Craig Anderton Dual Filter Voicing Unit

[MAO]

Update 12/11/2016 - If planning on building this with clipping options, I suggest using the 2nd layout. Though that one is not yet verified.

Project 10 from Electronic Projects for Musicians

"Combines a preamp, two variable bandpass filters, and a three-input mixer in one unit for flexible tone-shaping capabilities"

A mini pedalboard of sorts - a preamp that feeds 2 separately tuned filters which feed a 3-way mixer allowing blending either or both filters along with desired amount of the straight sound.

The filters resemble a cocked wah pedal, with the lower tuned filter resonating along the lower end of the fret board and the higher tuned filter resonating along the higher end of the fret board.

It's like having two differently tuned wah pedals fixed in different positions along with your straight sound all blended in parallel.  

I built this a few months ago with the intention of combining with Project 25 to create a dual auto-wah. Unfortunately I wasn't able to get the auto-wah sounding quite right. I was only able to get a mild warble which did sound ok, but not worth the extra real estate and vactrol expense.  The STC (Project 17) as an auto-wah is much better. Might be why this particular combination wasn't mentioned in the book...

Then, just a couple days ago I discovered this video , although not the dual auto-wah I was going for, it sounded promising. Then found this build doc from GuitarPCB.com. (There is a PCB available fairly cheap too)  

I hacked into my layout a bit and added a clipping daughterboard similar to what was done in the video & build doc. I was skeptical at first, but now think it's box worthy.  

The sum is greater than the parts for sure with this pedal. Listening to any one filter alone or just the straight sound didn't do much for me, but blending them together and finding the sweat spots, with and without the added clipping, sounds fantastic.

The clipping switches are all SPDT on/off/on. The main clipping switch selects one of two clipping diode pairs. I used 1n4148 for one pair and LEDs for the other. The filter clipping switches place it's own pair of diodes before or after its filter. For now I'm using LEDS for both filter clipping options. The center position on the switches bypass the clipping.

If adding the clipping daughterboard, I would suggest lowering the 22k resistor on the main pcb. This will allow for more distortion through the main clipping pair.

The only other changes I made to the original circuit, other than tweaks suggested in the book, was using Reverse Log pots for the 2 Frequency controls rather than Linear Pots as most of the action happens between 0 and 5k. I also increased the 33R as the Frequency pots would ground out the filtered sound when full on. Oh, and the use of a charge pump to supply the +9v/-9v and a TL074.

I may redraw the layout based on this build doc. ...with the clipping options on the main board.

Let me know if there is any interest.  

Verified by me
 




 


 



   

[Hozy31]

Great job, might give this a go. What is Z1? A Zener of some kind.

[MAO]

Yes , sorry. Zener is protection for charge pump. Anything between 9.1v and 12v will work with the 7660SCPA.  Must be a 9.1 if using a MAX1044CPA.

I did start another layout with the clipping diodes on board and the cap values per the linked build doc. Board size is 22x20.

Should have it posted later today once I look it over again.

[MAO]

DVF v3

Changes to the DVF v3:
Powered with onboard charge pump for more headroom.
Additional Gain clipping pair option. Use different diode types for each pair.  

Not yet verified, but looks ok to build

[mercury6]

have u ever used the ca bi-follower filter. its not in either of the craig Anderton books I have but it is on hammer.org.  but only a schematic. and I believe one sound sample. hammer claims that its a lot better than the bassballs. I believe its opto controlled unlike the bassballs. think it has 4 optos

[MAO]

I seem to think I have a layout for that one too.

It would be strange if i didnt post it so maybe not.

I'll check it out when i get home.

[MAO]

So I did draw up a couple layouts for the CA BFF, one stock version in 2016, and a couple with Mark Hammer suggested mods in 2018.

Not sure why I didn't post any of them.

When I get a chance, I will look them over again and post them if they look accurate.