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TOPIC: Re: clipping PEQ gain level

clipping PEQ gain level 8 years 4 months ago #1758

  • sladi
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I'm not sure how I should account for PEQ boosts to prevent clipping.

Should I lower the input level by 20dB if I use a PEQ with 20dB boost, or is there some hidden headroom (wishful thinking)? :)
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Re: clipping PEQ gain level 8 years 4 months ago #1761

  • dreite
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No, there's no hidden headroom. :)

If you're going to program boosts like that and your input signal is greater than 20db below 0.9 volts (0.09 volts) then voltage clipping is a possibility. (Depending upon other EQ you have implemented.)

Cheers,

Dave.
Last Edit: 8 years 4 months ago by dreite.
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Re:clipping PEQ gain level 8 years 4 months ago #1765

  • sladi
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Thank you!
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Re: clipping PEQ gain level 7 years 10 months ago #3167

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Hi, just to be sure:
So it wouldn't prevent clipping if I lowered the output level of the channel with the EQ boost? Only lowering input level would help?

Thank you!
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Re: clipping PEQ gain level 7 years 10 months ago #3174

  • devteam
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Not sure of where the confusion is so let's summarize.

You have a maximum level inside the DSP (i.e. Clipping). If you keep boosting your signal (e.g. multiple EQ at same freq), you WILL clip the DSP. It doesn't matter if you take it down after because it will be too late, damage will be done. Does that make sense?

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Re: clipping PEQ gain level 7 years 10 months ago #3177

  • sladi
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Thank you, but I meant something different I think.
I do understand that several boosts at the same frequency will clip the signal and this is also easily visible in the response graph.

I am asking what would happen if I used one +5dB boost for example. Would a full scale (0dB) input clip because of the +5dB parametric EQ?
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Re: clipping PEQ gain level 7 years 10 months ago #3186

  • devteam
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@Lom,

No, we perfectly understood what you mean. :-)
The answer is still no, you can't go over the signal inside the DSP else you will clip. Not sure how to explain it in simpler words, but inside the DSP you have a certain amount of "headroom". The maximum is called 0dBFS (full scale).

When you take a signal at 0dBFS, you saturate and will loose the signal integrity.

If you have an input signal that is say -20dBFS on the meter, you have 20dB of headroom. If you apply 5dB of boost at a frequency, you have 15dB of headroom. Makes more sense?

If it doesn't I recommend that you have a simple google search on the concept of "headroom". There are many resources out there.

Hope this helps

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Re: clipping PEQ gain level 7 years 10 months ago #3187

  • paalj
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Hi Devteam,
So conclution is to reduce the input level sliders by 5dB if you have added a PEQ boost of 5dB? (at least if you are using digital in.)
How about if you add a PEQ boost of +5dB outside the passband of the XO in the same channel? will it still saturate with 0dB on the input?

It would be nice if you could explain all this in the manual.

best,
Paal
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Re: clipping PEQ gain level 7 years 10 months ago #3189

  • sladi
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paalj wrote:
Hi Devteam,
So conclution is to reduce the input level sliders by 5dB if you have added a PEQ boost of 5dB? (at least if you are using digital in.)
How about if you add a PEQ boost of +5dB outside the passband of the XO in the same channel? will it still saturate with 0dB on the input?

It would be nice if you could explain all this in the manual.

best,
Paal

That's what I wanted to know too. I'm also assuming that lowering the input signal is the way to go but I wanted a clarification (the manual should explain it please). :)

Right now I'm switching crossover and PEQ views and adding dBs in my head in order to see if a signal adds up beyond 20dB.
An "overall response graph" would be helpful to see if the sum of all filters and levels exeeds the headroom in the DSP.
Such a graph could take up too much room, so another solution could be to show the total, final headroom when you point the mouse on any graph (where it currently shows frequency and "local" dB value).
Last Edit: 7 years 10 months ago by sladi.
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Re: clipping PEQ gain level 7 years 10 months ago #3215

  • devteam
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Guys,

It's a bit hard to explain with more words/details that what I tried and unfortunately, I'm running out of ways to try to explain it.. Let me try one last time! :-)

You have a limit (0dBFS = 24bit of 111111...11) which you can hit inside the DSP. If you increase above this limit, you saturate. Is everybody following so far? If you don't, please don't go further, have a look on wikipedia what's digital system and 0dBFS means.

What you need to look at is the input meter. What lom is suggesting about the overall curve has little to do with saturation. If you input a very small signal, it won't matter that you have many EQ on the path. Do you understand what I mean?

@ Paal,

Once again, back to the metering and the type of signal. Not a single YES/NO answer to your question. It's VERY rare that an audio signal will be at 0dBFS. No matter if it's digital. In other words, even if you had +5dB you'll be fine. Just check your input meter to know how much "HEADROOM" you have. Headroom is the magic word here.

That's all I can explain.. hoping the core keywords I just mentioned can be taken out of context and maybe looked out online if you need more info. Are we going to be able to summarize all audio and DSP basics into a user manual? Most likely not.. :-) There are things that you'll need to look online to understand a bit more how digital system works... (e.g. you buy a car, manual doesn't tell you how to drive.. :-)

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Re: clipping PEQ gain level 7 years 10 months ago #3216

  • curryman
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I think lom's suggestion to look at the overall response graph isnt that bad.

To be on the save side, the overall sum of all filters and PEQs should not exceed 0dB (this includes the question from paal: a boost outside the passband may not be a problem, if the overall response graph does not exceed 0dB). In case of a full scale input signal to the DSP (either from digital input or analog input), you could go into saturation especially in case of further amplification. Looking at actual music productions (charts) the dynamic (unfortunately) often is only few dB and maximum level is close to 0dBfs.

If you are looking at an optimal gain structure, you will try to go into the DSP with maximum possible level (peak as close to 0dBfs as possible) and attenuate the signal after the DSP (digital or analog). In this case, I would recommend to keep an eye on the overall gain of filters and PEQ.

In case you have a preamplifier before the DSP, you will likely be much lower in input level (as devteam explains) and in this case youll be on the save side also with some amplifying PEQs (e.g. +5dB).
Last Edit: 7 years 10 months ago by curryman.
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Re: clipping PEQ gain level 7 years 10 months ago #3218

  • sladi
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Thank you.
Those basics are clear to me, I was just figuring if I could lower the output level of a channel in order to prevent possible saturation. :) I just wanted clarification about this (I wondered if the internal gain structure differed from what would be visible in the software.
I'll continue to watch the input meter then. A check for possible clipping in case of a full scale signal could be helpful though.

Also thanks about the advise on how to use the preamplifier.
Last Edit: 7 years 10 months ago by sladi.
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Re: clipping PEQ gain level 7 years 10 months ago #3225

  • paalj
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@ curryman
Thanks for your answer. I was hoping it was like that. I have no preamp in my system and is running full level spdif into my 2x8. The output from 2x8 is going into the poweramps. The poweramps gain is matched so that the maximum listening level means vol potmeter of 2x8 adjusted to 0 attenunation. I think some of my program material reaches -3dB so to be on the safe side I do not want much total "gain" through my minidsp.

@ devteam
I am not asking for how to drive my car, but for the maximum speed limit in first, second gear and so on... This because the rpm counter is not showing the real values :P
The lines from curryman had been enough for me. e.g. "with 0dB on the input, the total XO + PEQ attenunation/gain must not exeed 0dB. If total exeeds 0dB, the input level must be reduced the same amount.
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