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Old 06-04-2019, 05:25 AM   #63
cyrano
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Join Date: Jun 2011
Location: Belgium
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Quote:
Originally Posted by ChristopherT View Post
I don't know about this Kenny.
My past experience tells me that mic pre's introduce more noise as you get closer to 100% full gain.
I could be totally wrong with this assumption, but that would mean many decades years of deluded beliefs < very possible.

EG: a (non digital) guitar amp, there is little noise at a medium loud setting, then wind up the gain to full and the noise very much increases.


Would be good if a much more tech person could chime in on this:
Does signal to noise ratio increase the more gain that is added to an amplifier ? (analog)
Guitar pre's suffer from a different problem: high impedance.

Due to neodymium magnets, most guitars these days produce a very high output level. Very little gain needed.

But they need impedance transformation. From 1 Mohm to 1 kOhm very roughly. Current gain, not voltage gain. And that makes for very different behaviour, compared to mic preamps. Pumping a lot of current through a high value resistor means a lot of white noise is produced. Add to that unbalanced inputs that might pick up mains buzz and radio signals, and you're in an entirely different world.

Mics have an impedance of around 200 Ohm, needing an input of let's say 1 to 5 kOhm.

I don't know what the impedance of a guitar is, as they seem to vary very wildly, but I believe the input should be 1 M ohm. A thousand times different...
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