Automatic Gain Protection

Support questions for Neutron Player only.
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blaubär
Posts: 3389
Joined: Tue Apr 02, 2019 6:48 am

Automatic Gain Protection

Post by blaubär » Wed Jan 20, 2021 8:57 am

"AGP" means "Automatic Gain Protection". It has the purpose to prevent distortion due to excessive amplification in the equalizer.

It can be switched on or off via Settings > Playback > Automatic Gain Protection or a button below the equalizer settings, which exact location can be controlled via Settings > User Interface > DSP Effect: Button .

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You use AGP to prevent the signal from exceeding the maximum possible value of 0 dB. This could happen if eg you increase the signal in the equalizer by 20 dB and then an input > -20 dB arrives. If you have activated AGP Neutron will reduce the preamp by "Sensitivity" multiplied by the signal excession, so that the resulting signal after the equalizer won't exceed 0 dB. Therefore it is a good idea to keep Sensitivity at 1.00 .

The correction will persist until the next track starts, then it ( meaning the corrected preamp level ) will be reset to the value of "Reset Level". That is unless you deactivate "Reset on new Track", then it will will stay. To test the AGP you can eg temporarily increase the bass in the eq and then play a track with loud bass. Without AGB the sound is distorted, with AGP Neutron will reduce the preamp.

The preamp-level at the time of the correction is taken over to the agp reset level.

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fankyy
Posts: 9
Joined: Mon Jan 03, 2022 5:45 am

Re: Automatic Gain Protection

Post by fankyy » Mon Jan 03, 2022 6:06 am

Most of the time AGP doesn't kick in fast enough to prevent some distortion. Is this by design or could you make it react faster?

blaubär
Posts: 3389
Joined: Tue Apr 02, 2019 6:48 am

Re: Automatic Gain Protection

Post by blaubär » Mon Jan 03, 2022 8:02 am

fankyy wrote:
Mon Jan 03, 2022 6:06 am
Most of the time AGP doesn't kick in fast enough to prevent some distortion. Is this by design or could you make it react faster?
That would be a bug - if this isn't the known error AGP vs FRC then could you describe how to reproduce it ? For me generally AGP works well.

fankyy
Posts: 9
Joined: Mon Jan 03, 2022 5:45 am

Re: Automatic Gain Protection

Post by fankyy » Mon Jan 03, 2022 6:53 pm

I don't use FRC. But i use the parametric EQ in 12-band mode, and for some in-ears i add quite a lot of subbass:

42Hz, Q 5.00, Gain 13 dB
48 Hz, BW 0.78, Gain 12 dB

Like this, to be safe i would have to set the preamp to at least -20dB, but then, the overall volume is just too low, so i set the preamp, depending on how much bass the current songs have, to around -15 dB. If then a bass heavy track starts, the AGP kicks in, as it should, but the first bass slam will clip for a few 100ms. (Also shows on the neutron oscilloscope). Additionally, AGP over-reacts and sometimes goes directly to -30dB, even if -22 dB would be enough for a certain track.

This behaviour appears on both of my Snapdragon 835 and 720G phones, over the headphone jack as well as over bluetooth headphones (even though on some it seems to be quicker).

Also, sometimes if i set one of the EQ bands to 0 and re enable them, even if it's only 1dB, sometimes the signal pops and AGP immediately goes down to -30dB, why does that happen? It can be quite painful because i have the overall volume sometimes on maximum, as i listen with -15 to -22 dB preamp with that basshead subbass-eq setting.

blaubär
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Joined: Tue Apr 02, 2019 6:48 am

Re: Automatic Gain Protection

Post by blaubär » Mon Jan 03, 2022 7:51 pm

Okay, I suggest you ask neutronmp@gmail.com whether the AGP should prevent any distortion in any case no matter what ( as I assumed, which would make the behaviour that Neutron shows in your case a bug ) or whether the developer regards this as a feature ( perhaps such a level of protection wouldn't be feasible or possible ).

blaubär
Posts: 3389
Joined: Tue Apr 02, 2019 6:48 am

Re: Automatic Gain Protection

Post by blaubär » Sun Feb 27, 2022 4:30 am

blaubär wrote:
Mon Jan 03, 2022 7:51 pm
Okay, I suggest you ask neutronmp@gmail.com whether the AGP should prevent any distortion in any case no matter what ( as I assumed, which would make the behaviour that Neutron shows in your case a bug ) or whether the developer regards this as a feature ( perhaps such a level of protection wouldn't be feasible or possible ).
That has been solved, see here :
dmitrykos wrote:
Mon Jan 10, 2022 11:21 am
I still think that the control of overloading with AGP should embrace FRC, just in case somebody misconfigures EQ, Preamp + FRC with its Preamp. In the end we anyway must get non overloaded sound but if it is detected then it is a problem and it is better to allow an action from AGP rather than get overloaded, harsh sound as output.
Bugs have been fixed, and now AGP takes the FRC into account and corrects any signal exceeding 0 dB.

blaubär
Posts: 3389
Joined: Tue Apr 02, 2019 6:48 am

Re: Automatic Gain Protection

Post by blaubär » Mon Jul 11, 2022 6:51 pm

Also see here for a discussion about AGP and its (in)ability to detect and prevent intersample overs.

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