Roctave Divider mod question

[SonicVI]

I'm going to be building the Roctave Divider with the mod to allow different divisors. My question is, is there an alternative to the 4017 IC that can divide by less than 2?  I'd much rather have a fifth below than an octave and a fifth below.

[toneman]

the 4017 is a CMOS "decade counter".
It has 10 outputs.  
After a clock pulse,
ONE (& only 1) output at a time goes hi (Vcc)
Only a few outputs are usefull(musically).
U don't get a "perfect fith" *all* the time.
A TTL decade counter would work,
but can only work with TTL voltages (5V).
With a decade counter, U have divide by 2,3,4,5,.....10.
Don't divide...multiply...  
staycounting
tone

[Mark Hammer]

The 4017 is an integer divider.  That means that it can only divide by numbers that are multiples of 1.  In this particular universe, the only integer that closely follows 1 is 2 :oops: , which gives you an octave down.

If you want intervals between unison and an octave down, the approach you need to adopt (in the analog processing domain) is one of starting out wqith a fundamental much higher than the one you played, and dividing that down by integers.  Take a look at the Harmony Generator project on my website (http://hammer.ampage.org  somewhere around page 8 or 9) and you'll see how its done.  

Warning: it ain't easy.  The good news is there is a PCB mask for the project.

[Paul Perry (Frostwave)]

http://home1.gte.net/res0658s/fatman/

Maybe some inspiration here! The Fatman is a basic monosynth kit from PAiA, and people keep trying to fatten it up, add fifths and etc. This site has the dope. Obviously, the circuits won't know that the square wave is coming from a Bluebox, rather than the Fatman :wink:

[SonicVI]

Mark, have you tried building it or heard from anyone who has?  It doesn't really look much more complicated than the Roctave Divider and having the option of higher intervals would be even better.  Anyway, the only problem though is that the article says it's not really suited for bass which is what I want to use it with. Though I probably would only be using it while playing higher up on the neck so it might not be a problem.   Ultimately what I'd like to do is piece together a bass synth unit with an octave/interval generator and a VCF with an LFO and EG possibly using MOTM kits from synthtech.com. Triggering the EG was the only hurdle I hadn't figured out yet, but maybe the trigger output on the harmony generator could work?  Is the trigger output strong enough to trigger a Moog style ADSR EG?  I know you're probably thinking just buy an EH Bass Microsynth or something, but where would be the fun in that?

[Mark Hammer]

You threw your hands up too fast.  Read the sentence that follows the caveat about bass, and you'll see a recommendation is made to change C7 for bass use.

My guess is that easy use will not likely immediately follow mere construction.  Some tweaking and component swap-outs may be necessary to complement any given instrument and playing style.  This is not a weakness of the design, but a property of anything that has to figure out what note you are playing without you explicitly telling it (ah, keyboards are so much easier!).  The circuit is a bit like someone who went to Berlitz school to learn a foreign language and now visits a country where everyone speaks that language but with different idioms and accents from each part of the country.  Figuring out what everyone is saying underneath all that "noise" is hard.  The E&MM HG *can* be made more competent and consistent at doing that for bass notes.  It may require a bit of signal conditioning up front, but it can be done.

Note that you *don't* want to use the PCB mask as is.  It needs to be flipped around for PnP purposes, and definitely needs to be rescaled and have its own noise trimmed back.  What I usually do in such cases is enlarge it in as fine a resolution as my screen can manage (so aim for the highest resolution your card can support, even if the monitor itself can't maintain clarity of that sort of image), take a screen capture (Alt+PrnScrn), and copy the screen capture over into a graphics editting program (I use a circa 1994 Win 3.1 shareware version of Paint Shop Pro, that should give you some idea of how primitive it can be).  From there you can "tighten up" the lines and pads, flip it, size it appropriately and print out.

While a strong advocate of glossy photo paper, this PCB looks like a job for PnP or something of equally high resolution.  If not, those little skinny-ass traces near IC5 will bring you nothing but heartbreak.

[SonicVI]

No I didn't lose hope I read that part but it read more like a 'this will make it a little better but not that much' kinda mod  Plus I figured you might have a few tips on improving performance. Thanks for the PCB caveats. I'll do a screen grab and open it up in photoshop or illustrator to flip, scale, and clean it up. I always use PnP Blue for my PCB's so that's no problem.  I'm sure I'll have plenty of tweak questions for you if/when I do attempt to build it.     Do you know if it tracks very well?  In doing reading up on octave dividers (and now multipliers) here it sounds as though the Roctave Divider may have the best tracking of any but mostly due to it's built in compression/filtering which could be added before any octave divider pretty much couldn't it?    Yeah, keyboards are much easier, but I can't play bass and keyboard at the same time unfortunately, not yet anyway

[Mark Hammer]

Do you know if it (E&MM HG) tracks very well?  In doing reading up on octave dividers (and now multipliers) here it sounds as though the Roctave Divider may have the best tracking of any but mostly due to it's built in compression/filtering which could be added before any octave divider pretty much couldn't it?

No personal experience with the Harmony Generator.  RG sent me the article years ago (could have been Mike, it seems like at least 8 years) and I scanned and posted it but never built it.  Some people did however, and maybe they could chime in.  I have not seen any threads starting with "I built the Harmony Generator and haven't been able to get it to work", however.  That maybe more an indicator of who attempts it, rather than how foolproof it may or may not be.

Although the Rocktave uses companding, it does so in an "asymmetrical" way, such that the two are not perfectly complementary.  This was deliberate.  Although compression before any sort of pitch-division/tracking pedal can improve its performance, no matter how constant you try to keep the level of the input sinal, if you are working in the guitar/bass domain, eventually the signal fades out.  The semi-complementary expansion AFTER the octave division has a quasi-gating effect so that the divided output (which becomes unstable at that point) is severely downward-expanded and made relatively inaudible just before the point where it would be annoyingly sputtery.

So, the "tracking" thing really has two aspects - detecting the fundamental, and maintaining detection of the same fundamental over its lifespan - only one of which is properly addressed by sticking stuff in front of the divider.  That being said, one *could* implement some kind of non-companding approach in which compression is used up front, in tandem with a simple post-processing gate that takes its envelope/sidechain feed from before the compressor.

You could also use something like the Anderton Utra-fuzz, which uses a comparator action to produce a constant-level fuzzed output that turns to zero when it dips below threshold.  Of course, this lacks any sort of real envelope itself, being merely an on-off thing.  Although it chops the tippy tail off the note, the Rocktave DOES preserve a fair amount of dynamics and relatively natural decay.  That's where it stands out.

[RickL]

I've built the Harmony  Generator and, as Mark said, I can confirm that it works. I haven't played with it for a while but from what I remember it is pretty much a Blue Box on steroids.

It tracks about as well as a Blue Box if you follow the procedure in the article to adjust for best tracking. I didn't do that at first and thought it wasn't working. Harmony notes are, as you would expect, synthy sounding. If you want clean intervals buy a digital pictch shifter. It will do a 5th down though.

FWIW I built it using the 4ms CBCB method, sort of a combination of PC and perf. I had to use insulated wire for some of the connections where the traces are very close together but overall it wasn't too difficult.

Rick

[SonicVI]

I want synthy, so that's ok.   Since there only seems to be 1 report on the quality of the harmony generator from someone who built it in the archives I may just go with the Roctave Divider and see how the divide by 3 option sounds.  Or maybe I'll just learn to play bass with my left hand while playing keyboard with my right, or get some bass pedals, or just stop playing bass while I play keyboard.