New CMOS design, help much appreciated

[gez]

Do people say to avoid the buffered versions because of current draw or for some tonal reason?  I imagine they would be more power hungry than the unbuffered, but at first listen they sound the same.   

Perhaps your ears need syringing? 

Gain is a lot higher as each buffered inverter is three unbuffered ones in a row.  End result is that you loose all that soft-clipping you're working so hard to achieve.  Scope it and weep!  Next, measure the current consumption.  Not exactly battery friendly.

I've used buffered inverters as the amp in simple filters.  They do a lot better job than unbuffered inverters in those types of circuit.  The disadvantages outweigh the advantages, though.  Only my opinion...

[puretube]

Similar opinion here: it took me quite a while, some time ago,
to find the problem in "a misbehaving 4049-circuit",
until I noticed that I had picked 1 of the totally 3 "bad" ICs in the "4049-drawer" (containing about 50 chips...)
who`re  printing was so tiny, that I hadn`t seen the missing: "U"   


[EDIT]: there`s a slight chance of difference in behaviour between various manufacturers...

BTW: I prefer XX69XXX over XX49XXX because of the lower pin-count!

and, BTW:
http://www.diystompboxes.com/smfforum/index.php?topic=20795.0
http://www.diystompboxes.com/smfforum/index.php?topic=46791.0

AND, btw: I MISS PETER S. !!!

[earthtonesaudio]

Perhaps your ears need syringing? 

Nope, not my ears, but maybe my memory!  I hadn't heard the unbuffered version in several weeks, and I had an untested circuit on there with the buffered 4049, so I didn't know what to expect.  So I breadboarded two Tube Sound Fuzzes, one with the 4069UB and one with the 4049B.  Very different.  The buffered one distorts very roughly.  Not as bad as a Schmitt trigger though! 

I think there are good possibilities with the buffered chips, just different applications.  Not best for "amp-like" tones, but maybe better for really raw "transistor fuzz" or square wave tones.  I have 3 days to finish my entry for this month's FX-X, so hopefully you'll get to hear something from me using unbuffered chips.  Fingers crossed...

[WGTP]

This is sort of funny/interesting.  Mr. Anderton did a Tube Sounding Fuzz and ROG/STM have "simulated/emulated/APPROXIMATED" the Tube Screamer and Big Muff Pie, EQ and Distortions.  Tim Escobedo has done some boost/drives...  Frank Clarke and Mark Hammer have done some very nice distortions and I'm sure I forgot some others, sorry.  What's left?  Distortions+/Rat/DS-1?   

[earthtonesaudio]

This is sort of funny/interesting.  Mr. Anderton did a Tube Sounding Fuzz and ROG/STM have "simulated/emulated/APPROXIMATED" the Tube Screamer and Big Muff Pie, EQ and Distortions.  Tim Escobedo has done some boost/drives...  Frank Clarke and Mark Hammer have done some very nice distortions and I'm sure I forgot some others, sorry.

Haha yeah, don't forget Tim Escobedo's inverter-based wah/filters (twin T like the ROG eq stuff).  And that page with all the synth circuits which has a bunch of CMOS stuff, including an all-CMOS synth.  Also, Gez has a nice cmos fuzz/wah I think. 

What's left?  Distortions+/Rat/DS-1?   

Why not?  4049UB and 4069UB were never meant for audio, but we use them to great success.  If everyone says not to use the buffered versions, I'm even more encouraged to try it.  It's in the spirit of the whole thing, anyway: "you're using a WHAT?  That shouldn't sound good at all!"  But it does.   

[grolschie]

n00b question: Could the stages of a CMOS replace transistors in most applications?

Do CMOS sound different per manufacturer? I built a Red Llama that sounded like crap. I kept modding, but was hairy and rough sounding. Not remotely amp-like at even low gain. Farty bass. Had plenty of boost though.

[puretube]

Yes, "Red Llamas" sound different from manufacturer to manufacturer...

[WGTP]

I have an old 4049 from my original TSF 20+ years ago and a newer one and they "seemed" to sound different.  It's not uncommon for transistors from one batch to another to sound different.

Try reducing the bass in the TSF to get rid of some of the negatives.  IMHO 3 stages sound better than 2.   

[earthtonesaudio]

Update: Buffered 4049 works fine for high gain/metal sound.  I don't know about soft-clipping, as I didn't look at it on the scope, but it does sound good to my ears.  As it has been repeated over and over, it looks like the key to getting a good sound from the buffered chip is rolling off bass/treble early on, then easing up later.

I did a 3 stage distortion with a notch filter at the end and small coupling caps in the beginning stages.
Input: 100k resistor, then 2n2 cap, next stage 4n7 coupling cap, next stage 6n8 coupling cap, then a notch filter and then a 10k volume.  1M feedback resistors on all stages, first stage is a trimmer.  Also, I rolled off lots of highs in the first stages: 470p feedback cap for stage 1, 330p for stage 2, nothing after that.

With a 1k/10uF power supply filter I got zero oscillations even at max gain/volume/filter resonance settings.  Greater than unity output, but not huge boost.

Oh, and 0.5mA current consumption, and it works at supply voltages down to 6V.

After that I messed it all up by adding a stage (to keep it in phase with the original signal) which oscillated badly AND reduced the output. 

So it can be done, but I have to re-trace my steps to see exactly what I did at first that worked well.  Then I'll draw a schem for y'all.  Maybe the next step after that is a dual pedal with "buffered" and "unbuffered" channels, otherwise alike, for compare/contrast purposes.

