Hi guys!
I've got few questions ;) I'm working on my special stompbox. It will be only 1 octave down (Boss OC-2 clone). I built two versions already (1% metal resistors & polyester film caps). First version was octaver only, but I know that analog octavers have tracking problems with lower notes so I decided to add compressor (CS-2 and Joyo mixed) before OC-2 in second version. In my opinion it didn't help, maybe tracking was even worst.
So there are questions:
1. Which compressor (with available schematic) could be the best to improve the tracking?
2. Which OP-amps will be the best for this project - something like: TL074, LM324 or LM358, TL072, or maybe TL022?
3. Compressor and octaver was connected on one PCB so I removed output buffer from compressor and input buffer from octaver. Do you think that octaver's buffer could change something with tracking?
Thanks for tips! :)
*Sorry for my English :icon_redface:
Best way I have found to improve tracking on this sort of thing is to use the neck pickup and roll back the tone knob a bit. I doubt a compressor would be much help, actually.
I built an OC-2 once that worked pretty well. I'll see if I can find my notes for it (it ended up getting recycled for reasons other than quality...).
Welcome!
I'm not sure about the compressor to improve tracking.
I would think in some buffer, boosting a little bit. :icon_confused:
1. I doubt you will find a compressor to be all that useful. What you need is something to accentuate the fundamental of the input so you don't run into the problem of having the circuit lock onto a harmonic of the signal. As EBK said, use the neck pickup (which has the highest content of fundamental) and roll off the tone control so you limit the upper harmonics.
2. The LM324 and TL022 (or TL062) are really not good enough for guitar-level audio. The noise level is too high. The others are OK but you may have a problem with dynamic range on the LM358. Check to make sure the output doesn't reverse from positive to negative or vice versa when you exceed the common-mode range.
3. If you have an input buffer, you may be missing out on the treble cut you get from having a low input impedance driven by a pickup coil. The coil has a typical inductance of 3 to 5 Henries and driving a low input resistance causes a rolloff of the input that emphasizes the fundamental. To get this effect, the volume control on the guitar has to be maxxed. Of course, it would be better to use a buffer and do the rolloff after the buffer so there is no difference in operation with any signal input.
You have to toggle a flip-flop to get the signal an octave down but this means you have to have some method of making sure you are toggling on the fundamental. Suppressing the higher harmonics enables you to do this without getting wolf notes - notes that suddenly go up an octave.
you could put a boost or overdrive before it and experiment with boosting the signal into the oc2 also if it has a tone control you can turn down the treble before it, see what helps.
Thanks for all answers! (I didn't received notifications :( )
I'm almost sure I've got a solution for my problem - Q-boat designed by Merlin! I never found this project before because I always looked for some OC-2 schematics.
I've found 3 versions of this effect, but I think I will build my using Merlins PDF (2014) and TH Custom Effects version.
hey swisher, welcome to the forum. yer english is fine (where are you from?), carry on.
if you are interested, I've been working at a sub-octave with Ben Lyman, based on (the idea of) the shocktave. I think I've taken it as far as I can, it needs some more hands/breadboards/ears to say if it's any good. it will 'track' the wound strings (with a few warfs) ok when played with the thumb.
I did some fooling with adding a compressor to the circuit to improve tracking, but it doesn't work/help. as the others say, it's all down to suppressing what you don't want, the other harmonics. (I also tried the U-boat, couldn't get it to sink to my likings.)
Maybe compressor is working only as an idea and technically it doesn't work. I wanted to build prototypes of octaver and compressor and tested them together with some part's values etc. but I was to lazy for that.
I saw few videos on YT with "Q-boat" yesterday, and I hope now it can works. Here is really good tracking:
Shocktave looks really easy. Do you have some videos how it works?
BTW, I'm from poland
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
This logic makes this whole hobby null and void.
I've used the tagboard layout to build an OC-2 and dalyk has a great OC2 layout in an a 1590b size.
You'll find many questions like the OP on this forum and others, all have resulted in a boost in front. I never cared for that answer myself, but I love THCustoms interpretation of the Uboat. It works well with high output pickups.
