MEEP super duper three mode filter effect (envelope/wah/modulation)

[letsgocoyote]

OK, so here is my modified DOD 440 clone



I don't have a schematic, but it's not needed if you know your way around effects and hear my words.


For the longest time, I never really liked wah, but I really liked envelope filters. one thing an envelope filter won't do is slowly sweep back and forth in the range.  i wanted this.  the electro harmonix worm has a modulated wah which does this.  there may also be a boss pedal ithink that does it.  i always wanted to have an effects that had both envelope and modulated filter in one box.  later on i realized i liked wah too.  i wanted this all in one.
so i built a dod 440 clone.  which was cool.  but now i took it another step.



So the basic 440 works off of a photocoupler/vactrol. Name the VTL5C4/2  vactrol. so heres the deal, the LED part has its positive and negative ends. what you can do is break the connection of the positive end of the led portion from its normal place in the circuit, apply some series resistance between it and the positive power connection, and control the filter manually.  if you go to BYOC and look up there envelope filter instructions, they now do this in their pedal.  you can toggle between envelope filter, or manual set filter with a knob.  so i decided to play with this idea.

i build a standard dod 440, and then attach the positive end of the vactrol to what will be the common lug on a rotary switch.  you will need a 1p3t switch for this, but what i actually used its a 3p2-4t rotary switch form small bear.  you take off the nut and use a little metal flange thing to set the number of throws, in this case three.  so theres going to be alot of unused lugs on this switch, but NBD. anyhow, so I attach the positive LED end to lug A of the switch. I attach lug 1 of the switch to where the postive end of the vactrol normally would go in the 440 circuit.  so this is my envelope mode on the switch.
next, i need to rig it up for expression control. i attach lug 2 of the switch to the ring or the tip (cant remember which) of a stereo jack. then the other non-ground lug (ring or tip, again, cant remember) goes to 10k resistor, i believe in order to keep some resistance in series with the LED of the vactrol so you dont blow the LED, and that 10k resistor goes to power.  Now, you can plug in an expression pedal.  I used the Moog EP-2.  worked great. i did have to turn down the adjustment knobn on the exp pedal a quarter turn to give it the right range, otherwise it would go way too treble.  you could also rig up a photocell, ala Devi Ever Peep, as a form of expression.  Or just use a 100k pot, as a manual filter set for %^&* wah tones, as used in the BYOC pedal.
last, i wanted a modulation mode.  this is accomplished with this circuit... Bill Bowdens Fading Eyes.


its some sort of LFO for making LEDs fade in and out for liek Halloween props.  and it will be perfect for controling the vactrol.  some modifications need to be made. first, to make a Rate control, the 47k resistor between Pins 2 and 7 of the 1458 IC will be replaced with a 250k pot in series witha 1.1k or 2.2k resistor.  The small resistor prevents the rate control from bottoming out and lighting the LED in the vactrol continuously.  The small resistor essentially sets the maximum speed, and the size of the pot sets the slowest speed you can get. I used 1.1k, which is so fast you can only barely here it.  The other modification that needs to be made is changing the 100 ohm resistor on the Emitter of the 2n3904 to 33k.  You could actually make this a pot set as a variable resistor, and it would control Depth... however values less than 33k will sound assymetrical in the sweep and I don't find it to sound very natural. I found 33k to have the most natural sweep range.  Admitted the rate of filter sweep is slightly assymtrical/syncopated, but not terribly so, and still sounds pleasing.  so basically, you mod this circuit for rate control, fix the emitter resistor, and then instead of those two LED's, it hooks to lug 3 on the switch, which would then connect to the positive end of the LED in the vactrol, when switch to do so.  viola!

Now, a problem I had was LFO ticking.  my wires are a huge mess in there, which could be a contributing factor, and keeping all the wiring neat and clean and doing good ground liek star groudning i suppose is going to help. but what took care of it for me, or at least 90% of it and made it usable, is putting a buffer in front of it.  this could be another pedal, like a buffered bypass pedal like a Boss.  or you can build a buffer in front of it. i built the simple JFET buffer off muzique.com and put it on a DPDT toggle in front of the MEEP circuit(s), and it kills most all the lfo ticking for me, to a satisfactory degree anyhow.  i imagine the ticking can also be a bit depending on power supply, and other pedals in the chain.

so there you have it!  now build it!

