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 Forum index » DIY Hardware and Software » Thomas Henry designs
A New Voltage Controlled Quadrature Function Generator
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Scott Stites
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PostPosted: Sun Jun 10, 2007 7:58 pm    Post subject: A New Voltage Controlled Quadrature Function Generator
Subject description: For the 21st Century.....
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OK, gang, I breadboarded Thomas' latest design...as the title says, it's a Voltage Controlled Quadrature Function Generator. And, I gotta say, it is awesome. I can't believe how smooth these waveforms are (triangle waves). I told Thomas the LED display was worth the price of admission alone Very Happy

It's voltage controlled (V/Oct), and covers about ten octaves. There's no sync - Thomas spent a huge amount of time on that, but it only served to snarl the works - the voltage control certainly makes up for that. This is what Thomas had to say about it:

Quote:
....the 1V/octave business is great for sequencer/rhythmic things;
just think in terms of period now instead of frequency. For example, if 1V
equals a period of 6 seconds then 2V will be a period of 3 seconds. If a
person has a two bank (parallel) sequencer (like my old SuperSeque), this means that the A row can control the pitch of each note, while the B row controls the duration (quarter note, eighth note, etc.). Since we're
talking time now and not period, a simple expo is good enough, and there's no need for the thermistor. (Ears are sensitive to frequency but not period).


As with all of his circuits, it's an easy build - no exotic parts used (three ICs). It's based around the LM13700 (triangle core), and there are a couple of TL074s. In fact, Thomas figured out a method of avoiding the reliance on using the slow slew rate of an op amp to squelch the 'pip' that joins up the two sections during cal. It certainly works, because there is no pip!. Better living through mathematics Very Happy

This design is great - I want one in my synth. I'll probably move this one up in the queue and make it my next page.

Note: There is no PCB. Any takers on designing one?

Cheers,
Scott

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Thomas Henry



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PostPosted: Sun Jun 10, 2007 10:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Two things to fix in the post above:

1. In my quoted comment, I meant to say, "Since we're talking time now and not frequency..."

2. And there are four chips in this circuit, not three.

Thomas Henry
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PostPosted: Mon Jun 11, 2007 1:40 am    Post subject: Reply with quote  Mark this post and the followings unread

YES! Given a bit of time I'd love to do a PCB layout (..not actually make the PCBs). Quadrature is a big desire for me at the moment (..haven't yet gotten around to doign the old TH quad osc yet..)

Is this a new design for the 21st Cent Synth book? (..I've not had time to read all the recent posts --- so much great stuff going on its scary!)

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Scott Stites
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PostPosted: Mon Jun 11, 2007 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
And there are four chips in this circuit, not three.


Yeah - I was making the long drive today and I thought of that - oops! I was in a hurry posting that last night - the kid was warning me that a new episode of "Family Guy" was coming on. (Favorite quote from this episode: Death to Molly Ringwald: "I'll be back for your career.").

Mysterious fourth chip is a CD4001.

Quote:
Is this a new design for the 21st Cent Synth book?


Nope, this one was just finished this weekend, or shortly before.

Thanks for the PCB offer! - I'll PM you the details tonight (Kansas time).

Cheers,
Scott

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PostPosted: Mon Jun 11, 2007 11:27 am    Post subject: Reply with quote  Mark this post and the followings unread

I just thought I would post that we spent Saturday on Lake Geneva in Switzerland (just) and what a wonderful experience it was too, with a first class lunch. It occurred to me that it would be a great place to solder up stuff - on one of the large boats that is! Plenty of good daylight and large tables - important to spread out. I don't know about power for a soldering iron though, but one can always daydream. Nearest I got was a read of the TH VCO stuff, whilst my wife was sleeping. Keep up the great site.
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PostPosted: Mon Jun 11, 2007 12:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

StephenGiles wrote:
It occurred to me that it would be a great place to solder up stuff - on one of the large boats that is!


Sounds like fun indeed, I would have liked a ship for the European electro-music event. Ah well a castle is fun as well of course.

