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DIY Stompboxes => Building your own stompbox => Topic started by: slacker on March 24, 2007, 12:49:22 PM

Title: The Slacktave, CMOS octave down fun
Post by: slacker on March 24, 2007, 12:49:22 PM
Ladies and gentlemen allow me to present the Slacktave, an all new octave down pedal I've been working on for a while. It uses a CD4024 (http://www.kpsec.freeuk.com/components/cmos.htm#4024) ripple counter to generate 1 or 2 octaves down that can be used on their own or mixed with a nasty comparator fuzz for a wide range of fuzzy synth like textures.

Here's the schematic
 
http://www.eskimo.plus.com/fxstuff/slacktave.png (http://www.eskimo.plus.com/fxstuff/slacktave.png)

and some samples, all played around the 5th and 12th frets
one octave down (http://www.eskimo.plus.com/fxstuff/1down.mp3)
two octaves down (http://www.eskimo.plus.com/fxstuff/2down.mp3)
fuzz (http://www.eskimo.plus.com/fxstuff/fuzz.mp3)
fuzz plus 1 octave mix (http://www.eskimo.plus.com/fxstuff/1downmix.mp3)
fuzz plus 2 octave mix (http://www.eskimo.plus.com/fxstuff/2downmix.mp3)

The basic idea of using the 4024 came from Ken Stone's sub-oscillator (http://www.cgs.synth.net/modules/subosc.html) and I've tried a few different ways of hooking it up to a guitar to get decent tracking, this is the first version that I thought was worth sharing. It uses a modified version of the fundamental extractor from the Electrax guitar synth (http://rubidium.dyndns.org/cag/pdf/electrax.pdf) that Stephen Giles posted a while ago to drive a comparator that's hooked up to the clock pin of the 4024. The divide by 2 and 4 outputs are then used to give the octaves and these can be mixed with the comparator output. If my maths is correct the mix pot also acts as a variable highpass filter so as the octave is blended in more low end is rolled off the fuzz side which helps bring out the octave.
It tracks pretty well between about the 3rd and 17th frets and works best on the middle 4 strings. As with most of the these things you get the best results using the neck pickup with the tone rolled down, this gives the most stable octave down. However if you use the bridge pickup you can get an octave jumping effect.
This is still on the breadboard so if anyone's got any ideas for improvements I'd be happy to hear them. Any comments on how it sounds compared to the other octave downs out there would also be cool.
Title: Re: The Slacktave, CMOS octave down fun
Post by: petemoore on March 24, 2007, 01:33:39 PM
  Tha's working good !
  Nice and synthy, good tracking ! cool
Title: Re: The Slacktave, CMOS octave down fun
Post by: birt on March 24, 2007, 02:08:26 PM
cool sound. very very synthy! :)
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 24, 2007, 02:29:45 PM
thanks :) I'm thinking of using it as the input stage for a guitar synth type project, so synthy sounding is good.
Title: Re: The Slacktave, CMOS octave down fun
Post by: jpm83 on March 24, 2007, 05:19:16 PM
That's really cool. Are you planning to do a vero layout for thisone?
Title: Re: The Slacktave, CMOS octave down fun
Post by: jmusser on March 24, 2007, 05:31:45 PM
That came out well, and is simple to boot! It is quite a bit more sythy than the Shoctave, which is good or bad depending on what you like. Some people like it to sound like a bass, which takes a horrible amount of filtering. I like both type of tones. It sounded like it was tracking pretty well too. I wasn't hearing a bunch of what I call "sonic bumblebee" where it finds the note initially, but then hunts around for it and warbles up and down. That gets annoying after awhile. Good job!
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 24, 2007, 05:53:41 PM
Thanks, I did think about trying to filter the octaves to clean them up a bit and make it sound more bass like but I like the fact that it's synthy. It could probably be used a building block to make a more natural sounding pedal though.
The fundamental extractor really improves the tracking by removing a lot of the high frequencies giving a cleaner signal to the comparator. The comparator then puts out a decent constant voltage square wave, which suits the 4024. The earlier versions did suffer with the "sonic bumblebee" effect, which is why I never posted them.

