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previous: Chris B Has anyone tried this with humbucke... -- 9/6/2003 3:04 PM View Thread

Re: on-board emitter follower

9/7/2003 4:36 AM
Tim EscobedoRe: on-board emitter follower
The biggest advantage would be impedance conversion. Which would also mean less susceptibility to noise and loading effects. Particularly the closer to the signal source as possible. On-board, or even built into the pickups.  
I wouldn't call it excessively bright. More like more lively. I'd tinkered with a couple circuits to do this. One is a simple source follower, using a single JFET, a source resistor, and a output coupling cap. Pickup hot goes to gate, drain goes to V+, source goes to ground via 10k resistor. Output is taken from source via cap. Nice thing about this is very few parts. Sounds good. However, you may have to look hard to find a apropriate JFET that will bias well enough for good headroom. The best I had was a 2N3819, with the source floating around 3V (using a 9V supply). Some JFETs were as low a .6V. Another possible concern with this design may be battery life, which can be as high as 1mA. Not ridiculously high, but could be better for a on board circuit.  
Another possibility could be found here: page 11, a article showing a nice op amp based preamp. It could easily be used as a non-inverting buffer. Can be used with low power op amps quite well. Like the JFET based circuit, it's DC coupled input, makes for lower noise and simplicity. The article seems to imply a true bipolar power supply, which would mean two batteries. But it seemed usable with a single 9V battery using a simple resistor divider as a reference/pickup ground.