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Line level signal vs. Instrument signal, the difference?
jeremija
post Feb 17 2010, 10:37
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Can somebody tell me (or point at somewhere to read about) what is the main difference between the line level signals and instrument level signals?

Also, what should be the output impedance of line level signals generators and instrument signal generators?

All I know for now that the line level signals have a maximum voltage of 2 V peak to peak, and that guitar amplifiers usually have the input impedance around 1Mohm (because the pickups have the impedance at around 250500kohm). Does this 1M refer to the impedance that is measured with a test constant voltage of a single frequency which has the biggest current Z = U(f) / I(f) ?

I'm considering building a device which will transform the signal from my sound card sand send it to a guitar amplifier's input (something like a re-amp box). I have found a scheme here, but I would like to know more about the requirements of such device (what should be the input impedance, output impedance, output max voltage and such...)

This post has been edited by jeremija: Feb 17 2010, 10:38
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jeremija
post Feb 20 2010, 09:50
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QUOTE (DVDdoug @ Feb 19 2010, 19:42) *
I wouldn't use a transformer (at least not as a 1st attempt). I'd first try a simple resistive voltage divider (or a pot). Transformers are an easy way to convert between balanced & unbalanced lines, and they can isolate grounds, but I'm not sure you need that here. Transformers don't require power, but neither does a resistive network.

Hmmm... This connection should be more immume to high-frequency roll-off than the direct guitar input, even with longer cables. What is your source? Is your guitar plugged into the Terratec? Maybe the Terratec's instrument input has lower impedance than the guitar amp, and it's the input that's affecting the tone????

As I said in the edited post, there is no problem with treble:
QUOTE (jeremija @ Feb 19 2010, 18:38) *
EDIT: There is no problem with treble, there was a EQ switch for a lowpass filter left turned on in Cubase. The only difference that I can currently hear is the difference in the volume.
Sorry for the confusion smile.gif

Thank you for the in-depth explanation of the impedance matching, it helped me a lot! As I have no problems with sound quality (at least I can't hear it right now), it works great! I was afraid that the sound would be muddy, like it was some time back when I used some digital guitar effects, which had no true bypass.

This post has been edited by jeremija: Feb 20 2010, 09:53
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