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 Forum index » DIY Hardware and Software » Thomas Henry designs
X-4046 VCO Page is Up
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forbin



Joined: Jan 29, 2009
Posts: 118
Location: Fremantle, Australia

PostPosted: Wed Jul 28, 2010 3:01 am    Post subject: Reply with quote  Mark this post and the followings unread

A couple more notes of possible interest.

Put in the Fairchild 4046 and the signals are much closer to +-5V than the NXP. Still a little high at +- 5.2V but really pretty close. I don't think that the Triangle is as clean for the Fairchild but the Sawtooth was better than the NXP !?! Will try and take some photographs of the output to describe what I am burbling on about...

While reading the Birthofasynth web page for X4046 again and more carefully, I noticed the link to the Scott Gravenhost harmonic multiplier. After a bit of a read through that and some further hacking away at the board I now have my second sync mode doing some pretty interesting things! I ended up changing the filter a fair bit and also the way I divided the output from the phase discriminator was a bit odd. I need to do some more head scratching before I am happy with it as a useful option...
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forbin



Joined: Jan 29, 2009
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PostPosted: Wed Aug 04, 2010 9:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Done some testing of the tracking of some of the 4046 devices. I only have a Fairchild, NXP and TI parts. I used a Ruby script driving a MIDI interface and collecting the serial feed from a frequency counter. The results were then plugged into Excel. I took the natural log of the frequency and then did a linear fit over a reasonable useful range (the green bit) of about 50Hz to 1.5kHz. I then found the deviation from the best fit to give me some idea of the tracking... In an ideal world I would try and adjust for the best fit and then measure but I was to lazy to adjust each individually... Remember that the graph is logarithmic!

The TI part really doesn't cut the mustard... I did use this exact TI part in a very similar circuit that Tom designed for the VC Noise in the Synthesizer for the 21st Century and in that design it seemed to track fine? I will have to drag the board back out and check it again now...
see: http://forbinthesynthesizer.blogspot.com/2010/01/more-noise.html

The NXP and Fairchild Parts are very similar but I have found that the voltage that the NXP develops across the capacitor is quite a bit higher than the Fairchild so I have stuck to that part.

One of the datasheets that I found for the TI 4046 said that the design was from Harris (and so I suppose originally RCA). I am not sure how much individual variation there is some of the internal designs between manufacturers?


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Uncle Krunkus
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PostPosted: Thu Aug 05, 2010 3:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Great work Forbin!
That is definitely above and beyond the call of duty. Very Happy

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adambee7



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PostPosted: Thu Aug 05, 2010 3:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Great work Forbin!
That is definitely above and beyond the call of duty. Very Happy


I agree. That's a great tool Forbin. Cheers. Very Happy Very Happy
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forbin



Joined: Jan 29, 2009
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PostPosted: Sun Aug 08, 2010 2:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Guys -- i ran a test overnight of the Fairchild 4046 without a tempco and am currently running another one WITH a tempco -- i have always been interested in how bit a difference it is... will post the results tomorrow

Next I will run the other 8 or 9 VCO's through my measuring system, including the Thomas Henry XR, VCO1 and 21st Century... I have sped up the averaging a bit and brought back the steps to 3 semitones so it should be quite interesting...
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Uncle Krunkus
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PostPosted: Sun Aug 08, 2010 3:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Remember that a tempco adjusts the whole V->I converter depending on ambient temperature changes so it would be more meaningful to check the tracking of a particular note for various temperatures, rather than the linearity across a selection of notes.
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adambee7



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PostPosted: Sun Aug 08, 2010 5:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Like you would callibrating any vco by octaves ?? Very Happy Very Happy
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forbin



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PostPosted: Sun Aug 08, 2010 6:26 am    Post subject: Reply with quote  Mark this post and the followings unread

The "result" that I am measuring against, is the slope of the best fit through the readings 50Hz -> 1.5kHz -- if it is perfectly in pitch the value would be 0.057762 in my configuration... It is probably better than watching just one value as it is more a representation of the "tuning" of the oscillator
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forbin



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PostPosted: Mon Aug 09, 2010 3:05 am    Post subject: Reply with quote  Mark this post and the followings unread

This is probably getting a bit out of hand now but I am seeing ripple in the result when I increased the number of steps 0->10V. This was then a lot of testing of the MIDI interface and changing of DAC's -- this was improved things a bit...


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Don Erskine



Joined: Jun 17, 2010
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PostPosted: Thu Sep 09, 2010 1:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

The switching glitches on the peaks of the triangle waveform (and the derived sawtooth and sine waves) look a bit ugly but, as Thomas Henry points out, sound acceptable musically. They introduce a lot of rich high harmonics and could change the sound considerably compared with a pure triangle wave. Not a bad thing though; we all want harmonics, don’t we?

