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 Forum index » DIY Hardware and Software » Thomas Henry designs
The Thomas Henry VCO-1 Page Is Up
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StephenGiles



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PostPosted: Sun Jun 03, 2007 2:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Might TH design a guitar pitch to voltage converter with which to play this wonderful VCO? Laughing
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Thomas Henry



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PostPosted: Sun Jun 03, 2007 4:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

StephenGiles wrote:
Might TH design a guitar pitch to voltage converter with which to play this wonderful VCO? Laughing


Hah! You'll not sucker me into that one!

Thomas Henry
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StephenGiles



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PostPosted: Mon Jun 04, 2007 4:31 am    Post subject: Reply with quote  Mark this post and the followings unread

I think I knew that answer in advance! This might give me an excuse to rebuild the EH Guitar Synth front end, because this worked very well on single notes. See here
http://hammer.ampage.org/?cmd=lt&xid=&fid=&ex=&pg=7

This includes a fundamental extractor providing a good sinewave at it's output which is squared, frequency doubled and fed to some magic around a couple of 4047s and VCOs forming a loop. The "how it works" was explained to me about 27 years ago but I've long since forgotten!
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Thomas Henry



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PostPosted: Sat Jun 16, 2007 2:16 am    Post subject: Reply with quote  Mark this post and the followings unread

philpeery wrote:
DOH! The suspense is killing me! Must be part of that afore memtioned "Global Domaination" plan! Can't wait, but I am sure it will be worth it!


And now here we are several weeks later...obviously I was referring to the 566, 8038 and XR-2206 ideas in the VCO Chip Cookbook, put out by sMs Electronics. You will also see a variation of this used in An Analog Synthesizer for the 21st Century, to be published by Magic Smoke in the near future.

Yes, if you have access to the derivative of the triangle wave (for all you calculus fans) you can make a ramp from a triangle.

Thomas Henry
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philpeery



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PostPosted: Sat Jun 16, 2007 6:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Yes, if you have access to the derivative of the triangle wave (for all you calculus fans) you can make a ramp from a triangle.


The same day I got the book, I breadboarded the ramp converter on page 38. It works like a charm, and I was able to trim the little wave blip almost all the way out, you never hear it. Now I have get my hands on some 8038's and XR2206's to try the other circuits.

You gotta get this book, three VCO's implemented with different chips, that's too cool for words!

Phil
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slo



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PostPosted: Fri Nov 09, 2007 7:53 am    Post subject:
Subject description: TH-Vco-1 coarse range
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I built this and it all worked first time, and it sounds great. Thanks to Thomas and Scott. Only wrinkle is the coarse pot audio range is only from about 9 o/clock (lows) to 12 (highs), how can I spread the range out over the full travel of the pot?
I used a linear pot.

George
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Scott Stites
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PostPosted: Fri Nov 09, 2007 8:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Hmmm....I'd check into that a little further. The coarse pot should give operate smoothly across the range, IIRC. Of coarse (pun intended) my memory slips. In any event, increasing the mix resistor for the coarse control will limit the range more. But, I don't recall it being any diff from the coarse control of any other VCO I've worked with.

Glad to see you got that bad boy going though! Very Happy

Cheers,
Scott

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CJ Miller



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PostPosted: Sun Apr 27, 2008 2:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow.. this looks great. And sounds great! How did I just discover this now? This morning I've been looking all over for my PNP pairs - they are not in any of the usual places, which means that they could be anywhere else! I wonder how a dual with 13600 instead of 3080 will work. Can hardly wait to play with a triangle VCO!

I am grateful for the inspiring ideas for us n00bs
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Peake



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PostPosted: Sat May 10, 2008 11:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice PWM!

This is a triangle core oscillator? Has anyone routed two together, sine wave out to frequency input, one to the other, and increased the FM index? The exponential FM on the Buchla 258b goes to chaotic results (pitched noise) and I'm wondering if this will as well, if such amazing expo FM is the domain of all triangle cores.
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ryktnk



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PostPosted: Thu May 15, 2008 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
This is a triangle core oscillator? Has anyone routed two together, sine wave out to frequency input, one to the other, and increased the FM index? The exponential FM on the Buchla 258b goes to chaotic results (pitched noise) and I'm wondering if this will as well, if such amazing expo FM is the domain of all triangle cores.


