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Analog guitar synths

5/29/2000 6:02 PM
Truck	Analog guitar synths Hi there, does anyone have a schematic for one of those(Roland,Korg)? I'm figuring out right now how to built a pitch detection device but it's pretty hard. Once I have the pitch detecting device I'm saved, so if anyone has some tips/ideas on building one I'd love to hear them. Thanks in advance, Truck P.S. In case you don't know:A pitch detection device is a device that can filter out the base frequency of a guitar signal and in turn drive a VCO with it.

5/29/2000 6:02 PM

Truck

Analog guitar synths

Hi there, does anyone have a schematic for one of those(Roland,Korg)? I'm figuring out right now how to built a pitch detection device but it's pretty hard. Once I have the pitch detecting device I'm saved, so if anyone has some tips/ideas on building one I'd love to hear them.

Thanks in advance,
Truck

P.S. In case you don't know:A pitch detection device is a device that can filter out the base frequency of a guitar signal and in turn drive a VCO with it.

5/30/2000 2:51 AM
eth	Many analog synth's use a low pass filter- Second order atleast. Doing it this way will atleast get you zero crossings cleaned up. There are some schematics around for the EH synth. Check out any ovtave effects too. - Eth

5/30/2000 2:07 PM
Mark Hammer	ATTN GFR!! Re: Analog guitar synths I have a schematic/article for a mono pitch-2-CV convertor that appeared in Practical Electronics about 16 years ago or so. I scanned it, but for the life of me can't find it. I do know that I sent the scan to a few people. GFR, do you still have it? This guy would be interested in it. Another thing to consider is a guitar processor, rather than synthesizer. One of the limiting things about guitar synths is their ability to reliably detect the pitch. This often (though not always) requires a fussy picking style and also takes time. It may only be a few milliseconds, but you'll NOTICE it. There is also the issue of the additional delay involved in detecting the pitch of lower notes, and the complexity/reliability of detecting the pitch of more than one note at a time. What some would suggest is that using the guitar signal itself, and processing guitar events is a preferrable and less problematic approach. Within that context, what you would need would be a reliable note-onset detector (AKA trigger extractor + envelope follower), and a system of voltage controlling sound-modifying modules using the trigger, gate, and envelope voltages. Things like Auto-wahs and Slow-Gear/Attack-Delay units are examples of this, except you would be using a more integrated system with many more modules. Once you go analog, you're able to link up with the universe of analog synth modules out there (and believe me, there are LOTS). It can be a more responsive and reliable system, responds to whole chords as well as single notes, and lends itself well to real-time foot-control. If that's all you need, I can plug up your mailbox with a ton of stuff. Just say the word.

5/30/2000 2:07 PM

Mark Hammer

ATTN GFR!! Re: Analog guitar synths

I have a schematic/article for a mono pitch-2-CV convertor that appeared in Practical Electronics about 16 years ago or so. I scanned it, but for the life of me can't find it. I do know that I sent the scan to a few people.

GFR, do you still have it? This guy would be interested in it.

Another thing to consider is a guitar *processor*, rather than *synthesizer*. One of the limiting things about guitar synths is their ability to reliably detect the pitch. This often (though not always) requires a fussy picking style and also takes time. It may only be a few milliseconds, but you'll NOTICE it. There is also the issue of the additional delay involved in detecting the pitch of lower notes, and the complexity/reliability of detecting the pitch of more than one note at a time. What some would suggest is that using the guitar signal itself, and processing guitar *events* is a preferrable and less problematic approach. Within that context, what you would need would be a reliable note-onset detector (AKA trigger extractor + envelope follower), and a system of voltage controlling sound-modifying modules using the trigger, gate, and envelope voltages. Things like Auto-wahs and Slow-Gear/Attack-Delay units are examples of this, except you would be using a more integrated system with many more modules. Once you go analog, you're able to link up with the universe of analog synth modules out there (and believe me, there are LOTS). It can be a more responsive and reliable system, responds to whole chords as well as single notes, and lends itself well to real-time foot-control.

If that's all you need, I can plug up your mailbox with a ton of stuff. Just say the word.

5/30/2000 6:30 PM
GFR	I don't remember if I received it. I'll look for it. I have a pitch-to-midi schematic too (you need to burn a EPROM). By the way - the EH Microsynth is a processor as Mark noted - it doesn't have tone generators (oscillators). I've downloaded a pdf file with an interesting "synth" - it processes the guitar signal to turn it into a square wave or a triangle wave. You have the usual VCF/VCA efects, plus octave up/down. The square wave also goes to a frequency multiplier and the multiple frequencies are added by a mixer stage to give you a (rough) staircase approximation of an arbitrary waveform. I would call this real synthesis and not processing. Also devices that use a PLL like the boss DF-2 or PLL based harmonizers should be considered synths as they have a VCO inside the PLL and generate their own tones. Anyway to detect the pitch most of these synths use a steep active lowpass filter (to remove the harmonics and keep only the fundamental from the guitar signal) and then a schimitt trigger to make it a square wave.

