gain adjustments between preamp & DAW...and levels mics 'wants' to see.?

dupedd

New member
I'm new to computer recording so I'm not sure I'm setting levels right. I'm miking a drumset right now using an FMR RNP for overheads(sm81's) and a mic each on the snare and kick. Both those mics are going into the MOTU 828mk2 preamps. The RNP's gain is at 18db and the readout maintains (green)signal level for the most part. The kick and snare's preamp gain are both below 9 o'clock(below 25%) on the gain and read between the -24 and -6 meter, never hitting the -6. On the Logic Express mixer the levels read great, between -18 and -12, never peaking above -9/-8.

Now here's where I'm confused.

According to my reading these levels are in the right range but I can't help but wonder if the mic's are seeing enough gain to perform their best. I remember reading somewhere that microphones want to be amplified a certain amount, like somewhere between 45 and 60 db depending on the type, in order to perform their best. If this is correct then I must not be setting things right, correct? Should I maybe be setting the gain higher on the preamps and then adjusting the gain on the inputs on Logic, like bringing the faders down to between -18 and -12 after setting a particular amount of gain on the preamp? Does this make any sense or am I way off here?

We'll be recording this whole weekend so I'd love to know I have this figured out now before we really get into it. Thanks for reading.
 
The absolute best thing you could do would be to just listen to different setups as far as how much gain and where, and see what you like best. You may like the sound you get when you put very little gain on the mic pres and do most of the amplification at the motu. Just because most people do it a certain way doesn't make that way "right"- it just works for them. Do whatever works for you.
 
Thanks for the response.
I understand I should probably test out the way i'm describing and I intend to, I just wanted to know if how I have things setup is typical of how one usually sets gain stages and if it is indeed true that microphones supposedly sound their best when they're amplified a certain amount at the preamp stage. BTW, I'm talking about adjusting the gain at the preamp and then at the Logic mixer input, not the MOTU.
 
Oh, sorry. I don't know much about computer recording, so I'm not sure what's typical in regard to software levels. I've definitely noticed that lower gain dynamics (well, a shure 57 to be specific) sound a lot "sweeter" when the gain is increased at the preamp stage... I use a RNP too actually. I can't hear much difference with any of my large diaphragm condensors... once the phantom power goes on the tone is pretty much the same until it gets loud enough to distort.

Take what I say with a grain of salt... I'm far from professional and there are plenty of amateurs on this board who know a lot more than I do. ;)
 
dupedd said:
I remember reading somewhere that microphones want to be amplified a certain amount, like somewhere between 45 and 60 db depending on the type, in order to perform their best.
The general rule of thumb is really based upon impedance. There is some disagreement on the exact values, but the general rule is that input impedance on the preamp should be somewhere between 5-10 times higher than the output impedance of the microphone.

Typically signals do wind up needing to be amplified some 40-60dB to get microphone signals up to line level (+4dBu, or ~1.23vrms), but in that equation it's really the line level that the ultimate idea, not the specific boost numbers.
dupedd said:
Should I maybe be setting the gain higher on the preamps and then adjusting the gain on the inputs on Logic
Ideally you'd want to keep your RMS somewhere around line level (+4dBu) throughout the chain (with occasional exceptions being made for special distortion effects.) This would mean sending nominal signal levels averaging around 0VU/+4dBu into your converter on the analog side. Then you should be able to just leave your input faders in Logic at unity gain (zero boost/cut) for recording; i.e. let your converters automatically decide the digital input level.

G.
 
dupedd said:
According to my reading these levels are in the right range but I can't help but wonder if the mic's are seeing enough gain to perform their best. I remember reading somewhere that microphones want to be amplified a certain amount, like somewhere between 45 and 60 db depending on the type, in order to perform their best.
That is a gain specification for comparing mics, it's not a target to hit.

When they test mics, the mics are put in front of a sound source that is a specific volume and distance away from the mic. Then the amount of gain required to bring the signal up to line level is measured.

The point of the mic preamp is always to bring the mic level signal up to line level. The louder the source is, the less gain you will need. The quieter the source, the more gain you will need.

You sound like you are setting the levels correctly.
 
It is true that certain mic pre channels will have a range where they tend to perform better. And the most challenging areas are at the extremes -- very low gain and very high gain, as noise and distortion specs tend to be less ideal in these ranges.

But if boosting your level a bit in order to get it in to some sort of sweet spot means clipping the phuck out of your digital converters ... then it's probably not worth it. :D

.
 
dupedd said:
Thanks for the response.
I understand I should probably test out the way i'm describing and I intend to, I just wanted to know if how I have things setup is typical of how one usually sets gain stages and if it is indeed true that microphones supposedly sound their best when they're amplified a certain amount at the preamp stage. BTW, I'm talking about adjusting the gain at the preamp and then at the Logic mixer input, not the MOTU.
There's some relevant points here though. Job #1 is to establish optimum gain, signal to noise/distortion at the earliest stage.
The idea being this sets the signal quality that can not be corrected for or 'made up' later.

2nd in line (with regard to some pre's more that others) is to push the pre's gain one way or the other in order to take advantage of their cleaner side or more saturated.