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PostPosted: Mon Jun 11, 2007 3:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
This design is great - I want one in my synth. I'll probably move this one up in the queue and make it my next page.


This sounds like a nice circuit. A good source for LM13700's is here at "Debco Electronics"

http://safe.dhwd.com/cgi-bin/debco/index.html

They also carry CA3080's for the TH VCO and XR2206's for the TH XR VCO and the "VCO Chip Handbook" experiments.

Bill
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RF



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PostPosted: Tue Jun 12, 2007 5:16 am    Post subject: Reply with quote  Mark this post and the followings unread

So - ummm - is there a schematic of this around somewhere?
Scott - you are such a tease.
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The Alison Project



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PostPosted: Tue Jun 12, 2007 10:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

I can't wait for this one, like Scott mentioned this one will move up the list.

Does anyone know why I can't keep up, Thomas designs new stuff faster than I can build them... Damn

Thanks again..... and to think I thought my synth was almost finished earlier this year....
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Randaleem



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PostPosted: Wed Jun 13, 2007 6:22 am    Post subject: Re: A New Voltage Controlled Quadrature Function Generator
Subject description: For the 21st Century.....
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Hi,

I'd like to announce that the prolific and venerable Mr. Henry has given permission for me to do a run of professional PCB's for this project. I started last night and have it mostly laid out, and am expecting to have the design ready for fab by Friday. Turnaround to have boards in hand should then be 2 weeks or less. Thomas has given the okay for me to offer kits as well; if the desire is there?

The board is currently half-Euro size (80x100mm; or about 3.2 by 4") and I've included an MOTM and Doepfer Power input connector, and may add the Blacet style power protection circuitry. Boards will be two-sided PTH, Soldermask both sides with screen print component location.

All inputs and outputs go to individual 2 and 3 pin AMP .100MTA style headers like Dotcom boards. (Of course you can wire direct if you wish. There is a GND to go with each pot and jack that needs one. I'm not setting it up for the shielded cable or wire tyes that MOTM uses; but you could use a stooge style bracket to get these if they are important to you. I can fab these brackets to work with the board and any panel layout if needed or desirable.
The 4 Panel LEDS ( 0°,90°,180°, and 270°) are also taken out to 2 pin connectors.

Thomas has suggested a wide range of possible timing capacitors. So I've included pads for five different caps and a header to take them to a range switch on the panel if you wish. (I don't know that you'd really need all five; but pads and holes are cheap! Very Happy I expect that using 1-3 with either a DPDT, 7211 3 way or a rotary will fill most every need.)

This is my first offering here at electro-music; but hopefully many other projects will follow.

I have the equipment to make Stooge style pot brackets and Shaeffer or screen print front panels. Right now I'm concentrating on boards; but I do expect to be able to offer complete kits a la MOTM and Blacet in the near future.

I'm interested in hearing any comments about what you need or want. Things like desired hole sizes and or trimpot/ capacitor types come to mind. I've a good relationship with my board house; so a few extra holes to deal with some of the variables is not a big deal...

I'm also pursuing bringing other designs to market so if there's something you're looking for; please let me know by private message so we don't hijack this thread.

Thank you,

Randal

Scott Stites wrote:
OK, gang, I breadboarded Thomas' latest design...as the title says, it's a Voltage Controlled Quadrature Function Generator. And, I gotta say, it is awesome. I can't believe how smooth these waveforms are (triangle waves). I told Thomas the LED display was worth the price of admission alone Very Happy

This design is great - I want one in my synth. I'll probably move this one up in the queue and make it my next page.

Note: There is no PCB. Any takers on designing one?

Cheers,
Scott
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mark_olson



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PostPosted: Wed Jun 13, 2007 7:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Randal:

I would be keenly interested in a board.

Thanks!

