Understanding DBs

I'm pretty clueless on this, but hoping its obvious to some of the more technically-minded here:

I'm having to do some boring work on my keyboard patch levels for live work, and need to decide how loud to make everything.

Live I'm outputting a mono signal to a radial passive DI box - one of these:


Spec says maximum input +20db

The patches can be anything from a single piano through to some more complex multis with lots going on.

So if I were to put the DI box on one side for a moment and plug the mono jack lead straight into my focusrite interface, with the input gain turned right down, just to test the level I'm outputting with the keyboard up full, am I right that I need the level shown by the focusrite software to stay lower than -20 (e.g. -21 for example) to avoid risking that signal clipping the DI box input?

Or am I maybe just thinking about this all wrong?!?

Any help much appreciated!
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Comments

  • Danny1969Danny1969 Frets: 10357
    dB is a way of expressing a ratio, for audio work generally log 10 so a gain of 10 is 20dB, a gain of 100 is 40dB and a gain of 1000 is 60dB .... notice how small increase in dB leads to huge change in gain ratio ... this keeps audio dynamics within manageable figures

    Assuming they are referencing their 20dB to the standard dBv of 1V  then it means a maximum 10V input before clipping

    Do you even need a DI box, a lot of KB outputs are balanced anyway and low Z by default ... mine is 
    www.2020studios.co.uk 
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  • horsehorse Frets: 1563
    Danny1969 said:
    dB is a way of expressing a ratio, for audio work generally log 10 so a gain of 10 is 20dB, a gain of 100 is 40dB and a gain of 1000 is 60dB .... notice how small increase in dB leads to huge change in gain ratio ... this keeps audio dynamics within manageable figures

    Assuming they are referencing their 20dB to the standard dBv of 1V  then it means a maximum 10V input before clipping

    Do you even need a DI box, a lot of KB outputs are balanced anyway and low Z by default ... mine is 
    Lol - I really don't understand this! :-)

    The keyboard does have balanced jack outputs, and I suppose I could get rid of the DI box if I got a trs jack to XLR cable I could attach to the longer run xlrs going to the PA?
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  • Danny1969Danny1969 Frets: 10357
    horse said:
    Danny1969 said:
    dB is a way of expressing a ratio, for audio work generally log 10 so a gain of 10 is 20dB, a gain of 100 is 40dB and a gain of 1000 is 60dB .... notice how small increase in dB leads to huge change in gain ratio ... this keeps audio dynamics within manageable figures

    Assuming they are referencing their 20dB to the standard dBv of 1V  then it means a maximum 10V input before clipping

    Do you even need a DI box, a lot of KB outputs are balanced anyway and low Z by default ... mine is 
    Lol - I really don't understand this! :-)

    The keyboard does have balanced jack outputs, and I suppose I could get rid of the DI box if I got a trs jack to XLR cable I could attach to the longer run xlrs going to the PA?
    Sorry i'm not the best at explaining

    Max 20dB means max input swing of 10V ....... they say 20B because 0db = 1V and 20B means a gain of X 10 

    Voltage gain of 10 = 20dB
    Voltage gain of 100 = 40dB
    Voltage gain of 1000 = 60dB 

    Basically set your patches so the loudest peak on the loudest patch doesn't exceed around -6dB and your be fine for both digital and analog desks ... it's not an exact science it's just a question of making sure the signal strength coming from the KB is well above the noise floor of whole circuit 
    www.2020studios.co.uk 
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  • horsehorse Frets: 1563
    edited January 2020
    Thanks @Danny1969 ;;
    ;;
    With the keyboard up full and interface input gain right down I'm around -20db at peak, but that's definitely no quieter than I have been in the past so should be ok.

    This band doesn't seem to mind going out without a soundman, which makes things more tricky for me as I'm used to someone out front being able to reduce my input gain or channel level if my output strays too high. So I'm trying to make sure that none of my patches can ever go louder than what we soundcheck with. Id  rather be too quiet than distorting or deafening anybody...
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  • andy_kandy_k Frets: 818
    It is my understanding, that the outout level of your keyboard will be stated in your manual as something like +20db, Most consumer grade audio puts out a similar level, which is why the PA usually has a switch for -10 dbv or +4dbu, to allow for various input. 
    What you are trying do do is match volumes between patches on the keyboard, which is independant of the volume of mix through PA, it is a bit of a waste of time to try setting things up through your interface, via the DAW, because there is no guarantee the PA will have the same gain structure, ie- thresholds.
    I would set the keyboard volume at 75%, which allows a bit of gain at your output stage, set up your balanced patches without adjusting this level.
    Next time you set up, either direct or through DI box, get the levels right, and make notes for reference-but do not change your keyboard output, you need to work with a reference, and your keyboard master is set to give max signal to noise-with a small allowance for headroom. Let the PA do the work.
    There is adjustable gain on the PA to allow for mic placements, and different mics, but it is easy to get the input to clip if you are already putting out a hot signal, 
    It is hard working without a soundman, but if you have to it will take a bit of trial and error. For example, your basic solo piano patch will SOUND a lot louder than the washy pad sound during a verse, and that will have to be baked in to your patch volume, normally a sound man can help you out if you get too loud, you will have to learn the difference by trial and error while practicing. If you have to make corrections during a performance-a matter of reducing your output vol, you should re-do your patch to compensate for next time-it will get there eventually, but it can be a slow process if others are not consistent with their levels.
    Good Luck