[WGTP]

http://www.guitar-pedals-effects.com/LinkedDocuments/hotharm2.gif

Looks like Frank is back in business.  I always liked the basic Hot Harmonics.   Other cool stuff too. 

[WGTP]

How about a cmos Boss DS-1 imitation?   

http://www.aronnelson.com/gallery/main.php/v/WGTP/Cmos+DS-1.GIF.html?g2_imageViewsIndex=1

[earthtonesaudio]

May I suggest a name?

DS+1  (Instead of DS-1 because it uses INVERTers)  Yes, I already know I'm a dork.

[grolschie]

Very interesting. What does it sound like? I might have to buy some different 4049s. My ones sounded sucky. They were unbuffered ones.

[earthtonesaudio]

Haven't tried the CMOS DS-1 yet, but it looks pretty promising.  (Watch the layout to avoid shrieks and squeaks, as always.)

Semi-update:
Not a distortion, but I built a simple active bass/treble circuit using a Buffered 4049 last night.  I just copied and pasted values from a design using op-amps (2 stages: gain of 2 input buffer, bass & treble in feedback loop output buffer), and it worked pretty well.  The circuit was meant for hi-fi so the treble was too high frequency for proper "guitar treble," but it clearly did what it was supposed to do, with very little distortion.  It got slightly more than unity gain and wasn't harsh sounding. 

I think it was a variation on a Baxandall, but I'm not certain.  I'll have to check the Tone Stack Calculator sometime.

Since the bass control was more useful, I think I'll try it as part of the input to a fuzz/distortion circuit, and label the bass control as "Mud" or something similar.

I'll post a schem later.  Cheers!

[WGTP]

If I can read some resistor values by memory, does that make me a dork?  Probably.

I have tried various combinations of diodes and inverters, but not the DS-1 specifically.  My guess is that it  would have a smoother sound than the real DS-1.  Probably could leave out some of the buffers, but I wanted it to duplicate the original.

Check out Brett's post about the "gain soak" stage we have been messing with.   

[earthtonesaudio]

What does it sound like? I might have to buy some different 4049s. My ones sounded sucky. They were unbuffered ones.

I didn't notice this part when I first read Grolschie's post.  A better answer:

What does it sound like?
To me, the "sound" of the CMOS inverters (when using them like we have been here in this thread) is generally a sort of soft-clipped, compressed tone.  Most of the designs we've been talking about (don't know about the DS-1 emulator yet) clean up well when you play softer, and have more distortion when you play louder.

My ones sounded sucky.
However, if you really max out the gain of a SINGLE stage, the clipping is much harder, and kinda rough/yucky sounding.  Not as much of the musical "smooth transition to clipping" that reminds us of tube amps etc.

The key (at least in my experience so far) to mucking around with these chips (if you want the soft-clipped, rich tone) is keeping them out of hard clipping by running stages at less than full-blast.  The, uh, OTHER key, is running them at lower voltages (5 or 6V is about right) by putting resistance between the supply voltage/ground and the chip's power connections.  If you stick a 10k pot wired as a variable resistor between +9V and Vdd, you'll notice that there's a good range of tones in there.  (Note: equal resistors on Vdd and ground will give symmetrical clipping, unequal resistors produce asymmetrical clipping)

If you're just trying out the CMOS chips for the first time, experiment with some of the simpler circuits, such as the Red Llama, Hot Harmonics, or the Tube Sound Fuzz.  Also check out the different ways of implementing a gain control as discussed in this thread.

They were unbuffered ones.
Those are the kind you want for the soft-clipped, more "amp like" tone.  Most of the DIY designs use them.  They're easier to tame, in  my opinion.  That said, I've been getting good results with the Buffered versions, you just have to take into account that their output currents are higher and so the gains have to be reduced.

[grolschie]

However, if you really max out the gain of a SINGLE stage, the clipping is much harder, and kinda rough/yucky sounding.  Not as much of the musical "smooth transition to clipping" that reminds us of tube amps etc.

The key (at least in my experience so far) to mucking around with these chips (if you want the soft-clipped, rich tone) is keeping them out of hard clipping by running stages at less than full-blast.  The, uh, OTHER key, is running them at lower voltages (5 or 6V is about right) by putting resistance between the supply voltage/ground and the chip's power connections.  If you stick a 10k pot wired as a variable resistor between +9V and Vdd, you'll notice that there's a good range of tones in there.  (Note: equal resistors on Vdd and ground will give symmetrical clipping, unequal resistors produce asymmetrical clipping)

Thanks for that. I built the Red Llama. The bass notes really suffer on mine. It has an insane amount of boost. I am not sure how to prevent hard clipping at each stage, i.e. how the gain is set at each cmos stage. I noticed recently a schematic using diodes to prevent full saturation at each clipping stage with transistors. Interesting.

[puretube]

I prefer CMOS-devices to prevent full saturation...

[earthtonesaudio]

The ultra-basic gain calculation for a CMOS inverter like the Red Llama uses is:

Feedback resistor/input resistor.  So if you have 100k at the input, and 1M in the feedback loop, then the stage has a gain of 10 (1M/100k=10).

If you want to get more detailed than that, it's actually feedback impedance divided by input impedance, but most of the time you can get by with the above formula.

2 easy ways to control clipping:  small input caps and using the above formula to keep gains low (gain of 10 seems like a good number to start with).  Diodes to ground and diodes in the feedback loop work as well.

[grolschie]

Thanks for that. I might have to dig out the RL again and have a play...