Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Preamps and Effects => Topic started by: PhredE on May 28, 2015, 10:51:15 PM

Title: DIY Boost / Preamp pedal The Piledriver
Post by: PhredE on May 28, 2015, 10:51:15 PM
Hi guys,

Hey, I suspect the issue of The Piledriver DIY pedal has come up before, but I found no reference to it (and searched, to no avail).  Anyway, I thought I might throw this out to more experienced and technically adept (eg. everyone but me!).

I built the Piledriver boost pedal several months ago. It works pretty well and as claimed.  It appears to be simple design based on the BS170 MosFET.

To be sure, I do like it and it works fine.  Heck, I built it and it works -- my first DIY pedal -- so, I guess I should be happy with it and leave it at that.
But.. As designed, it sounds fairly good -- considering the simplicity of it.  It has good gain overall with some clipping/breakup when the pot is dialed up around max.   However, the one thing it really leaves lacking is any ability to tweak the 'tone'. Is there a component(s) that can be swapped or a location where I can 'insert' a pot to give basic ability to tweak treble/mid/bass ?  If so, this thing would be about 4x more useful to me.

Here is the schematic (openly posted in public from distributor's site, so I don't believe there is any problem including a link here -- to the best of my knowledge):

Anyway, thanks in advance. I'll happily listen to all your comments and suggestions.
Title: Re: DIY Boost / Preamp pedal The Piledriver
Post by: phatt on May 29, 2015, 04:21:42 AM
Hi PhredE,

All you can do with these circuits is wipe a bit of bass off at the input (i.e. make C1 smaller, try .1uF ~ .05uF, instead of 1uF)

Then maybe a treble cut,  a cap from gate to ground might help. Play around with values like 250pF up to 1,000pF. suck it and tweak till you hear a flavor you like.

Reality is ,,, you will likely want more control than those mods which means you need a proper tone circuit but that is a lot more work. So there is no free lunch.
Title: Re: DIY Boost / Preamp pedal The Piledriver
Post by: PhredE on May 29, 2015, 10:51:25 AM

Thanks.  That's about what I suspected I was up against. I will work through  those suggestions as a starting point -- hopefully over the weekend. I'll post back here to give some feedback for anyone lurking that might be interested..

Thanks again!
Title: Re: DIY Boost / Preamp pedal The Piledriver
Post by: robdean on June 08, 2015, 03:22:28 AM
What I found educational when I needed to add EQ to something was to build this simple add-on circuit: (

It has only a single tone control, but it can be scooped (well, there is a mid-scoop by default) and offers active boost to treble and bass as well as cut (albeit not independent of each other: boosting treble is coupled to cutting bass and vice versa).

Here's the best bit: this free software simulates the circuit (amongst others) so you can see what effect changing component values will have: (

I guess you could even add switches to 're-voice' the EQ with different component values. I found it a great intro to active EQ, and built it with an 'unscooped' response for use in an active acoustic guitar circuit, where due to careful choice of component values it does pretty much exactly what I needed.

Of course there are more sophisticated tone-stacks, but I found this an ideal first step...
Title: Re: DIY Boost / Preamp pedal The Piledriver
Post by: PhredE on June 08, 2015, 09:36:44 PM
Hi robdean,

Hey, thanks! I will give that a look.