Helix DSP PRO MK2 and Sony RSX-GS9 sample rate - Car Audio | DiyMobileAudio.com | Car Stereo Forum

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Old 1 Week Ago   #1
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Default Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

So I read this: https://www.magicbus.biz/sony-rsx-gs9-tips.html

Raymond goes on to explain that RCA provides higher resolution than optical output.

He mentions that going through optical will induce the following limitations:
-The GS9's sophisticated volume control is defeated, and
-Native DSD cannot be played, and
-The GS9's internal DSP controls (subwoofer adjustments, for example) are defeated.
-Playback is limited to 24-bit/96kHz

If the Helix is limited to 96khz sample rate why would it matter if we're going through RCA which has a DAC that could sample at 32-bit/768khz resolution?

The signal that the processor is processing is bringing the Sony's DSD signal down to 96khz sample rate right?

Could someone clarify this for me? Thanks.

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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

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Originally Posted by tonynca View Post
The signal that the processor is processing is bringing the Sony's DSD signal down to 96khz sample rate right?
That’s my understanding of it. Anything over 96kHz is downsampled to 96kHz to be processed.
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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

Exactly so optical still wins because it has zero noise. The RCA cables he uses on that bus are thousands of dollars.

Once the DSP downsamples to 96khz/24bit it can't restore what was lost during downsampling.


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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

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Originally Posted by Bnlcmbcar View Post
That’s my understanding of it. Anything over 96kHz is downsampled to 96kHz to be processed.

The analog inputs are not "downsampled." They are sampled at 96kHz.

Downsampling is where a digital signal is kept digital but the sample rate is changed via mathematical means. Sometimes this can be as simple as cutting half the samples out, i.e. going from 96kHz to 48kHz. But other times the math does not work out so simply. i.e. going from 48kHz to 44.1 kHz. In these cases, there must be some degree of decimation or interpolation of the data to make the sample rate change. There are different types of resampling and they have different effects on the sound quality.

When you feed an analog signal into the DSP, the AD converter samples the analog signal and does so at a fixed rate. There is no interpolation going on, it simply takes accurate samples at a fixed rate of the signal coming into it. No guessing, no mathematical calculations to modify the data, etc...


Now, if you use the optical output on the Sony to play DSD files or any audio above 24/96 resolution, then there will be downsampling taking place inside of the Sony before the audio gets to the optical port.

And then, chances are you would be using a really long optical cable that stretches from the head unit to the trunk. Optical cables lose quality over distances. 15 feet or more and you're starting to get to the point where it can be important, especially if there are any bends in the cable.

Personally, I will take high quality analog over optical any day.

There's a reason why you don't see optical on high end home audio gear much anymore.

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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

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Originally Posted by subterFUSE View Post
The analog inputs are not "downsampled." They are sampled at 96kHz.
^Correct!^

Downsample was the wrong word to use.

Optical or RCA for ‘noise’ will be a user preference at the end of the day. As subterFUSE mentioned, long optical runs can be susceptible to problems just as long RCA runs can be. I feel issues are less likely to occur with optical over RCA in terms of ‘noise’ qualms from my experience but I too have also veered away from optical when going digital and stick to using USB or digital coax cables when possible. Hence, why I mentioned downsampling. Feeding a Helix Pro a digital signal via USB or SPIDF Coax over 96kHz will be downsampled by the Helix. The RCA inputs will be as subterFUSE explained, sampled at 96kHz.

Which is better? Kind of up to you, your ears, and your gear. The Digital optical route is a more direct signal path but limited in maximum bitrate. RCA route will not get downsampled but it does place another conversion into the signal path.

Question becomes which caveat is more audible for you in your setup?
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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

Quote:
Originally Posted by subterFUSE View Post
The analog inputs are not "downsampled." They are sampled at 96kHz.



Downsampling is where a digital signal is kept digital but the sample rate is changed via mathematical means. Sometimes this can be as simple as cutting half the samples out, i.e. going from 96kHz to 48kHz. But other times the math does not work out so simply. i.e. going from 48kHz to 44.1 kHz. In these cases, there must be some degree of decimation or interpolation of the data to make the sample rate change. There are different types of resampling and they have different effects on the sound quality.



When you feed an analog signal into the DSP, the AD converter samples the analog signal and does so at a fixed rate. There is no interpolation going on, it simply takes accurate samples at a fixed rate of the signal coming into it. No guessing, no mathematical calculations to modify the data, etc...





Now, if you use the optical output on the Sony to play DSD files or any audio above 24/96 resolution, then there will be downsampling taking place inside of the Sony before the audio gets to the optical port.



And then, chances are you would be using a really long optical cable that stretches from the head unit to the trunk. Optical cables lose quality over distances. 15 feet or more and you're starting to get to the point where it can be important, especially if there are any bends in the cable.



Personally, I will take high quality analog over optical any day.



There's a reason why you don't see optical on high end home audio gear much anymore.


Great good to know. Will try Stinger 9000 series RCA vs my optical cable on my Clarion NX807 to see if there are any Sonic difference.

I just don't know which DAC this Clarion unit is using and if it's any good.


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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

General cases of optical spdif has a limit of 96k/24bit stereo pcm. So your limiting factor seems to be the optical medium not the chip inside the Sony.

What you’re getting with the sony’s optical-out is a usb to spdif conversion, pcm only. It doesn’t convert dsd to pcm. The dsp inside the Sony to control volume doesn’t get utilized on this path. Purely a bridge from one digital medium to another.

The helix will do 192k/32bit stereo pcm over coax spdif.

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Default Re: Helix DSP PRO MK2 and Sony RSX-GS9 sample rate

Yes, there really is no reason to have the Sony if the optical is being used. Nearly all of the features which the Sony was designed and marketed for are bypassed when going optical out. It would be better to simply go USB to the DSP directly, like the Helix USB HEC module.

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