The Crank by Mark Hammer

[aquataur]

An intermediate report.
The DOD250 / MXR D+ does not work for this application.

I stuffed it according to what is known as the "grey specs", but made the diode stack switchable. 2x2 silicon diodes, 2x1 red led, 2x1 silicon diode with series resistor, 2x1 germanium diode. All sound useful, GE very special (at least for heavy overdrive). I also tried a slew rate limited OPA, the OP07.

It is a eminently useful little box, but impossible as last instance before a clean amp. Waaay too many trebly artifacts. This is made to give e a dull amp the third degree. Heavy HF filtering betters, but affects the clean tone negatively. Compression is either too low or quickly too distorted. Verdict: not useable as tone-shaper.

Next stop: The Crank.

[Mark Hammer]

Just as a last ditch suggestion, stick a back-to-back pair of red LEDs in the feedback loop of the op-amp,and replace the pair of germanium diodes with a pair of silicon diodes (1N914 or similar) with a 1k-2k2 resistor between the diodes and ground.  Finally, scrap the .001uf cap in parallel with the diodes for something a little more effective at screening out the fizz, like 3900-4700pf.

[aquataur]

Hooray, the Server is alive again!

Funny, this is exactly what I did!
It sounds quite useful that way.

Back to The Crank...

Per se quite pleasant, but not for the purpose I envisioned. Although distortion is increasing, it hardly does anything to compress the preceeding fuzz, and it adds too much of its sonic
Signature. I used individual opa's because I wanted one that has a low slew rate like the Op07
in order to tame fast transients. But no, it does not much to tame a fuzz.

[Mark Hammer]

It doesn't really "compress" like a compressor would, because the diodes only limit peaks, and do nothing to raise the gain during quiet parts the way a purposely-designed compressor would do.  Many people describe the Ibanez Tube Screamer as having a "compressed" sound, and that's sort of the way I was using the term here.

But, that said, the circuit does what it does, and it works for some things but not everything.

I've never used it after another distorting device, only before, or feeding an amp directly.

[aquataur]

As I said, this way it works perfectly. Into the amp however you are at the mercy of a darkish amp to filter out the fizz it introduces by itself.
What I use the last instance before the amp is technically closer to a brick wall limiter, albeit distorting. Then it is just a matter of how benign it does this.

[Mark Hammer]

Fizz can be easily filtered out at the pedal.  The Crank provides enough increase in signal level that a passive treble cut between the output of the 2nd gain stage and volume control can be used to tame fizz.  That treble cut could be in the form of a variable control, like the SWTC, or a fixed filter.  The .001uf cap in the feedback loop of gain stage 2 provides for a 6db/oct treble cut just under 5khz at max gain.  That's often enough for many, but if it's not sufficient for a bright amp/speaker, try this:

Put two 1k resistor in series between the 10uf output cap and the volume pot, with a .039uf cap to ground after each 1k resistor.  That will provide a 2-pole (12db/oct) fixed cut at just over 4khz.  Because we're using 1k resistors, there won't be much passive signal loss.  As a fixed filter, its effect will be in place at all gain settings, whereas the feedback cap in stage 2 provides increasing treble cut as gain is increased.  A 2-pole filter also provides for a more defined and obvious treble cut, because of its sharper slope.  If you need more treble cut, you can bump the cap values up to .047uf, OR you can leave the caps as is and increase the resistor values to 1k2 or even 1k5, although that will reduce the maximum output level.

[amptramp]

BTW since this ia about a project from Mark Hammer, I have found a couple of parts sources I didn't know about in the Province of Ontario:

http://nettyelectronics.com/

Netty is in North Bay ON

https://fletcherelectronics.com/

Fletcher is in Elliot Lake ON

Many of their products are for amateur radio but a number of items like guitar lever switches appear to cater to the stompbox crowd.  I found out about them through a post in a site about FM radio.  They ship anywhere and seem to carry a varied bunch of parts.

[Mark Hammer]

Are you in Northern Ontario?  If so, I could simply mail you a populated board to tinker with.  That should ease some of the pain from the upcoming provincial election.

[soggybag]

I have spare some pcbs I'll mail. They have an error where the pots are wired backwards. Message me and I'll throw then in an envelope. I have about 10 so I can easily spare some.

[amptramp]

Are you in Northern Ontario?  If so, I could simply mail you a populated board to tinker with.  That should ease some of the pain from the upcoming provincial election.

I'm in Mississauga, about two km west of Toronto.  Pain?  What pain?  I just have to go somewhere and put an "X" on a piece of paper.

[Mark Hammer]

Voting is never a pain, being exactly as you described.  It's always the weeks of relentless TV, newspaper, and radio ads, and the constant calls from polling firms.

Thanks for volunteering, soggybag.  You're saving me one more task on the list.

[soggybag]

Mark and Ron, message me your address and I'll put some board in the mail today. I have some international stamps, it'll go USPS, so it might take a couple days to reach your latitude.

I'll post some docs later. You can check my work. I know I reversed the pots.

[Mark Hammer]

Kind of you to offer, but I have several stuffed boards in a bag already.  So, I'm good, thanks.

[PRR]

.....go somewhere and put an "X" on a piece of paper.

Way ahead of you. Voted a week ago. Town office, say "Absentee, we'll vote here" (saves a stamp and a lot of paperwork). But we had a voting irregularity.

Get seated in the meeting room (nice chairs our council-critters{*} voted themselves!), the town clerk dealt pencils, ballots, envelopes, and because she does not want our tongue-germs, one of those stamp-licker bottles to seal the envelopes. We "licked" our envelopes, they popped right open. She must have grabbed a dry bottle. OMG, will the clerk see our votes? Do I care?

{*} This being New England, the council is "Selectmen". Even if both candidates are female. When "Selectwomen" is mooted, they say "that's stupid". Same with fishing: Linda Greenlaw is a fisherman. (And yes, fined for poaching Canadian waters.)

https://youtu.be/Yk4CziNHxpQ?t=27

[Mark Hammer]

Many things get called "brilliant", but that outshines them all.  Rube Goldberg lives!!