4069 (or 4049) clean boost?

[earthtonesaudio]

Can anyone help me get a loud and *clean* boost out of one of these CMOS chips?  Here are my goals:
-High input Z, Low output Z
-Uses only 1 of the inverters (I have plans for the other 5)
-not too much distortion (a little clipping at max gain is fine)

This could be a buffer or a boost.  Either will work for me.

I built this (thanks Tim E!) but it just barely boosts before distorting:

Just to make sure, I tried a couple other 4069's and got the same results.  I like the sound of it (especially for so few parts) but I am hoping to get more clean gain out of it or something similar.

Thanks!

[Dragonfly]

I got a decent amount of clean headroom from it...not a ton, but a decent amount.

I would try "cascading" several stages of the 4069 or 4049...controlling any distortion a little at a time...the breadboard is your friend ! 

[earthtonesaudio]

Thanks for the quick reply Dragonfly.

I stepped back and re-analyzed my setup, and I think I figured out what the problem was.  I'm using a 500k linear pot for the input gain, and I listened closer, and it turns out there is definitely a "decent amount" of clean gain in there.  It's just all concentrated in the first third or less of rotation, and starts distorting around 9 o'clock.  I think I'll use it after all.

I changed one thing though: I'm using 1.0nF for the input cap instead of .1µF as it says in the schem.  Seems to help get more "clean" out of the inverter before it starts to clip.  I also kinda like the treble booster type of sound.

Now that that's settled, on to the fun part 

[Dragonfly]

I think I figured out what the problem was... I have been monitoring with headphones from the output of my own Noisy Cricket, and I had the headphone volume turned down so low I couldn't tell how much boost I was getting.  Upon closer inspection, I would have to say that I get a "decent amount" of clean headroom from this circuit as well.

Now that that's settled, on to the fun part 

NOW...add a footswitch that switches in / out another stage....  (clean boost / overdrive switch)

oh...and you can use another stage to amplify a baxandall tone stack...

I "might" have played around with 4069's a year or two ago...

[earthtonesaudio]

You got it.  I'm going to use another inverter for a filter, and a third for a Q control, if all goes well.

[Dragonfly]

You got it.  I'm going to use another inverter for a filter, and a third for a Q control, if all goes well.

Let us all know how things progress !

[earthtonesaudio]

Of course!  And a schematic too, when (if?  ) I get it to sound good.

One note regarding Tim's circuit: I didn't have any 5M resistors, so I used a 10M pot instead (wiper/midpoint to the .1µ cap).  From turning the 10M pot, I have come to the conclusion that the 5M biasing resistors can be VERY unequal with no change in tone.  Maybe this is an obvious thing, but it was interesting and unexpected to me.

[Dragonfly]

Of course!  And a schematic too, when (if?  ) I get it to sound good.

Somewhere I have a great "CMOS DESIGN" PDF.. I can try to find it and email it to you if you'd like....

[nordine]

I would try "cascading" several stages of the 4069 or 4049...controlling any distortion a little at a time...the breadboard is your friend ! 

i fear that would 'stack' white noise, beyond bearable amount (at least thats my experience with 4069's)

i saw someone putting like three of those inverters in paralell, for headroom purposes, you could try the same

[earthtonesaudio]

Somewhere I have a great "CMOS DESIGN" PDF.. I can try to find it and email it to you if you'd like....

By all means, do!  It would be much appreciated.

[earthtonesaudio]

i saw someone putting like three of those inverters in paralell, for headroom purposes, you could try the same

I read something about that as well, but I'm unclear on exactly how to implement it.

[Dragonfly]

I would try "cascading" several stages of the 4069 or 4049...controlling any distortion a little at a time...the breadboard is your friend ! 

i fear that would 'stack' white noise, beyond bearable amount (at least thats my experience with 4069's)

i saw someone putting like three of those inverters in paralell, for headroom purposes, you could try the same

Look to ROG Double D and similar designs....

[Dragonfly]

I just found this...


Could be interesting...


Designing a CMOS Ring Mod

[Dragonfly]

http://www.geocities.com/cmoslayoutdesign/layout/index.html

[Dragonfly]

FREE EBOOK !

http://www.ebookee.com/CMOS-Analog-Circuit-Design_152139.html

[gez]

Although output swing is rail-to-rail with CMOS inverters, gain starts to drop off as the output signal approaches the rails which is why you get that 'toob-like' compression.  This translates as a distorted sound, so you don't get a lot of clean headroom (quick onset of distortion).

For more headroom the easiest thing to do is up the supply voltage.  The downside of this is that current consumption goes up dramatically, but that probably isn't too much of an issue as you'd most likely use a PSU to power the thing if you're using 12V or above.

Personally, I wouldn't use a CMOS inverter for a clean boost.  Wrong tool for the job.

[slideman82]

Yeah, I agree with Gez, try a JFET or a MOSFET, and if you are using any OD in your pedal chain, put it after one of them, those trannies make them sound better!

[Renegadrian]

I saw an IC on Banzai marked 4049U, is it different from 4049UBE or it's so similar it'd fit/act the same?! 

[Dragonfly]

Yeah, I agree with Gez, try a JFET or a MOSFET.....

CMOS is essentially a bunch of mosfets in a single IC.   

[slideman82]

Yeah, yeah, that's right, it's a bunch of mosfets, but you're are wrong!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! THEY'RE 6 Cmos BASED INVERTER BUFFERS, that means, there are 6 op-amps! Not discrete Mosfets. Maybe you were refering to the 4007... anyway, I preffer a discrete booster than an IC based one.

BTW, 4049U and UBE means "unbuffered"... they are the same.