# Truth About >> head unit digital output spdif



## 4saleongrcraigslist (Oct 21, 2020)

Can someone share the truth about head unit *digital output spdif. *

so many installers talking smack about this as a trend. Especially with so many high end amp and DSP digital inputs.

who’s correct?


----------



## ckirocz28 (Nov 29, 2017)

4saleongrcraigslist said:


> Can someone share the truth about head unit *digital output spdif. *
> 
> so many installers talking smack about this as a trend. Especially with so many high end amp and DSP digital inputs.
> 
> who’s correct?


What trend? There are very, very few aftermarket head units with digital out, but there are more factory systems with digital out. I'm anxiously waiting for optical out in the good aftermarket brands.


----------



## 4saleongrcraigslist (Oct 21, 2020)

Really looking for someone that knows how to explain the *QUALITY* of the digital output SPDIF.

Are all digital output SPDIF created equal? I'm guessing not but when you account for not having to deal with 2V, 4V & 5V pre amp outputs how do we understand the quality.

Let's say you take 

*JoyingAuto* JY-UQ128N4G
*vs. *
*Sony's* RSXGS9
I've heard that when you use the digital output from the Sony it's not as high quality as if it's coming from the other outputs. What's really true?

Who has actual knowledge and details of how this stuff works?

Thanks!


----------



## daloudin (Nov 2, 2020)

4saleongrcraigslist said:


> I've heard that when you use the digital output from the Sony it's not as high quality as if it's coming from the other outputs. What's really true?


What other outputs are you referring to and what is "not as high quality" mean?

SPDIF is digital - it's ones and zeros - what *quality *are you trying to figure out?

Are you talking about resolution, bit depth, jitter, judder, quantization noise, dsnr, snr... the list goes on?


----------



## Ge0 (Jul 23, 2007)

It all comes down to chip sets and how well they are implemented. Their is no blanket statement about the quality of the technology.

From some of the feedback I've received recently it would not surprise me if Sony's quality has gone down hill.


----------



## clange2485 (Dec 10, 2020)

Optical/toslink/fiber whatever you want to call it has been a standard in the residential electronics world for a long time. I don’t see the cable limiting any signal at all being glass vs copper, and it’s probably being buried in your neighborhood at the moment if it already hasn’t been done. If any limitations are being done it’s on the source end.


----------



## 4saleongrcraigslist (Oct 21, 2020)

I think that was well put.

By many here, digital medium of glass and light is tried and true.

maybe the better question is how can you tell the quality of what is feeding this tried and true digital medium from the head unit? I gave examples of Joying and then Sony, I did this as you have an inexpensive unit and a more expensive unit.

thanks all just trying to make sense of all of this. Maybe it’s super obvious to some but that’s what’s nice about this forum.


----------



## Ge0 (Jul 23, 2007)

4saleongrcraigslist said:


> I think that was well put.
> 
> By many here, digital medium of glass and light is tried and true.
> 
> ...


If you are going digital source to TOSLINK optical broadcast you should have no losses and very low noise assuming you have a stable clock (Jitter). 

However, if you are converting an analog source (such as radio or aux input) to digital signal for transmission via TOSLINK then you are totally at the mercy of the DAC used. Go cheap on the DAC and sound quality suffers.


----------



## daloudin (Nov 2, 2020)

And to further that as it relates to your Sony v Joying comparison; there are currently no Android OS HU's that natively bypass the internal Android Audio Layer (like a Fiio or A&K DAP) so the output on the Fiber is going to be 16 bit / 44 kHz regardless of source quality. I've yet to hear of anyone successfully using an App to bypass this and output bit perfect HiRes audio. The Sony will output at the source resolution so in that comparison the Sony is leaps and bounds ahead. 

As for the loss of bit depth on volume controlled fiber optic output, AFAIK all HU's or DAP's or anything else that modulates the volume of a digital signal will all be the same. Currently the best SQ option (that I'm aware of) is using a DAP and controlling the volume with the analog output of the DSP.

Sent from my SM-G965U using Tapatalk


----------



## 4saleongrcraigslist (Oct 21, 2020)

I love how technical this gets.

Analog = Subject to DAC to make good/great quality.

Digital = Digital should be fairly high quality.

If you could pick any head unit to pair with a Helix V Twelve integrated DSP. What would it be and why?

Assume you want the following...

