Tone stack question

[notneb]

  Still experimenting with the DOD 250 as in http://beavisaudio.com/bboard/projects/bbp_DOD250Overdrive_Rev_1_1.pdf Sounds great. Added a 100K pot and 2.2nf cap for a tone control. Here's the thing: I connected it parallel to the clipping diodes (cause that's where it fit) between the diodes and C6 (to ground, y'know, like all the schematics say yer supposed to) and it has no effect what so ever. I connected it in series between the diodes and C6 and I get a sweet little tone control that does exactly what I was hoping; shaves off a little top end stays fat on the bottom. 'SUP?  I lose a bit of volume, but there's plenty to play with.

ALSO, when I first put it together, I liked the sound of LEDs best (though is was STUPID loud). I redrew the schematic in Eagle, cuase I need to learn Eagle, and after I put it back together a few weeks later, I couldn't get the same smothness with the LEDs installed. The string attack was really jagged sounding, like the speaker was just getting bashed. It smothed out as the signal faded but the attack sucked. Switched back to 4148's and it sounds good but less bite than the LEDs. Any ideas?

[teemuk]

y'know, like all the schematics say yer supposed to

No. "All The Schematics" do not really advice this.

Perfect example why not to "copy&paste" circuits:

When you fitted the tone control in "shunt", that is parallel to clipping diodes, it didn't work properly because of overall impedance mismatch to surrounding circuitry.

Think about it, you have a 2.2nF shunt cap with a series resistance of 100 kilo-ohms. In parallel to it is another shunt cap, 1 nF, without any series resistance. Now, which do you think shunts higher frequencies to ground most effectively, your 2.2nF cap with huge series resistance or another capacitance in pretty much the same ballpark without any series resistance?

I wager you tone control did actually somewhat work but had a very limited range because the 1nF cap was already bypassing most of those frequencies you wanted to control to ground. Now, if you would have removed that 1nF parallel cap....

I connected it in series between the diodes and C6 and I get a sweet little tone control that does exactly what I was hoping; shaves off a little top end stays fat on the bottom. 'SUP?

Considering overall impedances this scheme made a whole lot more sense. You now formed a RC circuit with the 100K pot and the 1nF shunt cap. And another RC circuit with the 2.2nF coupling cap and the 100K pot working as a series resistance to it. Now such scheme can actually work in this particular circuit.

[notneb]

  So obnoxious, asking questions I should already know the answer to. I recently finished my first year of electronics school, at home study. I had to put it on hold because of my job, I work 11 to 14 hours a day and it's just to much right now. AND... because I'm not good at memorizing things if I'm not using it for something. I feel like I've been dumping info in my head and it's all spaghetti. I got into building pedals and I'm now having to apply it... which is great, but frustrating. This msg board has been a Godsend. You guys have been such a huge help in remember stuff I've already learned. I've had a bunch of DUH moments on here already and I expect to have a bunch more. Hope you guys don't get tired of my stupid questions. Maybe one day I'll be on the other side of the eye roll.

[notneb]

Thanx, teemuk. Perfect explanation. You're a great teacher.