That's really cool. Are you planning to do a vero layout for thisone?

thanks. I've done a vero layout it just needs labelling, once it's done I'll post it.
Title: Re: The Slacktave, CMOS octave down fun
Post by: ambulancevoice on March 24, 2007, 05:56:47 PM
fuzz octave 2 sounds a shit load like a blue box!  :icon_eek: :icon_biggrin:
Title: Re: The Slacktave, CMOS octave down fun
Post by: birt on March 25, 2007, 06:02:58 AM
this is actually the guitar sound that is closest to what i've been looking for for some time now.

i want something that is capable of "Gap Band - you dropped a bomb on me" upt to the fantastic sound of "Chemical Brothers - my elastic eye". if it can only do the last one it's fine by me :p

maybe the last one is possible by taking only fast samples of the guitar signal and generate octave down sounds with those. i'm definatly gonna try that if i have the time.
Title: Re: The Slacktave, CMOS octave down fun
Post by: markusw on March 25, 2007, 06:30:03 AM
Very cool!!  8)

What are you using for the comparator? Is it an opamp?
Since it's still on breadboard it would probably be worth changing it to a LM311 because it's faster. The 4024 might prefer this. Once I tried to feed the output of a LM311 into a 4013 divider an it worked very nicely.
Maybe also check for offset voltage at the +ve in of the comparator. It might be worth a try to AC couple the +ve input with a e.g. 100n cap and a 100k to Vref.

Markus
 


Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 25, 2007, 07:53:38 AM
Thanks for the advice :)

The comparator is just an opamp, which seems to work fine and means the circuit only uses a quad opamp and the 4024. Having said that, adding an LM311 would free up an opamp, which could be used to do something else, like an octave up!
I might try AC coupling the input of the comparator and see if that improves anything.
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 25, 2007, 10:41:45 AM
If anyone fancies having a go at building this here's a vero layout.

http://www.eskimo.plus.com/fxstuff/slacktaveboard.jpg (http://www.eskimo.plus.com/fxstuff/slacktaveboard.jpg)

I haven't built it yet so it's unverified and as the design is still somewhat experimental things could change.
By the way apologies for the odd resistor values, I've got one of those resistor multipacks and I've used up most of the common values and I'm trying to use up the rest of the values rather than buying any more.
If you haven't got the exact resistor values just use whatever you've got that's within 10% or so, after all it's only a fuzz  ;D
I don't know if it matters but the actual code on my CD4024 is CD4024BE
Title: Re: The Slacktave, CMOS octave down fun
Post by: gez on March 26, 2007, 04:26:49 AM
Clever use of the 4024.  Gets round the problem of picky flip-flop clock inputs (especially chips made by ST, which I've always had to buffer to get them to work).
Title: Re: The Slacktave, CMOS octave down fun
Post by: calculating_infinity on March 26, 2007, 04:35:03 AM
Damn slacker, sounds sick!  This is definately on my to build list.  Thanks for sharing!  Now I need to get me a 4024.

Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 26, 2007, 01:24:53 PM
Clever use of the 4024. 

Cheers, to be honest it seemed so simple that I was quite surprised that no one had done it already.
Listening to the soundclips I think the 4ms Nocto Loco (http://www.4mspedals.com/nocto.php?mode=sound) is based on the same idea, but using the rest of the dividers as well. I did try using those and you can get some intersting effects but I thought a basic octave down pedal might get more interest.

Damn slacker, sounds sick!  This is definately on my to build list.  Thanks for sharing!  Now I need to get me a 4024.

Thanks, it shouldn't be too hard to find a CD4024, I don't think smallbear has them, but any of the usual electronics suppliers should.
Title: Re: The Slacktave, CMOS octave down fun
Post by: gez on March 26, 2007, 02:37:09 PM
Clever use of the 4024. 

Cheers, to be honest it seemed so simple that I was quite surprised that no one had done it already.

