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RME ADI-2 Pro as digital DSP

dehati_paul

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Hi - I have recently purchased an RME ADI-2 Pro with the purpose to use it as a digital DSP.

The chain:
spdif coax in (from Sonos) -> RME ADI-2 Pro (only as DSP) (spdif coax out) -> DAC -> AMP

I know I can use the RME ADI-2 Pro as DAC, but I'd prefer to use it only as digital DSP. So my question is - What setting gives me the optimal setup for this? I have been using it in AD/DA mode, but is there any way to skip/disable the digital volume, so that I have the DAC control volume. If I set the volume at 0dB, the meters show red 'OVR', suggesting clipping. Setting it up at something lower suggests that there's additional volume-related processing that I'd like to avoid. Suggestions are welcome.
 

Jimbob54

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I think you are trying to do the impossible but the experts will tell you why. My understanding is if you add a peak to a full scale signal without an overall reduction in overall level you will get overs/ clipping. No free lunch.

Personally I wouldnt worry about the reduction you have to make in the RME as any downsides will be trivial , especially compared to the upside of DSP to your requirements.
 

dougi

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You can "fix" the volume so that it at least can't be changed via knob (still via the remote though I believe, but the manual covers it.
The RME has a bit of headroom, so a small "OVR" may not actually be clipping. However, the EQ displays should indicate whether gain overall is positive and hence if you should reduce the volume a bit. That won't cover the effect of bass/treble controls or dynamic EQ though. With only 5 PEQ per channel, you may find you need to use the bass/treble along with PEQ, especially if you are using the RME for a basic room EQ.
 
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Kundroc

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The level meter can be set to display the levels before or after DSP processing. If your music has such high levels to trigger the "OVR" warning, you will see it in both cases, even without any DSP effects activated (volume, EQ, etc.).

Why do you want to use a separate DAC (additional to the RME) in the first place?
In any case, have a look into the post about volume control with the RME for optimal settings.
 

KSTR

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I know I can use the RME ADI-2 Pro as DAC, but I'd prefer to use it only as digital DSP
See manual, section "17.6 DAC". Set "Digital Out Source" to "Main Out" to send the processed audio (EQ, etc) to the digital outputs.
Any processing will need some headroom so it's best to reduce the volume by several dB until you don't have any digital clipping. Leave the volume at that position or use the "lock volume" option (Section 12.2).

Are you sure your DAC is better than the ADI-2 Pro's DAC, given the excellent "Auto Reference Level" feature of the RME which keeps the DAC chip proper always in the optimum range regardless of (lower) volume setting?
 
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dehati_paul

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See manual, section "17.6 DAC". Set "Digital Out Source" to "Main Out" to send the processed audio (EQ, etc) to the digital outputs.
Any processing will need some headroom so it's best to reduce the volume by several dB until you don't have any digital clipping. Leave the volume at that position or use the "lock volume" option (Section 12.2).
Between this forum and the RME forum that digital volume is unavoidable to manage the DSP headroom. I guess the best approach is as you suggested, i.e. apply EQ and then reduce the volume to avoid clipping and then lock.
Are you sure your DAC is better than the ADI-2 Pro's DAC, given the excellent "Auto Reference Level" feature of the RME which keeps the DAC chip proper always in the optimum range regardless of (lower) volume setting?
I am using LKS Digital Audio DAC (dual ESS9038Pro), which I am assuming will be better than RME single AKM4493. Additionally, I am using external DAC because my DAC is also connected to the computer using USB. I have heard that maintaining two inputs (Sonos spdif + Computer USB) is difficult for switching in RME. Related question - Doesn't the Reference Level setup only affect analog out, so how is Auto Reference Level going to help for digital out?

Thanks to everyone for the inputs!
 

Jimbob54

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Between this forum and the RME forum that digital volume is unavoidable to manage the DSP headroom. I guess the best approach is as you suggested, i.e. apply EQ and then reduce the volume to avoid clipping and then lock.

