Better understanding how Aries (Femto) and Roon interact


#1

I’ve read a number of posts and the Roon documentation to better understand how Roon and my Aries “interact” but haven’t been able to find/understand the answer.

My Setup:

I’m running an Aries with Femto clock with Firmware 6.0. It feeds an NAD M51 DAC (which is not DSD-capable but can receive PCM files up to 24 bit 192kHz). I’m running Roon 1.6 (build 401 64-bit) core on an SSD attached to a QNAP NAS. My library is on separate drives on the NAS. I control Roon using my iPad, iPhone, or MBP.

The settings I’m using on Roon for the Aries endpoint:

a. No MQA support
b. Fixed Volume
c. 0ms Resync Delay
d. Max Sample Rate (PCM) Up to 192kHz
e. Max Bits Per Sample (PCM) 32
f. Zone Grouping Delay (ms) 0
g. Clock Master Priority Default
h. Enable MQA Core Decoder No
i. Multichannel Mixing Downmix As Needed

The relevant settings (I think) on the Aries:

a. Enable Volume Control: Disabled
b. Delay Time: Disabled
c. Available Input Methods: only Roon Ready enabled
d. Streamer Mode: Lightning Device
e. MQA Pass-through: Disabled
f. Decoding Method: Auto
g. PCM Auto Detect: Enabled
h. Convert DSD to PCM: Enabled
i. Filter Mode: Precise
j. Parametric Equalizer: Disabled
k. Speaker Placement: Disabled

My questions:

  1. Both the Aries and Roon have the ability to do DSP effects such as equalization, etc. How do I ensure that both the Aries and Roon are not processing the signal sent by Roon to the Aries and then to the DAC?

  2. Are my Aries settings “correct” to ensure minimal signal processing by the Aries?

  3. I notice when I play DSD files using Roon that it automatically converts from DSF DSD64 to 32bit 176.4kHz. It appears that this signal is then sent to the Aries using RAAT as a DSD file. I base that hypothesis on the fact that if i turn off “Convert DSD to PCM”, I don’t hear any music coming from the NAD. Why wouldn’t Roon automatically convert this to PCM since it know that I have an NAD USB Output from the Aries?

  4. Is there a way to have Roon only send an unprocessed, bit-perfect signal to the Aries and let the Aries handle all conversions (which is what happens if I use Aurelic’s Lightning app)? If so, what settings would I use?

  5. Conversely, is there a way to have Roon do all processing so that all the Aries does is send the Roon-processed signal to the NAD? Based on my experiment with DSD files it appears that both Roon and the Aries are processing the signal under the settings I’m using.

Thx in advance for helping me to better understand how the Aries and Roon are interacting…will help me experiement with settings/filters moving forward.


(John) #3

Hello @Pacoinmass

  1. Both the Aries and Roon have the ability to do DSP effects such as equalization, etc. How do I ensure that both the Aries and Roon are not processing the signal sent by Roon to the Aries and then to the DAC?

You can always check what DSP processes are being applied to your audio stream by checking Roon’s Signal Path.

  1. Are my Aries settings “correct” to ensure minimal signal processing by the Aries?

Yes.

  1. I notice when I play DSD files using Roon that it automatically converts from DSF DSD64 to 32bit 176.4kHz. It appears that this signal is then sent to the Aries using RAAT as a DSD file. I base that hypothesis on the fact that if i turn off “Convert DSD to PCM”, I don’t hear any music coming from the NAD. Why wouldn’t Roon automatically convert this to PCM since it know that I have an NAD USB Output from the Aries?

When you see the conversion from DSF DSD64 to 32bit 176.4kHz PCM in Roon’s Signal Path happening before the AURALiC ARIES element, Roon will be sending the AURALiC the PCM audio stream.

  1. Is there a way to have Roon only send an unprocessed, bit-perfect signal to the Aries and let the Aries handle all conversions (which is what happens if I use Aurelic’s Lightning app)? If so, what settings would I use?

As mentioned previously, all DSP operations performed on the audio stream in Roon will be shown in the Signal Path pop-over. You can check at a glance if the audio stream is being sent “bit-perfect” to the DAC by looking at the “light” displayed next to the now playing information in Roon. If the light is purple, the audio stream is being sent bit-perfectly.

  1. Conversely, is there a way to have Roon do all processing so that all the Aries does is send the Roon-processed signal to the NAD? Based on my experiment with DSD files it appears that both Roon and the Aries are processing the signal under the settings I’m using.

From what I can tell from what you’ve explained about your setup, you already have the proper settings for this playback strategy.

-John


#4

John,

Thx for the reply. I’m still confused by the interaction, especially when looking at Roon’s Signal Path.

Here is a Signal Path for a DSD64 file being played through the Aries to the NAD. The Aries settings are as described below. With these settings I can hear the music.

Based on the above path I assume that Roon is sending a PCM signal (176.4kHz, 32bit 2ch). Is that correct?

If so, why can’t I hear music if I toggle the Aries’ setting for Convert DSD to PCM to the Disabled position as shown below:

Shouldn’t I be hearing what I presume is a PCM signal from Roon to the Aries if I disable the Convert DSD to PCM switch on the Aries?

I thought that Roon would (should?) detect both the streamer (Aries) and the Output device (NAD M51) and would convert from DSD to PCM because it “knows” that the NAD M51 doesn’t play DSD files (regardless of how the Convert DSD to PCM setting on the Aries). Is my understanding of how Roon handles downstream devices not accurate?

Thx for clarifying for me.


(John) #5

Hello @Pacoinmass,

Roon Ready devices handle DSD detection and reporting in different ways. While some devices will automatically detect DSD DoP or DSD Native support and relay that information to Roon, many devices provide the ability to override the auto-detect settings for a variety of reasons. When you disable the Convert DSD to PCM toggle, the device is likely reporting that the USB DAC supports DSD DoP signaling, which is sent in a 24/176.4kHz PCM container. This is due to some devices not reporting their DSD DoP settings correctly when probed by the connected USB host.

-John


#6

John,

Thank you for the explanation…make sense (finally!). Thx for your patience.