So at this point you may have a single or a few possible 'sweet spots to shoot for depending on the pre. For example; RNP, relatively clean (at fairly wide ranges), vs Chameleon -variable.

Next up is if the pre and A/D's nominal line levels are roughly matched then the record level may need just a small bump one way or the other.

With regard the Logic mixer- would this be a software adjustment that would have no effect of record level?
Wayne
 
Next up is if the pre and A/D's nominal line levels are roughly matched then the record level may need just a small bump one way or the other.

With regard the Logic mixer- would this be a software adjustment that would have no effect of record level?
This is what I'm wondering, getting optimum levels at the pre and then yes, adjusting the Logic software at the record level to get the RMS setting where it should.

2nd in line (with regard to some pre's more that others) is to push the pre's gain one way or the other in order to take advantage of their cleaner side or more saturated.

So at this point you may have a single or a few possible 'sweet spots to shoot for depending on the pre. For example; RNP, relatively clean (at fairly wide ranges), vs Chameleon -variable.
This makes things confusing again...if I wanted to take advantage of the saturated preamp character of say my ME-1NV then would this be a situation where it's better to hike the gain at the preamp and then lower the input level at the Logic mixer level or should I just expect to have a lower volume source?

It sounds like most of you think I have things setup fine though and preamp gain is really only to establish a line level, so I should be fine at least for now to go ahead but I am curious about these last couple of points.
 
dupedd said:
This is what I'm wondering, getting optimum levels at the pre and then yes, adjusting the Logic software at the record level to get the RMS setting where it should.
By the time the signal ges to your software, it's too late to do much of anything worthwhile. Once again, the key there is the level you're sending to your converter. You don't want to clip the converter, nor do you want/need to send it less than you can, as that'll just windup increasing your noise floor during post. If you have everything set up right up to an including the converter, there should rarely - if ever - be a need to boost the tracking levels in Logic. Boosting at that point will do nothing but increase your noise floor and decrease your digital headroom.
dupedd said:
This makes things confusing again...if I wanted to take advantage of the saturated preamp character of say my ME-1NV then would this be a situation where it's better to hike the gain at the preamp and then lower the input level at the Logic mixer level or should I just expect to have a lower volume source?
If you want to saturate your preamp, then you'd normally bring the levels back in line at the INPUT to your converter, not at the input to your software.
dupedd said:
It sounds like most of you think I have things setup fine though and preamp gain is really only to establish a line level, so I should be fine at least for now to go ahead but I am curious about these last couple of points.
Yeah, that sums it up pretty well. Of course if you want to saturate the pre on purpose, that's cool. But unless you want to chance also saturating downstrem, then throttle back on the input of the next device in the chain so that you're sending it nominal levels again. This way you're getting that pre saturation sound but still hittting the converter in the sweet spot.

G.
 
If you want to saturate your preamp, then you'd normally bring the levels back in line at the INPUT to your converter, not at the input to your software.
Pardon my newb ignorance but what's the differnce between the input at the converter and the input to the software?
 
dupedd said:
Pardon my newb ignorance but what's the differnce between the input at the converter and the input to the software?
Note that in each of our examples of 'clean or saturating' style pres there is an input gain and an output control. We use the output to control the level back down to 'nominal when we crank the input up past 'clean. This is akin to 'trim and fader on a mixer for example.
Once it's into the prog', past the A/D, that stage is done. Everything after that is digital gain/effect, or what ever.
:)
 
dupedd said:
... I remember reading somewhere that microphones want to be amplified a certain amount, like somewhere between 45 and 60 db depending on the type, in order to perform their best.
This is what really caught my eye. I don't see the point of saying something like that. As mentioned before, the gain needed is gverened by mic sensitivity, distance and source volume.

Case in point. A QTC-1 two to three feet from a loud kit, directly into my A/D set "+4" clips. (The thing can put out several volts, no pre needed.) In that app I'd still toss another ten or so with an in-line pad! :p
:D
 
dupedd said:
Pardon my newb ignorance but what's the differnce between the input at the converter and the input to the software?
The signal has to go through the converter to get to the software. It's possibe to clip the converter, then turn the signal down in the software to make it look like the levels are good. That defeats the purpose of recording at the proper levels and you're fooling yourself.

The whole point of the -18dbfs rms thing is to not clip anything in the analog chain or the converters. Once the signal is in the computer, the levels really don't matter much anymore. All of this only matters outside the computer. There really is no reason to take the logic faders off of unity.
 
dupedd said:
Pardon my newb ignorance but what's the differnce between the input at the converter and the input to the software?
Your chain looks something like this (only prettier :p ):

Mic A---> Pre A---> Converter D---> Software

A---> = analog signal path
D---> = digital signal path

By the time the signal gets to the software, it's already been converted to digital, the software is just reading and recording the digital output of your converter.

As Mixsit said, if your pre has an output level control, you can use that to bring the signal back down after saturating the pre so that the converter is getting a "sweet spot" signal level. If you have a pre that lacks an output level control, then you can dial it back to nominal at the input of the converter.

But if you saturate your pre and wait for the software to try and bring the signal back down, you risk sending a hotter-than-expected signal to the converter. This may not always be a sure-fire problem, but it will reduce amount of usable headroom within the converter and also risk an extra stage of excess coloration.

G.
 
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