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Discussion Starter · #1 ·
Hello DIYMA members -

I just bought a Helix DSP Pro (from a DIYMA member) and I am interested in optimizing the SQ possibilities of my setup. To do this I would like to utilize one of the DSP Pro's digital inputs, preferably the coaxial input over the optical due to the improved specifications (12-96kHz optical; 12-192kHz coaxial, as per the manual). Does anyone know of a currently produced head unit that has digital outputs?

I am collecting equipment now and nothing is installed, but I will have two Brax MX4 amplifiers with six of the eight channels actively running a Focal Utopia 7 kit in front and the other two channels running a Utopia 7 kit through the Crossblock for the rears. An MX2 will be running two JL Audio 12TW3 subwoofers under the rear seats. This will be in a 2015 Ram Crew Cab Longhorn (the truck currently has the 8.4 Uconnect system).

So far my research has produced the Alpine x009 series, of which the universal version is the one that would work in my Ram. It has an optical output. I feel that I would be happy with this unit, but I would appreciate having more options to choose from before making a decision.

Thanks.
 

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The current Alpine 7", 8", and 9" AV units are the only thing that I know of currently having digital (toslink) out.
 

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I don't know of any Car Audio components which used a coaxial digital output. That being said, in this case I don't see value in it. The DSP section of the DSP Pro operates in 24bit/96khz max. Anything above that will be downsampled in order for the DSP to process the signal.
 

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I don't know of any Car Audio components which used a coaxial digital output. That being said, in this case I don't see value in it. The DSP section of the DSP Pro operates in 24bit/96khz max. Anything above that will be downsampled in order for the DSP to process the signal.
There's probably a few, and at least one. Though likely all old school stuff.

MINT Denon DCT-Z1 for sale!!! - diyAudio

I think also Pioneer DVD Double Din of a few years ago came with a Coax digital output via a 3.5mm socket in the rear.
 

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Discussion Starter · #6 ·
Thanks for the information. I will be using the Helix URC-2A controller until the "Director Controller" is released (six weeks out still according to Brax this morning).

teldzc1: where can I find data like this? I only skimmed the manual of the DSP Pro, but I didn't see anything about downsampling. It's not that I don't believe you, I just want as much information as I can get my hands on.

I will look into the Denon. I am looking for current units due to the extra features that they might offer, but if I can't find what I am looking for I will get into older SQ decks.
 

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I asked them directly via Facebook Messenger. They responded with that information. I posted that in the Helix DSP Pro thread.

Sent from my SAMSUNG-SM-N900A using Tapatalk
 

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teldzc1 is correct. The spec listed for the digital inputs are resolution limits for the particular input. The 96kHz is the sample rate the processor runs at. DSP works by sampling the incoming signal, analog or digital, then manipulating it however. It does that at a given sample rate. Everything out there does it at 24bit/48kHz, The DSP pro is the first to move this up to 96kHz. You can see it in the specs where normally the frequency response limit of a processors is ~20kHz (ie the limit for 24/48). The DSP pro should show something into the 40kHz range. That's around where that sample rates limit is. It's not quite the digital limit because of the inherent degradation from the analog outputs.

Edit:

http://www.audiotec-fischer.de/lng/en/helix-dsp-pro.html

"The signal processor for all those, who are only satisfied with the best! The new HELIX DSP PRO raises the bar to a new level, not only in terms of sound quality. Due to the implementation of the latest generation of ultra-fast Audio DSPs with enormous 64 Bit resolution, this device provides more calculating power than every other signal processor available on the market today. In addition, it is the first of its kind which performs the full signal path with a sampling rate of 96 kHz, resulting in an extended audio bandwidth up to more than 40 kHz."
 

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There have been relatively few head units with any sort of digital output, let alone coaxial ones. Careful about Denon as I thought those were only digital input, not output.

You can still get a couple of Nakamichi models (if you really look around) that had digital coaxial output though, the MB-X and MB-100. They both used an outboard processor for the D/A conversion, but it could be bypassed for that.
 

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HELLLLPPPPP!!!

We've installed an alpine x009 "restyle" H.U. in my bosses Jeep, we ran the optical out to a Rockford 3sixty.3, but no sound.

I tested the optical out of the alpine and discovered that it runs at 44.1kHz, and the 3sixty.3 wants a 48kHz input!

What to do? Is there a way to select a higher sample rate on the alpine skiing digital out? Probably not!! Arggggg!
 