Hello

I have tried this with the TH vco, although I was trying to get
a stable fm modulation, it is quite good for fm, but the carrier pitch
does detune quite a bit once you modulate quite heavily.
[ I think maybe this is what you are liking about the 258b ]


The electronotes tzo is much better at stable fm, as you can go a lot
deeper with the modulation before it detunes.
Also in turn you can go a lot deeper for crazy stuff

I think i have some "conservative" test's I did with both oscillators, if you want to hear.

-ryk

PS Mr Scott did you know that the link at the top of this thread goes to the
TH mps instead ?
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Peake



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PostPosted: Thu May 15, 2008 8:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

"Stability" is definitely not desired. I'm just after the acoustic terror that the Buchla 258B can produce with the exponential FM. If you or anyone has a soundbite of the VCO-1 outputting a sine wave of medium or higher frequency, modulated by another sine wave that is higher in frequency, I'd love to hear it, especially a demo of the FM index increasing from zero to full. Thanks for replying and offering.

(Not tooting my own horn, but this all-Buchla 200 piece IIRC uses no white or pink noise- the noise-like sound is oscillator FM through filters. Many of the sounds are sine wave exponential FM, with a lesser index. I'm looking to add this back to my setup.)
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Scott Stites
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PostPosted: Mon May 19, 2008 5:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the heads up, ryktnk. I re-ordered some of the links on my page, and it looks like the sw changes the URL to do it - I imagine some other stuff has fallen out in other links I've sprinkled here and there. Rolling Eyes

Mike, as far as I'm concerned you don't blow your own horn enough! I'm looking forward to this download (spoken like a true dial-upper here Very Happy )

Cheerio,
Scott

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Peake



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PostPosted: Mon May 19, 2008 7:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
Mike, as far as I'm concerned you don't blow your own horn enough! I'm looking forward to this download (spoken like a true dial-upper here Very Happy


I'm looking for similar sounds. I'd be enthused if the TH VCO could do this. I have to depend upon forumites to say yay or nay...thanks for any insight.
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Peake



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PostPosted: Fri May 23, 2008 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's a 1:1 parts placement/parts list diagram. Instead of "C2", etc., the actual value is present. I find it a bit quicker than other methods, but understand the ease in updating a parts list at a later date.

Please point out any mistakes, if so inclined.


THVCO1Parts_c.pdf
 Description:
1:1 Parts placement guide to the TH VCO-1 PCB. Untested, may contain mistakes.

Download
 Filename:  THVCO1Parts_c.pdf
 Filesize:  1.93 MB
 Downloaded:  408 Time(s)

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Peake



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PostPosted: Fri May 30, 2008 7:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi, I plan to build one or more VCO-1s and have a question. I've just received a THAT 320 matched trannie IC for use with this VCO, just to see what happens (and to add a switch if needed to use a pair of 3906).

The much-appreciated VCO-1 reference page says "An exponential converter is a rather sensitive device and a mass of tangled wires coming and going from it can often create stray capacitance problems." Obviously, I'm going to have to daughter-board the IC, and since it has a second set of matched trannies in there, I can use it for another VCO as well. However...due to the above statement, am I getting into trouble if I run wires to another PCB, or if the daughterboard is positioned in between two VCOs, with wires running to each? Should I use shielded cable to ground? Should I just try it and simply see for myself? Very Happy

Thanks for the great project!
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Scott Stites
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PostPosted: Sun Jun 01, 2008 12:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm going to be honest and say - I dunno! Laughing If it's any consolation, I would probably try it as you describe as well.

I think you would probably be OK - I'm not sure if shielded cable would help or not, but it wouldn't hurt to try I suppose. I sure would be interested in hearing your results - especially your experience with the THAT device.

Take care,
Scott

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Peake



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PostPosted: Sun Jun 01, 2008 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you Scott! The THAT device is rated seven times better than the SSM but I don't know if that sort of difference is important, at those depths of decimal points! Incredibly quiet for audio, though.

I've been rearranging the PCB to work with the inexpensive trimpots from a local supplier- not very difficult so far (photoshop). I've been wondering about the waveshaping as well- will post any results.