Good luck on your quest, I love octavers too.
Sent from my iPhone using Tapatalk
Quote from: jimilee on September 02, 2017, 07:56:43 PM
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
This logic makes this whole hobby null and void.
I've used the tagboard layout to build an OC-2 and dalyk has a great OC2 layout in an a 1590b size.
You'll find many questions like the OP on this forum and others, all have resulted in a boost in front. I never cared for that answer myself, but I love THCustoms interpretation of the Uboat. It works well with high output pickups.
Good luck on your quest, I love octavers too.
Sent from my iPhone using Tapatalk
Don't get me wrong, that's why I say 'my humble opinion' :)
Some people like the old octave monophonic tracking...and some people not.
BTW, I suggested the same upgrade as you.
This where I should confess that the E-H Pitchfork is partly what caused me to recycle my OC-2....
At the time I first saw/heard the pitchfork, I had just recently finished boxing up this:
(http://i.imgur.com/9WHNuTJl.jpg)
It was an OC-2 in the same box with a Maestro Brassmaster. I wired it up so I could feed the Brassmaster input with the dry signal or either of the two OC-2 octave signals, which was rather cool sounding. Giant box. A 1590BBS, I believe.
I was quite pleased with it. Feeding a sub-octave into a Brassmaster made a powerful sound, which I could still freely mix with the OC-2 outputs (there's a third circuit board hiding under somewhere), making it sound as demonic as I pleased. :icon_twisted:
But.... Once I saw/heard the Pitchfork, my pride was deflated. I felt I had way too many parts in way too huge of a box, with much less agility than that tiny, less expensive commercial pedal. Anyway, there's most of my OC-2 story. I still love the Brassmaster though.
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
The pitchfork is a digital effect and I believe at some point he said he wanted an all-analog approach.
--
Scarlett Johansson uses a Burst Box with her Telecaster.
Perhaps consider the Madbean Lowrider:
http://www.madbeanpedals.com/projects/LowRider/docs/Lowrider2015.pdf
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics
If anyone tought "go buy some" you would have nothing to buy :)
Here is my octave v1.5 (CS-2 + OC-2). As you can see it's Sabro layout but on designed PCB.
(https://s26.postimg.org/lakx62o2d/IMG_20170412_142341.jpg) (https://postimg.org/image/lakx62o2d/)
I want to build simple pedal. Only first octave down on 100%, mix pot only for adjust the sound, then replaced with resistors.
there is a thread, with some sounds, and some reading ......
http://www.diystompboxes.com/smfforum/index.php?topic=117811.0
Quote from: Hatredman on September 03, 2017, 09:53:58 AM
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
The pitchfork is a digital effect and I believe at some point he said he wanted an all-analog approach.
--
Scarlett Johansson uses a Burst Box with her Telecaster.
I mean, its a personal case to the thread "f*ck it! I'll better purchase one" [emoji23]
Great looking builds here...but I havent the patient to that kind of stuff
Quote from: Plexi on September 03, 2017, 11:51:59 AM
Quote from: Hatredman on September 03, 2017, 09:53:58 AM
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
The pitchfork is a digital effect and I believe at some point he said he wanted an all-analog approach.
--
Scarlett Johansson uses a Burst Box with her Telecaster.
I mean, its a personal case to the thread "f*ck it! I'll better purchase one" [emoji23]
Great looking builds here...but I havent the patient to that kind of stuff
Yep. I can relate to that. Fuzzes are a more immediate Satisfaction :)
--
Scarlett Johansson uses a Burst Box with her Telecaster.
Quote from: Hatredman on September 03, 2017, 07:14:38 PM
Quote from: Plexi on September 03, 2017, 11:51:59 AM
Quote from: Hatredman on September 03, 2017, 09:53:58 AM
Quote from: Plexi on September 02, 2017, 04:18:11 PM
Again...sorry my brutal sincerity...but I wouldn't waste my time on this [emoji16]
Go for a Ehx Pitch Fork...and save time/ lose one's temper with complicated and inneficients old schematics hahaha
Just MHO
[emoji16]
The pitchfork is a digital effect and I believe at some point he said he wanted an all-analog approach.
