XLR in - line out?

A

adventureboy

New member
Hi guys,
I am going to use two separate mics (Behringer C1 and Rode M3) on separate pre-amps (Ultramic 100 and Art Tube MP) for stereo guitar recording. I have an M-audio fast track interface with an XLR input on one channel and a line in on the other channel, if anybody is familiar with this, I'm sure they are. Both mics will be connected to the pre-amp inputs by XLR but I can only take one XLR signal from one of the pre-amps into the M-audio on XLR, the other will have to be 1/4 inch jack, seeing as the M-audio only has one of each. So, for the other pre-amp out, should I use an XLR to 1/4 inch jack lead (is there any point?) or just go jack to jack. I know the obvious solution would be to get a twin XLR channel interface with two XLR inputs but I'm on a home studio budget:) Kindest thanks
 
Your Fast Track has 1 built in preamp on the 1st channel with the XLR input. If you use a preamp before this, you are sending a preamp into a preamp, not a great idea. You will have to balance the gain very carefully.
Easiest thing is to use 1 mic directly into channel 1 of the fast track. Use the second mic through one of your other preamps, and bring this output into channel 2 of the fast track. XLR into the preamp and 1/4" out to the 1/4" channel 2 input.

Channel 2 of the fast track accepts line level inputs which is what you get out of a preamp.
Hope this helps.
 
It gets worse. The second input of the basic Fast Track is a high impedance instrument level input, not a proper line level input. There may be enough adjustment in the gain to cope with a line level source but it's far from ideal.
 
thanks for the replies, really helpful. I'm going to go and see how it's behaving now with the line signal.. see how much gain I can get. so what might be my options? Is there any kind of impedance matching device that could help?
 
To expand on what mjbphotos said:

An XLR is just a connector, one capable of carrying balanced audio signals. It doesn't particularly care about the levels of the signal it carries. Indeed, back in the 1970s and early 1980s there was a variation of the XLR connector that was marketed to carry mains electricity up to 250 volts. (Dumb idea, huh?)

XLR is the usual connector on microphones so some people assume it only carries mic level signals but a lot of audio equipment also uses it for Line Level sources--look at the main outs on sound mixers and you will often see XLRs.

More important than talking about the connector is knowing the levels being used. There are 3 main levels you will encounter doing sound work:

Line Level: The level used by most powered gear as a standard. There are several variants (depending on whether you're talking about pro gear or domestic stuff) but the level is typically up not too far short of 1 volt.

Microphone Level: The extremely low signal generated by a microphone. Since mics generate (or at least modulate) electricity using the very slight movements in the air caused by sound pressure waves, these are typically about 40 to 60 dB lower than line level. Think of them being measured in millivolts (thousandths of a volt) rather then volts. As such, they are very susceptible to outside interference until they are raised to Line Level by a mic pre amp.

Instrument Level: A half way house between mic and line level--usually a generated by the pick ups on electric guitars. However, this one is also designed to go into a very high impedance input. Don't worry about that in this discussion.

Anyway, either mic or line level can be carried by an XLR or TRS jack connection. Mics are almost always XLR connections but a Line Level feed can be either XLR or TRS jack. The connectors make no difference at all to the sound--but plugging the wrong LEVEL into something makes a huge difference. Too high (like line into a mic input) will result in severe distortion and too low (mic into a line input) will be barely audible.
 
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