good booster (non stompbox)

[amonte]

A few weeks ago, some of my gear was stolen - specifically, a dual MOSFET boost pedal that I built and my Agile RK500 guitar.  I've replaced the original RK500 with a second model, and I'm hoping to build another booster pedal one day.

In the meantime, I'd like to build a booster circuit into my RK500 - the guitar sounds great, but it really doesn't have enough gain the stock pickups.  

Has anyone done this?  Rather then go with a treble booster, I just want something that will be transparent and put out more volume and more gain.  Originally, I had planned on incorporating a switch in one of the pots so that I can switch the effect on and off - but now I'm thinking of simply having it on all the time, and adding capacitors to the volume pots so that I can roll off gain without cutting tone.  Is this a good idea?

Also, I'm a little unclear on what the wiring would be in the guitar - as in, which wire do I tie to the input and output of the effect - but I'm assuming I'd attach it to the lead that goes to the output jack, so that it's active on both pickups.  Would I have to tie the common ground of my effect to the ground of the guitar?  And do I have to worry about shielding issues with a guitar?  I've never done anything like this before...

On a side note, this guitar is perfect for this - the pickup cavity is routed and seperate from the pickups - so it can easily be removed without taking the strings off.   There should be plenty of room for the circuit as well.

Sorry for the novel - any comments are appreciated.

[Peter Snowberg]

Sorry to hear of your loss.

You may want to take a look at the design of Jerry Garcia's guitars.

He used three passive pickups in a fairly normal strat configuration, but instead of going from the selector to the volume pot, the signal goes into a unity gain amplifier with low output impedance.

From there the signal takes a trip through an effects loop down to the pedals and then back to the guitar where it goes into a 25K pot for volume control.

In this configuration the effects get 100% signal and the volume works like a master volume. With such a low impedance, you don't need a tone bypass capacitor on the volume, and you can get a good signal through a long cable.

Check out this site for more:

http://www.dozin.com/tiger/dougirwin.asp#

The same buffer designed for him is available here. Of course, you can always build your own with a couple resistors, a couple caps, some perf board and a good opamp.      

Unity gain with high imedance input and low impedance output is a wonderful start. If you want a little more gain, just add a pot in the opamps feedback loop.

-Peter

[RDV]

http://www.generalguitargadgets.com/v2/index.php?option=displaypage&Itemid=124&op=page&SubMenu=

Here's the Stratoblaster.

Regards

RDV