Questions about impedance, volts, current, etc.

[ahrenba]

You should certainly get a faint signal plugging a guitar directly into a line input, but if you are talking about recording only one guitar at a time, then no worries --you can use the Omega's "instrument" input, which has a published input impedance of 1 Mohm. If recording two guitars simultaneously, you will need a preamp for the second guitar. For this I use a single channel cheapy Behringer preamp, on which the TRS input impedance is 1 Mohm to specifically meet this application. The Behringer also has an XLR mic input, with a published impedance around 2 Kohms, optimized for microphones.

Thanks for the explanation. So basically, you don't need a preamp if you plug a guitar into an instrument input, but you do if you plug it into a line level input? This seems to make sense because of the impedances.

However, one thing that I do not understand is this. Even if you plug a guitar into a dedicated instrument input that will ensure maximum voltage transfer, doesn't the signal still have extremely weak voltage (since the guitar produces very little)?

I guess I don't really understand what benefit there is to a instrument input vs. a line level input, other than that the instrument one (higher input impedance) assures that more voltage will reach the input.

Yes, it assures that most of the approx. 1mV from the guitar gets to the instrument input, but isn't this low signal of 1mV still too low to work with?

I mean, I understand why you can't plug a guitar straight into a line input (lower impedance).... because it will not allow maximum voltage transfer, but my initial impression was that the voltage a guitar creates is too low to work with.

Would you mind explaining this? Thanks a ton!

Would is be correct to say that a "+3dB gain" is a gain of twice as much voltage?