The Slacktave, CMOS octave down fun

[tommy.genes]

Ahhhhh....   so it's a binary counter.....   

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. --

[jrc4558]

Awesome!

[slacker]

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.



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.

[slacker]

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.

[caress]

is the 4024 using vref on pin 14 as well, a full 9v or not connected?  also, should pin 7 be grounded? 

[slacker]

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.

[caress]

great

[slacker]

Here's the updated schematic 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.

[David]

That's slick, Slack!     Nice work!

[Dingleberry Electronics]

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

[krachbox]

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

[markusw]

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.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

[slacker]

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 

[loss1234]

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

[slacker]

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.

[loss1234]

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

[loss1234]

is your vero layout viewed from underneath? and with both chips facing the same way?

thanks

[slacker]

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.

[Dragonfly]

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.

[drewl]

Awesome, looks easy!
I think I have some 4024's.
Hey, those 4ms pedals looked whacked.....but in a good way!