Mark
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Wild Zebra



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PostPosted: Wed Jun 13, 2007 7:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Boy things sure are moving right along in the DIY SYNTHS department. I like to say I'm interested. I'm starting to think I'm a fan of the kit cause the bare boards are piling up. At least with a kit I know I can get started right away.
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PostPosted: Wed Jun 13, 2007 10:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Dang, he's quick - he designed a board before I could even squeeze the bits through my phone line to put up a page! Very Happy

Quote:
and to think I thought my synth was almost finished earlier this year....


To paraphrase the Floyd: "Don't sit down, it's time to build another one"

Cheers,
Scott

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PostPosted: Wed Jun 13, 2007 6:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hehe & I got one out today too...

...more words tomorrow I guess!

Thomas Henry & Scott -- thanks so very much. I just had some wondrous sound times trying it out (along with, actually, a fresh 566 vco from the bits of the TH 566 cookbook).


TH_Quadrature_VCO.gif
 Description:
...love those lights!
I grabbed some videos too of it in the heart of a twin osc feedback section plus 4step seq/pattern - plus filter feedback and mmm it was driving itself, slowly evolving, hopping a bit mad.
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TH_Quadrature_VCO.gif



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PostPosted: Wed Jun 13, 2007 6:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmm, looks like an aluminium panel or somesuch but its actually tinned pcb material (still trying that idea out).. Details tomorrow..
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PostPosted: Thu Jun 14, 2007 3:09 am    Post subject: Reply with quote  Mark this post and the followings unread

So.....

First off - well, I'd been keen to do this for personal use but also to offer a pcb plan. Now that Randaleem has moved so quick and is going to be doing pro-boards, I dunno whether I should submit my version pcb (for etching - single sided - so DIYable at home..). What do people (Randaleem, Scott, Thomas) think? I don't want to tread on toes or anything! But'd be happy to submit it. Its pretty compact at about 2.5 x 4 inches, with pots mounted on board. Not the absolute cleanest layout but does the job fine (about 12 jumpers). Darn, I should have snapped a pic of it.. duh.

Setup is, indeed, very straight forward -- one thing I noted was that, 'cos I don't have any MPF102s, I tried some other JFets - in the end I went for 2n5457. Looking at the little triangle pip bits, when I was using a J201 Jfet I was still getting a small bit of pip on one part of the waveform no matter how I tweaked. Strange.

I also added a range switch for Osc or LFO rates - haven't decided on the particular cap values yet - I have pin headers in there at the moment for changing values over. I haven't done any tuning of the V/Oct part either yet..

I was happy to get it fitted into a one-width Frac unit - ahh, so compact.

Shame the sync tests seem to have been snagging 'cos that'd be a great addition. I've also been wondering whether a future mutant should have a pulse with PWM section for each output... multiple pulse trains, harmonically (/speed) related could be damn cool, especially for sequencing.

Last night I also added decent inputs for the gate controls of my Dual-Pattern module -- this makes things much more useable as the steps can be selected by almost any waveform - perfect for being driven by the QuadVCO therefore - and this gives some very interesting results. Depending on which outputs you use, what speed its going, the patterns you get are great. I had a very nice unstable chaos feedback system going last night where the Pattern Gen, Quad Osc and new 566 osc were wired into a living, stuttering, popping organism.. very very fun.


So.... let me know what you think on submitting my pcb (..I'm off out of the city for about 10days from Saturday, so that may hold things up a little...)

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PostPosted: Thu Jun 14, 2007 6:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, the way I look at it, people who are going to dive into a vat of chemicals or throw themselves under a CNC machine will want to do just that. There are those that prefer to build on protoboard, and there are those that would prefer to buy the PCB.

I fall into either the protoboard or premade PCB family myself. I think the majority of people fall strictly into the premade PCB family, and that (IMO) is where Randaleem would step in and make it available. So, I don't think there would be too much of a conflict there.

My site is dedicated to the freebies - people can learn about the circuit, and the choose to make it using one of the three methods described above, which would include providing a layout. My gut feeling is, most people would wind up buying the PCB anyway.

However, that is my uneducated opinion - Thomas, Randal?