P.S. I'll be having a handful of these Vactrols, so if'n you need one...

[soggybag]

Hey that's pretty nifty. Good work.

[andrew_k]

Great write up man, thanks for taking the time to do it.

Any plan of a youtube demo for this one?

[letsgocoyote]

yes there is a youtube video

http://www.youtube.com/watch?v=OHX_9iPXwVY

[Barcode80]

yes there is a youtube video

http://www.youtube.com/watch?v=OHX_9iPXwVY

That is by far the sweetest and most versatile filter i've ever heard!!!!!

i will be mine....

also, i'm out of vactrols.... 

[foxfire]

thanks for the right up. i liked the flow of it. i just woke up and yet i was still able to follow what you were saying. it sounds darn good too. nice job, rylan

[~arph]

Very nice, what about wiring the LFO depth pot at the base of the 3904 ?

[letsgocoyote]

you could do a depth pot, i think it might sound a bit funny though, and here is why.

lets say you have a mid point in the sweep, lets call this 0.  and a potential range of +10 (treble/toe side) and -10 (bass/heelside). i think with a 33k value, im getting a fairly even sweep between about 7 to -7... maybe 6  to -6.  but ify ou adjust the emitter resistor to a smaller value, like 10k, it will sound like its sweeping from 7 to -3... you follow?  it just sounds really lopsided and not so good.  now, if you could figure out how to control the top end of the sweep too, so that it is more of a range control rather than depth, so that it would be able to expand from 3/-3  to 7/-7 or whatever, keeping the it all pretty symmetrical, that would probably sound good.

also, as i have probably noted, the rate of the LFO is kind of assymetrical, IE the time of the fall from peak to trough is not the exact same speed as the rise from trough to peak.  it still sounds good though i think, and isn't TOO assymetrical. it's almost like how a rotary speaker simulation LFO might work

[PurpleStrat]

Fantastic!

[DWBH]

Great one

[Sweetalk]

I love it!!!!!!!

[letsgocoyote]

glad you guys like it.  i hope this is a welcome addition to things people can build for fun.  i might still build some myself to sell after all, but all the same, you're welcome to build one yourself!

it's funny, it was a little over one year ago a friend and I just started building electras and bazz fusses

[~arph]

And what about hooking up the envelope detector to the speed control of the modulation lfo?  you have some spare poles on your rotary switch..

[Tuemmueh]

I drew up a schematic following your instructions, letsgocoyote.
Thanks for sharing your informations with us!

Schem: http://img.photobucket.com/albums/v673/Tuemmueh/DOD440EnvelopeFiltermod-letsgocoyot.gif
I added a little v+ -filtering to the lfo, this might help keeping the noise out of the audio path ... but I'm not sure

[Ben N]

Great project, LGC, thanks! I have thought about doing something like that with the Anderton BFF, but this looks a lot simpler and the demo sounds great. Onto the list it goes.

One other possibility for control is to be able to mix say the LFO with the envelope--I think the Boss lets you do that, IIRC. Also from the Boss, a "Manual" control lets you set a "%^&*ed wah" fixed BP. I guess all you would need would be a linear pot added to the choice of LFO/envelope/expression jack. Or just use the expression pedal.

[letsgocoyote]

thanks for making up the schematic.  i actually haven't tried the power filtering, ill do that later today on my prototype!

[joegagan]

i like this.

[slacker]

me too

[letsgocoyote]

i was also getting some switch popping pretty bad, and the jfet buffer in combination with the cap between between two resistors, the r-c tihng from AMZ.  i still get some occasional slight popping so i dont know what the deal is really.  definitely a problematic build, but worht it for the usefulness of it all

[letsgocoyote]

also, the way i built it, i bought a dod440 PCB from GGG, and then buikt the LFO on one of those single IC proto boards from radioshack