• jipe
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Topic: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

Hello,

Please allow me to ask you a question regarding the RME ADI-2DAC FS DAC setup in Fixed Output Level - Lock Volume mode and XLR connection.

I am currently using this home hifi audio system:
- MF M8sPRE preamplifier https://www.musicalfidelity.com/product … ies/m8spre 
- 2 × MF M8S-700M monoblock power amplifiers https://www.musicalfidelity.com/product … es/m8-700m
- DAC RME ADI-2DAC FS https://www.rme-audio.de/adi-2-dac.html
- Streamer - Audio PC
- Stereo Speakers

The wiring path looks like this:
Streamer > USB cable > DAC RME ADI-2DAC FS > XLR cable > preamplifier MF M8sPRE > XLR cable > 2×monoblock power amplifier MF M8S-700M > speaker cable > stereo speakers

Now what is it:
I use the RME ADI-2DAC FS in Fixed Output Level - Lock Volume mode. I use the RME ADI-2DAC FS as a pure DAC. I control the volume on the MF M8sPRE preamplifier. I have the DAC RME ADI-2DAC FS set to Ref Level + 13 dBu and Volume -4.5 dB. Are these values (Ref Level + 13 dBu and Volume -4.5 dB) set correctly for the given type of XLR connection and MF M8sPRE preamplifier device? Or is it better to make other settings? Could you please help me in this matter?

Thank you

2 Reply by KaiS (edited by KaiS 2023-12-17 07:02:26)

  • KaiS
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

Practically, too high level limits the dial range of the preamp’s volume control.
Set ADI-2 DAC’s Reference Level to -5 dBu and Volume to 0 dB.
This is on the safe side for signal quality and nice to handle.


If you want to go into details:

Unfortunately, the specs published by Musical Fidelity in M8s pre’s manual are a bit strange and hard to believe:

Input sensitivity 0.352 V
Overload margin 12 dB

Calculating based on this, the highest input the XLRs can take would be 1.4 V or +5 dBu.
A typical standard CD-player puts out 2 V / +8 dBu, which should overload  M8s’ input ?!
I don’t think so.


Best, check with a full scale 400 Hz sine wave, from any source e.g.:
https://soundcloud.com/liv-zanfardino/4 … -frequency

Or an online sine wave Generator, set 400 Hz, and volume to 100%:
https://www.szynalski.com/tone-generator/

Bring down M8s’ volume dial close to minimum, but not off.
Play the sine wave through ADI-2 DAC and slowly turn volume and Ref Levels up until audible distortion kicks in.
The transition is clearly audible.

This is the max. level M8s can take.
Now use any level not higher than this one.

Reference Level +1 dBu, Volume 0 dB would improve SNR from 120 to 123 dB.
This is not audible anyway, but ….


If you run through this, I’d be curious to know your results smile

KaiS's Website

  • jipe
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

Thank you very much for your professional response and recommendation.

So I set the ADI-2 DAC Reference level to -5 dBu and Volume to 0 dB. I noticed that I need to increase the listening volume by about 10-15 dB compared to the previous setting (Ref Level + 13 dBu and Volume -4.5 dB) on the preamp. The average listening volume was about 55-60 dB (scale on the preamp) and with the new setting it is about 70 -75dB (depending on the type of recording).

The original (inappropriate) setting of Ref Level + 13 dBu and Volume -4.5 dB was done according to the ADI-2 DAC manual see page 66 (paragraph Fixed Output Level - Lock Volume) see https://www.rme-audio.de/downloads/adi2dacr_e.pdf  where it states:
"For example when the analog output should operate like a typical HiFi unit @ 2 V output level (RCA, equals +8 dBu), set the hardware Ref Level to +7 dBu and Volume to +1 dB. Or +13 dBu and Volume to -4.5 dB."
But these are values for RCA and not XLR.  So apparently I somehow incorrectly deduced that Ref Level +13 dBu and Volume -4.5 dB is for XLR. So I hope that this incorrect setting (that I used XLR values for RCA) could not have caused some damage to the device - both ADI-2 DAC and M8sPRE preamplifier.

I was of course intrigued by the other details you mention.  So please allow me a few questions:
As you write, the specification in the M8sPRE manual on page 12 states for XLR:
Input sensitivity 0.352 V
Overload margin 12 dB

I would like to know how you calculated that the highest input that XLR can accept will be 1.4 V or +5 dBu?  Could you please explain this a bit?
What would lead a manufacturer to quote these values? Or could it rather be a mistake in the manual? If I look in the manual for the lower range M6S PRE AMPLIFIER on page 13 https://www.musicalfidelity.com/uploads … manual.pdf  it states for XLR:
Input sensitivity 4.4 V
Overload margin 12 dB
Are these values okay, please?

