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 Forum index » DIY Hardware and Software » Thomas Henry designs
TH’s Quadrature Function Generator sync mod
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funkyfarm



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PostPosted: Fri Apr 27, 2007 9:54 am    Post subject: TH’s Quadrature Function Generator sync mod
Subject description: Thomas Henry’s QFG mod according to POLYPHONY 1984
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I’ve build the QFG.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Here is the test...


QFG Test 03.mp3
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Last edited by funkyfarm on Fri Apr 27, 2007 10:00 am; edited 1 time in total
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funkyfarm



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PostPosted: Fri Apr 27, 2007 9:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Here is the core circuit and editor's note.

The trick is to bypass C3 cap with a CMOS switch...


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funkyfarm



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PostPosted: Fri Apr 27, 2007 10:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Do you think a 4016, as in mark's 292, would do the job ?

http://www.simple-answer.com/lopass-gate.jpg

or maybe the CD4066...

There is no single CMOS switch available ?

Here is the document : http://hammer.ampage.org/files/quad-shep.pdf


BTW, does anyone build the Jim Patchell’s VC Quadrature Oscillator ? Wink
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sneakthief



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PostPosted: Sat Apr 28, 2007 12:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Maybe Mr. Henry would like to chime in here? It really sounds quite nice and looks simple to build!
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Scott Stites
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PostPosted: Sun Apr 29, 2007 12:55 am    Post subject: Reply with quote  Mark this post and the followings unread

I built a module for Jeff Pontius that had Thomas' quadrature function generator in it and Rene Schmitz's tri-phase VCLFO. Here's a pic of it when I built it, and a pic Jeff took later after he had a Schaeffer panel made for it.

Thomas' QFG is also included in my long-neglected MultiPhase project....


newtpqfg2.jpg
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After Jeff put the Schaeffer panel on it.
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3pqfg2.jpg
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The module after I built it.
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funkyfarm



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PostPosted: Sun Apr 29, 2007 11:31 am    Post subject: FRYING ICs... Reply with quote  Mark this post and the followings unread

Yep !
my 3P LFO is waiting for one 4052 Cool

As I have three "CD4016 CMOS Quad Bilateral Switch" as spare (?!), i will give a try with this IC for the modification...bzzz...
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funkyfarm



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PostPosted: Mon Apr 30, 2007 2:58 am    Post subject: Reply with quote  Mark this post and the followings unread

I've tried with a 4016...something like this...

Posted Image, might have been reduced in size. Click Image to view fullscreen.


Whenever SYNC gate s high or low, it freezes LFO oscillation...

Even with a good switching solution, maybe the incoming SYNC signal should be "trigged" (small RC network or cap in series) ; as in the CGS Gate to Trigger Converter



Posted Image, might have been reduced in size. Click Image to view fullscreen.
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v-un-v
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PostPosted: Mon Apr 30, 2007 4:25 pm    Post subject: Re: TH’s Quadrature Function Generator sync mod
Subject description: Thomas Henry’s QFG mod according to POLYPHONY 1984
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funkyfarm wrote:
I’ve build the QFG.

Here is the test...


that's a test??? Shocked

It's beautiful! Very Happy

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mosc
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PostPosted: Mon Apr 30, 2007 5:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

It IS beautiful. How about some real music. Very Happy
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Scott Stites
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PostPosted: Mon Apr 30, 2007 6:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Doh! I downloaded the sample on dial-up then realized I'm sort of in Uncle K's shoes - I moved my speakers downstairs.
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Scott Stites
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PostPosted: Tue May 01, 2007 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

OK, I heard it. Tom was right - that's beautiful!

Do you have any details on the patch?

Were Vactrols involved? Very Happy

Cheers,
Scott
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RF



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PostPosted: Wed May 02, 2007 4:26 am    Post subject: Reply with quote  Mark this post and the followings unread

That's a very cool sound sample! I'm also interested in what the patch consisted of...
Thanks for the link to the article, too. This one goes on my list of things to do.
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fonik



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PostPosted: Thu May 03, 2007 1:03 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
I've tried with a 4016...Whenever SYNC gate s high or low, it freezes LFO oscillation...

so it didn't work? what could be the cause? didn't the switch refuse to switch?

and what a nice sample! i suddenly reminded my old pocket calculator Wink

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funkyfarm



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PostPosted: Thu May 10, 2007 3:48 am    Post subject: Reply with quote  Mark this post and the followings unread

(for sure this is off topic, but :

Thank you , thank you, thank you !

The trick was to throw three Oakley VCOs into stereo space !

and you know I like drawing ! (while it's a little messy for this one, and it cames from my blurry memories...)

Quote:
Were Vactrols involved?


But..hey ! with the dual mixing panner, I can count 11 of them !
Both 292 were static through...let's say 9 ! Wink
)


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funkyfarm



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PostPosted: Thu May 10, 2007 4:06 am    Post subject: Reply with quote  Mark this post and the followings unread

about the sync mod, I have to admit that when I test firing the ENABLE input of the IC (which was ok), I've read strange "switching" values on my ohmmeter for what we're dealing with...

Guess I have to check the specs of the 4000 switches (and all the boring stuff...)
I have a 4066...will give a try...re-bzzz...


PS : Scoop about the sample : main sequence is from a SH-101 but I've swapped my real-shit-computer-based midi beat clock (1/32 as master clock) with Art Blakey's real funky riding groove

SWING is the key Wink
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fluxmonkey



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PostPosted: Thu May 10, 2007 7:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

is anyone thinking about doing a PCB or stripboard layout for this one? quadrature function generators being one of the harder-to find modules (along w/ quantizers), diy or assembled... sure would be nice...

b
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Adam-V



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PostPosted: Thu May 10, 2007 9:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Doepfer have got a VC Quadrature LFO planned for release in July.