I am using LKS Digital Audio DAC (dual ESS9038Pro), which I am assuming will be better than RME single AKM4493. Additionally, I am using external DAC because my DAC is also connected to the computer using USB. I have heard that maintaining two inputs (Sonos spdif + Computer USB) is difficult for switching in RME. Related question - Doesn't the Reference Level setup only affect analog out, so how is Auto Reference Level going to help for digital out?

Thanks to everyone for the inputs!
If the pro switches inputs like the non pro it's a button press on the remote......

As to assuming a 2 chip device is better automatically than a single chip, nuh huh. The RME is way beyond transparency and using 2 $1k plus devices to do the job of one makes no sense to me and I suspect many others. But it's your money......
 
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dougi

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If the pro switches inputs like the non pro it's a button press on the remote......

As to assuming a 2 chip device is better automatically than a single chip, nuh huh. The RME is way beyond transparency and using 2 $1k plus devices to do the job of one makes no sense to me and I suspect many others. But it's your money......
Only if you set the PRO into DAC mode. The USB playback is not selectable on the main output in some of the other modes like AD/DA.
 
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dehati_paul

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I am using the external DAC, because I already had it. Will do a comparison, and will probably get rid of it. Yesterday, I spent some quality time setting up the EQ for my three headphones and what I found seriously limiting is the 5-band PEQ. Oratory1990 suggested settings are 10 bands (his list for RME settings doesn't include my headphones), and even if I ignore the smaller adjustments, working with just five ends up in compromise. I know miniDSP has 10 bands but is limited to 24bit/96kHz, and one of the reasons I got the RME is because of it's DSP support for higher samples rates, which I will need for DSDs converted to PCM (24bit/176.4kHz), knowing DSDs can't be DSPed. Any suggestion on how to fit the 5-band EQ to fit Harman target?
 
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I am using the external DAC, because I already had it. Will do a comparison, and will probably get rid of it. Yesterday, I spent some quality time setting up the EQ for my three headphones and what I found seriously limiting is the 5-band PEQ. Oratory1990 suggested settings are 10 bands (his list for RME settings doesn't include my headphones), and even if I ignore the smaller adjustments, working with just five ends up in compromise. I know miniDSP has 10 bands but is limited to 24bit/96kHz, and one of the reasons I got the RME is because of it's DSP support for higher samples rates, which I will need for DSDs converted to PCM (24bit/176.4kHz), knowing DSDs can't be DSPed. Any suggestion on how to fit the 5-band EQ to fit Harman target?
You cant, without degrading EQ quality. And such degradation will be far more noticeable than difference between dacs or 96khz resampling (which i think will be not noticeable at all)
 

Jimbob54

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I am using the external DAC, because I already had it. Will do a comparison, and will probably get rid of it. Yesterday, I spent some quality time setting up the EQ for my three headphones and what I found seriously limiting is the 5-band PEQ. Oratory1990 suggested settings are 10 bands (his list for RME settings doesn't include my headphones), and even if I ignore the smaller adjustments, working with just five ends up in compromise. I know miniDSP has 10 bands but is limited to 24bit/96kHz, and one of the reasons I got the RME is because of it's DSP support for higher samples rates, which I will need for DSDs converted to PCM (24bit/176.4kHz), knowing DSDs can't be DSPed. Any suggestion on how to fit the 5-band EQ to fit Harman target?
Find the preferred setting on AutoEq and use the first 5 bands.
 
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dehati_paul

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Find the preferred setting on AutoEq and use the first 5 bands.
Thanks a million! AutoEQ has been a lifesaver. In Python mode, I was able to select the number of bands (5). Though the final curve is not perfect, it's close to what I can live with.
 
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dehati_paul

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(also posted this on RME ADI-2 forum)
I have finally set up the RME ADI-2 Pro as DAC (got rid of the external DAC), and now my setup is

Sonos spdif coax -> RME ADI-2 Pro (with PEQ) XLR -> Topping A-90 -> headphones

Now the questions that have been bothering me, and I am sure you can clarify, are -

1. The input digital signal from Sonos (or from any other digital sources) is very close to clipping (OVR), and if I add Parametric EQ to it, the output signal at 0dB is obviously getting clipped, so I have dialed down the volume to say -12dB. The question is how does the RME ADI-2 do pre-DAC headroom management? Everywhere, I see there's a suggestion of -6dB pre-DAC headroom adjustment to make the headroom available for EQ gain, but I do not see anything like that to adjust in the RME ADI-2. Moreover, my worry is that if the signal gets clipped after DSP -> DAC (assuming this is the sequence), the digital volume gain reduction will be working on the clipped signal, which will not help much.

