ProTools Reference Level Settings (+10 dBu vs +24 dBu)

[jgiannis]

Hi.

I am running PT10 HD on OSX 10.7.5.

My interface is an AVID HD OMNI.

I use ProTools daily, but what I don't use too often is another piece of software that, I think, came installed with the HD OMNI. The program is called "Avid CoreAudio Manager."

When I open the program, it recognizes the HD OMNI as my interface. (It simply says "Interface: HD OMNI.")

Under the "HW Setup…" button, I click on the tab "Analog Out." I am then given a "Reference Level" for channel 1 through channel 8. Each channel allows me to select either:
(a) Speaker (+10 dBu), or
(b) Line (+24 dBu)

If I set them to +10, then my playback levels are quieter than if I set them to +24. However, the output meters on the OMNI do not change. The output meters give me the same reading, whether I select +10 or +24.

I am not sure which one is "correct," nor do I even understand what this stuff means. But this does affect me because I am currently trying to balance the overall levels of my session. If I am balancing them at +10, then I send my session to another party who has theirs set to +24, their ears will pop off.

Can anyone make sense of this?

Thanks!

[Top Jimmy]

The output reference level only affects the output level, not the level of what you are doing in Pro Tools. This setting is designed so that you can feed the output to other gear or an external monitoring controller at +24 peak. If you are going to feed powered monitors directly from the Omni, it's better to use the +10 peak setting so that you get full resolution with the volume control rather than blasting the speakers with the volume only up 25%.

[sailor]

Originally Posted by Top Jimmy

The output reference level only affects the output level, not the level of what you are doing in Pro Tools. This setting is designed so that you can feed the output to other gear or an external monitoring controller at +24 peak. If you are going to feed powered monitors directly from the Omni, it's better to use the +10 peak setting so that you get full resolution with the volume control rather than blasting the speakers with the volume only up 25%.

Resurrecting this old discussion about analog output levels on the Omni...

I'm looking into getting an Omni and feeding the outputs 1-6 to a surround receiver which has power for passive speakers. I'm assuming the receiver uses the "consumer" -10dbV operating level so I wouldn't want to feed it the +24dBu-peak line level out of the Omni.

So could the +10dBu peak out level be considered roughly analogous in practical use to the -10dBV nominal operating level? Those conversions still throw me off.

Appreciate it if you or someone can confirm for me.

[Top Jimmy]

Originally Posted by sailor

So could the +10dBu peak out level be considered roughly analogous in practical use to the -10dBV nominal operating level? Those conversions still throw me off.

Very roughly, yes. If used full scale, the -10dBV level reference would have about 17 dB of headroom from the Omni.




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[sailor]

Great, thanks for the confirmation.

[Siddhant Bhatia]

Hitting this discussion up, since it's quite similar to my question! I never gave this a thought before up until now since I could hear audible hardcore distortion everywhere!

Windows 10 > Pro Tools 2022.10 > HD Native > HD Omni > SPL SMC 7.1 (Surround controller)

When I hit +10dbu - speaker level - no distortion but the levels are quite low and I have to literally turn the knob all the way up to get good levels.

When I hit +24dbu - line level - the levels are beautiful and the knob is a lot lower - but in only a 'few' pro tools sessions I am hearing MASSIVE distortion (proper digital clipping) on both speaker out and headphone out.

I am feeding Analog 1-8 via DB25 straight into SPL SMC 7.1 from HD Omni. Levels are being controlled by the Hardware section from within Pro Tools.

What's interesting is that I am pretty sure I never had this issue on my Mac before. I've just switched from Mac to Windows after a literal 20 years. And amongst a ton of adjustments - this one bewilders me.

Can someone help make me understand what is happening?

Reading more about SMC 7.1 in the manual - it allows up to +22dbu on it's input - but that's as good as what almost all analog mixing equipment allows ... then what is going on and what's going wrong? I am pretty sure we are not hitting clipping anywhere. Not from within Pro Tools for sure ... then why is the output so clipped?

No clipping happening AT ALL when it's on +10dbu ... Speaker level.

All meters are fine, levels are within -3 dbfs ...

I would be very grateful if someone can make me understand what's going on?!

Thanks!

[nednednerb]

Originally Posted by Siddhant Bhatia

.....
When I hit +10dbu - speaker level - no distortion but the levels are quite low and I have to literally turn the knob all the way up to get good levels.

When I hit +24dbu - line level - the levels are beautiful and the knob is a lot lower - but in only a 'few' pro tools sessions I am hearing MASSIVE distortion (proper digital clipping) on both speaker out and headphone out.

No clipping happening AT ALL when it's on +10dbu ... Speaker level.

All meters are fine, levels are within -3 dbfs ...

If I had to guess, sending line levels to speakers is not good, and you should send speaker level. Because: On the SMC the volume knob says "0" at the max, and attenuation to the left. That means it's "Unity Gain" to my understanding.

I would use +10, turn the SMC to zero or just below, then turn up your speakers or amplifier directly to your desired listening level.

Avoid clipping, and virtually ignore the "non beautiful meters". I would use the +24 to connect to, say, a professional analog mixer taking line level, which THEN goes out to Speaker Level to the monitors, anyway. If you don't have such Line Level gear in between the SMC and the Speakers, maybe that's part of the issue.

[Darryl Ramm]

Originally Posted by Siddhant Bhatia

When I hit +10dbu - speaker level
...
When I hit +24dbu - line level - the levels are beautiful and the knob is a lot lower - but in only a 'few' pro tools sessions I am hearing MASSIVE distortion (proper digital clipping) on both speaker out and headphone out.

You are missing a big part of the description: what exact amplifier and speakers or audio monitors do the output of this monitor controller connect to? What are the input specs on those?... start by setting your Omni accordingly. Any weird things happening, test with the monitor controller out of the signal path.

The SMC 7.1 controller specs max input as "+22dBu" without any hard spec (e.g. distortion specs or a distortion graph) clarification of what that means. And it's likely to mean God awful signal degradation near that, so no surprises if you are just driving that too hot.

Is your output actually clipping? Does a clip light go on on the master fader? Is a plugin getting slammed earlier in the Pro Tools signal chain? If you are getting digital clipping you should see it inside Pro Tools. Setting the Omni analog line output level will not change if something is digitally clipping or not. So it's something else happening or you are not noticing the clipping at lower SPL. But if you suspect digital clipping use Pro Tools and track it down.

Have you calibrated your monitors? At what target SPL? If not get a SPL meter and doing a calibration is likely time well spent and a good learning exercise.