--
Scarlett Johansson uses a Burst Box with her Telecaster.
I mean, its a personal case to the thread "f*ck it! I'll better purchase one" [emoji23]
Great looking builds here...but I havent the patient to that kind of stuff
Yep. I can relate to that. Fuzzes are a more immediate Satisfaction :)
--
Scarlett Johansson uses a Burst Box with her Telecaster.
I would say: go for a Foxx TM...and instead of play the higher octaves to get the lowers...play the lowers and get the highers hahaha
One of the big hurdles in any octave divider that uses a flip-flop to divide the pitch by half is the intermediate zone where the signal level is sort of close enough to trigger the flip-flop, but not quite. That's what produces the sputter that drives folks crazy about octave dividers. A compressor can hold the the signal level high and consistent enough to be above triggering threshold more of the time, but it also boosts parts of the signal that might not otherwise trigger the flip-flop into that sometimes-yes-sometimes-no zone. So, less sputter, but not NO sputter.
In some respects, what can be better than a compressor at squelching the in-betweenies is a simple gate or comparator; something that forces the signal to be either clearly above or clearly below the triggering threshold. One simple strategy is to stick back-to-back diodes in series with the signal at some point prior to the flip-flop so that unless the signal is clearly above the forward voltage of the diodes, there won't be any false triggering. What sort, or how many diodes, would depend on the overall gain structure of the circuit, and the most sensible and effective spot to insert them.
Yes, this will produce crossover distortion, but I'm assuming the octave generated will either be very square so you won't notice how much sideways clipping is produced, or the octave will be heavily filtered to make it sound more like a bass, which will soften the crossover distortion and make it less apparent.
The "buy or build" argument needs to take into account relative costs versus benefits too.
There are many, many **WAY** overpriced boutique fuzzes and overdrives out there that you can *easily* build yourself and tune to your personal idea of fuzz/drive heaven for less than they sell them for, and with twice the satisfaction.
At the same time, there are some *amazing* and very low cost digital pedals out there that do a brilliant job of some of the things that analog electronics will never be any good at (like pitch shifting and some delay effects).
So if you just want to get the job done well, get a EH pedal. If you want to build an old-school flip-flop octave down divider, go for it, but "caveat constructor", to hack the latin.
T.
Of course I could buy digital octaver and there will be no tracking problems, but:
1. I want to build it myself
2. I don't want any knobs (just one setup)
3. All closed in enclosure with special painting
4. That satisfaction...
I've done 80% of U-boat (I don't have all parts). This project looks promising so I will try it :)
Thanks for all answers!
I'm not so sure such a unit can be produced in a set-and-forget manner. Not unless you know you will always use it with guitar X, and that it will never have anything else between the guitar and pedal to change the signal in any way. These things CAN be twitchy, and require adjustments to eliminate, or at least reduce, the twitchiness. If you are blessed with the circumstances that allow you to anticipate only one set of conditions, more power to ya. But I'm not entirely convinced such a circumstance actually exists.
Still, kudos for pushing on ahead instead of buying.
I need this effect for one tone only. Octaver as first effect in chain, then some gain from preamp - and that's all. Maybe some delay, but probably not. I can use it with one guitar if it will be needed.
