Hi,
I'm looking for an Octave down schematic , but a "clean octave down" like the Boss OC2 does (yes I saw the scheamtic in the layouts gallery) instead of Slacktave MK2 schematic (that produce more a synth octave down)
Thanks.
DIY analog octave down circuits are generally not clean. There will be a fuzzy distortion along with the octave down effect which is the nature of the beast. My favorite analog octave down is the MXR Blue Box that I built about 4 months ago. I modified it to have a 1 and 2 octave down selection. If you want clean you need to go digital which I believe may be beyond the scope for DIYer's.
Quote from: fuzzo on June 08, 2009, 01:27:33 PM
Hi,
I'm looking for an Octave down schematic , but a "clean octave down" like the Boss OC2 does (yes I saw the scheamtic in the layouts gallery)
So you're looking for a schematic for something like the OC-2, and you've seen the schematic for the OC-2...? Is my brain dissolving slowly?
Lol. Yea dude, if you want hommes, sound just get the boss.
Shocktave is a good one.
Why are people so meam on this forum?
I did read a thread here where people were trying to emulate the pog with analog stuff. Like a green ringer mixable into a shocktave. Wutever happened with those guys?
the picture of his project is in the gallery.
i actually wanted to do that, but was then pleasently suprised that i could buy a pog, so i did, my life is forever changed
Quote from: Br4d13y on June 09, 2009, 12:11:08 AM
the picture of his project is in the gallery.
i actually wanted to do that, but was then pleasently suprised that i could buy a pog, so i did, my life is forever changed
What project?
Quote from: El Heisenberg on June 09, 2009, 12:06:23 AM
Why are people so mean on this forum?
I think that's what you were going for here.
I really didn't intend to be mean, I just don't get what the question is. He's looking for an analog octave schematic like the OC-2. He's seen the OC-2 schematic. I can't figure out what he could be looking for that he doesn't already have.
FWIW, with perhaps myself excluded, I think the people on this forum are way cooler and more helpful than any other forum I've ever seen.
Quote from: El Heisenberg on June 09, 2009, 12:20:36 AM
Quote from: Br4d13y on June 09, 2009, 12:11:08 AM
the picture of his project is in the gallery.
i actually wanted to do that, but was then pleasently suprised that i could buy a pog, so i did, my life is forever changed
What project?
Quote from: El Heisenberg on June 09, 2009, 12:07:51 AM
I did read a thread here where people were trying to emulate the pog with analog stuff. Like a green ringer mixable into a shocktave. Wutever happened with those guys?
Could you please point it out to me? I dunno which album. I might find it tonite, but just in case.
Hi
To answer to El Heisenberg, I saw the OC2 schematic but it's maybe, too complexe although I understand how it works. Beside I'm gonna buy one. I'm looking for something simpler and easier to build. The OC2 isn't complicated but needs a lot of attention to make a layout or worst, a veroboard. But maybe there's any other ways to build an octaver down pedal.
I'd like to build an octave box that contains an octave up and octave down with a clean blend (similar to Foxrox Octron or a Pearl pedal). I've almost finished to design the octave up effect but I know nothing about the octave down and how this octave is produced. So maybe my question can be stupid.
For the Shocktave, I think I read that sounds more like a vintage synth, producing a kind of scare wave , a nintendo sound (but maybe because of the outuput drive gain stage)
For the pog isn't analog, it uses a DSP.
http://hammer.ampage.org/files/SuperOctaver.ZIP
Check this out. It maybe of your interest
You could always build a Shocktave or Blue Box and lowpass the output to get rid of some of the square wave bite. It'd be worth trying since it only takes a couple minutes to rig a blue box up on the bread board.
Quote from: MusicAudio on June 09, 2009, 11:37:03 AM
You could always build a Shocktave or Blue Box and lowpass the output to get rid of some of the square wave bite. It'd be worth trying since it only takes a couple minutes to rig a blue box up on the bread board.
This is a great idea--I did this to my BB as an extra control, and it sounds great--however, you'll want a gain recovery after the LPF unless you dramatically raise the gain before going INTO the LPF.
IMO Boss OC-2 circuit could by significantly simplified if you would go true-bypass and wanted only one octave:
- very input and output buffers could be removed (since all output signals are buffered by op-amps, pasive output mixing could be used)
- 4027+A+D branch could be removed
I'm not saying, that what remains is simple, but maybe it's necessary for good analog octave-down (and OC-2 sounds really sweet).
