So, what's the difference between...

[pinkphiloyd]

...your typical guitar amp tube pre-section and a mic tube pre-amp?

[Enzo]

A ton.

A mic preamp is designed to faithfully amplify the original signal without adding any distortion, coloration, or in any other way change what was fed to it.

A guitar amp is designed as part of the instrument. It's whole purpose is to add character to the original signal.

[pinkphiloyd]

So, it's more like a hi-fi design? Are they any recommendations of good ones that I might find a schem of to study/build? I don't know anything about them, obviously.

[Enzo]

And there is a lot more when it comes to the excecution of one. Guitars put out a MUCH hotter signal than the average microphone. The microphones are almost always low impedance with balanced outputs, coompared to guitars' high impedance and unbalanced output. Mic pres might have extra featurs like a low-cut to prevent rumble.

Guitar amps are rolling off by 5kHz, while a good mic pre will be essentially flat for the entire audio range and beyond.

Here, Waltzing Bear has an interesting collection of old classic mic pres and other studio gear.

Pro Audio Equipment Schematics

[jrfrond]

Enzo is spot on with his descriptions of both, but it all must be tempered with the fact that many engineers, when searching for a sound, will try putting mics and instruments through almost anything. Mics have been plugged into guitar amps, Leslies, stomp boxes, etc. over the years looking for that just-right (or just-wrong, depending on your viewpoint) sound when needed.

Also, building a quality tube mic pre will be pricier due to the balancing transformers required, and good ones are not cheap. You will also tend to see dual triodes with lower plate impedances used e.g. 12AU7, 6922, etc., vs. the 12AX7's that are so ubiquitous in guitar amps.

[pinkphiloyd]

Thanks guys. Sounds like a pain in the ass, ha ha. Maybe later.