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Topic: Curious if anyone does the same? Outboard Mastering Roundtrip

Sometimes I use my ADI-2 Pro FS for mastering my own material in the analogue domain by using the outputs and inputs on the device to do a round trip to my outboard and back in.  In this instance, I have alternate devices I like for monitoring. Sometimes, I change the filters on the D/A outputs on my ADI 2 PRO and it changes the sound (obviously) on the track I am mastering. Not drastically of course...  I don't know if it's considered good practice or not that I am doing that and not just sticking to 1 filter on the D/A side of things but I find different filters sound better for different tracks even though sometimes the differences aren't huge. Just to be clear, once again, in this situation I am not using the ADI-2 Pro to monitor material but only as a roundtrip from D/A back to A/D.

Does anyone else do this? What do you guys think? Obviously I just use my ears and I choose what I think fits the material but I am always second guessing myself if this is a "correct" method. Is there any reason I should not be doing what I am doing?

Cheers.

2 Reply by larst (edited by larst 2022-01-21 20:13:59)

  • larst
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

Hi dubcaravan,

my Adi-2 pro fs arrived yesterday and one of my intended scenarios is the same as yours.

I also wonder about those filters.... so far I've only experimented with different filters while listening on Tidal HiFi in headphones, and maybe I'm imagine it but I feel the SD Slow results in less ear fatigue. For playback one could of course use the one sounding best at the moment... but for mastering and recording... yeah, is it yet another personal reference choice (I'm trying to minimize those darn choices, but failing big time..) or might there be a way prefered by a seasoned mastering engineer?

Cheers,

Lars

3 Reply by larst (edited by larst 2022-01-21 22:45:43)

  • larst
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

Here's some info/opinion about filters.
https://forum.rme-audio.de/viewtopic.ph … 68#p177168
https://forum.rme-audio.de/viewtopic.ph … 26#p130026

4 Reply by larst (edited by larst 2022-01-21 23:33:12)

  • larst
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

Sorry if I'm hijacking the thread but hopefully our interests are similar...

Re-reading the chapters about AD/DA Impulse Responses and looking at the curves my conclusion is that for mastering in the given scenario the (theoretically) best filter choices should be:

d/a (filter: SD LD - Short Delay Low Dispersion or Slow, FIR) -> analog outboard gear -> a/d (Slow,FIR). Sample rate >= 88.2/96 kHz.

Thoughts?

  • KSTR
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

larst wrote:

Sorry if I'm hijacking the thread but hopefully our interests are similar...

Re-reading the chapters about AD/DA Impulse Responses and looking at the curves my conclusion is that for mastering in the given scenario the (theoretically) best filter choices should be:

d/a (filter: SD LD - Short Delay Low Dispersion or Slow, FIR) -> analog outboard gear -> a/d (Slow,FIR). Sample rate >= 88.2/96 kHz.

Thoughts?

Technically best, in terms of best signal integrity (when used in straight cable loopback as the simplest "mastering chain"), is to use the FIR (linear-phase) Sharp filters on DAC and ADC. All other combinations will create larger timing or frequency response errors. That is for 44.1kHz or 48kHz. Above 48k filter types don't matter anymore.

Actually I'd use what sounds best. As the analog chain already (and purposely) technically corrupts the signal big time trying to preserve best theroretical signal integrity in the DAC-->ADC process does not make too much sense.

6 Reply by KaiS (edited by KaiS 2022-01-22 17:51:55)

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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

Choose your filter by listening, without any prejudice by looking at the curves.

Watch out for the resolution in the treble range:
• Can you distinguish between hihats, shakers, sibilants, etc.?
• which filter has the more transparent ambience definition?
• How are the attacks of sounds?

Finally, the differences of the filter’s frequency response can be compensated by ADI-2’s equalizer.
MC Matthias Carstens has posted the values in this forum:
https://forum.rme-audio.de/viewtopic.ph … 26#p130026


For analog mastering I would go a different approach:
I would take the chance, after going through an analog chain, to record with a higher samplerate, I’d suggest 96 kHz.
This way you could make your files HiRes, kind of, and the filters don’t have any audible impact anymore.

Typical chain:
• Top notch offline upsampling 44.1 (48) kHz -> 96 kHz
• ADI-2 Pro DA-conversion
• Analog processing
• ADI-2 Pro AD-conversion
• optional downsampling into the release format’s sample rate, i.e. 44.1 for CD release
• Digital Peak Limiter (if needed) and redither, to the release formats Bit Depth’, i.e 16 bit for CD, as final steps for each release format.

KaiS's Website

  • larst
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

KaiS wrote:

Finally, the differences of the filter’s frequency response can be compensated by ADI-2’s equalizer.
MC Matthias Carstens has posted the values somewhere in this

Thanks, found those values yesterday and posted the link above. But maybe there are more somewhere... !?

8 Reply by larst (edited by larst 2022-01-22 12:23:46)

  • larst
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

For mastering and recording I bought the adi2 pro fs r to, as far as possible, take conversion out of the equation.

For these scenarios I will never go below 96kHz (never say never, right!?) and it seems like in this case the filters doesn't matter, but to me it it also seems that FIR slow should be the least intrusive!?

What I would like is to hear the same thing when monitoring the analog signal, either at recording, before first da, or after analog master chain, before reentering the digital domain, and when monitoring the signal after ad-conversion.

Anyway, in the end our precious (and subjective, and different from day to day...) ears has to decide what sounds best, and I have to put the adi-2 pro fs r to work to see what happens!

  • KSTR
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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

larst wrote:

For these scenarios I will never go below 96kHz (never say never, right!?) and it seems like in this case the filters doesn't matter, but to me it it also seems that FIR slow should be the least intrusive!?

Hhm, I tend no never use the Slow filters as they have the most DAC imaging and the most ADC aliasing error.

Of course at 88.2kHz and above both errors are way less of a problem. For the Slow ADC filter, aliasing is more than 60dB down below fs/4 and frequency response is good to fs/4 as well, same for the DAC filter.

10 Reply by KaiS (edited by KaiS 2022-01-23 07:32:44)

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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

larst wrote:
KaiS wrote:

Finally, the differences of the filter’s frequency response can be compensated by ADI-2’s equalizer.
MC Matthias Carstens has posted the values somewhere in this

Thanks, found those values yesterday and posted the link above. But maybe there are more somewhere... !?

Thanx, I did put this in my posting.

The EQs are for Slow and SD Slow (being the same), and NOS.
The other filters don’t need a compensation.

KaiS's Website

11 Reply by larst (edited by larst 2022-01-22 22:21:51)

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Re: Curious if anyone does the same? Outboard Mastering Roundtrip

Here's the eq correction for NOS and Slow at 48kHz
https://forum.rme-audio.de/viewtopic.ph … 50#p130950

This comment, from the same post, by MC might also be of interest:
https://forum.rme-audio.de/viewtopic.ph … 49#p130949

"But the point is: the Pro is a Pro tool. Calling a filter 'SuperSlow' has no meaning for anyone. Imagine someone transfers precious recordings through an analog chain, uses the Pro (or DAC) as DAC, processes it, records it again at Hi-Res. Then a year later the engineer discovers that all transfers are completely messed up with high frequency noise, aliasing, and even the expected response in the higher treble lacks. Then that guy is fired and our reputation completely destroyed.
In HiFi people can do to the music whatever they like, it's their fun and usual has no serious consequences, right there at the end of the chain. In a studio environment R2R and NOS are an absolute no-go. So is 'SuperSlow'."