Author |
Message |
zipzap
Joined: Nov 22, 2005 Posts: 559 Location: germany
Audio files: 24
|
Posted: Tue Jan 17, 2006 7:30 am Post subject:
pulse to Complex Waveform generator |
|
|
Hi there
Some of the nastiest sounds i ever heard ocured when i was clocking my 4017 sequencer at audio speed, using the output as sound sorce.
The shemati is an idea i had that should make it possible to use the pulse output of a vco and use the pulsewidth, transfering it to the new waveform.
1 The diode eliminates the negative part of the pw
2 the uper r-c-buffer reacts on the pulse going up, the lower with the inverter reacts to the pw going low. the resulting short pulses are added and cklock the 4017.
I´m not sure about the values for r and c, i guess a much shorter pulse with eg. 50n/10k would be better to get a decent clocking signal and to assure that the two parts dont overlap. What do you think?
3 The rest is standard 4017 sequencer, maybe variable step length, and the output glide (very effective on harmonics), offset, level, buffer.
The frequency of the waveform will be linked to the vco, but it can be varied depending howmany steps form one cycle.
When i will build this i want to use faders instead of pots, so you can see the waveform you´re drawing.
Of course this circuit can be used as a modulation sequencer at lower clock speed also.
By the way, if i want independant rise and fall glide, do i use 2 Diodes an 2 pots so the cab is charged and discharged over different resistors?
Description: |
|
Filesize: |
28.07 KB |
Viewed: |
18286 Time(s) |
|
|
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Tue Jan 17, 2006 9:07 am Post subject:
|
|
|
Looks like it would work. To avoid general glitchiness, I usually try to square up anything that's going to be clocking CMOS.
An alternative plan would be to use a dual comparator and an EXOR gate. One section of the comparator could be used to square up the input from the VCO after you've chopped off the lower section of the waveform with the diode (it could even respond to VCO waveforms other than pulse). This signal one could send to one input of the EXOR gate.
After that, the second comparator would be used to square up a delayed signal that's applied to the second input of the EXOR - this would double your frequency. The EXOR would pulse when the input went high and pulse when the input went low.
This circuit would run like a bat out of hell:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/3327
The output is inverted from the clock in. If that's a problem, one could always use another section of the EXOR IC to flip it back to the polarity you want.
In lieu of the MAX9010, an LM358 would work wonders. For the EXOR, use a CD4070. A CD4030 would work as well, but check PS ratings.
For a good working app on the LM358, check out Ken Stone's Pulse Divider:
http://www.cgs.synth.net/modules/cgs36_pulse_divider.html
Of course, you could just use an EXOR with one leg having an RC delay and drop the comparators, but it would probably run better and faster with them.
Lag - here's an example from the inestimable Harry Bissell. Bonus 'shape' feature to fade between linear and expo response (oftentimes I prefer linear response for keyboards, I suppose it might give you some variation for sequencer out as well).
Cheers,
Scott
Description: |
Harry Bissell's Morph-Lag Design |
|
Filesize: |
10.84 KB |
Viewed: |
18272 Time(s) |
|
|
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18195 Location: Durham, NC
Audio files: 211
G2 patch files: 60
|
Posted: Tue Jan 17, 2006 1:37 pm Post subject:
|
|
|
What does R2 do in Harry's circuit? Seems to me like it shouldn't be there... _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Tue Jan 17, 2006 2:05 pm Post subject:
|
|
|
Summing resistor for AR3? Wouldn't it put inverted CV out at virtual ground if it were not there? |
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18195 Location: Durham, NC
Audio files: 211
G2 patch files: 60
|
Posted: Tue Jan 17, 2006 2:11 pm Post subject:
|
|
|
OK, I don't get it though. I'm sure it works but I've never done lag processors like this myself. |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Tue Jan 17, 2006 2:16 pm Post subject:
|
|
|
Right, I understand it's for summing - do you mean by the original question that one wouldn't want to sum the inverted signal with the input? |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Tue Jan 17, 2006 2:26 pm Post subject:
|
|
|
I guess that makes two of us. I've read build reports on it though - seems to work pretty well. I guess it's also handy for the other lag duties (shaping gates into envelopes, etc).
The only other lag I've ever used is a linear design, which warn't nothing like this (much simpler). Having the ability to move between the two responses would be a lot of fun. I guess I'll have to try it out! |
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18195 Location: Durham, NC
Audio files: 211
G2 patch files: 60
|
Posted: Wed Jan 18, 2006 7:59 am Post subject:
|
|
|
Maber that feedback has some effect on the operation. duh...
Yes, everything I've built has a linear response - just simple integrators really. _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Wed Jan 18, 2006 10:59 am Post subject:
|
|
|
I haven't grokked what the shape pot is doing.