T.
Quote from: MusicAudio on June 09, 2009, 11:37:03 AM
You could always build a Shocktave or Blue Box and lowpass the output to get rid of some of the square wave bite. It'd be worth trying since it only takes a couple minutes to rig a blue box up on the bread board./quote]
Or you could just look at Craig Anderton's Roctave Divider which does this and much more.
Quote from: R.G. on June 09, 2009, 12:11:04 PM
Or you could just look at Craig Anderton's Roctave Divider which does this and much more.
Are there any sound samples of Rocktave Divider? E.g. digitalized original "Roctave Divider Demo Tape" would be nice ;) I tried to find some, but did not succeed so far..
Thanks, T.
Hi guys and thanks for all those answers !
So, I study a little bit the Octave divider working principle, and that no really so hard that I thought.
http://www.bossarea.com/forum/uploaded/ssanyee/Boss_oc2.jpg
The signal passes through a buffer that ,after, divides it into 3 parts :
one does the low pass filter for the Octave divider section.
Tow others creates low pass filter for both octaves coming from BA634 and µPD4013C. Octave signal going through these filters by the transistor linked to the "+" input of op-amp. But there's also the ouput of input buffer connected to this AOP input; It mixes the dry signal with octave to remove a little bit the scare wave sound ?
So, for an Octave I've to keep the lowpass filter with IC creator of Octave, and a low passfiler to filtering the octave coming from it.
Hi, here is an abbreviated 2 knob version of the OC-2 schematic I put together for people looking for a simpler, cleanish (ie not a square wave) octave down. From the nature of the effect, it can't really get any simpler than this, boss's fundamental extractor (the bit on the bottom) is quite elegant and works better than most.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=9449&g2_serialNumber=2) (http://www.aronnelson.com/gallery/main.php/v/Processaurus/OC_2_chopped.gif.html?g2_imageViewsIndex=1)
Some explanation of how the boss circuit works and whatnot:
http://www.diystompboxes.com/smfforum/index.php?topic=58609.0 (http://www.diystompboxes.com/smfforum/index.php?topic=58609.0)
A nice octave down is the EBS OctaBass.
Quote from: Thomeeque on June 09, 2009, 12:30:12 PM
Are there any sound samples of Rocktave Divider? E.g. digitalized original "Roctave Divider Demo Tape" would be nice ;) I tried to find some, but did not succeed so far..
The Rocktave is a DIY pedal article published before the internet. It comes from a time before sound samples were common. You'd have to find someone with a Roctave and get them to make a sample.
I'd do it but my Rocktave is packed away in a box... somewhere...
I have the book. Its a huge schematic though. Never bothered. Maybe cuz i dunno what itll sound like.
Quote from: R.G. on June 09, 2009, 11:08:02 PM
Quote from: Thomeeque on June 09, 2009, 12:30:12 PM
Are there any sound samples of Rocktave Divider? E.g. digitalized original "Roctave Divider Demo Tape" would be nice ;) I tried to find some, but did not succeed so far..
The Rocktave is a DIY pedal article published before the internet. It comes from a time before sound samples were common. You'd have to find someone with a Roctave and get them to make a sample.
For Roctave Divider there was demo tape created by Mr. Anderton himself ;) And it seemed to be quite popular project (e.g. it is one of projects on GGG and even Line6 emulates it in higher models of their PODs!)..
Hey, you have heard this tape?? Where! Id love to hear anderton play!
pick up a mandrake memorial record!
A whos who record?
Does that iPhone not have Google? :icon_smile:
I didn't realize Anderton was in a band before now. It's kind of goofy stuff, but sort of illuminating in a way. So far, I'm not hearing much in the way of effects, just some volume swells. Now whenever I read his articles, I'll think about him bringing his newest creation to band practice, then having his bandmates tell him, "yeah, sounds cool, but let's try it clean instead". Poor guy.
Quote from: El Heisenberg on June 10, 2009, 06:07:38 PM
Hey, you have heard this tape?? Where! Id love to hear anderton play!
Nope, I only know it was made - it's listed here (http://www.craiganderton.com/) (Partial Discography/Tapes section) ;)
Edit: There is CA's Music (http://www.craiganderton.com/music.htm) subpage with some samples, unfortunately all links there are down :( You can try to google for those WMA's however (at least one (http://bitzi.com/lookup/GJLQKAGBADBEHAURNTC43I5JSYTR2AZ3?v=detail) could be maybe downloaded via eDonkey), good luck :)
T.
