Fixed Volume vs Device Volume on Grimm MU2

There is a very big difference in sound quality between using fixed volume in Roon vs using Device Volume in Roon and selecting fixed volume on the MU2. Selecting fixed volume in Roon is better…less digital sounding less sibilance and a wider and deeper soundstage. This contradicts what is recommended by Grimm which is to use Device Volume and preferably to use the volume control on the MU2 or if you are to use your amp to control the volume to select fixed volume on the MU2 control.

I guess my question is what exactly is going on when you select the fixed volume control in Roon? If there are any MU2 users out there am I going crazy?

Can you post a Roon Signal Path screenshot for each of these configurations.

The signal path is the same in both cases:

You would only use device volume if using the MU2 as a preamplifier to a power amp. If you feeding it to a preamplifier then you would use the volume control on the preamplifier to control volume and have it fixed at full output or you have two controls of attenuation in your chain which could cause loss of fidelity.

Your signal path shows the Grimm as the DAC at the Alsa stage. It’s not showing any DSP for the DAC so the preamp section is in the analogue domain and is always in the signal path even when set to 0 according to reviews. All Roon will do is control this analogue volume control nothing is being added. If you can play it fixed then it sounds to me like your using it to another preamp so this is likely your issue with levels. What are you hooking it up to pre amp it active speakers?

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Thank you very much for your response. I am not having an issue. I am trying to understand why there is such a difference in sound quality between selecting Device Volume and Fixed Volume when using my integrated amp to control the volume. What is the difference? Grimm uses a unique, very high level of filtering of the input signal to bring the noise floor way down. If the Device Volume in Roon is creating noise/distortion/whatever the “Pure Nyquist” filter should take care of it. Grimm states that it is not necessary to add any kind of treatment (filters, switches, etc.) because of this presumably. The Fixed Volume setting in Roon is much preferable on my system and creates a much wider deeper soundstage with very precise imaging and a natural and engaging sound. The Device Volume setting is brighter in general and the soundstage in narrower and shallower with a touch of sibilance on some vocals.

Thoughts on why this could be?

You using two analogue preamplifiers when using device volume, you should not use device volume preamp with an integrated amp as its going through another analogue attenuation stage in the amp and you can possibly get a mismatch of gain. Fixed will send out full signal level and any attenuation would be done via the integrated volume control. Use it as a pure DAC/Streamer and leave it alone, If your concerned ask Grimm as its their analogue preamp, Roon isn’t doing anything to it it just adjusts its volume which is all Grimms implementation. Roon is just sending bit perfect out to the MU2 dac.

Thanks very much for your help in understanding.

So if you select Device Volume and it is set at 92 (which is supposed to be unity with the MU2) will that be equivalent to full signal level as would be when selecting Fixed Volume in Roon?

Sorry I have no idea what value would equate to it being fixed, unity would imply it as it might have extra headroom over fixed, you need to really ask Grimm this is all there side of things and not Roon.

Thanks. I am just trying to understand what is happening in Roon when you select Fixed Volume vs Device Volume. I understand what it does I am trying to understand why there is a difference in SQ.

Nothing happens in Roon other than it sends commands to change the preamp volume via RAAT API when in Device Volume mode, the stream sent is the same nothing changes here as its not touched in the digital domain by Roon, all the volume control is done via the PreAmp section of the MU2. The Preamp is in the signal path all the time regardless of Roon being fixed or device volume. Most likely level matching and perhaps gain matching from having two preamps in your chain.