And then your recommendation to check with a 400 Hz sine wave.  I'd like to do that, but I'm not sure I fully understand everything.  So let me summarize the process as I understand it:
1. the RME ADI-2 DAC is in Fixed Output Level - Lock Volume mode.
2. I run this generator in my streamer (audio PC) https://www.szynalski.com/tone-generator/  and set a 400 Hz sine wave and set the volume in the generator at the link above to 100%
3.On the M8sPRE preamp I set the volume to minimum.
4.I will start the sine wave playback by turning on play at the link above and listen to the 400Hz sine wave signal from the speakers
5.In the next step I will stop the playback and make a new setting on the Na ADI-2 DAC. That is, I'll set higher values, for example Ref Level to +1 dBu and Volume to -1 dB, gradually increasing (for example Ref Level to +7 dBu and Volume to -2 dB and then higher), and then I'll gradually monitor the speakers for audible distortion of the 400Hz sine wave signal. Now here's the important thing - what does such distortion sound like? What kind of sound could I expect? Is there a sample somewhere on the internet, for example, please?
6.As a result, I will find out where the limit of distortion is and then set the level lower than the one at which the signal distortion occurred accordingly.

Thanks so much for the answers and help.

4 Reply by KaiS (edited by KaiS 2023-12-18 18:12:19)

  • KaiS
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

The ones that write the manual might not have checked with the tech department - or the figures simply are true.
The specs for the M6S sound more reasonable, 12 dB above 4 V equals 15.9 V


It‘s really easy to check:


For convenience, switch: I/O / Line Out / Settings / Auto Ref Level: “On”
Now you can control ADI-2’s volume continuously across it’s full range without interruption.

Play 400 Hz / 100% from the linked generator.


Listen at med/low listening level (preamp volume dial) while turning up ADI-2’s VOLUME dial continuously, until the sound starts to become different, kind of bright or scratchy.
It’s obvious, you will clearly recognize the transition point for sure.

Ignore the little momentary glitches when ADI-2’s relays switch the reference level, these are normal.


Remark:
With Auto ref Level “On” Volume will be shown in –dBr instead of straight dB.
dBr references to ADI-2’s maximum output of +19 dBu on XLR.

With:
SETUP / Options / Display / Hor. Meter: “Post-FX dBu”
you can directly read the output’s dBu (add 6 dBu for the XLR I think).


BTW: nothing can break during the process.

KaiS's Website

5 Reply by jipe (edited by jipe 2023-12-18 19:34:19)

  • jipe
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

Thank you for your reply and other tips.

I just did 4 x testing with 400 Hz sine wave playback with this result:

The signal does not change in any way during playback from -5dBu to +13dBu and I did not notice anything. The only thing that changes is that the volume increases, but the signal itself still sounds constant.  Then I have noticed a clicking when switching levels (-5 dBu, +1 dBu...) but this is normal.

So can you please help me interpret the findings?  What would be the best setting for Reference Level and Volume? I can think of some middle values to use - could you please recommend?

Thank you

6 Reply by KaiS (edited by KaiS 2023-12-19 08:50:26)

  • KaiS
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

As suspected, this means the specs in the manual are wrong.

You’re quasi free to select any Ref Level you find convenient.

Reference Level +1 dBu and Volume 0 dB maxes ADI-2 DAC’s SNR / Signal to Noise Ratio, while the level is still low enough that the pre’s volume should preserve some dial range.
To gain more dial range - 5 dBu / 0 dB sacrifices 3 dB SNR - still magnitudes ahead of any audible noise - if you don’t hear noise there is no noise problem.

DAC’s resolution - much more important than SNR - is the same for all reference levels.

KaiS's Website

  • jipe
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

Thank you for your reply.

So I set the RME ADI-2DAC FS Reference Level +1 dBu and Volume 0 dB.

I also tried to compare the volume level with this DAC from MF M6x DAC https://www.musicalfidelity.com/product … es/m6x-dac

The referenced MF M6x DAC at the same source and when connected XLR, it turns out that the MF M6x DAC sounds louder than the RME ADI-2DAC FS.

My goal is to unify the loudness of the MF M6x DAC and the RME ADI-2DAC FS.

Would it please be possible to somehow find out from the parameters in the technical specification on page 12 see https://www.musicalfidelity.com/uploads … ssue-1.pdf what Reference Level and Volume values are set by the manufacturer for the MF M6x DAC?

And then I would set the Reference Level and Volume values on the RME ADI-2DAC FS in the same or similar way.

Thank you

8 Reply by KaiS (edited by KaiS 2023-12-21 00:53:06)

  • KaiS
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

As mentioned, choose any level you like.

Approximate by ear to unify the loudnes.
ADI-2’s volume works in steps of 0.5 dB, so a perfect equality might not be possible.

MF M6x’s XLR’s 4V equals 14.26 dBu.
Setting ADI-2 DAC to nominal +7 dBu (= XLR +13dBu) / Volume +1.5 dB would be the closest you can get.

KaiS's Website

  • Registered: 2022-07-20
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Re: DAC RME ADI-2DAC FS - Lock Volume and XLR connection

@Jipe,

IIRC, according to your initial post, you mention only one source (PC) :
Is the MF preamp really mandatory ?
(Here, no more preamp : PC-> RME -> Power amp(s))

Season's greetings,