25db boost from 9v batt???

[Alpha579]

Hey all,
I was looking at the EC mid boost schematic, and wondering how they got 25bd of clean mid boost. When im putting together bjt boost circuits, the best i can do is around 18db, and if i really dig in, it still distorts a tiny bit. And im using single coils.
Anyone know any secrets on this?
Alex

[ExpAnonColin]

The LM386 can, according to the datasheet, provide a boost of 46 db with a 10uf capacitor from pins 1 to 8, or a V gain of 200 if that's how you want to talk.  That's pretty clean, not totally.  You could put a 1-5k pot in series with the 10uf cap if you wanted to be more exact towards 25db, which would certainly be clean.  In terms of making it mid, I'd just make 2 simple low and highpass filters (active or passive).

-Colin

[Alpha579]

Yeh, but is that LM386 clean boost run off 9v? Coz i can get plenty of gain, it justs distorts. Another one is the seymour duncan booster, which is 25db too. Pete cornish has a booster that runs on 18v, and it gives 27db of clean gain, and it can handle high inputs. If he can get 27db with 2 9v batteries, theoretically you can get 24db of clean boost with lots of headroom.... :?

[ExpAnonColin]

Yeah, the LM386 runs off of 9v...

But, that would depend on if the output was greater than 9v (or is it 4.5?  Someone correct me hear).  If you're trying to amplify something higher than your supply (or bias, I think, since it's not bipolar) voltage, you're going to clip almost no matter what.  Just from personal experience I've gotten the max boost (10uf between pins 1 and 8) with not a whole lot of clipping, and you don't even need the max boost.

-Colin

[Paul Perry (Frostwave)]

If you look at the maximum signal from your pickup, maybe adding 25db gain to this gives you more than 9v peak to peak? in which case, it isn't ever going to be clean on peaks!

[Mark Hammer]

Well that's just it, Paul.  It's a potential 25db boost from some arbitrary starting point.  Feed a 9v-powered pedal a 2v p-2-p audio signal, and obviously it won't be possible to squeeze more than a few db of *clean* boost before one runs out of headroom.  Feed that same pedal a 10mv signal from a weak dynamic voice mic, and you have a LOT more room to apply gain before the signal bangs its head against a 9v ceiling.

[Alpha579]

Can anyone show me a simple 25db boost pedal, coz i think my simulation programs a bit off spec...