Question for Mark Hammer, RoseyRay

[tungngruv]

I put this together last night, worked on the first try but I noticed a couple things. There is a slight "motorboat" type noise when on the OD side of the tone control that gets a lot more noticeable when going to the extreme distortion side. Also, the extreme setting sounds very promising but it seems that the low end is too much while there is really no highs coming through. I can easily hear a great mid scooped, distorted tone underneath this though. I did have to use two 100k pot's instead of the 250k pots (they are on order) and I only had a 150pF cap instead of the 100pF by the LED's. The overdrive side seems fine, just the high gain needs the help and the stuttering tone und the guitar sound. I really like this pedal though, I think once these two things are cleared up, it's going on the pedal board. I can hear the versatility (and the rediculous gain :lol: )even though it's not at 100%. You did a good job on this one, Mark. Any ideas? Thanks

[Mark Hammer]

Then clearly yours works like mine...unfortunately.

I don't really notice the motorboating on the "warmer" side, but it is clearly there on the "hot" side.  I wish to heck I knew what to do about it, because under it are some wonderful tones.  This thing REALLY likes wahs in front of it.  I stuck a 10uf polarized cap between the output of the notch filter and the tone control, reasoning that there was possibly some feedback/oscillation from the output of the second stage back to the input.  That didn't seem to do it, though.  Actually, I'm kind of hoping someone with more chops than you or I would take a stab at it and come to the rescue of this little beast.

As for tailoring the mid scoop, bear in mind that the notch filter is essentially like a fixed-value version of the Foxx Tone machine tone control  Dig up your FTM schematic, and you'll see that one end of the tone pot is fed by a simple small-value cap.  The other side of the tone control is fed by two series resistors with a cap between them, going to ground.  

If you increase the value of the cap that forms the "top" of the T (3300pf in the FTM, 1000pf in the RR), you let more bandwidth through starting from the mids and going downwards, decrease it and the mids get more cut out, leaving only the upper treble.

If you increase the value of the cap going to ground in the FTM control (.047uf) or the notch of the RR (0.1uf), that rolls off more upper bass, leaving only the deeper stuff.  Note that the 22k/0.1uf RC network forms a lowpass filter, which is presently set at F= 1/(2pi*R*C) = 72h.  That sounds pretty low but bear in mind it's a shallow rolloff.

If I've understood these things, though, you can also up the value of the 10k resistor after the RC network, which will keep the same rolloff but movbe the low end a bit more in the background, for a somewhat different hi/lo balance.  In any event, take a look at the stuff Jack Orman has at AMZ on BMP tone controls, notch filters, etc., to learn a little more about how changing part values in this arrangement can yield different sorts of scoops.

Double clippers are where it's at, baby.

[RDV]

Shouldn't you have a DC blocking cap between the diode to ground(or 1st) stage and the tone control? I know you tried one after the second stage notch filter, but perhaps both need one, like a largish value so you don't filter any bass away.

RDV

[tungngruv]

This is weird Mark, remember when I first posted about this circuit? I took the circuit of the RoseyRay from pins 5,6 and 7, and tacked them to my OD 250clone. The gain was huge and there was no noise. I might actually perf your second stage onto another 250 clone and see what happens. I'll keep on it (in my limited skill and knowledge).

[WGTP]

I've been dorking around with a similiar circuit and found a couple of things:

When the gain is high and there is no noise, something is haywire and it gates at lower levels.  

When the gain gets too high it starts doing wierd things like motorboating, gating etc.

Using asymmetrical clipping can make it do wierd things that symmetrical clipping does not, which may tie back to the high gain thing.

I don't know how to get past these "issues".

Using a big notch increases the noise.

Thank goodness for dual op amps.  You can run your favorite clipper into a different/or same favorite clipper on the same board.

Double clipping IS where it's at.