Mic Pre-amp Question

[Ranman]

I have a Tascam 788. I noticed when I played the 1st CD I made that the volume was way down and had to turn the CD player way up to hear the track on the CD. So on the advice of someone on this forum I bought a Behringer ultragain pro-8 (ada8000) to boost my input levels. I get a bad hissing noise when I hook it up. Not a tape hiss, but the kind of hiss you get when you are flipping channels on the tv and come across a station that is off the air. Here is how I did it. I plug the mic directly in to the front of the ada8000. I then go out of that into channel one of the recorder. I have to use an adaptor because the input on the 788 is 1/4 inch. When I bypass the ada8000 it works fine. When I go through the ada8000 I get the hiss. Have I got it hooked up wrong? It is pretty simple and I don't think I am that stupid but maybe I am missing something. I have tried different channels on the ada 8000 and different cables. Same result. Any help with this would be appreciated.

 

[NYMorningstar]

Try toggling the HiZ switch. Are you using the Adat interface? If so make sure you are processing the signal at the same sampling rate.

 

[AlChuck]

It's not the cables or the compressor. You're lacking a basic understanding of signal levels.

A compressor needs a line level signal -- it's not usually a preamp too, unless I'm mistaken. So, what happens is you are trying to compress the dynamic range (lessen the difference between loudest and softest parts of the track). Of the entire signal's too low, you have to boost is too much. The noise floor, which is always present in any electonic circuit, but usually pretty inaudible, is boosted up just as much. In other words, the signal you're trying to work with is so low that it's not that much louder than the "noise floor." The signal to noise ratio is close to 1. You need to improve the signal to noise ration, not make everything -- noise and signal alike -- louder.

The standard way to use a compressor is to patch it across an effects bus on the mixer and route the signal through it using the Aux Send and Aux Return. I'm sure the Tascam must have an effects send.

Alternatively, you could use an external preamp, run its (line level) output through the compressor, and run the compressor's output to a line input on the recorder.

Another issue that might be affecting you -- what mic are you using. All normal mics require a preamp (mic inputs on mixer have a preamp in-line), but condenser mics also need a power supply to charge the capacitor that is its signal-producing element. Without that power, it won't produce a signal.

And finally, there's the issue NYMorningstar mentioned -- perhaps you are using a transformer in line that you don't need, and are thus weakening your signal.

Read a book or two about basic recording -- all this stuff is in there.