Radio (Rarely used but needed)
Play FLAC or whatever super high quality files.
Wireless Apple Car Play
Stream Tidal from phone
There is also add on cards for Helix like...

HEC Bluetooth
HEC HD-AUDIO USB-INTERFACE
Thanks in advance.


----------



## Holmz (Jul 12, 2017)

4saleongrcraigslist said:


> Can someone share the truth about head unit *digital output spdif. *
> 
> so many installers talking smack about this as a trend. Especially with so many high end amp and DSP digital inputs.
> 
> who’s correct?


Christ only knows...

We were told in the olden days the CDs make a truer and more accurate source,
I watched a shoot out of high end DACS, and the magic required to get a good sound out of them.

It is seeming like it is mostly magic, BS, and sales psychology that reigns supreme.


----------



## preston (Dec 10, 2007)

My answer is the Joying. I'm not even aware of any other option besides the very expensive Sony. Many people have raved about the SQ of the Sony but it seemed like a joke to me without even a real interface. From what I understand you have to use a phone app to navigate a plugged in USB for instance. That's a non starter. 

I think there is one Stinger brand HU that has digital out. That's it other than dis-continued legacy units or other even more off brand Chinese Android units. 
Of course you always have the option of your phone and/or a DAP player. 

I've been running the Joying for 3 months and it has


Radio
Car play for android and iPhone as well as BT pairing. I'm 90% sure the latest car play is wireless I haven't tried it as I loaded a SIM card directly into the Joying and it has its own data plan.
Yes it can play high res but as mentioned above it will default to the android audio layer. However it also has USB OTG capability so it can be paired with a Helix USB HEC. In which case an app like USB audio player pro can bypass android limitations for bit perfect sound - in theory anyway I'm not an expert on all this.

TBH I've kind of given up on trying high res music, the whole topic has thoroughly confused me. I stream at the max quality available in the Tidal or Sirius XM application drop down and or save it to my own files at the standard 44kHz albeit stored as a full length WAV file. I haven't played aorund with high res because of the aforementioned "incompatibilities" so that even if I did high res I'm not sure the hu would really be playing it by the time it gets to the DSP . And then I get into the whole conundrum of do I then feel like I want to re-download my 1000 hours of music in high res because once I do one song why not all of them ? 

As far as digital quality, I had the very well regarded P99rs deck, and I played analog directly into the Helix DSP. I then connected the Joying digital as well. I level matched the 2 sources and then played the exact same WAV file at the exact same time. I could swithc back and forth instantaneously and hear the exact same passage in the music. 
I get that I am comparing a 10+ year old DAC in the P99 but I was frankly shocked at how much better the pure digital sounded, and I'm not one of those guys who can notice minor differences like the people who claim different DSPs sound different. Heck I don't even believe different quality amps sound different.

Thosre are my random thoughts on it !


----------



## daloudin (Nov 2, 2020)

4saleongrcraigslist said:


> I love how technical this gets.
> 
> Analog = Subject to DAC to make good/great quality.
> 
> ...


Helix Conductor with a Smartphone and use iHeart Radio. There are NO "affordable" HUs that support 24bit Audio and NONE that do any kind of semblance of integration that we are used to in today's cars. Keep the OEM HU for phone calls, radio, satellite, CDs, etc. and stream the rest from your phone.


----------



## 4saleongrcraigslist (Oct 21, 2020)

daloudin said:


> And to further that as it relates to your Sony v Joying comparison; there are currently no Android OS HU's that natively bypass the internal Android Audio Layer (like a Fiio or A&K DAP) so the output on the Fiber is going to be 16 bit / 44 kHz regardless of source quality. I've yet to hear of anyone successfully using an App to bypass this and output bit perfect HiRes audio. The Sony will output at the source resolution so in that comparison the Sony is leaps and bounds ahead.
> 
> As for the loss of bit depth on volume controlled fiber optic output, AFAIK all HU's or DAP's or anything else that modulates the volume of a digital signal will all be the same. Currently the best SQ option (that I'm aware of) is using a DAP and controlling the volume with the analog output of the DSP.
> 
> Sent from my SM-G965U using Tapatalk


Thanks this makes perfect sense. Most HU’s are not gonna have a DAC equal to (A&K or high-end FIIO , etc.)

im guessing this why Helix offers the HEC HD-AUDIO USB-INTERFACE so you can have that high-end DAC pipe right into the AMP + DSP. 
By pass any junk people make whether it be Sony, Kenwood or JoyingAuto.

