1 (edited by Karmatron 2022-12-05 18:09:45)

Topic: Auto ref level @ PEQ on ADI-2 DAC fs

I get an occasional overload when using both Auto ref level and PEQ. This is probably due to overlapping filters.
An additional down shift with Auto ref level when using gain in PEQ would solve this. The amount depends on the PEQ settings.

As it is now I have to disable Auto ref level, which makes the DAC not really suitable to use as pre-amp.

Perhaps I am missing a setting to adjust Auto ref level manually.

Re: Auto ref level @ PEQ on ADI-2 DAC fs

Where and what situation exactly this overload happens? What I/O´s Auto Ref Level you are referring? In output side it shouldn´t affect like that. On Analog Input, Auto Ref activated, its´s possible.


What kind of settings you have in PEQ-filters 1-5 and B/T. Analog input and/or outputs? Do you have other channel level -affecting processing, like crossfeed, engaged?

ADI´s internal processing´s headroom should cope 24 dB of boost in total. If you have done extreme boosts on overlapping bands in PEQ / B/T and also use processing like crossfeed, this limit may get exceeded. As you suspected.
Try to asses your PEQ-filter + B/T + other processing -combined total boost amount, and fade them down to fit that 24 dB total limit if necessary. 
Note that if you have filters active on Analog Input AND outputs simultaneously, you may end up significant combined boost -amounts treacherously.

Otherwise (inside 24 dB limits) it shouldn´t happen from output (Main Out 1/2, Phones Out 3/4) side if your volume setting won´t exceed 0.0 dBr. So don´t normally ever exceed volume setting of 0.0 dBr. Do so only in cases of abnormally quiet source material.


From analog input side clipping can happen if your analog feeders output level exceeds Analog Input´s set Ref Level OR you use Auto Ref Level on it. Analog Inputs Auto Ref Level can´t necessarily react fast enough to signal spikes (by switching relays to next higher ref level). It works best when set manually.
So set ADI´s Analog Input manually to +24 dBu and watch and re-adjust your incoming analog input levels if necessary.
 
Be aware that ADI-2 Pro´s Analog Inputs maximum unclipped level is +22.5 dBu if input feed is UNbalanced. User manual or level meters won´t tell you this, you must just know it.


From digital input side more or less occasional 0 dBFS -touches (red bars on level meters) happen all the time due to music production -style of nowadays. This kind of "overloading" is normal.

3 (edited by KaiS 2022-12-05 12:57:12)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

I can replicate this, but only with artificial signals - steady sine waves.
With music I didn‘t yet see / hear it.

I do indeed combine EQ bands for quite extreme sub/bass boosts for my “hoover ear” headphones, up to ca. 18 dB.

4 (edited by Karmatron 2022-12-05 18:17:03)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

I should have mentioned that the device is an ADI-2 DAC fs.

My PEQ settings:

Base:      Fc  20  Hz  Gain -12.0 dB  Q 1.0
Filter  1: Fc  65  Hz  Gain   6.0 dB  Q 3.0  Peak
Filter  2: Fc 123  Hz  Gain   6.0 dB  Q 4.0
Filter  3: Fc 350  Hz  Gain  -4.0 dB  Q 5.0
Filter  4: Fc 620  Hz  Gain  -4.5 dB  Q 4.0
Filter  5: Fc 2.5 kHz  Gain   3.0 dB  Q 1.3

This performs a room correction, which I measured with REW. The Base setting is being used to attenuate below 30Hz.

Max gain is +6dB, and the steps of Auto ref level shift down accordingly. But that is not enough to prevent an occasional overload.

5 (edited by MstrC-117 2022-12-05 19:24:00)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

Karmatron wrote:

I should have mentioned that the device is an ADI-2 DAC fs.

