Can someone help me figgure this out?

[Quackzed]

BTW I raise my glass to ya Zurp!!
    right on for building the dam thing! I shoulda known the thing would thump, so sorry bout that. I think it's just the way it is with new designs and ideas , there are always speed bumps  but as long as your willing to try and learn from 'em they're the most valuable part. i dunno maybee i'm foolish, but i think you always learn something when things don't do what you expect because you're forced to fix them, and thats how you REALLY understand how things work. why is it doing that? what and where is the issue coming from? what can i change to remedy it? or is it a hidden perk? etc... but i digress... Good Man, you wanted to try something out and you put it out into the big world, took all criticism on the chin and in good spirit! and most valuable of all you got to work BUILDING IT!!!   

[zurpman]

Hey,

Thanks for the vote of confidence Quackzed, the whole thing is just a learning experience for me and I really don't mind criticism. I just got the parts in today for the new build and I did it! But, I couldn't figure out how to get part of it to work, so I built it without adding any of the 1 m ohm resistors, or the VR that they connected to.  I did try it the way I understood it from your schematic, but it didn't work. However, while testing I did get a really good money for nothing sound while one of my 9V batteries were dying on me. I couldn't duplicate that though... but it does make me wonder if I can do a dying battery mod......

SO the build i did was the basic build as if I were using the new chip to replace the 555 timer. I got a couple of sound clips so you could hear what it sounds like, the thump is much better and the speed variance is perfect for what I had in mind. Below are two sound files one is just the thump and open noise without me playing. The other is me playing guitar as my brother randomly adjusted the speed.


Empty sound
https://soundcloud.com/user-237422247/empty-sound

Distorted guitar
https://soundcloud.com/user-237422247/distorted-gtr


Now as to the part of the circuit I left out... I need a little help there.
From my understanding of the schematic I connected the output terminal of all three resistors leading from the 4066 IC to a 1 mohm resistor, the resistor also connected to a 0.1 capacitor, and with the other lead of the capacitor going to a second 1mohm resistor. The first 1 Mohm resistor I had going to VR*. The second going right to ground.

Pins 2,4, and 9 of the 4066 connected to a third 1 Mohm resistor which again had one end going to a 0.1 capacitor, and the other going to VR*. The other lead of the capacitor went to a fourth 1 Mohm resistor, which lead to ground just like the second 1 Ohm resistor did.

Now VR* may be where I am confused. From the schematic I take it that the components on the far right are "vr*". So to me VR* was a 22k resistor going from +9v leading to the positive side of a 10 mf capacitor and a lead of a second 22k resistor with the second lead of the second 22k resistor joining the 10 mf capacitor at ground.

The spot where that capacitor, and both resistors connect I jumped to 1 Mohm resistors #1 and #3.  And of course 1 Mohm resistor numbers 2, and 4 had jumper wires going to my pedal where I want to switch out resistors.

I got no noise at all with this, and tested resistance across the circuit with power going to it to see if there was a variance in resistance. It stayed at 2 Mohms.

Did I wire it as intended, or did I make a mistake in how I wired in the VR*... I'm still new with reading schematics and catching on as we go along.

Thanks again for any help you can give!

[Quackzed]

all those extra resistors are there to force the switches to be at half the supply voltage, or VR for short. the vr section is basically one 22k resistor to +9v and the other to ground and so the point where they meet is 4.5v (VR*). so using a 1m resistor connected to that 4.5v spot makes each side of the 4066's switches stay at 4.5v so when they switch theres no big change in voltage all of a sudden,this keeps the 4066 switches at 4.5v , keeps em happy and reasonably pop free... usually. the caps are there to keep the switching voltage (4.5v) separate from the circuit's replacement resistor. and the 1m's to ground are there to keep the circuit side un-referenced to 4.5v or rather referenced to ground which is where i'm ASSuming the circuit you're resistor switching is referenced to... it may not be.

so it might be that the caps and 1m's to ground are screwing up the circuit you're using by referencing the replacement resistor spot to ground. try it without the 2 caps and the 2 1m resistors that go to ground... and just connect the 'replacement resistor' wires to the tops of the 1m resistors that go to vr*, one wire to each...
       actually you could just leave that stuff alone but swap the 'replacement resistor' wires to the other sides of those caps. (the wire going to one cap to the OTHER side of that cap, same for the other wire and its cap.  that MAY work but it'd be easier to know if you could post or link to the circuit your using this for, and what resistor your replacing with this switching resistor thing...
but i think the caps and grounded 1ms may be mucking up how the switched resistor works in your 'replacement resistor' circuit...

it still sound cool as hell tho  with all the distortion on the second clip the pops arent that noticable till it gets fast then they're kinda noticable due to their fast repetitiveness. crazy! still it'd be nice to get rid of that dang popping. i'm no expert just figured i'd give it a shot but it's hard to say what the problem could be without the circuit its connected to. still it sounds pretty cool, you could probably use a rotary switch to add more steps, say 2 3 4 5 6 or 7 steps... but lets leave that for now and try to dump the thump first. 

[zurpman]

Thanks,

This is a danelectro fabtone, I got it when they were first released. Below is the image and I am replacing R10 in that circuit. I am replacing that resistor because in the Wampler pedal book it lists R10 as an optional place to increase gain. I will test it tonight and do some more troubleshooting with it. I will also try the suggestions in your most recent post. I will let you know if I have any results one way or the other.


Thanks again!

[zurpman]

Hey I tried your recent suggestion and here are my results.

First I'm going to continue to refer to the two 1m resistors that lead from my switching resistors as 1 and 2 and the ones leading from the other leads of the chip as 3, and 4.

I tried the schematic as is again to make sure I didn't miss a lead on the breadboard and I got a constant hum with no guitar signal at all. When I turned the speed to max I could hear a faint thump in the hum only audible at the fastest speed.

I then tried moving the leads that will plug into where my switched resistor will be over to the point where the 0.1 capacitors connected to the 1 m resistors 1, and 3. I was actually in this configuration for the sound file I posted earlier.

Lastly I tried having my leads for my switched resistor going from the side of the capacitors that would connect to resistors 2, and 4. But, I removed resistors 2, and 4 from the circuit. That gave me a very synthetic sound that didn't sustain at all.  When I struck a chord hard there was a strong synth sound that instantly died out to silence. 

What's interesting about the last result is early on in testing I tried connecting a 470k resistor in the pedals circuit where the switched resistors will connect. I got the exact same synth sound... or very near it. Turns out that an eyelet was broken lose from the circuit board, which I have since fixed.  I did double check the eyelet to make sure that wasn't going on again and it isn't.

I also went back to configuration #2 and was able to play without the synth sound. Tomorrow I will get back to it and try a few other things.

Any other ideas on this?

Thanks!

[Vinnie500]

Great Idea I would love a pedal that did this

[Quackzed]

ok, try these changes, got rid of the dc blocking caps and ground reference 1m resistors because you reported that was the setup that was working for your use.  this is 'basically' the same as your demo setup but instead of the single 1m resistor to VR  from where the three switching resistors meet,  each switching resistor now has its own 1m resistor to VR (your #1 resistor is now removed and replaced by the 3 1m's in the pic). this should at the very least minimize the popping a bit, hopefully noticeably so... one other idea i had, that MIGHT help is to add another smaller cap (maybee a .01uf or something close even a 1uf ) in parallel with the 10uf cap on the far right, the one in the VR 22k/22k section.  but try this version and see if it reduces the popping first...  that way you know what change had the biggest effect on minimizing the popping... then you can always try the added smaller cap idea...