"enable MQA core decoder" in Roon

Hi everyone,

I’m using Roon with HQplayer on a small form factor PC connected with USB to an Amanero AK4499 DAC. Lately I’ve been doing some listening tests and I’m not sure if my ears are playing me some kind of joke or it’s a real difference in the software. But I hear a difference turning “enable MQA core decoder” off compare to on. All settings are std. in Roon when using HQplayer, in HQplayer I’m using 0dB in volume(I have external volume control), I’m using no DSP and playing FLAC files from Qobuz.

I’ve confirmed that the chain in Roon is the simplest it can be (No MQA anywhere, no DSP, no Volume) thus preserving the original bit and sample rates. I will try to describe what I hear (don’t laugh): “MQA core decoder enabled - on” = 3D sound, “MQA core decoder enabled - off” = flat and slightly annoying sound.

Is the “MQA core decoder enabled” setting disabling more than just the capability of Roon to do MQA?

I’ve read in another thread that Roon recommends leaving it on and that it can create problems when using DSP, but I’m not using DSP?

With playing files from Qobuz I just want the file moved over to HQplayer as intact as possible with no alteration. The std. setting for HQplayer sounds good and I like it, so this is just a question about me not understanding what happens when I flip that MQA core decoder switch(I understand the meaning of it, but not what happens behind the scenes because what I’m supposedly hearing confuses me).

I have more “strange” things I’ve found, but let’s take one at a time and minimize confusion.

Mysterious. The MQA setting should not matter for non-MQA content. Is that the only setting difference you do?

It’s strange indeed. It sounds like a human error the most.

I would just like to be sure and hear it(maybe from Roon), that disabling “MQA core decoder” doesn’t leave the sound in a somewhat lesser stage? Even with no MQA source material, no volume or other DSP processing.

With this test the settings are all standard, except from flipping this switch.

Mqa decoder does not affect any content that is not mqa. It allows the first unfolding of MQA material to 96/24 or 88.2/24. Turning it off or on makes no difference to non mqa material. Yes I have tested it.

What is your Roon core running on?

Thanks for info, I guess that means I’m down to placebo or software induced jitter or other noise.

I’m running the core and Hqplayer together on a Dell optiplex 7060 micro PC with Ubuntu server 18.04 LTS installed as recommended for Hqplayer. With the test being “straight” an me being able to run everything on 1 core at 800Mhz, I don’t think more processing power is needed.

I’ve tried a network solution with an rpi and while that has something to it, I like this setup better because of simplicity.

If I’m in any more doubt about this I will just to a null test in a DAW with two identical files played through the system. That doesn’t measure the jitter or noise though.

I got help from an engineer to put a scope on the Amanero data pins and checked that the total bits arriving at the AK4499 is what Roon says it should be, so the wordlength is not being changed on the way either by Roon or Hqplayer. Same with samplerate.

So again, it seems to be either placebo or noise/jitter.

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If you connecting that direct to the DAC then it’s likely computer noise. I can’t imagine that being a very quiet system with both Roon and HQ player on it’s going to be generating a lot of CPU noise along with other computer nasties and that’s getting a ride into the DACs via the usb stage and along to the analogue section . So either seperate core and DAC or get a DAC that’s better at rejecting this noise or a usb cleaner.

Roon will use slightly more resources if the decoder is on as its another process running in the background I guess. Sounds like you need to seperate out the core and have a core endpoint solution which is what Roon recommend any way. I have a core direct to a DAC but don’t get any noise or change but I have an RME dac that’s noted for being able to clean up the USB.

I understand what you are writing as a general advice for a good setup, and that’s fine.
I’ve chosen to go another way after trying it, that’s my decision and I know the pros and cons about it.

This advice contradicts your earlier statement that: “Mqa decoder does not affect any content that is not mqa.”

That is unless you are saying that this MQA core switch is inducing jitter into the signal at either setting, even though it’s not processing anything?

Only a hypothesis, it makes no difference on mine anywhere on any device and it shouldn’t. It’s not touching the audio path for non mqa material but turning on the decoder is adding another sub process for Roon and the pc to deal with. It’s not altering the audio stream at all. It could be affecting the noise levels that your systems making that in turn is effecting the output of the DAC as usb is bad at doing this This is the very reason they say to decouple the DAC from the core. I am not contradicting myself as its not affecting the audio stream it’s just bad hardware decisions and configuration. You might not like that idea but it is the most likely answer.

If you’re doing any kind of upsampling/re-sampling in HQPlayer, you need to set max volume in HQP at least to -3db.

Not sure if I misunderstood something and you’re already doing it…

CrystalGipsy, that procedure you are recommending will require an answer from Roon that this setting does indeed introduce more jitter or noise when disabled. But without that kind of answer from Roon, your answer doesn’t apply to simple logic. I’m sure you know this already.

Rami, I’m not applying any processing at all, no upsampling, no volume control, no dither. I’m just doing simple sequential testing to find out what’s up and down.