gain structuring with AUs

Hi everyone,

I guess this might be a bit impractical, I just want to make sure i'm not missing something here.

My issue is this:

I've tested a few of the common AU's (Logic internal and 3rd party) and each one uses a different dB point e.g. a sine wave coming out of different AUs generates different levels (RMS, peak)

I've even began compiling a list...

my question is:

apart from having to set faders at different levels (obviously) simply to get the musical levels right, should I be concerned?

would an AU generating -28 dB for a sine wave be more susceptible to artifacts (e.g. uses less bits since volume is low) then one generating a sine at -6 dB?

anyway, while I'm OK with mixing theory, I'm rather new to the practical aspects. it all stems from starting to read up on a book which talks about gain structuring so I'm looking for a reference point: should I pay any attention to this at all ?

I'm pretty sure I know how to avoid distortion, not saturate any Aux etc, it's just that some instruments get into the mixer real "hot" and some are really low - in analog mixers there's "trim" but is there anything like that in Logic / AU?

btw did find a level control on most synths, e.g. in Albino it's very nice you can set it for 0 dB or +6 dB. naturally the meters in Logic read a completely different number but hey, that's technology for you right ?

should I go on and compile my small lists? would it be useful for other people as well ?

thanks for a great forum, sorry for the lengthy post

catman2u,

I think you come into self trouble too much. Just follow the simple theory of the channel strip audio path structure. It is top to bottom, so you can use gainer plugins, third party plugin main level controls etc... so you can control the level in many ways, bypassing the inserts etc. to keep the signal path out of distortion...

K, thanks for the input, I appreciate it.

BTW I work in 24 bit.

apart from having to set faders at different levels (obviously) simply to get the musical levels right, should I be concerned?

Not usually.

Rule 1: Use your ears.

In this context, some plugins have nominal levels, some can clip internally at 0 dBFS or another value. It depends on how the algorithm was written. *Most* AUs and Logic plugins use floating point arithmetic/storage internally, so you can safely exceed 0 dB FS. If it can't handle those signals, then the result is usually... nasty.

would an AU generating -28 dB for a sine wave be more susceptible to artifacts (e.g. uses less bits since volume is low) then one generating a sine at -6 dB?

*Most* AUs and Logic plugins use floating point arithmetic/storage internally, this is not an issue in that realm. When you bounce to a 24 or 16 bit file or output to the convertor or if you are using fixed point hardware or plugins and exceeding their operational range, you will produce audible artifacts. See rule 1

anyway, while I'm OK with mixing theory, I'm rather new to the practical aspects. it all stems from starting to read up on a book which talks about gain structuring so I'm looking for a reference point: should I pay any attention to this at all ?

There's a lot of hardware and software out there, gain structuring is a very common misconception. There are many dos and don'ts, they vary dramatically depending on what you're using. For example, it's always easy to hear clipping if you push the signal hot enough, assuming of course the algorithm will clip during your tests. Many floating point designs will not clip under such tests - Logic's plugins will generally handle extremely quiet and loud signals as well as 'healthy' signals - this of course can vary if the effect is intended to have a nominal operation range, but many of Logic's don't carry that requirement.

I'm pretty sure I know how to avoid distortion

Again, if you think you hear distortion, adjust the gain +6 or +12 dB before the suspected insert - make the distortion obvious if you are uncertain, or disprove it in the process.

not saturate any Aux etc,

???

it's just that some instruments get into the mixer real "hot" and some are really low - in analog mixers there's "trim" but is there anything like that in Logic / AU?

Sure, there are many gain stages builtin to the mixer and available via inserts. Mixing this way (in Logic and many other hosts - but not all) is perfectly fine - no intolerable noise will be introduced. You will need to identify which plugins can clip, and which have nominal ranges and abide by their terms (or else...).

Hope that helps,

J