I made a few edits to albert kreuzer's designįirst, i changed the bf245 to j201, they draw less current I have yet to put it on a breadboard so its all theoretical I cant seem to find the j201 nor the bf245 in my local electronics store so i might have to change to the mpf-102 design by james hawes
I'll post the design design in a few days. like a SPTT (single pole triple throw) if i can find one. This switch would also turn off the 9v supply. So, can i just put an on/off switch that bypasses the JFET stages and goes directly to the tone? also i would have the same switch bypass the 2nd jfet stage in albert's design and just have it end with a 1meg ohm resistor parallel to the output? I think im going to stick with the albert kreuzer design.īut i want to make it an active/passive circuit
#High headroom high impedance preamp onboard diy how to#
Ive been studying electronics engineering but sometimes everything gets so theoretical that i don't really know how to apply some of the stuff. saw it in an article on impedance matching.
i thought that it was supposed to do that so that i could deliver maximum power to the preamp circuit. thanks for the help with the impedance thing. You don"t need a Jfet to controll the volume, just a pot, and I would suggest useing 250k pots for Volume controlls. I warn you before hand that Passive bass and trebble controlls on a bass guitar suck, they only cut frequencies and don"t boost them so You will allmost never use them, I would suggest that you build an active tone controll set up or build an EQ pedal. If you want Bass and treble controlls that will controll the Bass and trebble for both the pickups and a volume for each seperate pickup then I think you will need to wire the Volume pots first, then paralell the Volume outputs which then go into the bass and trebble controlls which then go into the Preamp section then to the 1/4in Jack. If the impedance of your pickups is 20k then that is a bit high for pickups but not a problem, the preamp has a input impedance of 470k which is plenty high enough for 20k pickups and with both pickups in paralell they will be 10k total. Hi, I would change the 68pf cap that is in the feedback loop to say 220pf for bass use, you might also want to adjust the Value of the 100k resistor in the feedback loop, this controlls the gain, you might want to lower it a bit depending on the output of your pickups and how much gain you want.
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