How many inverters from a 40xx can you use...?

[earthtonesaudio]

Hi all,

I have a bunch of 4069 chips that I want to put into effects, but all I really know about this type of chip is what I've been able to glean from the datasheet, Tim Escobedo's designs, and runoffgroove.com. 

My big question is, can the inverters from a single chip be used simultaneously for different purposes?  For example, could you make a stereo boost using one inverter for Right and one for Left?  That would be really useful, and save on parts counts too.

Second question is regarding runoffgroove's statements about the phenomenon of increasing noise with each additional stage used (like in the Double-D)... Has anyone experimented with using multiple inverter stages in series, but designed for different effects? Such as... 2 inverters used for distortion going into one inverter used as a wah.

I have a feeling I'm just blanking out on something obvious from the datasheet, but I was hoping one of the many helpful people on this forum could save me from scratching my head. 


Thanks in advance to anyone with advice!

[earthtonesaudio]

I'm going to go ahead and try it out...

The Double D's "Bounce" channel into Tim's "Ghost Dance"

Hope it works! 
-And I just saw on the runoffgroove page that this topic has already been discussed here... I guess I should have hit the search button before I asked, but comments are still welcome.

[Renegadrian]

I was wondering how to build a bounce/bounce Double D with a one knob tone for each channel...

[earthtonesaudio]

I would put the "stupidly wonderful tone control" right before the volume for each channel.

Check it out:
http://www.muzique.com/lab/swtc.htm

[John Lyons]

Yes, The SWTC is a good simple one.
Things to try with it.
Put a small resistance (1k?) between the cap to ground and you get a shelved low pass filter which is nice for getting a more mid/high cut but still retaining the high end enough to keep the clarity.
Use a larger cap for more cut along with the resistance to ground to bring the cut towards the mid range.
These both work well for making a circuit heavier and mellowing out the high end.

John

[gez]

Has anyone experimented with using multiple inverter stages in series, but designed for different effects? Such as... 2 inverters used for distortion going into one inverter used as a wah.

You can use as many of the inverters as you like.  The only things to avoid are LFOs and audio all in one chip.  Guaranteed LFO tick (unavoidable as all inverters share the same power/ground path).  As for different effects, if you disengage your fuzz while using a wah, for example, then fine.  If you don't (if you leave the input connected during 'bypass'), then you'll get feint bleedthrough of the fuzz signal into your wah.

Inverters have high output impedance.  On their own, they don't make great amps for filters.  I appreciate there's that state variable filter thing - can't remember the name - that lots of people here build, and I'm sure it's nice, but compared to a 'real' SVF it's rather flat.  This seems to be the case with all inverter wah circuits/filters: rather subdued compared with the same circuit using higher gain devices.

Having said that, I once used a buffered chip to good effect.  The higher gain resulted in a better filter.  You could probably parallel chips too.  This would lower the output impedance.  The downside to both approaches is the huge current consumption at 9V (it's a lot less at 5V): the more inverters you use, the higher the drain on your battery/PSU.  The best result I had was with a Twin-T filter.  I buffered the output of the inverter and it had a decent quack.