PEQ and Preamp Gain Calculation

[middlemarch]

Simple question, I hope. When generating a new set of PEQs for whatever, my assumption has been that you set the preamp gain equal to the inverse of the highest gain PEQ filter. If the biggest boost is 6dB then preamp gain goes to -6dB.

But in looking at various PEQ sets published here as well as in the Oratory sets and others, this is seldom the case. Generally the actual preamp -gain settings are slightly more than the max gain setting, like a half dB or so. In some cases as much as a couple of dB more.

So this must be a bit more complex, but I've been unable to find what the calculation is, via Google, at least.

Can someone clear this up for me? It would be greatly appreciated.

 

[Rednaxela]

PEQ filters can add up when they overlap.

Generally the actual preamp -gain settings are slightly more than the max gain setting, like a half dB or so. In some cases as much as a couple of dB more.

Can you post an example of both?

 

[middlemarch]

These are from Amir's headphone suggested settings
Preamp: -4.9 dB
Filter 1: ON LSC Fc 60 Hz Gain 2.5 dB Q 1.0
Filter 2: ON PK Fc 310 Hz Gain -3.0 dB Q 2.0
Filter 3: ON PK Fc 900 Hz Gain -4.0 dB Q 2.0
Filter 4: ON PK Fc 3283 Hz Gain 5.0 dB Q 2.0
Filter 5: ON PK Fc 13300 Hz Gain -11.0 dB Q 3.5

Abyss Diana V2 (Not Terrible, N/A)[631]US$3000
Preamp: -8.6 dB
Filter 1: ON LSC Fc 35 Hz Gain 8.0 dB Q 1.0
Filter 2: ON PK Fc 1194 Hz Gain -2.0 dB Q 2.0
Filter 3: ON PK Fc 2705 Hz Gain 2.5 dB Q 3.0
Filter 4: ON PK Fc 3700 Hz Gain 5.0 dB Q 9.0
Filter 5: ON PK Fc 5464 Hz Gain -2.0 dB Q 8.0

Abyss Diana V2 (2nd review)(actually Diana Phi?) (Poor, N/A)[611]n/a
Preamp: -6.3 dB
Filter 1: ON LSC Fc 42 Hz Gain 4.0 dB Q 1.0
Filter 2: ON LSC Fc 120 Hz Gain 2.0 dB Q 1.0
Filter 3: ON PK Fc 1000 Hz Gain -3.0 dB Q 4.0
Filter 4: ON PK Fc 2000 Hz Gain 4.0 dB Q 3.0
Filter 5: ON PK Fc 3696 Hz Gain 4.0 dB Q 5.0

 

[staticV3]

@middlemarch on Windows, you can load the presets into Equalizer APO ("Include Configuration file"), and then it'll tell you the maximum filter gain and how low you need to set your preamp to avoid digital clipping.

As Rednaxela said, PEQ filters are additive, so the required preamp cannot be determined by the max gain of each individual filter.

Two peaking filters with identical frequency and +3dB each, will require a -6dB preamp.

Two peaking filters with identical frequency and Q value but inverse gain will cancel each other out, requiring no preamp at all.

 

[middlemarch]

@middlemarch on Windows, you can load the presets into Equalizer APO ("Include Configuration file"), and then it'll tell you the maximum filter gain and how low you need to set your preamp to avoid digital clipping.

As Rednaxela said, PEQ filters are additive, so the required preamp cannot be determined by the max gain of each individual filter.

Two filters with +3dB each and identical frequency and Q value, will require a -6dB preamp.

Two filters with identical frequency and Q value but inverse gain will cancel each other out, requiring no preamp at all.

So it sounds like it requires a software calculation to derive an accurate value, there is no corresponding "back of an envelope" method? As a Mac user is there a corresponding application that would do the same for me? I have a copy of Jriver and several Rogue Amoeba apps.

 

[staticV3]

So it sounds like it requires a software calculation to derive an accurate value, there is no corresponding "back of an envelope" method?

There is not.

As a Mac user is there a corresponding application that would do the same for me? I have a copy of Jriver and several Rogue Amoeba apps.

You can type your PEQ settings into one of the many different https://squig.link/ tools in the Equalizer tab, then export it, and the resulting .txt file will contain an appropriate preamp value.

Some PEQ tools will calculate the preamp automatically so that digital clipping is not possible. Mathaudio Headphone EQ for example.

 

[Rednaxela]

REW can do it too for you.

 

[Jimbob54]

If you use something that visually shows the overall eq curve you can get it by eyeball. In fairness, you can normally live with a bit less preamp than the max gain unless the music you listen to really maxes out on those frequencies. Especially at the right hand side of the spectrum

 

[middlemarch]

Thank you all for the links to the tools, etc. I also have REW but have only used autoEQ to this point, will have to play with that more. And have never heard of Squigs before! What a cool tool.

Jimbob54, I assume by eyeball you mean visually identifying overlapping PEQs and where they add, so basically look for the biggest peak. And I can see where adding a bit of boost above 10KHz probably will not drive the system into clipping with normal music sources.

 

[Jimbob54]

Thank you all for the links to the tools, etc. I also have REW but have only used autoEQ to this point, will have to play with that more. And have never heard of Squigs before! What a cool tool.

Jimbob54, I assume by eyeball you mean visually identifying overlapping PEQs and where they add, so basically look for the biggest peak. And I can see where adding a bit of boost above 10KHz probably will not drive the system into clipping with normal music sources.

Yes. Equalizer APO on PC with PEACE interface being the most common example but the EQ on the Qudelix 5k app and UAPP on Android allow you to do the same (sure there are many more) - you can see the cumulative impact of the EQ on the frequency response , usually with a dB scale on the Y axis that you can read across to from the highest peak.

You may also find whatever app you use has a clipping prevention setting that auto increases the preamp reduction if any part of the signal starts to go over full scale (EAPO and UAPP mentioned above both have this) - very useful.