My PEQ settings:

Base:      Fc  20  Hz  Gain -12.0 dB  Q 1.0
Filter  1: Fc  65  Hz  Gain   6.0 dB  Q 3.0  Peak
Filter  2: Fc 123  Hz  Gain   6.0 dB  Q 4.0
Filter  3: Fc 350  Hz  Gain  -4.0 dB  Q 5.0
Filter  4: Fc 620  Hz  Gain  -4.5 dB  Q 4.0
Filter  5: Fc 2.5 kHz  Gain   3.0 dB  Q 1.3

This performs a room correction, which I measured with REW. The Base setting is being used to attenuate below 30Hz.

Max gain is +6dB, and the steps of Auto ref level shift down accordingly. But that is not enough to prevent an occasional overload.


Ok, so its ADI-2 DAC FS´s line output which is causing this.

Your EQ´s seems to be pretty +-0, they shouldn´t be causing this.


Does this "overloading" happen during playback, namely in that very brief moment when you adjust volume up or down? Between volume scale -points, in which between happens to be one of the ADI´s Ref Level -transition point?

If so, my common sense says that in that case little glitches can well be normal, because in that brief moment ADI must ramp up/down its digital volume attenuation value + switch another analog hardware gain value to its line output. It may be impossible to do that without some occasional little glitches, if audio is coming out simultaneously.   


The Solution would be

A) live with it, because its normal

B) use manual Ref Level value on line outputs

C) avoid constant volume up/down -jerking + level meters -gazing during playback (leads to listening neurosis)



Karmatron wrote:

As it is now I have to disable Auto ref level, which makes the DAC not really suitable to use as pre-amp.

Why would it do so?

Not using Auto Ref Level does only change that you won´t be able to get ADI´s best available, "optimized" (astronomical high) SNR-figures. Which you wouldn´t hear anyway, in practice.

Its practically pretty insignificant if devices SNR is "only" 100 dB, instead of 115 dB. The end result is model "dead silent" i.e. excellent in both cases.

6 (edited by KaiS 2022-12-06 08:20:40)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

Karmatron wrote:

...

Base:      Fc  20  Hz  Gain -12.0 dB  Q 1.0
Filter  1: Fc  65  Hz  Gain   6.0 dB  Q 3.0  Peak
Filter  2: Fc 123  Hz  Gain   6.0 dB  Q 4.0
Filter  3: Fc 350  Hz  Gain  -4.0 dB  Q 5.0
Filter  4: Fc 620  Hz  Gain  -4.5 dB  Q 4.0
Filter  5: Fc 2.5 kHz  Gain   3.0 dB  Q 1.3

Max gain is +6dB, and the steps of Auto ref level shift down accordingly. But that is not enough to prevent an occasional overload.

Your max gain is 11.9 dB @ 50 Hz, BTW.

There‘s a headroom of 3 dB in the meter’s red above 0 dB output for the DAC.
Only if you see the meter show “OVR“ there’s real clipping.


If I replicate your EQ I see red meters, but usually don’t see any OVR with music.
The track Angel - Massive Attack can show occasional OVR, without audible distortions here.

Again, with a pure 50 Hz sine wave I can provoke OVR.


If you’re annoyed by seeing the OVR, a workaround:
step the Volume 1 dB lower or 0.5 dB higher than the Auto Ref transition level.

7 (edited by MstrC-117 2022-12-06 21:11:00)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

KaiS wrote:

Your max gain is 11.9 dB @ 50 Hz, BTW.

How you ended up to these figures? With those EQ´s, I got max gain +6,7 dB @ 65 Hz.



KaiS wrote:

There‘s a headroom of 3 dB in the meter’s red above 0 dB output for the DAC.

Where you got this figure? According manual, "overdrive" -reserve of ADI-2 DAC´s rear line outputs and front IEM -output is +2,5 dB.


KaiS wrote:

If I replicate your EQ I see red meters, but usually don’t see any OVR with music.
The track Angel - Massive Attack can show occasional OVR, without audible distortions here.

Again, with a pure 50 Hz sine wave I can provoke OVR.


If you’re annoyed by seeing the OVR, a workaround:
step the Volume 1 dB lower or 0.5 dB higher than the Auto Ref transition level.