Unfortunately, the spikes do limit the VCO’s uses if it is used as an LFO to voltage control another device.

The good news is that there is a simple fix. The spikes are on the ‘outside’ of the waveform. As long as the waveform amplitude (and DC offset) remains constant* over the frequency range, a simple clipping or clamping buffer could be used to slice them off, improving the waveforms.

Even simple diode clamping to the power supply rails might** work, if they are clean enough and the output of IC3c waveform swings close enough to the power rails. The resistor values around IC3c and IC3d may need revising to achieve this, and the input levels into the sine converter may also need adjusting as a result as well.

*As I have yet to build this VCO, I do not know if the DC level and amplitude are in fact constant over the frequency range on this design. I would presume so.

** a few decoupling capacitors on the power supplies physically near the clamping diodes might be a good idea if this is done, just to keep the supplies clean.

A minor point: on the circuit schematic, R37 and R39 are labelled ‘Triangle Connect’ . Should this be ‘Triangle Correct’, or even better, ‘Triangle Adjust’?
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fonik



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PostPosted: Tue Nov 09, 2010 8:24 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks for the ideas on the clamping, don. maybe i will try that out.

i assembled one of the two 4046 VCOs modules for my next cabinet today. i used my prototype PCB (the same i sent to scott) and an additional waveshaper PCB i designed - and everything worked from the start. Very Happy

i tried an ON Semiconductor MC14046BCP first and could not get it scaled correctly. it fell short of about 1/4 tone per octave.
i then tried the NXP part and scaled the VCO within 5 minutes using an LFO and a quantizer.

i will post a picture when i finished both VCOs (they share one frontpanel).

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fonik



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PostPosted: Tue Nov 09, 2010 4:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

could not resist and finished the complete dual unit. however, i did not calibrate the 2nd VCO yet. anyways, here some pix of the wiring desaster Wink


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spitfire



Joined: Jan 06, 2011
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PostPosted: Thu Jan 13, 2011 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

does anybody did a wiring diagram for this one ?
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camelneck



Joined: Sep 27, 2008
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PostPosted: Sat Jan 15, 2011 3:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Don Erskine wrote:
The switching glitches on the peaks of the triangle waveform (and the derived sawtooth and sine waves) look a bit ugly but, as Thomas Henry points out, sound acceptable musically.


I was looking at the various waveform pics of the X-4046 VCO that Scott Stites has posted on his website. The pic labeled X-4046 VCO Sawtooth Wave looks a lot like the sawtooth waveform produced by the Yamaha CS-80 as well as other CS synths that use the same VCO IC. (The pic can be seen at http://www.birthofasynth.com/Thomas_Henry/Images/X-4046/sawtoothl.JPG)

If my memory serves me correctly, the glitches found in the Yamaha Sawtooth Waves are even a bit wider than the glitches shown in Scott's X-4046 VCO Sawtooth Pic. Nevertheless, the sawtooth waves produced by the Yamaha CS Series synths sound incredible and if you don't believe me listen to the fat brass horn sounds that were produced on the CS-80 in Vangelis' Chariots of Fire. (I should point out that much of this fatness is due to the fact that the CS-80 uses linear tuned VCOs.)

Don Erskine wrote:
They introduce a lot of rich high harmonics and could change the sound considerably compared with a pure triangle wave. Not a bad thing though; we all want harmonics, don’t we?


That depends upon what type of sound you need. A pure sine wave is 100% fundamental with no harmonics. I generally like my sine waves as pure as possible and use them for whistle-type sounds, soft leads, and to boost the fundamental on low bass sounds (the kind of bass that can be felt more than heard).

If you add enough odd harmonics to a sine wave you basically have a triangle wave, which sounds a lot like a heavily filtered square wave. However, I wouldn't mind if the X-4046 VCO was capable of adding some even harmonics to the sine wave. (In fact, the shape pot for VCO 1 on the EMS VCS3 allows the user to add even harmonics to the sine wave.)

I am a bit curious about what kind of effect the peaks will have on the triangle waves. Boosting some of the triangle wave's odd harmonics will probably have little effect on the sound other than making it sound a bit more square wavish, but if the glitch adds "even harmonics" the sound of the triangle could change quite a bit.

