The Crank - Wiring/Layout Clarification

[mydementia]

Hi guys.
I built Mark Hammer's 'The Crank' a few months ago and it wasn't too impressive.  I used Paul's PCB layout (http://www.diyguitarist.com/PDF_Files/Crankster.pdf).  Since folks raved about this circuit, I thought I'd try it again.  I saw bluesdevil's thread on this subject here: http://www.diystompboxes.com/smfforum/index.php?topic=46576.0 which has a vero layout and detailed wiring for the dual ganger.  Here's what I did:

Note that I updated the 0.1uF cap in the diode feedback loop to 0.001uF per the schematic (http://aronnelson.com/gallery/Martys-layouts-and-photos/TheCrank).  I also made a trace cut between the 22k resistor and the 0.001uF cap per the bluesdevil thread and the schematic.  I wired the output to a 10kA pot for level control. 

I get a nice, highly overdriven tone - but the Drive control (10kB Dual) does NOTHING.  Did I misinterpret something here? 

Thanks for looking.
Mike

PS> Paul - if you have a problem with my use of your artwork, I'll take this down immediately... it's my intention to allow folks to use your work with minimal modification and build a successful circuit.

[Mark Hammer]

Ideally, you should be getting a fairly wide range of gain adjustment, and only a bit of hair (stubble, actually) on your signal at max, unless you're feeding it with something that is already hot.  A maximum gain of x42 is generally not enough to get serious sizzle out of a 1+1 diode pair, let alone a 2+2 pair as used here.

So something is wrong.  What is NOT wrong is your wiring of the pot.  It is wired up correctly, such that the "red" half goes lower in resistance as you rotate clockwise, and the "white" half goes higher in resistance in the same direction.

I have no idea from the information provided, though, what might be the problem.

[mydementia]

Maybe I was expecting something else... I've since reconnected the trace cut and pulled the 'other end' of the 22k resistor to the output trace - now I get zero grit (as you described) but the drive control does vary the boost level (as far as I can tell on my test amp...).  All I'm getting is clean boost...which, after re-reading your description, is exactly what this was supposed to provide!  Geez... I'd better try this circuit on my main amp and see what it does!!

Thanks for the quick reply Mark.
Mike

[Mark Hammer]

It's not ALL clean, just mostly clean.  The intent is to be able to drive an amp harder with a clean signal if you want it, or to drive the amp with the same intensity using a slightly colored tone.  At max it trims off a bit of treble at the same time as you get a touch of "stubble".  There is also a wee bit of bass loss, though not enough to really notice.  In principal, if you dropped that .47uf cap in the first stage down to .22uf, you would, in theory anyways, produce a rolloff starting around 153hz in the first stage at max gain.  That would tend to make the lowest notes from the wound strings push the second clipping stage not quite so hard, yielding a more consistent degree of clipping (as mild as it is) across the entire fretboard.

[Cliff Schecht]

Mark, I recently built a Crank for myself on perf and I must say, I @#$%ing love it! It doesn't distort at all, but it does color the tone in a very nice way. I bullshitted the dual pot (100k with 10k in parallel) and get about 9k at max, but I just wanted a loud, full sounding clean boost anyways. I keep the pedal on at all times, I've found that even pushing the Crank with high output pickups (EMG's, Bill Lawrence X500XL w/ about 7dB of gain from a preamp) produces no distortion, but it gives an great sounding fullness to any pickup. I love it and have already found it a permanent fixture to my pedalboard.