daviestar wrote:Thanks Dohmar, I'll be eagerly awaiting your update
Which dongle are you using?
Over the last few weeks I've been researching car audio with one good D/A conversion. The aftermarket situation is very strange in that there are plenty of good DACs, but almost no head units with digital outputs! Car audiophiles are using iPads connected wirelessly to Airports to provide optical out at 96kbps.
I started looking for DAB radio's outside of car audio, portable and separate, and found very few with a digital output. Am I thinking about it the wrong way? Isn't DAB radio a digital signal, meaning in theory it should be easy to provide a digital output? Or because it's still a "radio" does that mean the signal is actually interpreted as analog by the "tuner"? (I use parentheses here to highlight my stupidity
) If this is the case, maybe I should be less concerned with optical out from DAB, if it needs to be A/D converted to provide digital output.
The best portable DAB radio for in-car use I've found is the
Technisat DigitRadio 110, in case anyone is interested.
Hi Davie,
I have a RTL2832U + R820T2 Mini DVB-T + DAB + FM USB dongle. They're the most common on ebay and they cost around $10 including delivery! Nice and cheap!
DAB is digital, correct, however when considering the manufactured radios, internally it has its own DAC which converts to analog.
The DAC conversion happens after the tuner, so the tuner itself sets a frequency and the output is simply piped into a DAC.
A commercial DAB looks like this
Radio signal -> Antenna (Picks up radio signal) -> Demodulator -> DAC -> Amplifier
The tuner in this case directly controls the demodulator
On a pi, this is how it would be done
Radio signal -> Antenna -> Demodulator) -> USB -> Pi -> DAC -> Amplifier -> Speakers
The tuner in this case is controlled via software on the PI which then controls the Demodulator
The current issue I've got is driver support, I haven't gotten around to compiling a replacement kernel, and am hoping the devs here can incorporate the drivers in the form of a loadable/unloadable module. The whole Software defined radio is what makes this thing possible though it might take some doing to get working (I'm experienced with linux but arch seems to be quite different to slackware).
For using a PI, there are pi Hats that have optical digital output, and then whatever you're feeding that into does its on digital to analog conversion, that would be my recommendation if thats the solution you're after. I personally use the x400 from suptronics as my DAC and amplifier combo, but that probably wouldn't suit a car as it only has stereo outputs and rca out for a subwoofer (You'd need to have another amp or self powered/active rear speakers for more than 2 speakers in the car)
rpi-dac seems to be the best software solution so far as it is tailored for the pi and talks to MPD, I think via ALSA api but perhaps it can be configured as a source for MPD. I'll have to work on that for a bit I think, as there is no binary for ARCH linux and the source code won't compile for me - havent yet had the time to get back into it, I might be able to this weekend.
Will keep you all posted. I've requested the kernel have the drivers added for the next 0.4 release in the feature request part of the forum.
-D
** Edit ; I had some time to screw around with the pi tonight, i installed rtl-sdr via pacman and that detected the usb stick using the test software so drivers might not actually need to be compiled in. sdr-j is the other software that talks to rtl-sdr and then pipes the DAB/FM audio to something like ALSA or MPD, still not sure on the mechanism
