Should this work?

[digi2t]

The board is available, though it's double sided.



As is the wiring;



If I do end up building this, yes, it will be on vero.

On another development note, I found that you have to adjust the 470K resistor going to the base of the dual tranny. I found that reducing it (with a trimmer) to a 60K to 120K range gives the unit a really nice envelope quack on the note decay, not to mention that the VCF sensitivity adjust becomes much more apparent. I believe that this resistor should be tailored to the transistor, a bias resistor of sorts. It's sounding much cooler now. Now, if I can figure out how to calm down the notes from jumping octave so much, I'd have a real beauty on my hands. I believe that the VCO is responsible for this, so I have to figure out how to stablize this somehow. It really depends on how hard I hit the strings right now, but even if I pick steady, I still get some jumping/glitching.

[slacker]

Sounds promising, great that someone's finally taken this beast on. As you've already found out  a TL074 won't work properly in this, TL07x opamps don't like it if their inputs get closer than a volt or so to the negative supply, ground in this case. Depending on the settings of the threshold and duty controls those inputs can go all the way to ground. Those sections need a single supply opamp like the LM324 that has inputs then can go all the way to ground.

[digi2t]

Sounds promising, great that someone's finally taken this beast on. As you've already found out  a TL074 won't work properly in this, TL07x opamps don't like it if their inputs get closer than a volt or so to the negative supply, ground in this case. Depending on the settings of the threshold and duty controls those inputs can go all the way to ground. Those sections need a single supply opamp like the LM324 that has inputs then can go all the way to ground.

Well Ian, once again, I thank you for the insight on the 074. Something that I didn't know. Do you think I should bother with trying an RC4136, or would the LM324 do fine. After all, the pin layout of the original HEP6129 matches the LM324, so I don't think anything is to be gained by messing up the PCB layout either.

Any ideas on curing the VCO glitching? I get the the feeling that it's a "nature of the beast" thing. With a signal generator, it tracks steady.

[slacker]

I'd think the 324 will do the job just fine, I'm not sure an RC4136 would work, I had a look at a datasheet and it looks like it's input voltage range only goes to within a volt of the supply, so you'd probably get the same issues as with the TL074.

I don't know anything about the Freq to voltage converter so it might be fine but the input stage looks far too simple to me. There doesn't appear to be any lowpass filtering to reduce the harmonics from the guitar, this is possibly what makes it glitch as it jumps between tracking the fundamental and the harmonics.
You could try replacing the FET stage with the first 2 or 3 opamp stages of this http://www.eskimo.plus.com/fxstuff/slacktave.png that will boost the guitar signal and filter out a lot of the harmonics which will hopefully make it track better.

[digi2t]

Smashing piece of info there regarding the input side. It makes sense. I'll try that, and report back.

I'm really encouraged right now regarding the filtering. Since I adjusted the bias on the transistor, and I also found this drawing from the same book;



I noticed that they're using Ge diodes for the envelope follower section, so I swapped out the Si ones on the breadboard on the envelope follower section. It's much more "quackier" now, a bit like running an old analog synth through a Mutron. The VCF sensitivity is even more responsive now. I'm telling you brother, I feel like I'm getting close.

Another neat thing is pulling out the 0.22uF cap on the LM2907. It turns into a loud, obnoxious, fuzz grinder. I mean, really nasty. I think the only thing I have in my arsenal that can sound that nasty is my Geiger Counter. Might deserve an extra "lights out" switch here.

I hope rearranging the front end works, that would be that cat's ass. Thanks again Ian.

[Lurco]

Smashing piece of info there regarding the input side. It makes sense. I'll try that, and report back.

I'm really encouraged right now regarding the filtering. Since I adjusted the bias on the transistor, and I also found this drawing from the same book;



I noticed that they're using Ge diodes for the envelope follower section, so I swapped out the Si ones on the breadboard on the envelope follower section. It's much more "quackier" now, a bit like running an old analog synth through a Mutron. The VCF sensitivity is even more responsive now. I'm telling you brother, I feel like I'm getting close.

Another neat thing is pulling out the 0.22uF cap on the LM2907. It turns into a loud, obnoxious, fuzz grinder. I mean, really nasty. I think the only thing I have in my arsenal that can sound that nasty is my Geiger Counter. Might deserve an extra "lights out" switch here.

I hope rearranging the front end works, that would be that cat's ass. Thanks again Ian.

The upper 4700 cap of the bridged-T feedback filter in the output opamp is deadshorted in that drawing!

[glops]

Oh my, this thread is awesome!

[WhenBoredomPeaks]

It sounded more interesting to me than simple squares. (and i know that the octaver side is two squares mixed)

Is it possible that the MC14520's octaver output overdrives the filter?
(according to the datasheet it is a 9vpp square wave.

(or it was just your cam or amplifier?)

Btw we have 2 unused pins there (13,14) with even lower octaves.

edit: it sounds like you mixed up the BP and LP modes in the video.

[digi2t]

The upper 4700 cap of the bridged-T feedback filter in the output opamp is deadshorted in that drawing!