5/30/2000 6:30 PM

GFR

I don't remember if I received it. I'll look for it. I have a pitch-to-midi schematic too (you need to burn a EPROM).

By the way - the EH Microsynth is a processor as Mark noted - it doesn't have tone generators (oscillators).

I've downloaded a pdf file with an interesting "synth" - it processes the guitar signal to turn it into a square wave or a triangle wave. You have the usual VCF/VCA efects, plus octave up/down. The square wave also goes to a frequency multiplier and the multiple frequencies are added by a mixer stage to give you a (rough) staircase approximation of an arbitrary waveform. I would call this real synthesis and not processing.

Also devices that use a PLL like the boss DF-2 or PLL based harmonizers should be considered synths as they have a VCO inside the PLL and generate their own tones.

Anyway to detect the pitch most of these synths use a steep active lowpass filter (to remove the harmonics and keep only the fundamental from the guitar signal) and then a schimitt trigger to make it a square wave.

5/30/2000 7:22 PM
Mark Hammer	I'll check around at home. It may well be that I confused you with someone else (Tobias?), but I'm 85% sure it was you. Is it possible that the one you mentioned downloading is this one? http://omega.tellus.vallentuna.se/anders/pdf/electrax.pdf This adopt the "event processing" approach you noted about the Microsynth. I wouldn't go quite so far as to label anything with pitch extraction and a VCO as a "synth". I guess it's a bit like how some folks draw a line between computers and calculators. They both process information but generally only one is equipped to make conditional decisions. In this case, I would prefer to apply the term "synthesis" only to those devices or systems that strive to shape musical "events". In my mind, it doesn't take a lot more to do that; usually a VCA-like and VCF-like function are sufficient. A Slow Gear and a Mutron are both "effects". If you put them both in a box, and synced the two functions together in some manner, then you'd have a synth. The EH Microsynth is basically that. It generates a sub-octave and fuzz, extracts a trigger/gate, and drives the VCA and VCF to produce a musical "event". A good synth lets each note or strum you play be treated like such an event. Incidentally, if you have a Q-Tron+, the loop insert provides an excellent way to fake synthesis (I say "fake" because there is no trigger extraction, only envelope). Patch an octave divider in the loop and away you go. Actually, what would be better is to patch TO a splitter, and FROM a mixer. In between the splitter and mixer, you could run a variety of things in parallel. Stick an octave divider AND octavia in there, mix 'em down, run 'em into a noise gate with a very long attack time, and you have the beginnings of a decent guitar processing system.

5/30/2000 7:22 PM

Mark Hammer

I'll check around at home. It may well be that I confused you with someone else (Tobias?), but I'm 85% sure it was you.

Is it possible that the one you mentioned downloading is this one?

http://omega.tellus.vallentuna.se/anders/pdf/electrax.pdf

This adopt the "event processing" approach you noted about the Microsynth.

I wouldn't go quite so far as to label anything with pitch extraction and a VCO as a "synth". I guess it's a bit like how some folks draw a line between computers and calculators. They both process information but generally only one is equipped to make conditional decisions. In this case, I would prefer to apply the term "synthesis" only to those devices or systems that strive to shape musical "events". In my mind, it doesn't take a lot more to do that; usually a VCA-like and VCF-like function are sufficient. A Slow Gear and a Mutron are both "effects". If you put them both in a box, and synced the two functions together in some manner, then you'd have a synth.

The EH Microsynth is basically that. It generates a sub-octave and fuzz, extracts a trigger/gate, and drives the VCA and VCF to produce a musical "event". A good synth lets each note or strum you play be treated like such an event.

Incidentally, if you have a Q-Tron+, the loop insert provides an excellent way to fake synthesis (I say "fake" because there is no trigger extraction, only envelope). Patch an octave divider in the loop and away you go. Actually, what would be better is to patch TO a splitter, and FROM a mixer. In between the splitter and mixer, you could run a variety of things in parallel. Stick an octave divider AND octavia in there, mix 'em down, run 'em into a noise gate with a very long attack time, and you have the beginnings of a decent guitar processing system.

6/2/2000 11:54 AM

GFR

quote:
"I'll check around at home. It may well be that I confused you with someone else (Tobias?), but I'm 85% sure it was you."

It's me. I'm just not sure if the attachment arrived OK and WHERE I put it on my HD

I'll search it more carefully on the weekend.

quote:
"Is it possible that the one you mentioned downloading is this one?

http://omega.tellus.vallentuna.se/anders/pdf/electrax.pdf"

/>
I think that's it (I'll confirm this). What I think makes it "more synth" than the EH is the ability to synth (a staircase approximation of) an arbitrary waveform by mixing square waves of multiple frequencies (plus it has the usual VCA/VCF and octave fx).

I think one of the $chematic$ $ite$ (Pat?) have a schematic for the "360 Systems" mono guitar synth - a full analog synth with a pitch to CV designed for guitar.

6/5/2000 11:53 AM
GFR	I've found it (the pitch to voltage article). Mark, would you like me to send a copy for you (since you can't find yours)?

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