I didn't tell this but I'm satisfied with OC-2 sounding (and his bad tracking). But if it's possible to build something better, even a little, I want to build it :)
Hi swisher,
the thing with "OC-2 type" bass octavers is that they need to switch between an inverted and a non inverted signal "exactly" on the positive or negative peak. For that they need a peak-detector circuit, which is not a trivial thing to design if one is dealing with input waveforms that are not well defined. In practice, the OC-2 uses an envelope follower and compares the input of that envelope follower to its output using a comparator. (In fact it does that twice, once for the negative, once for the positive part of the signal because the flip-flop needs a set and reset signal.) So what that circuit really detects is when the original waveform drops below its own envelope. If that works with theoretical infinite precision and the input is a wave with exactly one peak point (as for example a sine wave), then the circuit detects exactly the peak. Problem #1 is: There is a difference between praxis and theory and it is bigger in praxis than in theory. In a real device, there needs to be a finite difference between the two signals that are being compared and therefore the comparator will switch a little after the actual peak. Problem #2 is: The less pronounced the peak of the original waveform is, the longer the delay between actual peak and peak detection gets. In the extreme case of a square wave input (which does not have a defined peak), "peak detection" happens on the zero transition. Guitar or bass signals can be seen as something between sine and square wave. The OC-2 deals with this problem by putting a 3rd order Sallen-Key low-pass filter in front of the peak detektor. the problem there is that this method is only effective over some frequency range. The deeper the input signal, the less effective is this method. That is why OC-2 type bass octavers do not like distorted (i.e. more "square-wavy") input, especially on bass.
So, in conclusion: Peak detection is difficult and there is no method to make it work perfectly with imperfect inputs, like a guitar.
The alternative would be something that relies on zero-transition detection instead, which is much much easier to do reliably for a guitar signal. Valve Wizards U-Boat and Slackers Slacktave use this method. With that you can basically just boost the $#!+ out of your input signal before you feed it to a comparator or better yet a Schmitt trigger, and get really good tracking at any volume. With this method, a compressor up front helps, with the OC-2 method it does not. Of course you then get a different sounding output than with an OC-2. I am working on a method to use zero-transition detection to detect peaks, but that is a bit more involved and I'm not sure yet if I will get it to work at all. So, I think it is possible to make a better tracking bass octave. But it will not sound like an OC-2 or it will be much more complicated. Things get much easier if you are OK with something synth-sounding like the Slacktave that uses the output of a ripple counter directly. Add some tone-filtering and that can sound quite nice. I think the old MXR M88 Bass Octave did just that (except with a flip-flop instead of a ripple counter) but I am not sure. This method of course kills all playing dynamics on the octave signal but thats not necessarily a bad thing and happens anyway when you stick to the usual playing caveats for analog octavers.
Good luck with your project and keep us posted,
Andy
Maybe some ideas from here? "M51134 OCTAVER" It's not the Meatbox... but kinda like it.
http://www.diystompboxes.com/smfforum/index.php?topic=101580.0
When the harmonics are stronger than the fundamental, even zero-crossing detection is fooled, since the harmonics can add extra crossings. This more likely early in a guitar notes life. The same strong harmonics create extra peaks. I keep thinking there must be a way to combine xing and peak detection, but every way I think of doing it fails. Our brains know what note is played because of the harmonic relationships, but the electronics are going to be fooled everytime.
As Andy notes, low pass filtering helps but ideally should track the fundamental or else it's at best a 11/2 octave range - which brings us back to the problem of pitch detection again.
If you can wait for something to average the signal enough to get the fundamental frequency (like your guitar tuner does), you have a chance, but you will always have some delay before you hear anything, which would be longer the lower the fundamental pitch is.
@ Jim
Well, yeah, one problem is that at the beginning of a note, the strings movements are quite chaotic before they settle down to oscillate periodically. For a bass played finger style this is much less pronounced than when playing with a pick (guitar or bass). Using a Schmitt trigger instead of a comparator to detect the zero crossing and putting a low pass before that should help. I tried to post that in another thread a minute ago but the image server seems to be down. I'll try again later. That thing also uses zero-detection to find the peak. Not sure if it works though, just an untested brain-child so far.
Also: even if our guitar signal was a perfect sine wave from the nanosecond the pick leaves the string, we would still run into an uncertainty, which is quite similar to some quantum phenomena. A frequency is only defined for a periodical oscillation but during the first oscillation, there is no periodicity yet. Consequently anything that analyses the frequency to produce another signal is always going to be a little late for the party. Damn physics...
So, I guess "perfect" tracking is simply impossible, both practically and theoretically. But I do think there is room for improvement over the designs that have been around since the dawn of time.
Andy
Edit: Now the upload worked:
http://www.diystompboxes.com/smfforum/index.php?topic=118550.0