Quote from: El Heisenberg on June 10, 2009, 06:07:38 PM
Hey, you have heard this tape?? Where! Id love to hear anderton play!
I saw him playing live :) He was using a midi guitar BTW.
Quote from: Processaurus on June 09, 2009, 08:46:04 PM
Hi, here is an abbreviated 2 knob version of the OC-2 schematic I put together for people looking for a simpler, cleanish (ie not a square wave) octave down. From the nature of the effect, it can't really get any simpler than this, boss's fundamental extractor (the bit on the bottom) is quite elegant and works better than most.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=9449&g2_serialNumber=2) (http://www.aronnelson.com/gallery/main.php/v/Processaurus/OC_2_chopped.gif.html?g2_imageViewsIndex=1)
Some explanation of how the boss circuit works and whatnot:
http://www.diystompboxes.com/smfforum/index.php?topic=58609.0 (http://www.diystompboxes.com/smfforum/index.php?topic=58609.0)
Hi
is this project verified?
and if i want add to second stage of octave down,how can i do? :icon_eek:
Thanx
I am completely befuddled by this circuit, but I'm sure it's very clever.
Quote from: andromeda on September 26, 2010, 07:19:10 AM
Hi
is this project verified?
and if i want add to second stage of octave down,how can i do? :icon_eek:
Thanx
I haven't built it personally, but a few other people have here.
If you wanted the 2nd octave down take a look at Boss's original schematic (http://www.hobby-hour.com/electronics/s/oc2-octave.php) for the OC-2, and substitute half of a CD4013 dual flip flop IC for the rare roland single flip flop chip they use (IC6). I never had much use for the 2nd octave down, but maybe it's good for something.
Quote from: StephenGiles on September 26, 2010, 08:40:17 AM
I am completely befuddled by this circuit, but I'm sure it's very clever.
I don't understand where the magic comes from either, the part with the two half wave rectified signals being compared to the low pass filtered signal with the two comparators, driving the set/reset on the first flip flop is quite strange. Maybe it does some kind of hysteresis so little harmonic burbles don't clock the flip flop doing the octave division. I'm curious if it is a circuit used in signal processing electronics outside of musical instruments, or if it is an invention of Boss's.
Still, if it works don't break it - or words to that effect!
Quote from: Processaurus on September 27, 2010, 12:08:21 AM
I don't understand where the magic comes from either, the part with the two half wave rectified signals being compared to the low pass filtered signal with the two comparators, driving the set/reset on the first flip flop is quite strange.
If you just have a single comparator driving the flip flop then you always get a tracking problem because the natural second harmonic of the string changes phase compared with the fundamental. You get a little "blip" that rides on the main signal, and when it gets to the right point on the waveform it will be detected by the comparator, causing a false trigger. EDIT: This usually happens about 1 second after you pluck the string, not just during the final decay period.
By using another comparator that triggers on a different part of the waveform you fix this, since the 'blip' can't be in two places at once.
One comparator in the Boss circuit produces a pulse at the positive peak of the audio waveform, and the other at the negative peak. So although you will still get false triggers from each comparator, they almost never happen at the same time, and that's what counts as far as the flip flop is concerned.
Incidentally I discovered all this by trying to design a simplified octave down. Eventually I realised that it was impossible to do without two comparators, so my final circuit eneded up extremely similar to the Boss, much to my chagrin :icon_lol:
(Actually my circuit has slightly better tracking than the Boss since one of my comparators detects the zero crossing rather than the peak, but hey... ;)
The Rocktave addressed the blip-n-sputter at the end of notes, during that portion where fundamental detection was hit and miss, by using two different time-constants for the compression and expansion, such that the expanded signal decayed before the sputtering began.
There are effectively two paths in the Blue Box that have to be co-ordinated. The 4013 flip-flop requires that the fundamental signal feeding it be consistently above a given threshold in order to actuate the change in flip-flop state that produces the frequency division. The signal is brought up to that critical level by the huge gain of stage 1, and the comparator-like action of stage 2.
