VTB1 working correctly? Simple techie question

[jhebert]

Perhaps a dumb question... but this is the first condenser mic I've ever used with it (an AudioTechnica 3035), so I'd like to know if this is normal: If input gain is at 0, and the output gain sitting at +6, should there be any measurable signal on the VTB1's output?

When I plug in and power on, if I speak into the mic, I get peaks up to about -40 dB passing through the system (input gain = 0, output gain = +6). Low, but certainly present. There are no other devices in the signal chain.

As I said, this may be normal, but it surprised me. I expected no signal to pass through the unit with the input gain at 0. Something to look into, or something normal I've just never experienced?

Thanks!

James

[stettoman]

James, I'd like to know as well, as my unanswered post may witness;

http://www.pmiaudio.com/forums/showthread.php?t=316

Eric

[hargerst]

I.m sure Alan and gang are still coming back from the San Francisco AES show, so maybe I can answer your question.

Microphones put out a certain level of signal, usually measured with a 94 dB signal at 1 meter. This 94 dB signal is from a calibrator or a very flat speaker system. Now, the microphone hears that and puts out a signal, which is measured from 0 DB; it is listed as a negative number that tells you how many dB of preamp boost you need to bring it up to 0 dB.

For large diaphragm condenser mics, that number is around -36 dB. The number is around -40 dB for small diaphragm condenser mics, around -55 dB for dynamics, and near -60dB or greater for ribbon mics. When you see this spec, all it means is hom much amplification is required to bring the signal up to 0 dB or "line level".

With this background, let's look at your situation. With the preamp set at "0" gain, you're hearing the output of the mic, without any boost from the preamp. That's normal and you're hearing what you should hear; the un-boosted output of the mic. As you turn up the gain control, you're adding the boost necessary to bring the signal up to a more usable level.

If the mic is outputting a -40 dB signal (with the preamp set at "0" gain, you need to turn the preamp gain to around +40 dB to get the signal up to the 0 dB level.

Does this make a little more sense now?

[Alan Hyatt]

Be sure the meter is on the input, and the do the same for the output controls so they are set correctly. Harvey seemed to say everything I could on this.

[Alan Hyatt]

James, I'd like to know as well, as my unanswered post may witness;

http://www.pmiaudio.com/forums/showthread.php?t=316

Eric

Sorry that never got answered...There is plenty of headroom on the VTB-1, so you should never have to worry about boosting the input gain...It will not crap out on you.

[jhebert]

Harvey, your explanation is perfect.

After a careful read of your reply, I think I get it. I was confusing power to the mic with signal from the mic... as if connecting the mic but having the input gain at 0 meant I was not providing power to the mic at that moment (with that line of thinking, of course why would I expect to see any signal?). I'm used to dynamic mics, and have never seen the behavior before. Sounds dumb, I admit, but I'd never used a phantom powered mic, so I'd never experienced that before. Without your explanation, I would not have figured that out.

Then, it took all of a split-second for me to look over and see that, almost prophetically, I had the gain on the AT30305 at the "just right" level for my recordings -- about 40 dB. Hmm...

How do you *do* that? :)

Thanks for taking the time to make it clear,

James

[stettoman]

Sorry that never got answered...There is plenty of headroom on the VTB-1, so you should never have to worry about boosting the input gain...It will not crap out on you.

Thanks for that...I didn't think I was incinerating anything but I wanted to be sure that a spike of some kind in a line-level input wouldn't ruin my day. I've found, if it's even possible, that my a. 370 gets just that much more added clarity from the Monitor out thru the VTB-1 (as opposed to direct-to-DAW), but a hefty input signal it is...

Eric