• Registered: 2024-07-13
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Topic: Please explain analog inputs reference level

Hi, I'm using an ADI 2/4 pro SE.
I'm recording 2 microphones, analog inputs 1 and 2.
I want all my gain staging to be done within my microphones preamp, and keep the RME at unity, not adding anything gain-wise to the signal.

What it says in the manual about reference level is this :
Ref Level
Sets the reference level for the analog inputs 1/2. Choices are +1 dBu, +7 dBu, +13 dBu, +19 dBu, +24 dBu, referenced to digital full scale level (0 dBFS).


But I'm confused, can you explain this please ?

Does this mean it changes the gain of the signal being recorded, or does it concern only playback level ? The trim gain settings should stay at 0, to my understanding, but what about this "ref level" ?

  • waedi
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Re: Please explain analog inputs reference level

Choose +24
This prepares the input for receiving a powerful signal, you have to give all gain in the preamp.

M1-Sequoia, Madiface Pro, Digiface USB, Babyface silver and blue

3 Reply by KaiS (edited by KaiS 2024-07-15 06:57:05)

  • KaiS
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Re: Please explain analog inputs reference level

Reference level is indeed an analog gain setting.
The higher the reference level, the lower ADI-2’s gain.

Typically choose +24 dBu if the preamp has active balanced outputs and balanced interconnection is used.
Choose +19 dBu for an unbalanced interconnection, as unbalanced electronics usually can‘t output +24 dBu.


A simple basic test of your preamp’s output capability:
• Set ADI-2 to 24 dBu.
• With a mic connected, max out your preamp’s gain.
• Look at ADI-2’s meter for the analog input:
If the meter does hit full scale, +24 dBu is correct.
If the signal stops somewhere below, lower the reference level until the meter reaches full scale.

If your preamp has a tube output stage, you might want to use a one step lower reference level for a cleaner signal - or just the one determined above for some amount of tube saturation.

KaiS's Website

4 Reply by chapitil (edited by chapitil 2024-07-15 17:18:14)

  • Registered: 2024-07-13
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Re: Please explain analog inputs reference level

KaiS wrote:

Reference level is indeed an analog gain setting.
The higher the reference level, the lower ADI-2’s gain.

Typically choose +24 dBu if the preamp has active balanced outputs and balanced interconnection is used.
Choose +19 dBu for an unbalanced interconnection, as unbalanced electronics usually can‘t output +24 dBu.


A simple basic test of your preamp’s output capability:
• Set ADI-2 to 24 dBu.
• With a mic connected, max out your preamp’s gain.
• Look at ADI-2’s meter for the analog input:
If the meter does hit full scale, +24 dBu is correct.
If the signal stops somewhere below, lower the reference level until the meter reaches full scale.

If your preamp has a tube output stage, you might want to use a one step lower reference level for a cleaner signal - or just the one determined above for some amount of tube saturation.

Thanks for the explanation !
Yes when I set it at 24 dBu on the ADI-2 and max out my preamp gain, it hits full scale pretty easily and goes above. So I guess that's the correct setting then.
But I'm thinking, do I even want all the gain to sit on the preamp's shoulder ? My preamp doesn't have a tube, and it's transformerless.
Maybe I want to lower the ADI-2 to 19 dBu, as to not overload the preamp and have a cleaner signal ?

5 Reply by waedi (edited by waedi 2024-07-15 18:15:20)

  • waedi
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Re: Please explain analog inputs reference level

That's what you should do, as explained by Kai.

Your signal seems to go clipping and you should lower the gain of the preamp.
Then adjust the reference level setting to the lowered signal if needed.
I would let it at +24dBu and just lower the preamp gain to a nice signal.

M1-Sequoia, Madiface Pro, Digiface USB, Babyface silver and blue

6 Reply by KaiS (edited by KaiS 2024-07-15 20:54:38)

  • KaiS
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Re: Please explain analog inputs reference level

chapitil wrote:

[Yes when I set it at 24 dBu on the ADI-2 and max out my preamp gain, it hits full scale pretty easily and goes above. So I guess that's the correct setting then.
But I'm thinking, do I even want all the gain to sit on the preamp's shoulder ? My preamp doesn't have a tube, and it's transformerless.
Maybe I want to lower the ADI-2 to 19 dBu, as to not overload the preamp and have a cleaner signal ?

It‘s hard to recommend such details without knowing the model of the preamp.

In general, analog electronics work cleaner if the gain isn’t maxed out and levels have a little headroom before clipping.

You could record some critical sounds like a triangle with a dynamic mic (a condenser isn’t suited well for this, as it’s internal amp can clip), and compare both settings.
If you hear a low frequency “tock” when hitting the triangle, the preamp distorts and ADI-2’s reference level should be lowered.


@waedi: the level test is about driving the preamp into clipping to see it’s full scale output.
This is not the normal usecase, where the preamp’s input gain of course has to be set for a proper recording level.

KaiS's Website

  • Registered: 2024-07-13
  • Posts: 21

Re: Please explain analog inputs reference level

KaiS wrote:

It‘s hard to recommend such details without knowing the model of the preamp.

In general, analog electronics work cleaner if the gain isn’t maxed out and levels have a little headroom before clipping.

You could record some critical sounds like a triangle with a dynamic mic (a condenser isn’t suited well for this, as it’s internal amp can clip), and compare both settings.
If you hear a low frequency “tock” when hitting the triangle, the preamp distorts and ADI-2’s reference level should be lowered.

I don't have a dynamic mic available to do that test unfortunately.
However to get to a comfortable level, I'm at around 60% gain from the preamp. So I guess that's reasonable.
But still, I'm unsure whether that gain should be shared between analog preamp and digital converter, or simply rely solely on the preamp.

Which technical spec of the preamp would you need to know, in order to be sure of the adi-2 reference level to set ? I can probably provide it to you, I have the specs sheet right there.

8 Reply by KaiS (edited by KaiS 2024-07-16 13:54:01)

  • KaiS
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Re: Please explain analog inputs reference level

Max. output level balanced in dBu, dBm or Volt.


For the test a condenser can work too.
Hit the triangle relatively soft, and stay clear about 1 meter.
This is to avoid overdriving the condenser‘s internal amp.

Triangle is a great testing sound, as it contains a mix of high frequencies only, no low frequency content.
Any distortion created by an amp will show up instantly as low frequencies accompanying the sound, specifically the attack phase.

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