At the same time, the Blue Box uses two transistors as gates. The envelope-follower path from stage 1 feeds the collectors of Q2 and Q3, treating them as voltage-controlled gates, to shut down the output before the signal feeding the 4013 falls below the point of stability and the sputtering begins. Of course, as anyone who has built one can tell you, the approach adopted by the Blue Box is NOT one size fits all. Sometimes it is effective at sputter-elimination, and sometimes not. I keep meanng to tinker with the envelope follower section to see if there are some simple mods that can be readily adapted to a 3-way toggle for a 3-sizes-fits-all arrangement.
In the meantime, the solution that Anderton came up with for the Rocktave, using a compander chip, more reliably tackles the de-sputtering across a wider array of signal inputs, by reducing the differences in those inputs through compression. The fact that the clean signal continues after the octaves are gated out, makes for a more natural-sounding decay. The BB, of course, has only distorted and sub-octave, so the abruptness of even well-functioning gating shows through.
The huge gain of the input stage in the BB that feeds the envelope follower sort of achieves some compression by reaching the headroom maximum, but not flawlessly. The problem is that the dynamic range below the critical threshold for triggering the 4013 is still maintained, even though the dynamics above a certain point are compressed. The compressor half in the Rocktave does us the service of not only reducing the dynamics of the peaks, but increasing the level of the softer portions as well. I wonder if some combination of a soft clip in stage 1 (e.g., a diode pair in series with a small-value fixed resistor in the feedback loop) and a compensating change in the collector resistor values of Q2/Q3 might succeed in applying some dynamic range constriction across a broader range of signal amplitudes.
.
Quote from: merlinb on September 27, 2010, 09:34:18 AM
Quote from: Processaurus on September 27, 2010, 12:08:21 AM
I don't understand where the magic comes from either, the part with the two half wave rectified signals being compared to the low pass filtered signal with the two comparators, driving the set/reset on the first flip flop is quite strange.
If you just have a single comparator driving the flip flop then you always get a tracking problem because the natural second harmonic of the string changes phase compared with the fundamental. You get a little "blip" that rides on the main signal, and when it gets to the right point on the waveform it will be detected by the comparator, causing a false trigger. EDIT: This usually happens about 1 second after you pluck the string, not just during the final decay period.
By using another comparator that triggers on a different part of the waveform you fix this, since the 'blip' can't be in two places at once.
One comparator in the Boss circuit produces a pulse at the positive peak of the audio waveform, and the other at the negative peak.
Incidentally I discovered all this by trying to design a simplified octave down. Eventually I realised that it was impossible to do without two comparators, so my final circuit eneded up extremely similar to the Boss, much to my chagrin :icon_lol:
(Actually my circuit has slightly better tracking since one of my comparators detects the zero crossing rather than the peak, but hey... ;)
The fundamental extractor portion of the OC-2, as well as the MFOS SubCommander, and possibly also Merlinb's circuit (if I'm understanding him correctly), is what I would call a window comparator. However, where a "textbook" window comp uses two fixed voltage references, here the upper and lower references are the positive and negative signal envelopes, respectively. This is probably what gives it good tracking, because it has an envelope detector (actually two!) built in. The signal is compared to its own envelope, and the envelope always lags behind the signal by the time constant set by the parts after the rectifiers, so you nearly always have a definitive difference in the two voltages which helps avoid false triggering.
QuoteBy using another comparator that triggers on a different part of the waveform you fix this, since the 'blip' can't be in two places at once.
That seems like a really good explanation, thanks!
Thank you both, Alex, Merlin. That sheds some interesting light. I still might need to see it at work on a gross input signal with harmonics to get a feel for how and when the pair of comparators trigger. Merlin, did you mean the comparators trigger right at the positive and negative peak of the waveform?
I wonder how fast the sort of DCish envelope voltage charge and decay on pins 2 and 12 of IC2, does it drain out completely during the second half of the input signal frequency's period?
Also, the precision rectifiers are curiously different than the textbook circuit, here the input signal goes to the non-inverting input, rather than through a resistor to the inverting input.
Quote from: Processaurus on September 28, 2010, 10:07:58 AM
Merlin, did you mean the comparators trigger right at the positive and negative peak of the waveform?
Yes. Well sort of. They compare the original audio signal with the smoothed output output of the precision rectifiers, so you get a pulse 'close' to the peak of the audio. Here's a simplified diagram of what I mean.
(http://i81.photobucket.com/albums/j207/merlinblencowe/OC.jpg)
QuoteAlso, the precision rectifiers are curiously different than the textbook circuit, here the input signal goes to the non-inverting input, rather than through a resistor to the inverting input.
