VO-BB - 20 YEARS OLD!

[D Voice]

Something confuses me and I haven't gotten a straight answer about:
How should levels be set (relatively) when a mic preamp and an interface with built-in pre-amps combined?
[Not talking about dedicated AD interfaces without pre-amps, or interfaces where you can turn off the preamp.]

Most AD interfaces (all that I have at the moment) have some sort of preamp built in, which can't be switched off. This means, when combined with a preamp, there is too much gain, so both need to be brought down compared with using only the interface alone, or the pre-amp with a straight interface. So how should they be combined?

a) Both approximately the same (close to midway)? (e.g 50-50)
b) Higher on the preamp, lower on the interface? (e.g 75-25)
c) Lower on the preamp, higher on the interface?
d) Higher on the "better" quality piece of gear, less on the other?
e) Higher on the lower quality gear, higher on the "better" piece?

[D Voice]

I assume that there is some sort of "sweet spot" for setting the gain. I have been led to believe that pre-amps "like" to be in the 50-90% range, that's where their efficiency and sound is best. Too high- obviously, means more distortion and noise. But setting too low is not ideal either, as I understand,


[BTW this is one of those things where answers like: "just try the various combinations use your ears" are pretty useless to me. There are too many variables and combinations of settings, and what may sound "better" at one stage in the work flow, after EQing and processing needed doesn't sound as good. We can argue this point in another thread- not here, please]

[D Voice]

related questions are:
Is a 10 or 20 dB "Pad" useful in VO?
(which would allow one to set the gain higher on the preamp and/or the interface)

Where to set the High-Pass/Low-Cut filter?


e.g. on this particular day, at this particular moment, I have a (SP C-1) plugged into a (modded TubePre) pre-amp into a USB mixer.
The mic and the preamp have a Pad switch.
The mic, the preamp, and the mixer all have Hi-Pass/Low Cut filter switches.
Which to turn on, I wonder.

[Yes, I have other gear, but am looking for general knowledge and information that will help not only in this particular case, but others as well]

[Leslie Humble]

Without speaking to your specific equipment, which I have not used, let me speak of what I understand and wait for the big time gear heads here to weigh in.

If you cannot bypass the pre in your interface but you can turn it down (which I'm assuming because of your percentage questions) turn the interface ALL the way down. You will to a large degree effectively bypass the interface pre if you do this. If you have to ask which is the higher quality Pre then you don't need your stand alone Preamp. If you have BALANCED inputs in the back of your interface you can of course bypass there.
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[Bish]

The first thing to remember is that each of these two hypothetical pre-amps will not only amplify the signal, but will also colour it to a greater or lesser extent. The distribution of the gain, if in fact, that's the only option, should be set to how it sounds, rather than any arbitrary low/high or percentage-based distribution of amplification. Personally, I would always want only one unit acting as the pre-amp, but I certainly understand the situation you describe.

My simplest narration set-up is to use (whichever) mic directly into my Apogee Duet firewire interface. The Duet's input is set for mic level and the pre-amp is set as required.

Next step up is using the mic connected to a Mackie 1202 VLZ3 mixer, and thence to my Apogee Duet. In this configuration, I'm using the Mackie's pre-amps. Output from the mixer at +4dB and have the Duet set for +4dB input which by-passes the internal pre-amps.

If I'm feeling adventurous, I'll connect my dbx286a to the Mackie. This is where things get tricky. If I connect the output of the dbx into the line input of the Mackie, I can set the levels pretty well on the dbx and achieve the correct levels into the Duet with the Mackie set to unity gain across the board. In theory, the effect of the Mackie is minimal, but the pre-amps are still in the circuit. If I connect the dbx to the aux return on the Mackie, I'm pretty much by-passing all the channel pre-amps and it's as close to a pass-through signal as I can get.

Of course, I can by-pass the Mackie by just connecting the dbx to the Duet, but sometimes ya just need the mixer to be there!

I just re-read all that and confused myself

I would always try to keep as few elements in the chain as possible. Hang the mic into the best pre-amp you've got and get the input level set as best you can. Try to make anything downstream of that transparent as possible. If the interface has a by-pass or unity setting, go for that and adjust your input level from the output of the pre-amp. Others will have their own ways of doing things... it's all so totally dependent on what kit you have. Setting the "sweet-spot" for me has always been a case of avoiding clipping at all costs while keeping the signal as high as possible to keep your s/n ratio as good as possible.

I have never used a pad in VO. They can be useful if you're close to a really loud source, but unless you're a real screamer, you should be fine! If the low cut filter is tuned well, it'll take out low frequency (mains) hum without messing with the mic's characteristics. I will sometimes use a low-cut on my mixer... never on my mic.

Aaaargh!
Bish
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[whalewtchr]

Pro Tools comes with the infamous MBox which of course has built in preamps. Since I like to drive the gain with the 528e, I bypass the pres in the MBox by plugging into Line/DI with 1/4 inch and depressing the DI button on the back. Like Bish I never have a use for the PAD which is really designed for Rock and Rap singers or anyone who plans to belt it good...though some recording engineer types will use the PAD to get a certain sound from a mic through calibration settings which honestly I don't understand.

There is a great website to learn about gain staging and preamps in general with Ronan Chris Murphy http://tinyurl.com/6tgmofm hope this helps you.
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jonahcummings

[georgethetech]

A big misconception is that the Mbox, or any similarly priced USB interface with built-in mic preamps has a way to bypass them. In almost every case, this is not true. Even when in DI/Line mode, you are still passing through the preamps. The original Mbox had a true bypass using a relay (you could hear it click when you pushed the little button on the front), but that's now a relic. Costs a lot more to build it that way!

Just because the Mbox is so common, I'll use it in my hypothetical system.
Like Bish mentioned, a dbx286a, Mackie mixer, and Mbox combo is something many have, and I've had to deal with this configuration numerous times. In this case you are running through THREE mic preamps. Yes, the line inputs on the Mackie mixer also pass through the preamp circuitry (a look at the schematic proves this).

Now, this in MY experience, not based in hypothetical EE theory...

The highest amount of gain should occur at the front end, the preamp directly connected to the mic. At the other end, the A/D, the gain should be at a minimum (as Leslie mentioned). The mixer gain somewhere close to Unity, and all level controls in the signal path of the mixer also set to Unity. I always found best results with the Mbox 2 series when using the Pad button, and running the input gain controls close to the Unity mark (the little white bump).

Here's a discussion elsewhere that may shed more light.
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[whalewtchr]

Thanks for clearing that up George. All I know is that there was a difference, but again I don't know or claim to know. It worked for my situation. Bad, then Good.
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jonahcummings

[D Voice]

[Bill Campbell]

On many small mixers you can bypass the preamp section by using an "insert".
I did it when I used a Yamaha mixer, It still goes through the mixer, but not the preamp.
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