I was slapping my forehead when I saw it.  Sometimes the obvious is staring us in the face, just needs someone to point it out to us.  Thanks!  :icon_wink:
Title: Re: The Slacktave, CMOS octave down fun
Post by: krachbox on March 26, 2007, 03:45:15 PM
4ms did.

http://www.4mspedals.com/nocto.php (http://www.4mspedals.com/nocto.php)
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 26, 2007, 05:15:02 PM
yeah, I already mentioned that :) I discovered the nocto loco while browsing one day after I'd been playing around with my idea for a while. As soon as I heard it and saw what it did I guessed it was using a similar idea and thought someone was bound to figure it out or they'd release a schematic, then it would look like I'd copied it.

Title: Re: The Slacktave, CMOS octave down fun
Post by: krachbox on March 27, 2007, 02:35:39 AM
Yes, but it will take some time before they (4ms) will release it as a kit. I know because I asked.
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 27, 2007, 08:09:57 AM
If you look at the data sheet for the 4024 you should be able to figure out some of the nocto's sounds  ;)
Title: Re: The Slacktave, CMOS octave down fun
Post by: tommy.genes on March 27, 2007, 10:38:48 AM
Ahhhhh....   so it's a binary counter.....    :icon_eek: :icon_idea: :icon_mrgreen:

i want something that is capable of "Gap Band - you dropped a bomb on me" up to the fantastic sound of "Chemical Brothers - my elastic eye".

I don't have a copy of "You Dropped a Bomb on Me" in my iPod right now to listen to that one carefully (I thought I did), but I'm almost certain that My Elastic Eye uses the ubiquitous TB-303 (or a clone). That machine is just a simple, switchable saw/square wave oscillator into a highly-resonant three-pole (yes, three) filter with simple envelope control ("decay" control only). So it would seem that the Slacktave into a cranked envelope filter would get really close to a TB-303 sound.

Now someone just needs to develop a portamento circuit...

-- T. G. --
Title: Re: The Slacktave, CMOS octave down fun
Post by: Constantin Necrasov on March 27, 2007, 10:53:45 PM
Awesome! :icon_twisted:
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on March 28, 2007, 03:47:11 PM
Finished building the vero layout tonight, so it's verified if anyone wants to try it. It's on the Smallbear vero that Aron sells, which seems very nice to work with, takes solder really well and is easy to cut and drill.

(http://www.eskimo.plus.com/fxstuff/slacktave.jpg)

I've also tried TI and Toshiba 4024s in it and they both worked fine so hopefully it won't be one of those circuits that needs specific chips.

If anyone fancies doing a PCB layout that would be much appreciated.


Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on April 09, 2007, 10:59:30 AM
Just a cheeky bump really, but here's a couple of pictures of the finished pedal. The board's a pretty tight fit, it sits on top of the pots and is held tightly in place by the lid. To stop it shorting out on the pots I used a piece of plastic packing from an easter egg box.

(http://www.eskimo.plus.com/fxstuff/slacktavebox.jpg)

(http://www.eskimo.plus.com/fxstuff/slacktaveguts.jpg)

Title: Re: The Slacktave, CMOS octave down fun
Post by: caress on April 09, 2007, 12:06:11 PM
is the 4024 using vref on pin 14 as well, a full 9v or not connected?  also, should pin 7 be grounded? 
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on April 09, 2007, 12:17:14 PM
Pin 14 of the 4024 goes to 9volts, pin 7 to ground. I'll add them to the schematic, for some reason my schematic software doesn't normally show the power pins.
Title: Re: The Slacktave, CMOS octave down fun
Post by: caress on April 09, 2007, 12:24:07 PM
great
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on April 09, 2007, 01:02:17 PM
Here's the updated schematic http://www.eskimo.plus.com/fxstuff/slacktave.png (http://www.eskimo.plus.com/fxstuff/slacktave.png) with added power connections to the CD4024. I've also noticed that the value of the input cap was incorrect, it should have been 10n not 47n, probably makes no difference.
Title: Re: The Slacktave, CMOS octave down fun
Post by: David on April 09, 2007, 01:48:17 PM
That's slick, Slack!   :icon_mrgreen:  Nice work!
Title: Re: The Slacktave, CMOS octave down fun
Post by: Dingleberry Electronics on April 09, 2007, 04:42:54 PM
I have wondered a long time how would these octave down effects sound if you add passive ring modulator module to it.
The one with two transformers and four diodes. If you feed normal signal to carrier input and octave down signal to other input.
Theoretically it will produce the sum and difference of the two frequencies. If you play for example a 880Hz note and
octave generator gives one octave lower 440Hz the result after ring modulator is 1320Hz and 440Hz. The 440Hz would be A note and 1320 would be E.
E is one octave and fifth higher than A. When the are in fifth relationship, would it still be too harmonic to sound even a little bit ring modulated tone.
Would it be just lame octave effect? Is this just another dumb idea from me...
Anyone tried?