Cheers,
Scott

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Scott Stites
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PostPosted: Thu Jun 14, 2007 7:39 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't recall any pips - I'll take a pic of the derived waveforms I have on my scope tonight, and post them to see how they match up with yours (I'm using MPF102). I plan to have pics of the waveforms on the site, also.

+1 on your ideas - there are a lot of things one can do with these 'staggered' waveforms.

Cheers,
Scott

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Thomas Henry



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PostPosted: Thu Jun 14, 2007 2:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

I tend to agree with Scott here. It seems to me that there isn't much overlap between those who will etch their own (and put up with jumpers, etc.) and those who want a nice double-sided, silk-screened board without any mess.

However, Randal is the one investing in the production run, so how about if we let him decide?

And thanks for asking; it's really great to have a Forum that cares about doing things the ethical way. It makes me want to contribute more...

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PostPosted: Thu Jun 14, 2007 3:14 pm    Post subject: A New Voltage Controlled Quadrature Function Generator
Subject description: PCB vs. PCB??
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Tom,

Nice module! I like the layout of your Frac panel. Cool

As for you putting up your pcb layout; I think you should!

I'd bet there are more than a few people who have both self-made and purchased PCB's in their synths. Probably even of the "same" module...

No worries, mate! Very Happy

Randal


bugbrand wrote:
So.....

First off - well, I'd been keen to do this for personal use but also to offer a pcb plan. Now that Randaleem has moved so quick and is going to be doing pro-boards, I dunno whether I should submit my version pcb (for etching - single sided - so DIYable at home..). What do people (Randaleem, Scott, Thomas) think? I don't want to tread on toes or anything! But'd be happy to submit it. Its pretty compact at about 2.5 x 4 inches, with pots mounted on board. Not the absolute cleanest layout but does the job fine (about 12 jumpers). Darn, I should have snapped a pic of it.. duh.
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Randaleem



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PostPosted: Thu Jun 14, 2007 3:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, so THAT's what those extra pins on the PCB are for Wink

You mean there might be a daughterboard?

Randal


Scott Stites wrote:
+1 on your ideas - there are a lot of things one can do with these 'staggered' waveforms.
Cheers,Scott
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PostPosted: Thu Jun 14, 2007 5:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
The board is currently half-Euro size (80x100mm; or about 3.2 by 4") and I've included an MOTM and Doepfer Power input connector, and may add the Blacet style power protection circuitry. Boards will be two-sided PTH, Soldermask both sides with screen print component location.


Sounds very nice ..........

Wow, you guys are too much !!! I love all this interaction !!! I would like a PCB also. Very Happy Glad to see DIY going so strongly!

Bill
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PostPosted: Thu Jun 14, 2007 11:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:

This sounds like a nice circuit. A good source for LM13700's is here at "Debco Electronics"
http://safe.dhwd.com/cgi-bin/debco/index.html


Hmm I thought components were cheaper in the States, but I can actually get LM13700's far cheaper here in The Netherlands (just over $1).

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PostPosted: Thu Jun 14, 2007 11:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd like one of these PCBs when they are available. I don't really have the space to etch my own boards.
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Randaleem



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PostPosted: Fri Jun 15, 2007 7:26 pm    Post subject: Re: A New Voltage Controlled Quadrature Function Generator
Subject description: For the 21st Century.....
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Hi,

Quick update:

I just heard from John Blacet giving me the okay to include the power protection circuitry. Still plan to get this up in the thread for review sometime tonight.

Should be able to have it verified and ready for orders by Monday

Randal


Randaleem wrote:

...am expecting to have the design ready for fab by Friday.

The board is currently half-Euro size (80x100mm; or about 3.2 by 4") and I've included an MOTM and Doepfer Power input connector, and may add the Blacet style power protection circuitry. Boards will be two-sided PTH, Soldermask both sides with screen print component location.

All inputs and outputs go to individual 2 and 3 pin AMP .100MTA style headers like Dotcom boards. (Of course you can wire direct if you wish. There is a GND to go with each pot and jack that needs one.
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