Not sure what you mean by that. They look like the standard precision rectifier I have seen in the textbooks...
Sorry to cut this intersting talking but , no one , made a PCB for the OC2 chopped ? (make it on veroboard would require a lot of bravery :icon_lol:)
Quote from: fuzzo on September 28, 2010, 12:53:32 PM
Sorry to cut this intersting talking but , no one , made a PCB for the OC2 chopped ? (make it on veroboard would require a lot of bravery :icon_lol:)
I think Taylor has something Planned in that department for a run of PCBs.
Hi guys,
Im fairly new to this octave stuff but have made other pcbs in the past.
I cant find any pcb layouts for this pedal anywhere on the net and Im fairly useless at reading schematics, anyone know where to find one/have pcbs (or just the layout) for sale?
Cheers,
Kris.
Musicpcb.cOm
Quote from: fuzzo on September 28, 2010, 12:53:32 PM
Sorry to cut this intersting talking but , no one , made a PCB for the OC2 chopped ? (make it on veroboard would require a lot of bravery :icon_lol:)
I built mine on overboard. I'd say it was more stupidity/naivety than bravery. I considered designing a board for an OC2 clone, but to be honest, couldn't be bothered.
It was about my 10th build or something and I approached it with childlike confidence, as nobody had told me it should be difficult. I had a dicky switch and a dry joint on one of the pots, so fortunately I didn't have to probe the board to trace faults on there.
Quote from: merlinb on September 27, 2010, 09:34:18 AM
Incidentally I discovered all this by trying to design a simplified octave down. Eventually I realised that it was impossible to do without two comparators, so my final circuit eneded up extremely similar to the Boss, much to my chagrin :icon_lol:
(Actually my circuit has slightly better tracking than the Boss since one of my comparators detects the zero crossing rather than the peak, but hey... ;)
I hope people forgive the necro (but it seems like the real necro happened back in November anyway). I'm really interested in this. If one of them detects peaks and the other detects zero crossings then does that mean the flipflop output is roughly 25% (or 75%) duty cycle? And what is the advantage of having one of them detect zero crossings? I've been reading this thread mainly for the stuff about the fundamental extractor because I was looking for some way to get a clean square signal to use with a PLL to make a (probably glitchy) synth octave up effect.
QuoteIf one of them detects peaks and the other detects zero crossings then does that mean the flipflop output is roughly 25% (or 75%) duty cycle?
From the first flip flop, yes. After being divided by the second flip flop it will be 50% (inasmuch as duty cycle has any meaning when it is tracking a constantly varying signal)
Quote from: SirPrimalform on March 31, 2015, 09:40:51 AM
And what is the advantage of having one of them detect zero crossings?
Zero crossing are easier to detect than peaks. Peaks are always changing in height. Zero crossings are always..well, zero.
http://www.diystompboxes.com/smfforum/index.php?topic=76997.msg732912#msg732912
http://www.diystompboxes.com/smfforum/index.php?topic=76997.msg733108#msg733108
Quote from: merlinb on March 31, 2015, 02:53:50 PM
QuoteIf one of them detects peaks and the other detects zero crossings then does that mean the flipflop output is roughly 25% (or 75%) duty cycle?
From the first flip flop, yes. After being divided by the second flip flop it will be 50% (inasmuch as duty cycle has any meaning when it is tracking a constantly varying signal)
Quote from: SirPrimalform on March 31, 2015, 09:40:51 AM
And what is the advantage of having one of them detect zero crossings?
Zero crossing are easier to detect than peaks. Peaks are always changing in height. Zero crossings are always..well, zero.
http://www.diystompboxes.com/smfforum/index.php?topic=76997.msg732912#msg732912
http://www.diystompboxes.com/smfforum/index.php?topic=76997.msg733108#msg733108
Well yes, I suppose that last one was a bit of a silly question. I guess I should have asked why Boss went to the trouble of detecting the peaks if zero crossings do as good a job (or better even)?
Quote from: SirPrimalform on March 31, 2015, 08:52:34 PM
I guess I should have asked why Boss went to the trouble of detecting the peaks if zero crossings do as good a job (or better even)?
Maybe they copied it from bits of an older circuit. Maybe they tried it but found it didn't work as well in their particular incarnation. Maybe they just didn't think of it (the world of FX pedals doesn't attract the cream of the engineering crop :icon_lol:). Who knows.