-T.E
Title: Re: The Slacktave, CMOS octave down fun
Post by: krachbox on April 30, 2007, 03:45:13 AM
hi slacker(and everybody else),

Dann Green has put up the schematic for his noctoloco, just for comparison:

http://www.commonsound.com/kits/doku.php?id=commonsound:nocto

cheers,

Janis
Title: Re: The Slacktave, CMOS octave down fun
Post by: markusw on April 30, 2007, 04:10:03 AM
I have wondered a long time how would these octave down effects sound if you add passive ring modulator module to it.
The one with two transformers and four diodes. If you feed normal signal to carrier input and octave down signal to other input.
Theoretically it will produce the sum and difference of the two frequencies. If you play for example a 880Hz note and
octave generator gives one octave lower 440Hz the result after ring modulator is 1320Hz and 440Hz. The 440Hz would be A note and 1320 would be E.
E is one octave and fifth higher than A. When the are in fifth relationship, would it still be too harmonic to sound even a little bit ring modulated tone.
Would it be just lame octave effect? Is this just another dumb idea from me...
Anyone tried?

-T.E

http://www.diystompboxes.com/smfforum/index.php?topic=55075.120 (http://www.diystompboxes.com/smfforum/index.php?topic=55075.120)

http://www.aronnelson.com/DIYFiles/up/Harmonic_Ring_Modulator_current_sch_15-04-07.pdf (http://www.aronnelson.com/DIYFiles/up/Harmonic_Ring_Modulator_current_sch_15-04-07.pdf)

With suboctave as square wave you don't have to worry that it sounds too harmonic  ;)
With suboctave as sine it sounds much "nicer" but still not boring IMHO.
If you want more "atonal" ringmodish sounds you can use an octave down plus a third or fifth as a carrier.

Markus
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on April 30, 2007, 08:50:20 AM
hi slacker(and everybody else),

Dann Green has put up the schematic for his noctoloco, just for comparison:

http://www.commonsound.com/kits/doku.php?id=commonsound:nocto

looks cool, glad it's very obviously a completely different beast to mine  :)
Title: Re: The Slacktave, CMOS octave down fun
Post by: loss1234 on May 28, 2008, 01:41:50 PM
I built this off of +/- 12volts and i just wanted to make sure that changing all the Vrefs to gnd, and removing the resistor to vref on pin 2 (or is it 3)

anyway, i love the sound of it! the high E and Low E have some tracking problems on my guitar but only on some notes. i did turn the tone down a bit and am using the neck pickup


anyone tried any mods or different values? someone mentioned using a 311-any improvement with that?

thanks for this great, easy, smALL CIRCUIT!

 thank you
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on May 29, 2008, 01:49:05 PM
Yeah to run it off +/-12 volts just connect all the points marked Vref to ground instead. The only issue I can see with doing this is that the comparator (the opamp feeding the 4024) will swing between +12 and -12. The 4024 datasheet says that the input voltage must be between -0.5 volts and 18volts as an absolute maximum, so feeding it -12 volts could damage it.
You can get round this by connecting a diode to the output of the comparator. Kathode to the output and anode to ground that will stop the output going more than a diode drop below ground, which will probably be enough to protect the 4024. Or it might be easier just to run it off 12volts, there's probably no advantage to running it on a bipolar supply.

