Oct 06, 2013 10:43 am

Get one of those cheap ebay USB thingies. They're OK. If you want something a little more solid (and bigger) have a look at the Behringer UCA range. Around 30 euro...

And use a Y-cable to split to your amps.

wouterel
Posts: 52
Joined: Thu Feb 14, 2013 3:09 pm

Re: RPi to 4 channel audio amplifier

Sun Oct 06, 2013 8:31 pm

Combining two outputs of a 7.1 card (front and back) into one input (with a simple Y-cable?) on your amp is not a good idea.
If your amp does not have enough channels to keep them separate, it would be better to leave the back output of the sound card unconnected and just channel the front output to both sets of speakers. (unless you plan to play a lot of true surround tracks with exciting stuff in the rear channels - in which case you'd need an amp with more channels anyway).

The thing you do to drive a subwoofer with a 4-channel amp that doesn't seem designed for it is a bit odd I guess (although I'm not a car audio expert so correct me if I'm wrong), but on the other hand I don't see why that wouldn't work.

EDIT: on the previous post: the cheap 2-channel usb sound cards can be really good indeed, but it looks like you need the feature that the 7.1 has a separate subwoofer output, right?

bbbenji
Posts: 2
Joined: Fri Oct 04, 2013 10:33 pm

Re: RPi to 4 channel audio amplifier

Sun Oct 06, 2013 9:23 pm

I have looked into those cheap USB cards, though at their price range, I'm afraid I won't be satisfied with the sound quality.

I can understand why joining front and rear channels is not a good idea. Though I definitely won't need the full 7.1 channels. As I stated in my original post, my entire music collection is in mp3 format which is stereo anyway.

As for driving a subwoofer with my amp, although it is not designed for running a single woofer, it seems to work just fine currently running a single 12" subwoofer bridged on the rear channel. The sub has frequency controls.

Thanks for the replies. So now I think I have boiled my decision down to either a DAC or UCA. Here are the two I'm looking at:
http://allegro.pl/muse-usb-do-s-pdif-ko ... 19354.html
http://allegro.pl/behringer-uca222-inte ... 88367.html

The only leg up I see the UCA having is that it has stereo aux input as well. That might come in handy if i want to hook up an mp3 player via 3.5mm jack. Can anyone give me any other reasons one might be better than the other?

wouterel
Posts: 52
Joined: Thu Feb 14, 2013 3:09 pm

Re: RPi to 4 channel audio amplifier

Mon Oct 07, 2013 7:57 am

I own the grey-colored brother of that behringer: the UCA-202. It's great. I'm still planning to do more careful listening tests but so far it seems to keep up with the DAC inside my 20 year old Denon full-size CD player. It's actually what I was thinking of when promoting cheap DACs in my previous post. Since you're going to use it in a car (noisy environment), I'd be extremely surprised if it turned out not to be good enough.

Iotwoot
Posts: 1
Joined: Mon May 06, 2019 6:51 am

Re: RPi to 4 channel audio amplifier

Mon May 06, 2019 8:02 am

@bbbenji Did You manage to solve this problem?
If so can you share your new car audio conection schema (did you use raspberry amp, wich sound card, etc)?
Any tips are welcome😀

I thinking of replacing my car radio as well.
Soo far I found raspberry amp with 2 channels, and im thinking to duplicate them (Y wire I think).

Thx.

drgeoff
Posts: 10765
Joined: Wed Jan 25, 2012 6:39 pm

Re: RPi to 4 channel audio amplifier

Mon May 06, 2019 8:45 am

@lotwoot
1. No need to post twice.

2. bbbenji has not logged in to the forum since November 2013.

energyi
Posts: 160
Joined: Tue Mar 24, 2015 9:39 pm

Re: RPi to 4 channel audio amplifier

Mon May 06, 2019 2:30 pm

Suptronics
energyi

thenrie
Posts: 10
Joined: Mon Feb 19, 2018 1:04 am

Re: RPi to 4 channel audio amplifier

Thu Jul 25, 2019 8:28 pm

Suptronics has a stereo 8-channel DAC hat for the rpi that would work for the OP's purpose. Model number is X6000K-8.0ch. The specs look better than most oem car audio head units produce. Indicates "8-channel stereo audio outputs at the same time even if playing 2-channel audio." Output is 2v/ch, so it would be perfect to connect to a car audio amp line input. Outputs are in the form of mini jacks, rather than RCA. The website doesn't offer much in the way of sales info. I just emailed them for pricing and purchasing info.
http://www.suptronics.com/miniPCkits/x6000-8.0ch.html

Hifiberry also has a very nice 4-ch amplifier for the rpi. Pretty steep price for DIY car audio, but forgoes the need to buy a car audio amp.
https://www.hifiberry.com/shop/beocreat ... amplifier/

There's another from Audio Injector that supplies 6 channels into 8 channel output at line-level output. You can go wild with this one.
https://www.kickstarter.com/projects/12 ... he-raspber.

It's now offered on Amazon:
https://www.amazon.com/Octo-channel-sou ... way&sr=8-5

Or you could use RCA splitter cables from a 2-ch DAC and connect to 4 inputs on the amp and get 4 speaker stereo output (not true four channel and no fader function) for a couple bucks.

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