Since I already have several VCO's that produce accurate waveforms, I'm glad that there are some less perfect alternatives. Otherwise, many VCO's would tend to sound the same and I like having the variety available to me.
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fonik



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PostPosted: Wed Jan 19, 2011 10:51 am    Post subject: Reply with quote  Mark this post and the followings unread

just wanted to contribute three short sound samples (300-400kb).

the first one is two X-4046, one is synced to the other, and modulated by an LFO. we hear both rampoid outputs.
http://www.modular.fonik.de/sound/dualTH4046VCO_01.mp3

the second one is almost the same setting, but a little bit more of modulated sync. a standing tone, no sequencer involed here, just for your pure amusement.
http://www.modular.fonik.de/sound/dualTH4046VCO_02.mp3

in the last one we hear both units. no sync, no modulation. one sine and one rampoid output. and i am happy with the scaling.
http://www.modular.fonik.de/sound/dualTH4046VCO_03.mp3

this is my new all time VCO!

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spitfire



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PostPosted: Wed Jan 19, 2011 2:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Guys, I'm confused. I made PCB by myself, panel, everything as always. But I'm stuck on wiring. I see two J1, two J2, in schematic is writen to connect volt/octave to J1, but there's two of them on PCB, and also 1v/octave is writen there... I'm posting some pictures how my works look like. I hope you will help me. I don't want burn everything after such a nice working.

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mrphgfx



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PostPosted: Tue Jan 25, 2011 11:41 pm    Post subject: Noob question Reply with quote  Mark this post and the followings unread

Hi there

I am newbie (both in terms of this thread and electronics/electronic music).

I have a dumb question (but if you don't ask you don't learn!) so please forgive this.

I am interested in this design to add some more wave forms onto stomp box producing a square wave output using the hard sync (I know I know it's sacrilege to ignore the wonderful 1 volt per octave bit Embarassed ) Could that part of the cicuit work on different voltages (+- 12, +- 9) rather than +-15? or would I have to significantly redesign?

Any help would be appreciated

Thanks
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shobley



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PostPosted: Thu Feb 24, 2011 7:24 am    Post subject:
Subject description: Which jumpers need to be set?
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Hi,

I made up one of these boards yesterday, I'm almost complete, and I wanted to ask a question about the J1, J2,J3 and J5 jumpers.

I take it these should be connected? I don't see the jumper connections on any of the pictures.

Also is there a J4? I can't seem to find it.

Finally I noticed some isolated J- and J+ - I take it these should be hooked to -ve and +ve respectively?

Thanks,
Steve

http://www.stephenhobley.com
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shobley



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PostPosted: Tue Mar 01, 2011 8:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Quick follow up (and a warning):

I made up the board following the Press 'n' Peel layout supplied in this forum - I assumed the orientation based on the mirrored text, however creating this board "as-is" resulted in all the power connections for the op-amps being reversed.

I'm not sure if reversing the design will fix it - but I got frustrated enough to transcribe the circuit in Eagle and layout my own board.

Pleased to say that using this, some TL082/84s, and cheap (unmatched) 3904 transistors from Radio Shack I got all the waves coming out as specified.

Nice.

Will have to post on my blog about this...

Steve
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TekniK



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PostPosted: Tue Mar 01, 2011 8:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Ppl. my mate who made several of these noticed an error in the layout that ryk did made its around the sine circuit,can't remember what exactly.
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spitfire



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PostPosted: Fri Mar 04, 2011 2:08 am    Post subject: Reply with quote  Mark this post and the followings unread

I spend so much money on this project... yes, there's something wrong with sine section.. no signals from tl074. And something wrong with course, i get from very high frequency to lower, and then it starts getting up again when turning course pot.

Can somebody help with this vco. A lot of people have troubles buuilding it
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spitfire



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PostPosted: Fri Mar 04, 2011 2:08 am    Post subject: Reply with quote  Mark this post and the followings unread

I spend so much money on this project... yes, there's something wrong with sine section.. no signals from tl074. And something wrong with course, i get from very high frequency to lower, and then it starts getting up again when turning course pot.

Can somebody help with this vco. A lot of people have troubles buuilding it
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fonik



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PostPosted: Fri Mar 04, 2011 2:23 am    Post subject: Reply with quote  Mark this post and the followings unread

i built two units using my own PCBs. don't have any issues, the circuit is proven to be fine.
so someone who built it with ryk's layout should chime in, if the common debug routines don't help you.

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TekniK



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PostPosted: Fri Mar 04, 2011 3:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Its not a error that influence the working of the module,its a design error.

you get a better sine then he told me,i ask my mate as soon i meet him again .
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fonik



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PostPosted: Fri Mar 04, 2011 3:42 am    Post subject: Reply with quote  Mark this post and the followings unread

TekniK wrote:
Ppl. my mate who made several of these noticed an error in the layout that ryk did made its around the sine circuit,can't remember what exactly.

TekniK wrote:
Its not a error that influence the working of the module,its a design error.


so it is an error in the layout, not the circuit, correct?
i built this VCO according thomas' schematics without any issues... or are you talking about the sine shape only? it might not be a perfect sine, but still quite nice (i actually like the "colored" sine).

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