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Car Audio, USB DAC recommendation, 24bit/192khz <$150

post #1 of 4
Thread Starter 

I'm currently installing a Nexus 7 tablet (USB audio out) into my car, to use as a head-unit.

Given that DAC technology seems to be constantly changing, I feel overwhelmed when selecting a USB DAC to input into my signal processor / amps.

-Audio files will be 24 bit, 192khz.
-Drivers will need to be compatible with Linux (Andriod tablet.)
-My signal processor has stereo RCA inputs.

Can you recommend a suitable DAC for this environment?

Previous threads have recommended the ES9023 DAC:Hifimediy Sabre USB DAC 2 External PSU 96kHz 24bit ES9023 SA9023 Coaxial OUT | eBay

However, I like this DIY DAC solution (DAC SABRE 9023 + XMOS2):
Building my reference dac (xmos2 to i2s dac sabre 9023) - RaspyFi

Thanks :regular_smile :

post #2 of 4
I don't understand, why do people keep using USB DACs (or even headphone amps as preamps) in their cars? First, where will the tablet be mounted that you can easily see the display, choose the next track, and have the traffic light in your peripheral vision? Even cops nowadays depending on the regulations in your area can consider that a driving hazard.

Second, how do equipment made strictly for two channel, equidistant listening help make the sound in a car "better"? All the better DACs and output stages in the world won't help much if you're still closest to the driver's side tweeter, the driver's side midwoofer next, then the passenger side tweeter, then the passenger side midwoofer, then finally the subwoofer? Plus all the reflections of the tweeter's sound due to its dispersion pattern being the least of the car manufacturer's concerns when they mounted it near the windshield as in most cars. None of these devices have the 3-way crossover (and matching car audio amplifiers capable of driving your upgraded 4-ohm speakers) with 3-way time alignment that you can find in a $349 Pioneer 80PRS receiver which, compared to the previous models, now has USB. Even //////Alpine has a dedicated media receiver (no transport) that used to support only iPods, but now supports other storage options, and a $149 processor that hooks up to its Ai-Net port (which used to be for their CD changers) so no need to blow money on a PXA-H701 and its dedicated control panel.

Why blow $150 or so on a DAC when the Pioneer 80PRS can work on its own, sending the same processed signal through the speaker amp built into it? You're not "reshaping" or "EQ-ing" the signal, you're introducing time delays to minimize harsh treble and make for a coherent soundstage. If not messing around with the factory-installed dash is a must, there are are two ways around it. First, the factory sound canm with the proper adapters, be routed through the new receiver, which can be mounted on a spare 1-DIN slot. Second option, but this will cost more, is to get one those newer "integration processors" which have basically the same features as other processors, except instead of SPDIF or Ai-Net digital inputs, it has high-level (amplified speaker inputs) to take a signal from the factory receiver, then through an ADC so you can apply the crossovers and time alignment in the digital domain (doing it analog will make the processor too large using whole circuits vs a few microchips), then through quality DACs. Sure, G.I.G.O. applies, but most factory receivers aren't that bad compared to the real acoustic issues in a car that can only be worked around through time alignment in the processor as well as proper installation of the drivers. As much as the 80PRS can be great with just the factory 2-way speakers, I still kind of think of jsut adding a DAC to a car seems like using the same DAC and an amp to use with stock earbuds.

http://www.pioneerelectronics.com/PUSA/Car/CD-Receivers/DEH-80PRS
Edited by ProtegeManiac - 9/26/13 at 9:16am
post #3 of 4
Thread Starter 

ProtegeManiac - thanks for your response. :normal_smile : I realised in my post below I hadn't outlined the system that I'm piecing together.

 

Nexus 7 (android tablet) --> DAC ---> JBL MS-8 (signal processor) --> amplifiers ---> speakers / crossovers etc.

 

 

Why use an external DAC in your vehicle?

To obtain a better conversion to an analogue signal. Why USB? This is the output of my tablet.

 

Concerns around the installation of the tablet.

The tablet will replace the existing head-unit. It will be mounted in place of the regular dual DIN display. I'm currently looking into controlling it via steering wheel controls, to address concerns of driver safety.

 

Why replace a regular head-unit designed for a car?

I view the majority as out-dated and insufficient for my needs in a modern vehicle. I require access to a computer for other tasks.

 

Concerns around time-alignment / signal processing etc.

These will be addressed by utilising a dedicated signal processor (JBL MS-8.)

post #4 of 4
Quote:
Originally Posted by bubbletea View Post
 

ProtegeManiac - thanks for your response. :normal_smile : I realised in my post below I hadn't outlined the system that I'm piecing together.

 

Nexus 7 (android tablet) --> DAC ---> JBL MS-8 (signal processor) --> amplifiers ---> speakers / crossovers etc.

 

 

Why use an external DAC in your vehicle?

To obtain a better conversion to an analogue signal. Why USB? This is the output of my tablet.

 

 

Concerns around time-alignment / signal processing etc.

These will be addressed by utilising a dedicated signal processor (JBL MS-8.)

 

Ah, that settles it - I thought it's going to be like all those other set-ups before where an iBasso or some other DAC-Amp decodes and feeds a line-out signal into a 3.5mm aux-in. In that case, I suggest the ODAC - if you're going to go custom as much as you plan to you could mount it creatively out of the way and protected (maybe even a copper chassis). I had a brilliant plan a few years ago to use Tripath kits mounted in my glovebox, with a computer fan* to cool them, but then all these fullrange Class D amps came out and I might move soon for my PhD. If and when I do move for a few years, and I get a car there, I'm just getting one of these finished amps with an integration processor. I wouldn't mind the decoding quality too much though - I'll just settle for EQ-ing peaks and dips if any. Traffic anywhere in North America can't be as bad as over here in Manila - not to mention I've spent a few nights in downtown mall/hotel parking lots while Zeus tries to drown the entire city, and I'm just cautious enough to drive up parking building instead of gambling I'd get home without submerging my car (and the audio system in it).

 

 

 

*specs for home use don't require it but since it's in the dash, it'll be blowing on heatsinks on the chips themselves, and a custom copper enclosure which wouldn't be too big considering the size of those things

 

 

Quote:
Originally Posted by bubbletea View Post

 

Concerns around the installation of the tablet.

The tablet will replace the existing head-unit. It will be mounted in place of the regular dual DIN display. I'm currently looking into controlling it via steering wheel controls, to address concerns of driver safety.

 

Why replace a regular head-unit designed for a car?

I view the majority as out-dated and insufficient for my needs in a modern vehicle. I require access to a computer for other tasks.

 

My workaround though for newer cars is to jsut hook up the regular GPS unit to the Aux-in, and use a spare 1-DIN slot for the Pioneer P80RS. Or, for simplicity's sake, I'll just not stress over GIGO as much, use an integration processor, then EQ out dips and peaks. I'm thinking of the Alpine H660 (did I even get the model number right? Can't find it on the website). If I could customize the entire dash like what you plan on doing, a tablet and ODAC would be a great idea though - it can have the GPS capability, plus a touchscreen interface for the music player and internet radio.

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