I bought some 311s to try in the circuit but never actually tried them, I might have a play with it one day.
Title: Re: The Slacktave, CMOS octave down fun
Post by: loss1234 on May 29, 2008, 08:43:19 PM
hmm

i switched it back to off of vref and it doesnt work. this was actually the reason i tried going to bipolar in the first place is i couldnt ever get it to work off of your vbias with my 12 volt supply.

any ideas? maybe the values need to change at 12v??

is there a vero for this around that is verified?

thanks
Title: Re: The Slacktave, CMOS octave down fun
Post by: loss1234 on May 29, 2008, 09:15:00 PM
is your vero layout viewed from underneath? and with both chips facing the same way?

thanks
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on May 30, 2008, 10:54:02 AM
Strange I can't see any reason why it shouldn't work on 12volts instead of 9.
I've built the vero layout that's in this thread so it's sort of verified and I think other people have built it. The layout is viewed from above, from the same side as the components. Both chips are the same way up, with pin 1 top left.
Title: Re: The Slacktave, CMOS octave down fun
Post by: Dragonfly on May 30, 2008, 11:08:30 AM
Somehow this thread had "slipped past my radar" until yesterday. REALLY nice design Slack ! Clever. I'm gonna see if my local place has a 4024 today :)

Thanks.
Title: Re: The Slacktave, CMOS octave down fun
Post by: drewl on May 30, 2008, 01:13:04 PM
Awesome, looks easy!
I think I have some 4024's.
Hey, those 4ms pedals looked whacked.....but in a good way!
Title: Re: The Slacktave, CMOS octave down fun
Post by: loss1234 on May 30, 2008, 04:53:01 PM
tried the diode trick you recommended and it works great. i figure it was user error that was giving me problems with single supply!

btw, this makes a great front end for a 4046

thanks
Title: Re: The Slacktave, CMOS octave down fun
Post by: Boogdish on July 10, 2008, 06:43:02 PM
I just finished breadboarding this and it is fun, fun, fun.  I'm doing this, the nyquist aliaser and an echobase before I go back to school.  Summer of Slacker.
Title: Re: The Slacktave, CMOS octave down fun
Post by: Boogdish on September 06, 2008, 04:44:27 PM
I modded my slacktave today.  I built the last half of the "simple square wave shaper" presented on Tim Escobido's page into the output of the pedal.  here's a schematic:
(http://img.photobucket.com/albums/v484/boogdish/slacktavemodschem.jpg)
and here are some sound clips.
http://www.aronnelson.com/DIYFiles/up/slacktave_demo.mp3

This in my opinion really brings out a lot of life in the pedal.  You lose some of the volume, so I'm thinking about putting a small booster/buffer between the output of the mod and the volume control. This was also really easy to do, I built it point to point using the back of one of the pots for ground and a little bit of shrink wire to keep things tidy.  I'd post a picture of that, but our old camera broke and we haven't gotten a new one yet.

Thanks to Slacker, Escobido and Bobby Beausoleil (who wrote the article Escobido got his idea from).
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on September 06, 2008, 05:03:19 PM
Very cool, I'll have to try that out. If you need some extra volume from the pedal try removing the diodes in the feedback loop of the last opamp or replace them with LEDs that should give a decent volume boost.
Title: Re: The Slacktave, CMOS octave down fun
Post by: mongo on September 07, 2008, 06:17:30 PM

 Ohhhhhhhh  we need a PCB layout for this!!!
Title: Re: The Slacktave, CMOS octave down fun
Post by: rnfr on September 07, 2008, 07:14:31 PM
this thing sounds great.  really like boog's mod.   

and anything by bobby beausoleil is going to have some REAL mojo! :icon_twisted:
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on September 26, 2008, 02:50:05 PM
Does anyone know if you can use more than one of the 4024's outputs simultaneously?  Like a volume control from pin 11, and a separate volume control from pin 12, going into the output mixer section... Would that work?
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on September 27, 2008, 10:25:14 AM
Yeah that would work fine.
Title: Re: The Slacktave, CMOS octave down fun
Post by: frequencycentral on May 27, 2009, 02:41:04 PM
Hi Ian, I'm breadboarding the Slacktave. I don't have all the resistor values, so I'm going for closest match I have. I'm getting good fun with the low E and A strings, although the notes cut off rather abruptly. The other strings do nothing. I'm using humbuckers. The opamp package I'm using is a RC4136 quad (741 type) opamp. The resistor values I'm using are 2M2, 1K, 15K, 47K, 100K, 4K7. I've replaced the 120K on the input of the 4024 with a 0.1uf cap, which helps a bit. Do you think my problem is the resistor values? I know to expect some glitch..........