This is super helpful. It does seem like the best DAC you get in most mainstream deck from $1500 to $400 are basically getting 16 bit / 44 kHz. Maybe the Sony is an exception but I doubt that $1500 deck is better than the A&K DAC’s.

Done, I’ll probably do the JoyingAuto and then buy the HEC HD Audio add on card (32bit @ 192kHz) so I can hook up an A&K.

The HEC BT card only does 24bit @ 48kHz and maybe that’s fine, but unsure the Helix V Twelve can do both the USB HD Audio card and the Bluetooth Card at once. Not sure you would want both either.

Thanks that was super helpful by the way.


----------



## dumdum (Feb 27, 2007)

4saleongrcraigslist said:


> Thanks this makes perfect sense. Most HU’s are not gonna have a DAC equal to (A&K or high-end FIIO , etc.)
> 
> im guessing this why Helix offers the HEC HD-AUDIO USB-INTERFACE so you can have that high-end DAC pipe right into the AMP + DSP.
> By pass any junk people make whether it be Sony, Kenwood or JoyingAuto.
> ...


If you’re using a usb hec you aren’t using the dac in the fiio or whatever player, you are bypassing it completely and using the dac at the output of the dsp... using the dac and going via analogue input you are using the dac, then the analogue to digital converter in the dsp, then the dac in the dsp also...

the usb hec is so you can plug a usb device into the dsp as extract digital, however Apple devices don’t play nicely with a usb hec, nor does android unless you use uapp to bypass the android audio layer...

this sends audio out with a sample rate of 48khz not 44.1 as someone said above...

also you are correct you can only use one hec at a time 👍🏼

also the dac in the Sony flagship isn’t implemented very well, it performs far better via its digital out (see audio science review for details)


----------



## 4saleongrcraigslist (Oct 21, 2020)

dumdum said:


> If you’re using a usb hec you aren’t using the dac in the fiio or whatever player, you are bypassing it completely and using the dac at the output of the dsp... using the dac and going via analogue input you are using the dac, then the analogue to digital converter in the dsp, then the dac in the dsp also...
> 
> the usb hec is so you can plug a usb device into the dsp as extract digital, however Apple devices don’t play nicely with a usb hec, nor does android unless you use uapp to bypass the android audio layer...
> 
> ...


Good stuff, although I’m even more puzzled.

Why are people like Matt Schaeffer (Musaic) using A&K DAC’s into DSP / AMPs on the cars he designs if what you say is true? Isn’t the A&K player wasted if the Helix v Twelve DSP is using its own DAC?

Sorry this is a rather confusing space for me as I try to gain clarity on this topic. Thanks!

“Simple is complexity resolved” Contatine B.


----------



## 4saleongrcraigslist (Oct 21, 2020)

Also,

The Helix HEC HD Audio has these specs (32bit @ 192kHz) from Audiotech Fischer?

Are these specs then, the *input* or the *output*?


----------



## dumdum (Feb 27, 2007)

4saleongrcraigslist said:


> Good stuff, although I’m even more puzzled.
> 
> Why are people like Matt Schaeffer (Musaic) using A&K DAC’s into DSP / AMPs on the cars he designs if what you say is true? Isn’t the A&K player wasted if the Helix v Twelve DSP is using its own DAC?
> 
> ...


Digital source uses dsp dac, a&k player uses its own dac, then dsp adc, then dsp dac...

are you 100% he doesn’t go digital from the A&K because it’s an excellently built high end player? And skip the dac portion? That’s what I’d do...

so yes it is a bit of a pointless exercise... it’s like buying the fiio m11pro and then using the coax output... the m11 and m11pro have the same digital out... the m11pro has an uprated dac... but with digital out you won’t benefit any over the m11

in my car there is a few dacs (iPad, topping d10, pioneer headunit... all go via the dsp dac after various other stages...) , but for critical listening the one in the dsp ultra is the only one that gets used as I go digital from source to dsp to dsp dac


----------



## BJG (Feb 7, 2021)

daloudin said:


> Helix Conductor with a Smartphone and use iHeart Radio. There are NO "affordable" HUs that support 24bit Audio and NONE that do any kind of semblance of integration that we are used to in today's cars. Keep the OEM HU for phone calls, radio, satellite, CDs, etc. and stream the rest from your phone.


