1.3 Sound Quality and Listening Observations

  • I’m just a week into my Roon journey and am quite nearly a fanboy. The leap forward in sound quality from Logitech Media Server was stunning, and I’m in love with the user experience. Kudos to the entire team for a pretty damn smooth roll-out yesterday.

That said, when I sat down to give 1.3 a close listen last night, something was missing. There was still fine-sounding music, but the magic was gone. Sound was flatter, duller. Not by much, but by enough to realize that the music didn’t arrest me the way it has since I came over to Roon.

So I started playing with settings. To reduce load on my processor (core is on a sonicTranspoorter i5) I switched Background Analysis from Throttled to 1 core, and turned off On-Demand Analysis Speed. No improvement. Shucks.

Then I went into the DSP Engine controls for my DAC. Resigned that it was too late at night to go down all the rabbit holes on offer there, I disabled the DSP engine itself (even though all the individual controls within DSP were all disabled.)

BOOM! We got the magic back. That spooky-good imaging, that energy that leapt out of the speakers, that 1.2 that made me swoon, was back. A/B/A/B comparison made me confident enough to come over here and stick my neck out to say that the DSP engine itself is degrading SQ relative to no engine. It’s not huge, but it’s there.

Thanks to Roon for giving us that little slider to turn the DSP engine off. Folks who need it, have it. Purist nerds can be purist nerds. Everybody wins.

What do your ears say?

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My view is that this could be confirmation bias, but then, so could my assessment of your situation…

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Hey @Rusty_Miller I’m curious… Do you have any MQA and an MQA decoder? (or any other means of verifying bit-perfect output?) I’m currently listening to some MQA which is being passed to my Meridian 818 for decoding.

The 1.3 per-zone defaults are to have the DSP Engine enabled with all Filters in the DSP engine disabled. This is a bit-perfect configuration (I get MQA decoding in the 818).

If I enable the Headroom Management filter, I lose bit-perfect replay due to the -3dB of digital gain applied.

However, if I then set the Headroom Adjustment to 0dB, I get bit-perfect replay again.

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Makes sense. It would stand to reason that you would want a DSP bypass based on a file tag (eg MQA).

The top-level DSP Engine switch doesn’t turn off anything if all of the subsections are turned off.

The switch defaults to displaying in the “on” state so people don’t need to do an extra click in a confusing place, but that is just a display trick to save extra clicks.

Nothing is actually being turned on/off–on the inside that switch is just a shortcut that means “treat all of the subsections as disabled even if they are enabled”. But the actual enablement/disablement all happens at the subsection level.

Something else must have changed during your testing to make you hear a difference–I can’t say what it is, but there is another variable here you’re not accounting for. It’s not the switch.

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Joel, thanks for coming by. No MQA hardware decoding on the Bridge II renderer in my PS Audio PWDII DAC.

Brian, you just answered (and shot down :relaxed:) my next thought, which was that disabling the DSP Engine might be lowering the processor load on the i5.

The DSP engine is awesome…

1 thing I find that does not work in the DSP engine is phase reversal in the speaker setup section , delay and gain work , but if you invert the phase of one channel there is no change?

It’s tempting to think of the DSP engine as something that “happens” during playback.

But really, the DSP engine is the thing that builds the signal path before playback starts. Either it puts processing elements into the signal path or not–after that it’s out of the picture, and the signal path is running the show.

In fact, even when it’s turned off in the user interface–if DSP is required to maintain compatibility (for example, playing a 192kHz file on a 48kHz only DAC), the DSP engine is the thing that figures out what needs to be done and assembles a signal path to do it.

(And of course, Roon keeps an audit trail of what it does when building the signal path and displays that to you, so you can check and see what it did).

Hope this sheds some light.

@Rodney_Gold, thanks for the report. We’ll try that out later today and see what we see.


Couple of questions and/or suggestions:
1- When software MQA decoding is added, will it be added “prior” to the DSP itself? Ie will I be able to post process the decoded (88 or 96) stream with upsampling, crossfeed, eq?
2- Will a configuration allow me to completely skip MQA software decoding for MQA files only? Ie switch off software decoding and DSP altogether based on the file being tagged as MQA?
3- What happens with DSD files? Do they get PCM’ed, DSP’ed, then DSD’ed again? Or do DSD files completely skip DSP?


Will the DSP engine understand it’s an MQA file and allow you to completely skip the

That is the approach we’ve proposed to MQA, and the one we are advocating for. I think it’s going to happen that way, but nothing is 100% until it’s done and shipped.

We understand that some people will want this. We will figure out options like that when we integrate MQA decoding support.

If you enable DSP features and play DSD, the processing happens in the DXD domain. Whether not it is upsampled back to DSD afterwards depends on how you’ve configured your sample rate conversion settings.

Very specific example: input file is a DSD64 dsf file, and I have set custom upsampling to DSD64->Default and turned off all other DSP modules.

Question is: will the file still be subject to DSD->DXD->DSD? HQP has a “Direct SDM” setting that makes HQP not touch any DSD streams.

I understand that if any DSP needs to be applied, it must be done in the PCM domain.

I have to admit, this had me laughing out loud for some minutes.

Seriously guys. Stop imagining things! :joy:

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DSD64->Default with no additional DSP stuff configured should leave the signal untouched assuming your DAC supports DSD64.

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