BTW, the PCB artwork PDF is printing at "93% zoom" for some reason. Something alerted me to this, and yes, pressing a DIP socket into the paper shows that it's a tad small. Obviously others have not been experiencing this or they'd have posted. Ah, the steps required to get from A to Z Smile
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Scott Stites
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PostPosted: Sun Jun 01, 2008 1:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

BTW, Mike - I remember you asking how the thing does with FM. I still have the VCO partially on breadboard, but I'd really have to do a re-build to get it back. I've been cobbing parts from it now and then (just snagged a 100K pot off of it last weekend for TH's latest project).

Anyway, I was going through the VCA 1 page and found a short sample I did of the VCO-1 being linearly modulated. Here's the text and link to the sample (it's not a very long sample):

Quote:
This next sample demonstrates how a VCA can help to modify a voice by providing a means to implement dynamic depth frequency modulation. The VCO-1 triangle wave is patched through the Mankato filter. The VCO-1 is controlled by the Klee Sequencer, and the Mankato Filter is controlled by both the Klee and an envelope generator triggered by the Klee.

A second VCO, Rene Schmitz's VCO3, has its sine wave patched to the FM input of the VCO-1, through the VCA-1. The VCA-1 is controlled by a second voltage output of the Klee Sequencer. The upshot is, because this voltage varies with each note, the VCA-1 lets more or less of the audio rate sine wave through to modulate VCO-1. The sample first starts with no modulation, and as it progresses, I increase the amount of modulation on VCA-1 by adjusting R21 to allow more of the Klee voltage through to "open up" the VCA.


http://mypeoplepc.com/members/scottnoanh/sitebuildercontent/sitebuilderfiles/vca1_dynamic_fm.mp3


Cheerio,
Scott

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Peake



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PostPosted: Sun Jun 01, 2008 6:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
BTW, Mike - I remember you asking how the thing does with FM.


Exponential FM, yes Very Happy

Thanks!
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a.b.o.z.



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PostPosted: Sat Aug 23, 2008 9:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Mike how did THAT 320 responded in VCO-1?
I'm soon to finish one and looking for something to substitute 2N3904s.
Ones that I got from local store had different pin-out. E-C-B instead of standard E-B-C. Weird stuff.
What other monolithic PNP pair should I look for? (beside SSM2220, THAT320 and 2SA798 are there any else?)

Thnx

Ivan


edIT: and with matching I came to find one with hFE 208 and other 215. This is closest I could find in this batch..is this close enough or need to be exact values?
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Peake



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PostPosted: Sat Aug 23, 2008 7:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

I believe that Thomas said that you can just drop in two 3906s and get good results. It's far less expensive than a THAT or SSM, etc., unless you have to have such extreme matching. I'm no expert; perhaps one might chime in?
Last edited by Peake on Thu Aug 28, 2008 1:07 pm; edited 1 time in total
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widdly



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PostPosted: Thu Aug 28, 2008 1:06 am    Post subject: Reply with quote  Mark this post and the followings unread

I just used 3906 in the two I built. Sounds good to me. If I was building another I might use one of those 2saxxxx (or should it be 2scxxx) dual transistors. They are cheap and easy to get in my neck of the woods.

I'd love to see a good saw ouput mod for these. It's the only thing missing.

Last edited by widdly on Thu Aug 05, 2010 10:07 pm; edited 1 time in total
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Tim Servo



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PostPosted: Thu Aug 28, 2008 11:07 am    Post subject: The Thomas Henry VCO-1 Page Is Up Reply with quote  Mark this post and the followings unread

widdly wrote:
I just used 3906 in the two I built. Sounds good to me. If I was building another I might use one of those 2saxxxx (or should it be 2scxxx) dual transistors. They are cheap and easy to get in my neck of the woods.

I'd love to see a good saw ouput mod for these. It's the only thing missing.


Hey Wid,

Thomas has designed a tri to saw waveshaper that works very well, and is detailed in AS21C or the VCO Chip Cookbook or even his "Reprints" book. You basically use the triangle and the square wave from the VCO core (look at the emitter of Q2). You use the square wave to drive a sign changer. The sign changer uses an FET or an analog switch and an op amp to flip between the non-inverted and inverted (and offset) versions of the triangle wave. There is one trimmer to adjust the amount of offset, which removes a small glitch from the center of the saw's ramp. I used the same tri to saw circuit in the Magic Smoke 566 VCO and it works very nicely.

Hope that helps. Smile

Tim (also has small glitches) Servo
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widdly



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PostPosted: Sun Aug 31, 2008 6:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the tip. I have the 3080 book which is very enlightening. Perhaps it's time for the VCO book too.
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