Huh, didn't notice that before. Good thing that it's not the part of the drawing that inspired me. 

Is it possible that the MC14520's octaver output overdrives the filter?

Maybe... could be worth trimming them down to find out. I'll put that on my Honey-do list, right after I rig up and try the Slacktave front end.

Btw we have 2 unused pins there (13,14) with even lower octaves.

Yeah, but the octave is already way deep enough. I don't feel like making mud here.

edit: it sounds like you mixed up the BP and LP modes in the video.

I'm just sticking the jumper in as per the drawing, and calling it out. I think it's a typo on the drawing. Maybe the LPF should read HPF, 'cuz there's no Low Passing going on when I use the so called LPF side.

Just for the record, all this insanity started when someone wrote me on my Youtube account, wondering if I could build a Schumann PLL clone, linking me this schematic. This ain't no PLL, though it may or may not represent a portion of it. But, it piqued my curiousity nonetheless. I'm still looking for a PLL, to either study, or even buy, to clone. I would LOVE to get my hands on that monster  .

[WhenBoredomPeaks]

The upper 4700 cap of the bridged-T feedback filter in the output opamp is deadshorted in that drawing!

Huh, didn't notice that before. Good thing that it's not the part of the drawing that inspired me.  

Is it possible that the MC14520's octaver output overdrives the filter?

Maybe... could be worth trimming them down to find out. I'll put that on my Honey-do list, right after I rig up and try the Slacktave front end.

Btw we have 2 unused pins there (13,14) with even lower octaves.

Yeah, but the octave is already way deep enough. I don't feel like making mud here.

edit: it sounds like you mixed up the BP and LP modes in the video.

I'm just sticking the jumper in as per the drawing, and calling it out. I think it's a typo on the drawing. Maybe the LPF should read HPF, 'cuz there's no Low Passing going on when I use the so called LPF side.

Just for the record, all this insanity started when someone wrote me on my Youtube account, wondering if I could build a Schumann PLL clone, linking me this schematic. This ain't no PLL, though it may or may not represent a portion of it. But, it piqued my curiousity nonetheless. I'm still looking for a PLL, to either study, or even buy, to clone. I would LOVE to get my hands on that monster  .

I wouldn't trim back on the signal level, "clean" squares are boring.

Btw what happens in the first IC?(LM2907) I guess they use the freq-to-volt conversion of the IC to make the filter open up more as you play higher notes. (the "VCF lineality" section)
But what actually comes out of the second pin of that IC? Is it just passes the guitar signal unmodified or the chip "did" something to the signal to make it into a more useful clock signal?
Maybe they use the freq. doubling feature of the IC and and the clocking signal is an octave higher than the guitars?

edit: it is interesting but we are interested in the opposite parts of the circuit, i found the divider/octaver part interesting (while you are about to replace it with something with better tracking/cleaner sound) and the others are not that interesting for me since i have all of that stuff in modular format but more advanced.

[digi2t]

OK, test number two.

1) I've used Ge diodes for the filter section.
2) Took Ians advice, and used a dual opamp for the input. Just the two stages is plenty. In fact, it's so hot that I had to used a 10K trimmer to ground to turn it down. A TL022 gave the best results. I found that 358's, or 072's, gave me too many "artifacts" as the note decays. 4558 lacks the sensitivity of the 022. Note that I'm using half of an LM324 in the video. I swapped out for a 022 thereafter, and noticed a bit better performance.

Here's the result so far;

I've noticed a difinite improvement with Ian's idea. Working with the neck pickup (I say bridge at the end of the video, sorry), seems to help as well. Using the lower registers makes the octave down so fat though, that it doesn't sound that great. Upper register work is better.

Btw what happens in the first IC?(LM2907) I guess they use the freq-to-volt conversion of the IC to make the filter open up more as you play higher notes. (the "VCF lineality" section)

Yes, that does make sense. I can set this trimmer to open up higher frequencies of the filter. Pin 2 of the LM2907? Plugging the amp into pin 2 directly, it produces one hell of a raunchy squarewave fuzz. It doesn't have a long sustain, and the decay gates. Very nasty  .
The struggle continues...

[WhenBoredomPeaks]

Why do they send that "hell of a raunchy" square wave into the clock input of the octaver ICs without any lowpassing? Wouldn't it make tracking worse?
On the other hand a square wave looks more like a "real" digital clock signal.

[Thecomedian]

are there any example of this being used in actual music?

[valvusmusicus]

Hi All-Is there really a PCB design/ready built for this please?

[Mark Hammer]

This is the layout that accompanied the original article.

And the wiring diagram accompanying that:

Whether it is accurate, or accommodates any suggested adaptations/mods, is a whole other thing.

[digi2t]

Woah! Blast from the past.

But kind of tempting to put on a piece of perf.

[KarenColumbo]

Could you re-up the Youtoob vid? Id love to hear a prehistoric cat driving a ferrari with octaves on both sides!!

[digi2t]

Sure sonny! 

[rankot]

Nice videos!

[Marcos - Munky]

I really liked this one! Sadly it doesn't fit in a 1590A