1 Topic by ning (edited by ning 2019-06-10 09:45:35)

  • ning
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Topic: Auto Ref Level on PH 1/2 bug?

Hi

I am able to understand how auto ref levels works for PH3/4, XLR and RCA output.

I have difficulty to understand the AutoRefLevel on PH 1/2.

In the former outputs, they will switch to different gains automatically.

- For instance, in PH3/4, the gain will jump from low (+7db) to high(+22db) when relative volume is 7-22 = -15 dbr

- If AutoRefLevel is disabled, each gain also has +6db digital attenuation at maximum. If AutoRefLevel is enabled, the maximum gain (high, +22db in PH3/4's case) has +6db digital attenuation at maximum. RCA does not follow the display as 19db is the maximum so the rest range (-5dbr to +6 dbr ) are digital attenuation.

Am I correct?


However, PH1/2 does not work this way

- gain jumps at -20 dbr from  low gain (+7db) to +13 db (+13 db on display, in HP out it means +16db) , and at -11dbr it jumps from +13db to  high gain(+22db).  However 7-22 != -20. 16-22!=-11.

- If AutoRefLevel is disabled, each gain also has +6db digital attenuation at maximum, including the high gain (+22db). This is correct behavior. However, when AutoRefLevel is enabled, high gain (+22db) has +1db digital attenuation at maximum. This is not correct.

I believe the -20dbr is got from 7 -22  +1db real world maximum digital attenuation - 6db theoretical attenuation

I'm using the latest firmware. no idea how it works in previous versions.

This is not consistent in related to how other outputs work. I believe it's a bug.

2 Reply by MC

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Re: Auto Ref Level on PH 1/2 bug?

The ADI-2 Pro shares its analog output stage (and such the ref level switching) between Phones 1/2 and rear Line 1/2. The values that you see when using 1/2 as Phones output are based on the refs and levels that you see when not plugging in a phone, with just +24 dBu omitted. They are all spot-on.

In case you see different swithing thresholds than -20 dBr and -11 dBr at Phones, and the additional -5 dBr on the rear, you have EQ, Bass/Treble or Loudness active.

Regards
Matthias Carstens
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3 Reply by ning (edited by ning 2019-06-10 10:17:18)

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Re: Auto Ref Level on PH 1/2 bug?

Ah I think I got it. Thanks.

So in this case, ph1/2 with auto ref off, high gain and 0db attenuation means 22dbu (10v) if given 0dbfs signal.  With auto ref on, high gain and 0dbr means 5db digital attenuation already applied?

With say -10dbfs signal, the former generates 12dbu, and the latter generates 22-10+5=17dbu?

This design sounds reasonable. However for someone uses both headphone outs auto ref levels looks very confusing because they have different behaviors for the two headphone outs. At 0dbr they have different volumes.


Also the UI needs to be improved— because in this situation the maximum digital attenuation is 1db. On the UI it looks there is still some space left for increasing the volume, because the space was designed for 6db.

I also hope there is an option for the user to see a dedicated volume page for headphone 1/2 out that looks exactly the same as 3/4.

4 Reply by MC

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Re: Auto Ref Level on PH 1/2 bug?

To avoid further unneccessary posts here are some more infos.

> gain jump from -20 dbr from low gain (+7db) to +13 dB

It's dBu, not dB. As maximum rear level is +24 dBu, at -20 dBr the max level exceeds +4 dBu (the current hardware ref level), so +13 dBu as next ref level is chosen.

> at -11dbr it jump from +13db to high gain(+22db)

At -11 dBr the switch from +13 dBu to +19 dBu (High Power) ref level happens (+24 dBu -11 dB = +13 dBu).

As the unbalanced outputs do not support the +24 dBu ref level, the max output level is +19 dBu rear. For Phones 1/2 that means with a 0 dBFS input signal volume values of -4.5 dB to 0 dB (the not available +24 dBu range) cause overload, which is clearly shown on the level meters and in the Dark Volume screen by the Volume number flashing red.

Nothing of this is relevant for the user. Just use it as it is. It works and does everything correctly.

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Matthias Carstens
RME

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Re: Auto Ref Level on PH 1/2 bug?

Thanks MC. This is truly helpful and informative. I now understand how it works.

I recommend you fix the tiny UI rendering bug in the volume screen when auto ref level is enabled. The Slider always assumes there’s 6dbr room available in all modes. but actually it’s only 1dbr in this case. so under maximum volume (+1dbr), the indicator cannot reach the rightmost position. That’s part of the reason I was confused when initially trying to understand the behavior. The correct behavior is when the volume is turn to the max, the Indicator should reach the rightmost position of the Slider and there should be no room left.

6 Reply by MC

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Re: Auto Ref Level on PH 1/2 bug?

The horizontal bar does not 'assume', it is fixed to the same +24 dBu = 0 dBr as the dBr value itself. In this very special case the available max digital gain is not +6 dB (as in other modes), but only +1 dB as the +24 dBu range already took away 5 dB. I don't see where this a bug nor that it needs a change. It is still consistent and correct. Yes, very complicated, but only if you try to think about things you simply should not worry about. wink

Regards
Matthias Carstens
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7 Reply by ning (edited by ning 2019-06-10 20:14:22)

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Re: Auto Ref Level on PH 1/2 bug?

>  I don't see where this a bug nor that it needs a change. It is still consistent and correct.

I understand the reasoning you provide here, and it does make sense when the gain stages are designed in this way.

On the other hand, from a newbie user's (my) perspective, if "they don't need to think about things they simply should not worry about", they expect ADI-2 Pro's volume slider to work in the same way as sliders in their other software programs/gadgets do, which is, being able to move the indicator/tracker to the rightmost position ---- because that's the behavior of all Slider UIs they see and use everyday, from smart phone to desktop, from consumer software such as system volume mixer panel on Windows,  to professional DAWs such as Ableton Live or Logic Pro. I believe on most OS platforms (iOS, Mac and Windows), the system UI libraries don't even have APIs to allow Slider to stop halfway. Also software Slider is a metaphor of hardware sliders, which could be found on many devices. It's rare to see a hardware slider (such as the one on hardware mixers) stops halfway.