Cheers,
Adam-V
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funkyfarm



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PostPosted: Fri May 11, 2007 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Adam-V wrote:
Doepfer have got a VC Quadrature LFO planned for release in July.

Cheers,
Adam-V


Yep ! but surely with sine waveforms...

maybe the same as Jim Patchell’s VC Quadrature Oscillator ? Wink
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Scott Stites
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PostPosted: Fri May 11, 2007 10:18 am    Post subject: Reply with quote  Mark this post and the followings unread

If it's sine waves you want, getcherself a Mankato filter - that baby's got quadrature out the ying-yang. Plus it's a filter, pocket fisherman, and makes wonderful julienne fries.

Looks like they're right around the corner.


Cheers,
Scott
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funkyfarm



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PostPosted: Fri May 11, 2007 10:57 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't know if it's the trick to get this cool quadrature triangle waveforms, but "NOTE UNUSUAL POWER SUPPLY CONNECTION TO IC3"

Whaouhhhhhhhhhhhhhhhhh !

I guess this IS the real luxe, being able to choose some "unusual power supply connections" to an IC Wink

Or, maybe, first result was convaincing, but with a positive 15 volts offset ?


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Scott Stites
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PostPosted: Fri May 11, 2007 11:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Yep - Thomas is great at manipulating a circuit to do what he wants. He's not violating any rules either - even though Vcc is connected to 0V (ground) he's still powering the IC from +15V, in relation to what he's got attached to the ground connection, which is -15V. He does that a lot Very Happy

I think Thomas would be the first to tell you he didn't invent this technique (it's more or less the same kind of thing as using Vcc/2 as the reference for processing audio with a single supply op amp, which nearly every stompbox in the world has to do), but I think it's a powerful part of his approach for wringing the most functionality out of an IC or a circuit. Where I look at a chip's specs and see "it requires X number of volts supply", I never think of it in terms of "X volts in reference to what?". Thomas does. Very Happy

Cheers,
Scott
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RF



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PostPosted: Mon May 14, 2007 6:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Question for the brain trust here....
I built the QFG over the weekend - but...... Not having a 1458 in the parts bin I stuck in an LM358.

So the 'derived' output is indeed 90 degrees out of phase...but a bit jumpy Smile. I played with the value of C1 and juggled a couple resistors to make it usable, but it's still a bit rough. Is this the issue Mr. Henry is refering to in the article re: the slow slew rate in the 1458 masking discontinuities?

Ooops. I just looked at the schematic again and realized I'm running it off +- 12 volts rather than the 15 specified. ummm....? Seems to work except for the derived being a bit rough...

Input?

Mr. Henry - Hi from 'up north'. I recall vividly (and with some trepidation) a few college days road trips to 'Kato. Shocked
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Tim Servo



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PostPosted: Tue May 15, 2007 8:51 am    Post subject: TH’s Quadrature Function Generator sync mod Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
I don't know if it's the trick to get this cool quadrature triangle waveforms, but "NOTE UNUSUAL POWER SUPPLY CONNECTION TO IC3"

Whaouhhhhhhhhhhhhhhhhh !

I guess this IS the real luxe, being able to choose some "unusual power supply connections" to an IC Wink

Or, maybe, first result was convaincing, but with a positive 15 volts offset ?


Hey Funky,

What the "unusual" power supply gets you is a signal that is conditioned correctly for the next stage in the circuit. In Thomas' original QFG design, an additional op amp inverter is used after the "normally" powered logic gate section. Running the gates off of -15V basically saves an op amp, and the logic chip doesn't really care as long as the voltage potential across the supply pins is the right polarity and within a certain range.

Just thought I'd chime in!

Tim (another "unusual" connection) Servo
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Tim Servo



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PostPosted: Tue May 15, 2007 9:07 am    Post subject: TH’s Quadrature Function Generator sync mod Reply with quote  Mark this post and the followings unread

RF wrote:
Question for the brain trust here....
I built the QFG over the weekend - but...... Not having a 1458 in the parts bin I stuck in an LM358.

So the 'derived' output is indeed 90 degrees out of phase...but a bit jumpy Smile. I played with the value of C1 and juggled a couple resistors to make it usable, but it's still a bit rough. Is this the issue Mr. Henry is referring to in the article re: the slow slew rate in the 1458 masking discontinuities?

Ooops. I just looked at the schematic again and realized I'm running it off +- 12 volts rather than the 15 specified. ummm....? Seems to work except for the derived being a bit rough...

Input?


Hey RF,

Just thought I'd jump in again, as long as I'm awake and on line Wink

You're absolutely right, Thomas uses the slow slew rate of the 1458 to filter some of the discontinuities in the waveform. The 1458 can't reproduce very high frequency info, and so acts as a bit of a low pass filter. This is a neat little trick, and you can get the same results with a 741 (but in a single package, of course). This is also a cautionary tale for people who go through and replace older op amps in vintage synths with modern units. Most of the time, this is okay, but you shouldn't replace an op amp with a different type unless you know a little about what's going on in the circuit. Waveshaping circuits (as you've seen) are the most likely to actually perform worse with a "better" op amp.

Tim (slewby doo) Servo
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mono-poly



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PostPosted: Wed May 16, 2007 1:49 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
Adam-V wrote:
Doepfer have got a VC Quadrature LFO planned for release in July.

Cheers,
Adam-V


Yep ! but surely with sine waveforms...

maybe the same as Jim Patchell’s VC Quadrature Oscillator ? Wink


I wouldn't be surprised if it would be another Doepfer rip off.
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