This Week on the Breadboard: The 'lectric Mama Flanger

fig said:
Thanks, that answers a lot of questions (I think). If the charge pump is the source, wouldn't all circuits utilizing similar charge pumps, BBDs and clock chips exhibit similar results?
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I would have thought so, but I just tried a ModTone Space Flanger and a Moen Chorus after the Crunch Captain Deluxe and the modded Chela. No squeal. One possibility is that neither one sweeps the clock freq low enough. The Space Flanger may have more filtering, I'll have to open it up and see.
 
Chuck D. Bones said:
The 3-day course I attended was a subset of that material. Part-way into the first day, I turned to the engineer sitting next to me and said "You know, I was already doing some of this stuff and I just chalked it up to laziness." He said "Yeah, me too." It felt good to have our "lazy" techniques validated.

I'm going to download all of this stuff, thanks!
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Late to this party, but what were the “lazy” techniques?
 
We would think of components in terms of their impedance or admittance, whatever made the equations simpler. We would express impedance and admittance as the Lapace transform. For instance, a capacitor's impedance is 1/sC. ("s" is the complex frequency, expressed in radians per second). We would express parallel components are their equivalent admittance and create a substitute variable to use in the equations. Example, the admittance of a cap and res in parallel is X1 = 1/R+sC. It's a lot easier and cleaner to write X1 instead of 1/R+sC. Lastly, we would arrange the equations so that each term had a clear physical meaning. This term represents the DC offset, that term represents the AC gain, that sort of thing. The whole idea was to turn a complicated calculus problem into a simple algebra problem. We didn't invent the technique, we just exploited it to make our jobs easier.
 
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Ooooo wait a minute Chuck! We could feed mayonnaise to the tuna. This is big!

That's not what I was going to suggest....hang on......ahhh there it is...

Could the ESR of the caps in the circuit play a role in poor DC filtration of the charge pump's incessant swine wave?

Forgive any ignorance that may be involved with that thar question.
 
It's possible, but I use good caps for the charge pump. No cap is perfect, so there is always going to be ripple on the 9V coming in and on the -9V, +18V, or whatever voltage we make.
 
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I should change the title of this thread to "This Month on the Breadboard." I think I'm about done polishing this turd. It's come a long way from the minimalist Electric Mistress based design to where it is now. The EM is a good design and it sounds great, but it's susceptible to 40KHz noise from the charge pumps in other pedals. I've done what I can to filter out the charge pump noise, and it's pretty effective, but if you listen real hard you can still hear it when the clock sweeps down to the bottom-end of its range. Some pedals are noisier than others.

Presenting version 3.5.2. As I state in the notes, L1 is optional. It helps reject charge pump noise, but if you don't have a 750uH choke (Tayda sells an 820uH, that's plenty close), just use a jumper there. I changed BLEND to C-taper. B-taper works, but most of the useful range is up near the top. Just about any JFET will work for Q1, you want something with Vp below 2V and Idss above 2mA. You could even use a MOSFET. Voltages marked are for reference only. Gain is unity. The active filters before and after the BBD are 3rd-order 8KHz low pass. This circuit has the usual pre-emphasis (C4-R6) and de-emphasis (R13-C8) to reduce BBD noise.

'lectric Mama v3.5.2 page 1.png
'lectric Mama v3.5.2 page 2.png
 
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Got my BBDs today in the GPCB sale.
I'm ready.

IMG-1134.jpg
 
Can’t believe I missed this thread for months somehow. Would I be correct in assuming that with minimal tweaks this could be adapted to accept the big-boy Tap-LFO chip for additional control over waveshapes via the distort input of the chip, as well as tap-tempo subdivisions, and an additional bank of 8 waveforms?
 
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Chuck D. Bones said:
Yup.
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Awesome looking circuit! When applying this modulation section to another flanger, would the voltage supplied to pin 5 of the BBD need to be 9v as it is in yours? I've seen other flangers where the BBDs are being fed 5v at pin 5 i.e the ibanez FL5
 
The 3207D will run on 5V or 9V. Higher voltage = more headroom. The BBD & clock driver have to be powered by the same voltage. When I used the 4KNOBFLANGE chip to provide the clock, I had to run the 3207D on 5V because the 4KNOBFLANGE runs on 5V.
 
UPDATE: I added C17 from Vgg to GND in accordance with the V3207D datasheet. Schematic has been updated (no change to page 2 except for title block).

I believe I'm done. Spent some time yesterday reacquainting myself with Bill's Law. If all you want is a triangle wave from the LFO, then the WAVEFORM pot could be replaced with two resistors or a trimpot.

'lectric Mama v3.6.2 page 1.png

'lectric Mama v3.6.2 page 2.png


All resistors are 1% metal film.
All capacitors less than 1nF are silver mica.
All capacitors from 1nF to 1uF are film.
C17 is tantalum.
All other electrolytic capacitors are aluminum.
 
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