Another Zombie Chorus Build

[oldrocker]

I received the IC's I ordered and the build is finished but I only get a clean guitar signal.  The oscillation part of the circuit seems to be working because I can hear the ticking and I'm able to speed it up or slow it down with the rate knob.
I added some mods like the ring modulation switch and blend pot.  I have a separate Vb voltage set up for the oscillation and audio portions of the circuit.  The audio and BBD are sharing the original voltage divider with the 10k and 15k resistors and the oscillation has two 10k's for its voltage divider.
I've ordered the CD4046BE and I'm not sure if that is a problem so I'm going to check some data sheets on that.  (Should've done that before I ordered them.)  I ordered both the MN3007 and the NTE1641 so I figured I could use either one but I'm not sure about that so I'm using the MN3007's. 
Any advice would be great thanks.

[oldrocker]

OK.  Never mind I forgot the 9 + plus voltage for the MN3007.  I'm getting some ticking which I expected so I'll have to see if I can cut that down although I'm not super concerned about it.  It actually sounds pretty nice.  The ring modulation for that Sci-Fi B movie effect is awesome.  I'm still trying to find how to work the blend knob but I'll play with it more after I box it.  As usual nice job John H.,  Mark H., R.G and all others who contributed to this chorus stompbox effect.

[soggybag]

I have not heard of ring mod mod for the zombie chorus. Where did you find this it sounds interesting?

[oldrocker]

I got it off MunkyDIY website.  The blend pot mod is there too.
http://www.geocities.com/diygescorp/

[Mark Hammer]

ALL modulation FX that use a 2-opamp LFO (chorus, flanger, phaser, univibe, tremolo, vibrato, modulated filter) can be easily altered to produce pseudo ring-modulator effects by simply dropping the value of the integrator cap (the medium-to-largish-value one in the feedback loop of the 2nd op-amp) by about 75% or more.  This bumps the speed range upwards so that the fastest speed settings are in the audio range.  All it takes to get "robot" sounds is to have the effect modulated at a rate above 20hz or so.  Most modulation effects generally don't go faster than about 4-5hz.  If that circuit used, say, a .47uf integrator cap, dropping it to .1uf or .047uf would do the trick.

Note that this shifts the range, so if the cap value change is not too severe, you'll still be able to get many of the normal faster speeds, though the slower speeds will not be available unless you switch back to the original value.

[oldrocker]

Thanks Mark for the info on making any oscillator effect a ring modulator.  I'll have to add some ring mods to some of my other pedals. 
I made comments before about ticking coming through but it's because I was listening through headphones.  After plugging into my amp I realize that it's not bad at all.  You can't really hear any ticking even with a distortion pedal in front of it.  Here's something funny.  My Voodoo Lab sounds great in front of my Zombie Chorus. (Voodoo-Zombies, get it  )  But I'm not kidding, they really do sound awesome together.  The Zombie and the Easyvibe are my favorite builds so far.

[Mark Hammer]

My Zombie has a 3-way mode switch on it.  Two modes are stock, and the third uses a smaller value cap (330pf or so, I think) to bump the clock frequency into the range normally shared by some flangers when attempting to mimic slow Leslies.  So, just a hint of comb filtering.  Sounds nice.  Reminded me of "Badge" when I first heard it.

[David]

Mark:

You gushed about that "Badge" sound when you first discovered how to get it.  Do you still feel as pleased about the Zombie as you did at that point?  In other words, with that and the de-tick mods, is it worth building?  Or perhaps should another chorus be considered?

[Mark Hammer]

At present, I have a finished/packaged/tweaked Zombie, modded CE-2 (Tonepad Corrral), modded Small Clone (Tonepad Heladito), Washburn SC-7 Chorus (modded), Line 6 Space Chorus, Line 6 Liqui-Flange, and Line 6 Roto Machine...among others.  So, I'm in a pretty good position to compare the Zombie to other things one might otherwise be using for those sounds.  I still find it fun and pleasing to play, and although it is obviously not in the same league as the Roto Machine with respect to authentically mimicking a slow Leslie, I still find that setting on the Zombie satisfying.  Like ALL swept comb/notch filters, though, it will sound more pleasing when the signal you feed it is harmonically rich. 

Though a bkt bigger, the CE-2/Corrral is also a good build and has all ticking issues already pretty much solved.  In principle, it can be made to do every trick the Zombie can, except that the stock clock cap is 47pf, providing a bit less choice of smaller standard values for zeroing in on a delay range that mimics the flanger/chorus overlap zone.  Still, one might consider, using two 100pf caps in series the same way Hollis uses a pair of 1000pf series caps in the Zombie.

The bigger issue superceding ALL of these various analog DIY pedals is the dwindling supply of MN3007 chips for folks like us.  It won't be long before people like Steve Daniels start having as hard a time scoring them at fair prices as he is having with SAD1024 chips now.  What is needed is a brave and diligent soul to redesign (and re-layout) these various designs for a BL3207/MN3207 BBD.

[puretube]

highways and dancehalls?

(a good chip takes you far...)