Did you get this OVR happening during volume change or volume in static -state (during NOT turning up/down)? How much total volume in dBr when this happens?

8 (edited by KaiS 2022-12-07 08:28:45)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

MstrC-117 wrote:
KaiS wrote:

Your max gain is 11.9 dB @ 50 Hz, BTW.

How you ended up to these figures? With those EQ´s, I got max gain +6,7 dB @ 65 Hz.

Your gains add up, I did set your EQ and measured it with sine waves.
Look at the frequency response graph, the upper limit is +12 dB, almost reached.

Be aware:
Phase shift can add another 3 dB of level on top with music.
Specially with all those hi-Q settings.


MstrC-117 wrote:
KaiS wrote:

There‘s a headroom of 3 dB in the meter’s red above 0 dB output for the DAC.

Where you got this figure? According manual, "overdrive" -reserve of ADI-2 DAC´s rear line outputs and front IEM -output is +2,5 dB.

Yes, 2.5 dB headroom.
The important thing: Meter red does’t mean clipping, only OVR does.

Still this doesn’t necessarily mean the clipping is audible.
Most contemporary popular music tracks are clipped at mastering for max. loudness all the time, but hardly anyone complains.

MstrC-117 wrote:
KaiS wrote:

If I replicate your EQ I see red meters, but usually don’t see any OVR with music.
The track Angel - Massive Attack can show occasional OVR, without audible distortions here.

Again, with a pure 50 Hz sine wave I can provoke OVR.


If you’re annoyed by seeing the OVR, a workaround:
step the Volume 1 dB lower or 0.5 dB higher than the Auto Ref transition level.


Did you get this OVR happening during volume change or volume in static -state (during NOT turning up/down)? How much total volume in dBr when this happens?

Static.
At the Volume Setting one step before ADI-2 switches to the next higher Reference Level, the dBu value shown above the Volume figure when turning the knob.

Re: Auto ref level @ PEQ on ADI-2 DAC fs

KaiS wrote:

Your gains add up, I did set your EQ and measured it with sine waves.
Look at the frequency response graph, the upper limit is +12 dB, almost reached.

Be aware:
Phase shift can add another 3 dB of level on top with music.
Specially with all those hi-Q settings.

That can´t be correct.

B/T (Bass) -low-shelf Karmatron used is -12 dB (= minus 12 dB).



KaiS wrote:

At the Volume Setting one step before ADI-2 switches to the next higher Reference Level, the dBu value shown above the Volume figure when turning the knob.


Ok. That´s red/OVR -flashing is just sign of being at the end of ref level -range i.e. Auto Ref -transition point then, as suspected. Being exactly at 0.0 dBFS isn´t a flaw, going past it (and distorting the sound) would be. 

Were any of these OVR´s you got audible? If not, thats just ADI´s designed way to inform user that this ref. level range and "SNR-optimization" of that range is pushed all the way to max, then.





As a practical solution, I would just stay away from ADI´s analyzer & meter screens when not particularly hunting some problems... and trust ADI´s judgment in its internal digital level optimization.

I would recommend meterless Dark Volume or AutoDark (display off) -display mode when just listening... ADI´s all telling meters can be very stressful for precise meter-people.

10 (edited by KaiS 2022-12-12 01:06:20)

Re: Auto ref level @ PEQ on ADI-2 DAC fs

MstrC-117 wrote:
KaiS wrote:

Your gains add up, I did set your EQ and measured it with sine waves.
Look at the frequency response graph, the upper limit is +12 dB, almost reached.

Be aware:
Phase shift can add another 3 dB of level on top with music.
Specially with all those hi-Q settings.

That can´t be correct.

B/T (Bass) -low-shelf Karmatron used is -12 dB (= minus 12 dB).

You‘re right, I missed the “Peak“ setting in Band #1, used Shelf instead.
Max gain here is in fact somewhere around +7 dB.

So take my observations, related to this case, with a grain of salt, but I didn’t have audible distortions with the even more extreme setting.


Personally I do use EQ’s with much higher band-combined gains, and, again, don’t get audible distortions with music.