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  • horsehorse Frets: 1563
    Thanks @andy_k ;
    The challenges you describe are familiar, but with the added challenge of limited rehearsal time in a room where you don't get an accurate representation of the sound through the big pa...

    I think I get what you are saying re interface gain may be different to the desk anyway, but hopefully having levelled off all my patches max levels in this way will have helped avoid clipping the desk input in future, and I can turn down my level to reduce my volume in the mix where it sounds like I need to and accept that in terms of the mix I might sometimes disappear. Id personally rather take a lower fee and have a soundman tbh but as the other band members don't have such varied sounds / levels they don't really get why it is an issue.

    Much easier in bands where I'm just doing some piano / organ
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  • octatonicoctatonic Frets: 33725
    On a tactical level every keyboard player I know eventually ends up with a small mixer on stage to adjust their levels.

    You can get a cheap Mackie for a hundred or so quid, will have adjustable gain, pan and eq.
    Cheap enough to replace if it breaks.
    Also means you can submix if you play at a place that has fewer mixer inputs (if you have 2 or more keyboards you can submix them into a single stereo pair (or a mono signal).
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  • horsehorse Frets: 1563
    octatonic said:
    On a tactical level every keyboard player I know eventually ends up with a small mixer on stage to adjust their levels.

    You can get a cheap Mackie for a hundred or so quid, will have adjustable gain, pan and eq.
    Cheap enough to replace if it breaks.
    Also means you can submix if you play at a place that has fewer mixer inputs (if you have 2 or more keyboards you can submix them into a single stereo pair (or a mono signal).
     I'm kind of heading in the opposite direction mixer-wise, but with a similar outcome maybe:

    On my main keyboard I can set up a multi patch which has its own zones / layers etc, but also sets the patch and volume for my 2nd keyboard. I've been running like that and sending 2 DI feeds to the desk - one for each board.

    I'm now going to trial taking the 2nd keyboards output into my main keyboard, and sending both together to the desk in a single mono signal from the main one. So I've been trying to balance levels so that the blend of both is correct and won't clip. My reason for trying this is it takes one variable out of the equation - the relative mix between both being changed at the desk. Having my own mixer inline would achieve similar I think?
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  • octatonicoctatonic Frets: 33725
    I guess my point is that you can keep the mixer in your road case if you don't need it, but having the ability to quickly patch in a couple of synths is a good thing.
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  • horsehorse Frets: 1563
    octatonic said:
    I guess my point is that you can keep the mixer in your road case if you don't need it, but having the ability to quickly patch in a couple of synths is a good thing.
     See what you mean - useful contingency
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  • horsehorse Frets: 1563
    @Danny1969 - I've tried testing with a balanced trs to xlr - the signal is certainly a lot hotter, but I've not seen it clip yet. Do you know if there's any risk to my keyboards balanced outputs if phantom power were to be accidentally enabled on a mixer channel they plug me into?
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  • Danny1969Danny1969 Frets: 10357
    horse said:
    @Danny1969 - I've tried testing with a balanced trs to xlr - the signal is certainly a lot hotter, but I've not seen it clip yet. Do you know if there's any risk to my keyboards balanced outputs if phantom power were to be accidentally enabled on a mixer channel they plug me into?
    That could reverse bias the caps if used on the output, totally depends on the keyboard and design .. for complete safety in that regard use a transformer DI box 
    www.2020studios.co.uk 
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  • horsehorse Frets: 1563
    Danny1969 said:
    horse said:
    @Danny1969 - I've tried testing with a balanced trs to xlr - the signal is certainly a lot hotter, but I've not seen it clip yet. Do you know if there's any risk to my keyboards balanced outputs if phantom power were to be accidentally enabled on a mixer channel they plug me into?
    That could reverse bias the caps if used on the output, totally depends on the keyboard and design .. for complete safety in that regard use a transformer DI box 
    Thanks - in that case i might stay unbalanced into my passive DI for live
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