The Crank - layout Incorrect? **UPDATE**

[bluesdevil]

Wanted to take a stab at Mark Hammer's "The Crank" and found a nice layout w/pcb for it. I noticed a few mistakes in the layout. When I did a search on the forum, I found noted in another thread one of the pots on the dual 10K was wired wrong, but there seems to be something wrong elsewhere as well. The 22k resistor that's in the second stage feedback loop should have one end just connected directly to lug 1 of the second pot of the dual 10k, not both leads attached  to both sides of the loop.
   I would really love to use the layout, but I was hoping somebody could double check to see if I'm not mistaken about the 22K resistor thing.

schematic:
http://aronnelson.com/gallery/Martys-layouts-and-photos/TheCrank


layout:
http://www.diyguitarist.com/PDF_Files/Crankster.pdf

Thank you

***********UPDATE**********
Since posting I found another mistake:
Should be a .001uf cap in the second stage loop, not the .1uf shown.
Will attemt to build it up today with a dual 100k pot with parallel resistors.

[bluesdevil]

I made the corrections and even fired up with my rigged dual pot!!! It distorts with the active humbucker in the bridge position of my guitar, but does boost the passive humbucker on the neck very nicely.  The drive control seems to fatten up the sound as you turn it clockwise, not really adding noticeable grit or clipping to my ears..... maybe very subtle.
     Pretty useless with active pickups, because you need to turn the guitar's volume down so low to get rid of the distortion that it's no louder than in bypass, but I can see this being really great for weaker humbuckers and single coils.
      Since I have a weird, uneven pickup combo in my guitar it'll be useful to kick on when I switch to the neck pickup going straight into the amp without any other effects in the chain.
     I found a vero stripboard layout with a tone control, might be easier to build from:
http://www.diystompboxes.com/smfforum/index.php?topic=44095.0

[Mark Hammer]

Thanks for the report!  I find it ironic because my first Tube Screamer build was tried out on a guitar with a built in preamp, and I just hated the pedal because I could get absolutely NO subtlety out of it.  When I switched to a guitar with normal pickup output levels, I quickly learned what people saw in the TS.  Looks like you had the same experience, only with a different pedal.

There is nothing that is intended to "fatten up" the sound at higher gains, however like the Tube Screamer the second stage rolls off more high end as gain is increased.  The rolloff is gentle, though, and compensates for the additional harmonic content introduced by clipping.  The real goal of the pedal is not to produce distortion of its own accord, but rather to push an amp's input stage harder, and do so with a signal modified to make the amp's distortion sound a little nicer and come forth a little more easily.

I found that a small value resistor in series with the diodes in the 2nd stage helps to soften the clipping a bit.  I used 330R on mine, but it might be reasonable to adapt yours by sticking resistors in series in both stages.  Try 220R or so in the first stage, and 470R-1k in the second.  That should, in principle, get you the gain with less distortion at the same gain settings.  Let us know if that works out.  I'm sure you aren't the only player with an active pickup who finds themselves hamstrung when it comes to being able to get softer distortion.

[boogietube]

As some of you have read in another post, I borrowed The Crank from Mark Hammer recently.
In my passive humbucker Hamer, this pedal provided a smooth harmonically rich ovedrive suitable for doing semi-distorted things.
Through my strat and through Mark's Tele it produced less of this fattening characteristic but stll the wonderful
low gain harmonically rich mild distortion that I was after.
It honestly did seem to "fatten up" my tone when ab'd with the clean channel on my amp at unity gain.
This I like!
There may be some differences between what I have and what you guys built.
Mark was kind enough to give me this link as reference.

http://hammer.ampage.org/files/The_Crank.gif

Maybe you could compare this with the pcb layout and note any discrepencies.
I'm going to have to give this pedal back soon and I MUST build one.
Sean

[boogietube]

Oops I gave you a link to the same schemo!!

[spudulike]

That was my layout ...

[bluesdevil]

Thanks for the tip, Mark. I soldered in the 1k and 220 ohm resistors as you specified and helped a bit, but still getting too much distortion on the bridge pickup than I think I should. I'm still really liking how it's sounding on the neck pickup, so I'm afraid to go higher on the resistor values.
      Does raising the values on those resistors lower the overall volume of the circuit or just the clipping threshold of the diodes?  Sorry if that doesn't make sense.... I'm not very technically advanced.

[Mark Hammer]

The gain is set by the resistance between input and output (fixed in stage 1, variable in stage 2) and the resistance to ground from the '-' pin (variable in stage 1, fixed in stage 2).  The series resistors I suggested soften the clipping action of the diodes but do not affect the gain per se.  What you might try is using a pair of red LEDs instead of the 2+2 diode combo in the second stage. That will not change the gain, but will raise the clipping threshold by about 50% in the 2nd stage.  Since the circuit does not clip that hard (or try to), you will notice a wee bit of level increase by virtue of lifting the clipping threshold, but not nearly as much as you'd notice on a true distortion pedal where the signal is banging its head against the diodes 98% of the time.  In that situation, changing from Ge to Si, or from 1+1 to 2+2 or Si to LED, etc., will produce a much more noticeable change in overall level.

I won't profess to this being the sort of circuit that demands orthodox adherence to component values, but it IS based on a set of expectations about input signal.  It may be possible to change some values in this circuit that would be well-suited to an active guitar such as yours.  On the other hand, it might end up turning the circuit into something different.  I suppose the other angle to consider is that if your guitar is hot enough to drive THIS into distortion, then it's not like you really need a booster to overdrive the amp, is it?  We can try and make this meet you halfway, but be prepared for it to be something that is only useful for fully passive instruments.

[bluesdevil]

Thanks for the explanation of the resistors in the loops, I really appreciate your time and efforts helping us all understand why and how these things actually work.... it's all sinking in and I'm getting the hang of it.
       I think I'm just going to save this circuit in case I get a guitar with all passive pickups one day or just kick it on when I switch to my neck pickup, because it really helps even it out volume wise when playing clean without other effects.
       The reason I have mixed passive/active pickups is at the time 17 years ago when I installed the EMG I never used the neck position anyway and wanted to save the money. Now for the last 2 years I've been using the hell out of the neck position pickup from using fuzzes/octaves/whatevers that I've been building here...... very ironic that I may be switching to all passive to suit my building obsession!!

Here's a pic of the offending instrument:

[$uperpuma]

that instrument doesn't offend me at all...

[bluesdevil]

that instrument doesn't offend me at all...

I think the guitar just offends pedals and insults the ears of the people I play to, haha!!!