Raspberry Pi-based Head Unit

Naxin

CarAudio.com Newbie
21
1
Software guy, Car Audio noob here.

Would be a wealth of cool **** I could build with a Raspberry Pi / Touch Screen interface as my head unit.

Features like:

  • Sim-based internet (or phone-based USB internet)
  • Music Streaming
  • GPS
  • Video games
Mostly stuff you'd expect in high-end (expensive) head units

Questions:

I know I'm probably way in over my head here, but with the Raspberry Pi as a Digital Audio Source (Noting the Raspberry Pi has USB capabilities) what could be the basics to achieve a decent sound source for my dedicated 4ch amp (Hertz HE-4) + Monoblock (Alpine MRX-M55) so that it won't sound like trash.

I've looked into possibly using a USB-based DAC + a DSP. Is there headless head-units that do all of this for me? This is all new to me though.

Not looking for someone to design this system for me, just any pointers, or for someone to tell me I'm wasting my time :)

Cheers!

 
Welcome.   As an EE, I appreciate your goals. 

We would call this a "Car Audio PC" or "Carputer" or some other names over the years.  You can get a touchscreen to pair with a Pi or MicroATX mobo.  Most have used a MicroATX mobo with USB audio and touchscreen.  Your plan can work similar. 

You'll want a DSP, but one that you can communicate with through the Car PC so you can tune it from there (ideally).  You'll want a DSP to do most of the work so you can just feed it a digital signal (optical is typical).   Note if you use optical, you'll need a separate volume knob through the DSP (common).   Most of the DSP on the market can do most of what you want, including preset recall, volume (main and sub), even source selection (including BT).  Audio Control, JL Audio, Alpine, Helix, PPI, MiniDSP, Dayton Audio, etc have nice options. 

 
Welcome.   As an EE, I appreciate your goals. 

We would call this a "Car Audio PC" or "Carputer" or some other names over the years.  You can get a touchscreen to pair with a Pi or MicroATX mobo.  Most have used a MicroATX mobo with USB audio and touchscreen.  Your plan can work similar. 

You'll want a DSP, but one that you can communicate with through the Car PC so you can tune it from there (ideally).  You'll want a DSP to do most of the work so you can just feed it a digital signal (optical is typical).   Note if you use optical, you'll need a separate volume knob through the DSP (common).   Most of the DSP on the market can do most of what you want, including preset recall, volume (main and sub), even source selection (including BT).  Audio Control, JL Audio, Alpine, Helix, PPI, MiniDSP, Dayton Audio, etc have nice options. 
Great info here, I'm interested - can a DSP act as a DAC? If so, how do they compare? As my knowledge goes, I want to be sending line level analogue to my dedicated amps, I figured DSPs would be digital in, digital out.

 
Great info here, I'm interested - can a DSP act as a DAC? If so, how do they compare? As my knowledge goes, I want to be sending line level analogue to my dedicated amps, I figured DSPs would be digital in, digital out.
Yes, the DSP is the preferred DAC to use since it does processing in the digital realm.  If you use a source DAC then the DSP needs to use an ADC then another DAC.  All DSP are analog and/or digital in with analog out (Audison has amps with a DAC and digital between its DSP and amps).  Modern units run 32bit processing.  Most have 24bit DACs and are very good quality (you get what you pay for). 

I have an Alpine PXA-H800 with the RUX-C800 controller.  I'm a huge fan and have had previous Alpine processors (ERA-G320 and PXA-H701).  Several of my friends are fans of the modern Helix DSP, the JL Audio Twk, and Audison BitOne. 

 
Thanks, I'll read through the whole thread!

Yes, the DSP is the preferred DAC to use since it does processing in the digital realm.  If you use a source DAC then the DSP needs to use an ADC then another DAC.  All DSP are analog and/or digital in with analog out (Audison has amps with a DAC and digital between its DSP and amps).  Modern units run 32bit processing.  Most have 24bit DACs and are very good quality (you get what you pay for). 

I have an Alpine PXA-H800 with the RUX-C800 controller.  I'm a huge fan and have had previous Alpine processors (ERA-G320 and PXA-H701).  Several of my friends are fans of the modern Helix DSP, the JL Audio Twk, and Audison BitOne. 


I've checked out each of the products you mentioned. All range between $600-1000. As you said 'you get what you pay for'. I'm willing to accept this is how much it will cost to achieve the sound I'm after, but also interested in your opinion on how cheaper DSP's may fare against equivalently priced off-the-shelf head units. Looking at the Raspberry Pi ($negligable) + DSP ($0-1000+) package, if you were to say.. purchase a $300 DSP(if these even exist) -> do you have any opinion on how this might fare against a $300 head-unit?

The reason this is important to me, is I'd love to open source this project into an easy solution for others to build into their systems with a variety of choice over sound quality (Just pay what you want for your DSP essentially...). If there's a $150 DSP that absolutely blows any equivalently priced head-unit out of the water, it could become a cheap solution to making low-end aftermarket speaker setups highly-functional for less!