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Currently the big hole in the market.. Which is bad because folks have to improvise, but good because folks are improvising. :) Tablet installs on the rise, and other signal converters being tried with much success to feed DSP's. Reason I'm in defiance and revolting against the head unit makers and doing an iPad build in the truck, whenever I ever get around to it, with some wired method or maybe wireless.. Depends on what's out by then for digital signal options. But the doggone tablet (iPad in my case) will do anything and everything a crazy head unit will do, except play a disk or have a sure-enough local radio tuner.

I should add, if you can do a 2-din, there is the option possibly of an E3io (PC-based) head unit, with whatever output you can have them hang off the back of it. I imagine they've had quite a few folks requesting a hi-def audio "SQ" based build. Prepare to shell some coin for one, but having seen them in action in Req's car, they're bad to the bone.
 

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Currently the big hole in the market.. Which is bad because folks have to improvise, but good because folks are improvising. :) Tablet installs on the rise, and other signal converters being tried with much success to feed DSP's. Reason I'm in defiance and revolting against the head unit makers and doing an iPad build in the truck, whenever I ever get around to it, with some wired method or maybe wireless.. Depends on what's out by then for digital signal options. But the doggone tablet (iPad in my case) will do anything and everything a crazy head unit will do, except play a disk or have a sure-enough local radio tuner.

I should add, if you can do a 2-din, there is the option possibly of an E3io (PC-based) head unit, with whatever output you can have them hang off the back of it. I imagine they've had quite a few folks requesting a hi-def audio "SQ" based build. Prepare to shell some coin for one, but having seen them in action in Req's car, they're bad to the bone.
...or wait for Sony Hi-Res HU:
Sony Hi-Res Audio For Car Due This Year | ceoutlook.com

Kelvin
 

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Yeah, it would be quite strange if that were true. CDs are 44100Hz... CDs aren't the only thing that people listen to but one might think that rate would be supported...
Oh, it's true all right. I have the ability, (it's quite easy really) to measure the sample rate and bit depth coming out of the Alpine H.U.

Plus, I have the ability to generate whatever bit depth/sample rate digital signal I want from 8k to 96k and from 8bit (I think, it's either 8 or 16) to 32bit. AES/EBU or S/PDIF.

Even when I play a DVD disc in the alpine, the digital out is 44.1k, which I thought DVD was 48k. maybe I didn't try enough DVDs. I seem to remember reading that they can be different sample rates, depends on the recording/disc?

Also, I can generate 44.1k audio (S/PDIF) and the RF 360.3 makes no sound.
Which, after looking into it, isn't that strange apparently, the bit one is the same way, according to the documentation. (Or so told me a co-worker yesterday, I was troubleshooting this for him)

What seems strange to me, is the Alpine running at 44.1 k regardless of source. I haven't tried any sources other than USB, CD, DVD, Tuner. So maybe HDMI would work. Who knows.

Even when I play 48k out of my iPad (I'm not talking iTunes here) into the alpine via USB, the digital out of the alpine is STILL 44.1k
 

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Even when I play a DVD disc in the alpine, the digital out is 44.1k, which I thought DVD was 48k.
DVD does not have one set sample rate. I know for a fact that it can be 48kHz, 96kHz or 192kHz, and am fairly sure that it can also be 44100Hz, 88200Hz (yes, it exists). Maybe even 32kHz, 16kHz, 8kHz, but hopefully nobody ever actually uses those ones.
 

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DVD does not have one set sample rate. I know for a fact that it can be 48kHz, 96kHz or 192kHz, and am fairly sure that it can also be 44100Hz, 88200Hz (yes, it exists). Maybe even 32kHz, 16kHz, 8kHz, but hopefully nobody ever actually uses those ones.
Right, that's what I thought, so maybe the choice of DVD disc is a factor, BUT, why no 48k output when running 48k input from iPad via USB?
 

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Right, that's what I thought, so maybe the choice of DVD disc is a factor, BUT, why no 48k output when running 48k input from iPad via USB?
Your HU may resample things to 44100 because maybe Alpine's DSP expects 44100... But I don't understand why they'd resample on the HU side rather than on the DSP side.
 

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It looks like too save money they did not add a sample rate converter to the 360. So it can only accept its native sample rate of 48kHz. Using an external converter like and Audison SFC or a Mini DSP Minidigi should fix the problem.

miniDIGI | miniDSP
AWESOME sir, thank you very much! This is exactly the kind of info I was looking for.

One more question, let's say I play a DVD that is KNOWN to be 48kHz, but the alpine outputs digital audio that's STILL 44.1k? What do we make of that? Or is that not possible?

I'm at work now, so I'll try this out as soon as the boss opens the shop.
 
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