2. In the chain of signal flow, where does the reference level adjustment come in? Am I thinking this correctly Digital input -> Ref Level -> DSP -> Digital Volume -> DAC -> Analog output?

Please let me know so that I can sleep better at night and prevent eyebags from appearing.

Thanks!

Dehati
 

Trell

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(also posted this on RME ADI-2 forum)
I have finally set up the RME ADI-2 Pro as DAC (got rid of the external DAC), and now my setup is

Sonos spdif coax -> RME ADI-2 Pro (with PEQ) XLR -> Topping A-90 -> headphones

Now the questions that have been bothering me, and I am sure you can clarify, are -

1. The input digital signal from Sonos (or from any other digital sources) is very close to clipping (OVR), and if I add Parametric EQ to it, the output signal at 0dB is obviously getting clipped, so I have dialed down the volume to say -12dB. The question is how does the RME ADI-2 do pre-DAC headroom management? Everywhere, I see there's a suggestion of -6dB pre-DAC headroom adjustment to make the headroom available for EQ gain, but I do not see anything like that to adjust in the RME ADI-2. Moreover, my worry is that if the signal gets clipped after DSP -> DAC (assuming this is the sequence), the digital volume gain reduction will be working on the clipped signal, which will not help much.

2. In the chain of signal flow, where does the reference level adjustment come in? Am I thinking this correctly Digital input -> Ref Level -> DSP -> Digital Volume -> DAC -> Analog output?

Please let me know so that I can sleep better at night and prevent eyebags from appearing.

Thanks!

Dehati

Just use the auto ref feature of the ADI-2, assuming that the PEQ is set in the ADI-2. You can see that the ref level changes when enabling/disabling loudness or use tone controls on the device.
 
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Wicky

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(also posted this on RME ADI-2 forum)
I have finally set up the RME ADI-2 Pro as DAC (got rid of the external DAC), and now my setup is

Sonos spdif coax -> RME ADI-2 Pro (with PEQ) XLR -> Topping A-90 -> headphones

Now the questions that have been bothering me, and I am sure you can clarify, are -

1. The input digital signal from Sonos (or from any other digital sources) is very close to clipping (OVR), and if I add Parametric EQ to it, the output signal at 0dB is obviously getting clipped, so I have dialed down the volume to say -12dB. The question is how does the RME ADI-2 do pre-DAC headroom management? Everywhere, I see there's a suggestion of -6dB pre-DAC headroom adjustment to make the headroom available for EQ gain, but I do not see anything like that to adjust in the RME ADI-2. Moreover, my worry is that if the signal gets clipped after DSP -> DAC (assuming this is the sequence), the digital volume gain reduction will be working on the clipped signal, which will not help much.

2. In the chain of signal flow, where does the reference level adjustment come in? Am I thinking this correctly Digital input -> Ref Level -> DSP -> Digital Volume -> DAC -> Analog output?

Please let me know so that I can sleep better at night and prevent eyebags from appearing.

Thanks!

Dehati
I read somewhere the ADI-2 reduces the input signal by -24dB prior to applying DSP. Also you can check if your signal is clipping as the level meters will go red. Try RMEs DIGIcheck software to check for this to see if it is really going to be an issue in your setup.

[Edit]
From the manual, page 26:
"The ADI-2 Pro has an internal headroom of 24 dB. Extreme boosts with overlapping filters could cause an internal overload. Such an overload will be visible as it is displayed by the level meter below the EQ, as well as the channel’s level meter. Reducing the output volume will prevent any clipping as long as the headroom of 24 dB is not exceeded. In real-world operation that is always the case, the ADI-2 Pro will not distort internally."
 
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