Cheers!

 
Thanks, I'll read through the whole thread!

I've checked out each of the products you mentioned. All range between $600-1000. As you said 'you get what you pay for'. I'm willing to accept this is how much it will cost to achieve the sound I'm after, but also interested in your opinion on how cheaper DSP's may fare against equivalently priced off-the-shelf head units. Looking at the Raspberry Pi ($negligable) + DSP ($0-1000+) package, if you were to say.. purchase a $300 DSP(if these even exist) -> do you have any opinion on how this might fare against a $300 head-unit?

The reason this is important to me, is I'd love to open source this project into an easy solution for others to build into their systems with a variety of choice over sound quality (Just pay what you want for your DSP essentially...). If there's a $150 DSP that absolutely blows any equivalently priced head-unit out of the water, it could become a cheap solution to making low-end aftermarket speaker setups highly-functional for less!

Cheers!
The latest "budget" DSP to hit the market is by Dayton Audio DSP-408 and is around $150 but it lacks a digital input.  It will certainly have components similar or superior to a $300 head unit.  It also has a BT option and remote control option.   

The JL Audio TWK-88 is a middle-of-the-road budget DSP with great features, optical in, and flexibility.  PPI has the DSP-88R which also boasts an optical in but i've seen negative reviews.  MiniDSP is an affordable solution that i'm working with in a buddy's build.

You can also find many DSP available used since people like to jump around between products, which can save some coin.

 
Thanks, I'll read through the whole thread!
good luck with that :D  its a pretty long thread. That being said, there are definite merits with going with something along the lines youre talking about

You can also find many DSP available used since people like to jump around between products, which can save some coin.
plus, its hard to physically abuse a DSP in the same way speakers and amps commonly get abused. 

 
good luck with that :D  its a pretty long thread. That being said, there are definite merits with going with something along the lines youre talking about 

plus, its hard to physically abuse a DSP in the same way speakers and amps commonly get abused. 
Thanks for the encouragement. I've been doing a tonne of research, invested in a RTA Mic and planning to go down the budget route to see what's possible for this system. I'm more interested in the Raspberry Pi Interface side for phase 1, and having an audiophile grade system can be phase 2 haha.

Hell, running Aux out to Amps RCA in high-Z mode from the Pis line out will be a start.

In Australia It's damn near impossible to find second hand DSPs, there's no distributors for MiniDSP either. Basically all I can get is brand new Rockford and Alpine gear - keeping in mind those are expensive brands in the Aus market, and then some of the even more expensive brands, so that's one challenge...
 

I noticed there's an open source hardware option called FreeDSP, some designs based on ADAU1701 and some ADAU1451. Anyone with opinions on these? I think though, if I went this route, Im back to square 0 in needing a DAC as this option is truly just a DSP.

 
Thanks for the encouragement. I've been doing a tonne of research, invested in a RTA Mic and planning to go down the budget route to see what's possible for this system. I'm more interested in the Raspberry Pi Interface side for phase 1, and having an audiophile grade system can be phase 2 haha.

Hell, running Aux out to Amps RCA in high-Z mode from the Pis line out will be a start.

In Australia It's damn near impossible to find second hand DSPs, there's no distributors for MiniDSP either. Basically all I can get is brand new Rockford and Alpine gear - keeping in mind those are expensive brands in the Aus market, and then some of the even more expensive brands, so that's one challenge...
 

I noticed there's an open source hardware option called FreeDSP, some designs based on ADAU1701 and some ADAU1451. Anyone with opinions on these? I think though, if I went this route, Im back to square 0 in needing a DAC as this option is truly just a DSP.
if youre forgoing a traditional deck and want more than just l/r outputs youre going to want a DAC or a DSP with a digital in of some sort so that dayton mentioned above wont be a viable option for you

these units are news to me, but based on the specs listed on http://www.freedsp.cc/ the two that would work for you are the PiDSP and Insanity models as they have S/PDIF inputs

 
Last edited by a moderator:
With no distribution of those FreeDSP chips in Aus and building that chip being out of the scope of this project - time to move on to another option.

By chance today, I found the Allo Boss DAC for Raspberry Pi

Based on PCM5122 and very reasonably priced! I found it when looking for a good S/PDIF digital out hat for the Pi. These guys make the best one apparently, and to me it appears like they really know their stuff.

The S/PDIF out is here: Allo DigiOne

Both my amps have crossover control, and although a fancy DSP would be very nice as I mentioned previously I'm very interested in how cheap I can keep this.

Any thoughts on this chip would be great!

 
A noteworthy alternative, is also the Allo Piano 2.1 Here

Based on dual PCM5142'S, with configurable X-over for the 2 sets of RCAs. Pretty cool!

 
You can always look at something like the Pi3 with the HiFiBerry DAC's. Ive used the Pi3 and DAC+ to do a multi media system in businesses with great success with something like RuneAudio. Could also look at the Digi+ for that optical connection to the DSP.

 
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