Anyone Made This Preamp?

[Moreau]

Hey there. About to make my first bass, and im going to use 2 Mightymite active Soapbars, and i want to make a preamp. I came across this in my searches.

Fet Preamp

I saw that , and found this as well

DIY guitarist

I just wondered how this circuit would be installed wit the 2 volume, 1 tone pot setup. does it go onto the tone pot instead of a resistor? I am unfamiliar. Also how would the diagram for the DIY preamp differ from the first? thanks.

[Devon Headen]

First off, resistors don't go on the tone pot. Capacitors do. I've made the till preamp. You'll need to run lower value pots, because the impedance gets lowered after the preamp. Really the till preamp is more of a buffer, anyway. It's not gonna give you a lot of boost. I think I used 50k pots.

[StratDudeDan]

i've been troubleshooting a Fetzer Valve for a good month on and off now, and i can't get it to work. i was actually about to try using that FET preamp/boost in its place. lemme know how it turns out.

[lovekraft]

To use the Tillman preamp with that setup, simply insert it after everything else (volumes, tone, etc), replace R4 with a 50k audio taper pot (outside terminals), and connect the wiper (center) lead to the output jack. Replacing R3 with a 10k trimmer and adjusting the drain voltage to 4.5 volts will give you maximum headroom.

Any particular reason why you want to add another preamp? Aren't the active pickups hot enough for you?

Edited January 19, 2005 by lovekraft

[Devon Headen]

To use the Tillman preamp with that setup, simply insert it after everything else (volumes, tone, etc), replace R4 with a 50k audio taper pot (outside terminals), and connect the wiper (center) lead to the output jack.

←

That's what I did with LKs advice.

[lovekraft]

Sorry, Dan, I completely misssed your post about problems with the Fetzer Valve - what JFET are you using, and how do you have things set up? With luck, we can put our heads together and get it working.

[Paul Marossy]

"To use the Tillman preamp..., simply insert it after everything else (volumes, tone, etc).... and connect the wiper to the output jack. Replacing R3 with a 10k trimmer and adjusting the drain voltage to 4.5 volts will give you maximum headroom."

This is exactly how I have wired the two Tillman FET preamps that I have built. I think it sounds great wired as I have it. You can get quite a boost by adding a 10uF cap in parallel with the source resistor, too.

That second link above is my page about the first Tillman FET preamp that I put in one of my guitars. It's the same exact circuit as Tillman's, except that I added a 4.7uF cap (not 10uF like I said on that page, I think I may have to correct that) in parallel with the source resistor and used a trimpot instead of a resistor. I just thought Tillman's suggestion of trying a bunch of resistors until you get 4.5V on the source was kind of inefficient...

EDIT: OK, I fixed the page.

Edited January 20, 2005 by Paul Marossy

[Kyle Cavanaugh]

I've made it 2 or 3 times! It's a great circuit. I use a 10K pot as a volume control AFTER the preamp. It makes a guitar with PAF sounding humbuckers sound like EMG's, and no clipping like the 81 can!!

[Paul Marossy]

I use a 10K pot as a volume control AFTER the preamp. It makes a guitar with PAF sounding humbuckers sound like EMG's, and no clipping like the 81 can!!

Cool, thanks for the tip.

[Recursion]

You should ask chris from www.ax84.com. Maybe you can find exactly what you are looking for there(If no one answers it here).

Edited January 22, 2005 by StudentGuitarBuilder

[transient]

Hi,

I've just built the Tillman preamp (and it seems to work). I've used a 10k trimpot instead of the 2.2 k resistor (R2) as suggested by Paul (diyguitarist.com). Now reading this thread, Lovekraft has suggested using that trimpot instead of R3 , not R2 . Which one's true?

And it's also suggested that the voltage at the FET drain should be 4.5 volts. I'm guessing that i should measure the voltage between the source and the drain, right? (is it AC or DC voltage?)

Thanks in advance...

...

emre

Edited March 4, 2005 by transient

[lovekraft]

Either will work. The voltage is measured between the drain and the circuit ground.

[transient]

Thanks

Should i set my multimeter to DC or AC for the measurement?

...

emre

[lovekraft]

DC, 20 volt scale is easiest. What you're doing is setting the DC operating point so the output sgnal can swing as far as possible in each direction to give the best possible headroom.

[transient]

Thanks a lot lovekraft

.

e

[cold95]

is this the same thing http://www.albertkreuzer.com/preamp.htm#descr

also where is best place for a n00b like me to learn how to read Schematic like that one on that site?

Edited March 5, 2005 by cold95

[rockthe40]

i dont mean to jack this thread, but i dont understand where to put the trim pots in that first circuit

im actually looking for a preamp to build to replace the shitty one on my brice bass, and i dont know what exactly i need. i need something with a bass and treble control (2 holes)

[lovekraft]

Cold95, check the pinned thread at the top of the electronics section for info on reading schematics.

Rockthe40, I've got an onboard two band active EQ that Phil Mailloux and I have been tweaking for bass use- here's the latest version:

I've got a board layout and a bill of materials with part #s - email or PM me if you need any more info.