RC4136 http://www.synthdiy.com/files/2006/4136-rca.pdf
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on May 27, 2009, 03:56:34 PM
That's a bit odd. The resistor subs should be fine, the weird values in the original were just because that's what I had, mostly the dregs of a resistor value pack. I don't know anything about the opamp you're using but I can't imagine that can be the problem.

I'd try and see where the signal is getting lost. Are you getting a strong square wave on the output of the third opamp stage or is the signal already weak at that point?
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 18, 2009, 05:34:56 PM
I modded my slacktave today.  I built the last half of the "simple square wave shaper" presented on Tim Escobido's page into the output of the pedal.  here's a schematic:
(http://img.photobucket.com/albums/v484/boogdish/slacktavemodschem.jpg)
and here are some sound clips.
http://www.aronnelson.com/DIYFiles/up/slacktave_demo.mp3

This in my opinion really brings out a lot of life in the pedal.  You lose some of the volume, so I'm thinking about putting a small booster/buffer between the output of the mod and the volume control. This was also really easy to do, I built it point to point using the back of one of the pots for ground and a little bit of shrink wire to keep things tidy.  I'd post a picture of that, but our old camera broke and we haven't gotten a new one yet.

Thanks to Slacker, Escobido and Bobby Beausoleil (who wrote the article Escobido got his idea from).


Does anyone know a way to get triangle, saw, and square out of this using a single potentiometer?  I can only see how to get two of three...
Title: Re: The Slacktave, CMOS octave down fun
Post by: frequencycentral on June 18, 2009, 05:48:34 PM
I posted a "theoretical" waveshaper in that other Slacktave thread, haven't tried it yet (ie. it might be a pile of crap!), but it's on the list:

http://www.diystompboxes.com/smfforum/index.php?topic=76695.0

Or there's this:

http://www.diystompboxes.com/smfforum/index.php?topic=77235
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 18, 2009, 08:10:54 PM
I was originally thinking to put a SSWSMS (simple square wave shaper made simpler) on each octave's output, but that could potentially be a LOT of knobs, so reducing it down to one would be nice.  If you made the two 1M resistors into two halves of a 2M pot, and brought the signal in through the wiper, as you turned the wiper, you'd get falling saw-triangle-rising saw.  On the other hand, if you made the two resistors fixed and put a variable resistor between D1 and D2, you could get triangle at max resistance, square at min. 

Then I had the thought that rising and falling sawtooth waves probably sound about the same, so it would be really handy if you could have a 1-knob control that went square-saw-triangle.  I think you could do it with a center-tapped pot, but that's somewhat of an odd item, and it'd probably be easier to develop an active version at that point.

Now I'm thinking maybe you wouldn't need the SSWSMS on every octave...
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 20, 2009, 10:33:04 PM
Alright, I think I figured out a way to get square/sawtooth/triangle from one potentiometer. 

Signal comes in, splits to the two antiparallel diodes as usual, then each diode goes to one end of a potentiometer.  The cap is attached to the wiper, and the signal output is taken from there also.  Here's the twist: one diode is a zener, with a threshold voltage that is lower than the peak square wave input voltage (so if you run the CD4024 from 5V, use a zener rated at less than 5V, such as a 1n522x).