Not to hijack the thread but:
Here's a linear glide circuit I pulled out of the SDIY archive a few years back. Coincidentally, it's a circuit of Harry's as well. I remember contacting him and telling him how much I liked it - I recall him mentioning he saw it as a sub-circuit to some medical device and just tried it out. He was insistent on this design to use a 741 or 1458 or similar (I think latch-up was the concern?).
My keyboard is one I built from Tom Henry's "Build a Better Music Synthesizer" and has expo glide built into it (pretty much the standard pot and cap sandwiched between two buffers, without the feedback of this design). Though I use expo lag a lot because it's built into the keyboard, I found linear lag to be really, really sweet. One thing about Harry's design though, in retrospect, is that I think it could use a 100 ohm resistor in series before the 1M pot. Moving the pot from min resistance to any resistance at all would slightly change the tuning of a VCO controlled by the output, so I'd always have to retune if I shut the linear glide all the way off.
This newer design by Harry would be the best of both worlds, I think.
If anyone's wondering what this is all about, generally speaking, and IIRC, the glide time of linear glide is determined by how far the first note is from the second note - IE, gliding up 2 octaves would take longer than gliding up one octave.
Expo glide, on the other hand, will take the same amount of time gliding up two octaves as it takes to glide up one octave, so the farther apart the glide points are, the faster the glide will appear to move.
Linear glide to me is definitely a lot more 'expressive' when using it with a keyboard. Didn't the MiniMoog have linear glide?
Description: |
Harry Bissell linear lag circuit |
|
Filesize: |
4.87 KB |
Viewed: |
18228 Time(s) |
|
|
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18195 Location: Durham, NC
Audio files: 211
G2 patch files: 60
|
Posted: Wed Jan 18, 2006 11:18 am Post subject:
|
|
|
That is a circuit I'm more familiar with. _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
|
Back to top
|
|
|
mosc
Site Admin
Joined: Jan 31, 2003 Posts: 18195 Location: Durham, NC
Audio files: 211
G2 patch files: 60
|
Posted: Wed Jan 18, 2006 11:55 am Post subject:
|
|
|
Just one switch to go from one to the other... _________________ --Howard
my music and other stuff |
|
Back to top
|
|
|
ian-s
Joined: Apr 01, 2004 Posts: 2669 Location: Auckland, New Zealand
Audio files: 42
G2 patch files: 626
|
Posted: Wed Jan 18, 2006 12:06 pm Post subject:
|
|
|
Scott Stites wrote: | Didn't the MiniMoog have linear glide? |
Yup, the rate varies a little over the range of the keyboard but I dont think this is a feature.
Going just from the description, expo sounds like it should be the best option. In practice though, it sucks. |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Wed Jan 18, 2006 1:58 pm Post subject:
|
|
|
Quote: | Yup, the rate varies a little over the range of the keyboard but I dont think this is a feature.
Going just from the description, expo sounds like it should be the best option. In practice though, it sucks. |
Thanks for that - I've heard that the Moog modular had expo lag - is that the case?
Quote: | Just one switch to go from one to the other... |
Yep, one switch. I've never looked into putting it on my keyboard - it's slightly more complicated (not much) because the buffer is a discrete FET buffer rather than an op amp buffer. That's not the hurdle. It's already soldered up on a board and my natural laziness has prevented me from actually *doing it*. That's the hurdle.
The idea of a continuously variable fade from one response to the other to me is intriguing - don't know if that's one of those things that sound better on paper than it really is, though. There's not a lot to the circuit, though obviously there's more than a dual op amp buffer and a switch.
Take care,
Scott |
|
Back to top
|
|
|
zipzap
Joined: Nov 22, 2005 Posts: 559 Location: germany
Audio files: 24
|
Posted: Thu Jan 19, 2006 4:30 pm Post subject:
|
|
|
Quote: | An alternative plan would be to use a dual comparator and an EXOR gate. One section of the comparator could be used to square up the input from the VCO after you've chopped off the lower section of the waveform with the diode (it could even respond to VCO waveforms other than pulse |
Do you think it could be possible to generate a pulsewave from an acoustic signal like a violin or guitar? I managed to trigger my sequencer with my bass, moving it one step each time i hit a note.
Would be great to have the complex waveform generator in tune with my bowed doublebass (just imagine that...) |
|
Back to top
|
|
|
Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
|
Posted: Thu Jan 19, 2006 10:03 pm Post subject:
|
|
|
Absolutely! Check out the Wilson Signal to Gate thread.
You would have to adjust the threshold so that the signal produced a gate on the attack of your note, and go low again before the next note so it could then go high and trigger as well. Certainly doable!
Take care,
Scott |
|
Back to top
|
|
|
|