That's exactly how I'd do it.. but then again I'm not qualified to even reply to this thread as it has gone way over head! LOL


----------



## doeboy (May 2, 2012)

I have always been curious about the joying products simply due to the utility they can provide. The wireless bluetooth code readers for example that give you car metrics via the OBD port was always interesting. Of course I have no idea of how well they last(quality) or how well they actually work compared to the normal big brands here like pioneer, kenwood, alpine, etc.

I guess if every level of your system is top notch then it would be time to spend the time looking into a more high res format over something that is CD quality. There is quite a back and forth about higher rated flac vs dsd. When looking at what high quality streaming services are using it looks like MQA is a popular format.


----------



## preston (Dec 10, 2007)

> are you 100% he doesn’t go digital from the A&K because it’s an excellently built high end player? And skip the dac portion? That’s what I’d do...


I've watched several Matt Schaefer videos and he explicitly says he uses the analog output of his high end DAP to feed the DSP. Claims that multiple listening tests have proven its the highest fidelity option. I have not opinion on the guy, just watched his videos, but the cynic in me says that he says this mostly because his high end installs utilize the MOST bus into the digital input of the DSP so he can maintain the client's expensive vechicle OEM head unit and functions. Therefore the only place to plug in the DAP for hi fidelity playback is into the analog inputs of the DSP. 

Its not impossible to imagine the high end DAP outputting an analog signal of such incredible quality that it could theoretically sound better than a lower resolution digital signal, even after going through the second conversion in the DSP. As I said I'm not inclined to believe it, but its certainly possible and that is what he is claiming.


----------



## MirageB. (Oct 18, 2021)

Everything is very very simple. The fewer conversions of the audio signal from analog to digital and then back to analog, the better the sound quality will be. Of course, in DSP it is better to transmit a digital signal, and this makes the whole point. For example, your head unit converts digital to analog, then transfer it to the DSP, and the DSP again converts from digital to analog, and then this signal goes to your amplifiers. I hope everything is clear here ... In addition, signal transfer via an analog RCA cable (whatever it is of high quality) also does not give anything good. Now many well-known European companies that produce DSPs have solutions for how to immediately drive a digital signal into a DSP. There are, for example, Bluetooth modules that allow you to transmit a signal to aptX HD and even to LDAC. And this is not even 48 kHz/24-bit, but even higher. There are other solutions as well.


----------



## Impossible Bill (9 mo ago)

I agree with keeping conversions to a minimum. In the old days it was common to use a high quality DAC. Apogee units even ran on 12V. The easy way was too connect a CD changer with a digital out and use that add the SQ source instead of the head unit on the analog side.
This way signal path was CD changer (optical) ==> D/A converter ==> (analog) processors / amps. All within a few feet in the trunk.

That was infinitely better than optical from CD changer to the head unit ==> D/A conversion ==> analog to back off car ==> A/D conversion ==> D/A conversion ==> analog to processors and amps. 

This was normal when OEM head units were used. The in dash CD player / tuner work via analog and Changer is superior choice. 

Same logic should apply today choose your best DAC and make it your point of conversion for SQ. If you buy the best DAC on earth and convert the signal back from analog to digital to convert it again the signal will only be as good as that conversion. You can't avoid conversion in a DSP so get the best DAC there you can and feed it a digital signal from a digital source.
Then focus on using that DSP to properly tune the system for the best possible SQ.
The best DAC will not magically make your system sound good.


----------



## dumdum (Feb 27, 2007)

Impossible Bill said:


> I agree with keeping conversions to a minimum. In the old days it was common to use a high quality DAC. Apogee units even ran on 12V. The easy way was too connect a CD changer with a digital out and use that add the SQ source instead of the head unit on the analog side.
> This way signal path was CD changer (optical) ==> D/A converter ==> (analog) processors / amps. All within a few feet in the trunk.
> 
> That was infinitely better than optical from CD changer to the head unit ==> D/A conversion ==> analog to back off car ==> A/D conversion ==> D/A conversion ==> analog to processors and amps.
> ...


That is also my view point, you will never get a better result than digital into a dsp and the dac at the end


----------



## Impossible Bill (9 mo ago)

I think no matter what brands or how many channels you run what you put before or after it has far less impact on SQ than what happens inside the DSP. It is the powerful tool in the system and with great power comes great responsibility. Don't ignore that responsibility by buying the latest and greatest new "cure". Put that DSP to use!


----------

