AMB Laboratories DIY Audio

[zaubertuba]

I'm finally getting around to wiring a couple of these up as input stages for an instrument preamp, but I have a quandary.

My NS/Stick uses EMG FT active pickups, which output .52V RMS, .75V Peak, according to the specs. I thought I'd like to run the internals of the preamp at a nominal +4 dBu level, 1.228V nominal or 1.737V peak (I run pro-referenced power amps).

Whether I calculate from nominal or peak levels, I end up with a gain a bit over 2, or 6 dB. Many instrument preamps I've seen run a variable gain of anywhere from 10 to 50 dB, assumedly for passive or piezo pickups, or in the case of tube amps perhaps also to have headroom to overdrive the next stage for effect.

So should I just configure these at maximum gain with a pot?

[amb]

Why not build the α20 at a relatively high gain (although I wouldn't recommend over 20dB), and then use a pot before the α20 for attenuation just like how it's normally used?

[zaubertuba]

Well, originally I guess I was concerned with not having the full travel of an input pot available to fine tune the input gain of my instrument. I guess I reckoned the output level of my active pickups may require a lot of attenuation with a high-gain input stage.

But, looking at what I just posted about how instrument preamps are actually built, I suppose this is a silly concern. Besides, I can always go back and fine-tune it later, right?