At the non-zener end of the pot's rotation, the cap charges fast and discharges slow, giving a sawtooth waveform. 
As you turn toward the zener side, the discharge is still slow-ish but the charge becomes slower: triangle
Keep turning and you'll charge and discharge primarily through the zener, so at this point the waveform is mostly square.
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 21, 2009, 12:29:58 PM
So I'm thinking you could use all 4 xor gates from a 4070/4077 to get 4 octaves up, then put that into the 4024 to get +3, +2, +1, 0, -1, -2, -3 octave square waves, put the single-pot waveshaper on each one, plus a dry blend.  So that's... 15 knobs.   :o  I'm thinking some of those should be internal trims.
Title: Re: The Slacktave, CMOS octave down fun
Post by: frequencycentral on June 21, 2009, 01:03:33 PM
So I'm thinking you could use all 4 xor gates from a 4070/4077 to get 4 octaves up, then put that into the 4024 to get +3, +2, +1, 0, -1, -2, -3 octave square waves, put the single-pot waveshaper on each one, plus a dry blend.  So that's... 15 knobs.   :o  I'm thinking some of those should be internal trims.

I'm listenin' ! But 15 knobs!  :o

I wanna see a schematic..........! ;)
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 21, 2009, 10:33:28 PM
Still learning Eagle, but this should convey the important bits:

(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=39978&g2_serialNumber=1)
(Rightclick and select "view image" if it's too big)

All the floating parts that "point down" should go to ground.  Like I said, still learning...  :icon_redface:

Also, the "waveshape" and "level" controls should be repeated for the other 6 Q outputs of the 4024.
Title: Re: The Slacktave, CMOS octave down fun
Post by: Cliff Schecht on June 22, 2009, 01:15:58 AM
Earthtones, go check out the library called "Supply1" and "Supply2", I think you'll find all of your power and grounding needs ;). Also on any of your parts with power pins, you have to right click the part and go to "invoke". Ditto for any parts with more than one device onboard (like the hex inverter your using, if you delete one by mistake then you'd have to right-click and invoke the deleted gate number).
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 22, 2009, 07:48:51 AM
Thanks Cliff, that helps a lot!
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on June 22, 2009, 01:18:31 PM
If you're going down the multiply up route, you could try the waveshaper from the PICsynth http://picsynth.000space.com/ (http://picsynth.000space.com/).
I'm not sure how successful the upper octaves will be though, I think the pulse width might get too narrow to hear. It would probably still work to drive a divider though.
I have another idea along these lines using a CD4046 to multiply the signal up about 8 or 16 times then divide it back down. In theory you would then have enough outputs to make a digital sine wave, or triangle at different octaves. From there you can get saws and squares. You could even go really crazy and make a vastly simplified version of Ian Fritz's DoubleDeka VCO, where you could actually draw the waveform you want.
It will probably have to wait until the winter though, I'm pretty busy with stuff most of the summer.
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 22, 2009, 01:31:27 PM
If you're going down the multiply up route, you could try the waveshaper from the PICsynth http://picsynth.000space.com/ (http://picsynth.000space.com/).
I'm not sure how successful the upper octaves will be though, I think the pulse width might get too narrow to hear. It would probably still work to drive a divider though.
I have another idea along these lines using a CD4046 to multiply the signal up about 8 or 16 times then divide it back down. In theory you would then have enough outputs to make a digital sine wave, or triangle at different octaves. From there you can get saws and squares. You could even go really crazy and make a vastly simplified version of Ian Fritz's DoubleDeka VCO, where you could actually draw the waveform you want.
It will probably have to wait until the winter though, I'm pretty busy with stuff most of the summer.

Agreed, 3 octaves up would be hard to hear in most situations.  Especially if you took the output from the XOR directly!  That's why I've tried to show the output being taken from the 4024, after 50% duty cycle has been restored.

That other stuff is crazy talk, way over my head!
Title: Re: The Slacktave, CMOS octave down fun
Post by: slacker on June 22, 2009, 01:36:25 PM
Sorry, I didn't look at the schematic properly  :icon_redface:
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 24, 2009, 08:56:11 AM
I just found a decent sized enclosure for the monstrosity that my interpretation of the Slacktave is shaping up to be... and I realize I have room for MORE FEATURES!!!  Mwa-hahaha!

So I'm thinking a sequencer to step through the octaves would be nice.  Does anyone know of a sequencer that can invert its outputs, or would it make more sense to go with a serial/parallel shift register a/la TheToneGod's Vanishing Point 1.0?

Also, envelope control over something.  Perhaps pulse width, before the signal goes through the waveshaper, for Uglyface-ish tones.

And tap-tempo, of course.
Title: Re: The Slacktave, CMOS octave down fun
Post by: gigimarga on June 24, 2009, 10:36:05 AM
Hello,

Can i use another 4070 for the +2 octave up?

Thx!
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on June 24, 2009, 12:28:36 PM
Hello,

Can i use another 4070 for the +2 octave up?

Thx!


Short answer: yes.


Long answer:
Anytime you put a square wave into one input of an XOR, and a slightly delayed (by the r-c network) version of the same square wave into the other input, you get a High output when only one input is high, which happens be twice the input frequency.

If the RC delay is 1/4 the period of the input frequency, the output will be a square wave (50% duty cycle).  For other input frequencies, the fixed RC delay will cause the output will be more or less than 50%, which in subjective terms results in a thinner or reedier tone.


Getting back to your question, stacking RC-delayed XOR networks (just like I drew in the schematic in reply #56) will result in doubling the frequency each time, but the tone will become much thinner, over a broader range of input frequencies. 

This is why I put the output of the 4th XOR into the clock input of the 4024.  The Q0 output is now one octave lower than the clock frequency, but the flip-flop circuit makes the duty cycle exactly 50%, and the output's timbre is independent of input frequency.  I chose this because I was worried the XOR output would be such a narrow pulse that it would be completely inaudible, not because I think it would necessarily sound better.  Having an output which changes dynamically per the frequency will probably sound more interesting, but that's up to your ear to decide.

I'm assuming you've also checked out the Slacktave MKII, correct?  There are many ways of putting this thing together.
Title: Re: The Slacktave, CMOS octave down fun
Post by: rousejeremy on August 25, 2009, 08:18:34 PM
I just built the Slacktave on vero.
I have to hit the strings REALLY hard (Stratocaster) in order for the Octave effect to happen, and the effect dies quickly, leaving just the clean guitar signal.

Title: Re: The Slacktave, CMOS octave down fun
Post by: Microscope on November 11, 2009, 09:43:02 AM
Maybe this is a dumb question but I don't see an "out" marked on the veroboard layout.
Title: Re: The Slacktave, CMOS octave down fun
Post by: jacobyjd on November 11, 2009, 09:46:03 AM
Maybe this is a dumb question but I don't see an "out" marked on the veroboard layout.

Not a dumb question :)

Vol lug 2 (the middle one) is where you take the output from.
Title: Re: The Slacktave, CMOS octave down fun
Post by: Microscope on November 11, 2009, 10:00:32 AM
Thanks.
Title: Re: The Slacktave, CMOS octave down fun
Post by: rexindigo on November 30, 2009, 09:15:21 AM
Hello, im new to this forum and just wanted to say "hi evrybody, great forum you have here!"
and ask a question about the slacktave which I just built:
The two diodes in the  output section, are they just the usual clipping diodes of a fuzz circuit?
Can they be omitted in order to get clean guitar + binary counter sound?
(btw: what a great sounding unit the slacktave is, thanx for sharing!)
thx for your reply
Title: Re: The Slacktave, CMOS octave down fun
Post by: earthtonesaudio on November 30, 2009, 10:13:04 AM
They are limiting the signal like in a fuzz, but in this circuit the signal going into that section is fuzzy already.  So they don't really add much distortion, but rather their main purpose is to limit the output volume and keep the op-amp itself from clipping.
Title: Re: The Slacktave, CMOS octave down fun
Post by: rexindigo on November 30, 2009, 10:49:38 AM
I will keep the diodes then, the sound is nice anyway,
thank you.
Title: Re: The Slacktave, CMOS octave down fun
Post by: Fuzz Aldryn on November 30, 2009, 10:57:40 AM
Yeah, definiitely keep them in. They are limiting the output signal to about 0,7V. Without them the voltage would jump from 0 to 9V in a squarewave manner as far as I did understand the circhuit.

Cheers
Helge