Living VCOs

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

PS thanks for another great design JH, I finally built myself a midi CV interface and the two oscillators that are working sound fantastic, even without any additional processing

jhaible · Posted: Tue Jan 05, 2010 12:57 pm Post subject:

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

Thanks for your reply JH,
I was just hoping that the symptom might shed light on a rather obvious problem someone else had come across or something I suppose.
But never mind - I'll just go back and give it a meticulous going over - only got one probe for the scope, but should manage it...

PS, did you see my question about the 1uf and 10uf caps in your transent gate schematic? I was just wondering whetehr they can be electrolytic?

Thanks

Joe

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

Gah...

Not having much luck here! Now the driver circuit - which worked perfectly before - seems to have gone down!

I can trace my changing v/oct signal to the CVs-in point in the driver section fine, but measuring the voltage on the driver out, it's just a static 5.5v, leading to an unpleasant tuneless drone...!

I switched all the chips in the section for fresh ones just in case one had blown for some reason, but, still not working!

I'm not expecting someone to solve this for me, just venting my spleen - I'm finding this circuit a bit hard to get up and running... due to my crude building abilities, I'm sure... just frustrated because it sounds LOVELY when it works!

Joe

jhaible · Posted: Thu Jan 07, 2010 9:34 am Post subject:

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

Thanks for the tip JH, but yes, the Portamento pot never left its socket, so in this case it's unfortunately not the issue. Once I get some time I'll give it a proper analysis with the scope. I haven't made things easy for myself by wiring all the ins and outs into a case already though.

numbertalk · Posted: Sun Jan 17, 2010 10:33 am Post subject:

Hi JH. I just noticed that the vibrato on my Living VCOs with rate all the way up is less than 1Hz. Is this normal?

Thanks.

jhaible · Posted: Sun Jan 17, 2010 2:00 pm Post subject:

numbertalk · Posted: Sun Jan 17, 2010 2:54 pm Post subject:

EDIT - I found it - I have a 1uf cap for C31, which is supposed to be 47nf. How on earth did I manage to do that?!?

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

got all oscillators running - bizarrely, i swapped out the tl072 of the faulty oscillator with another oscillator's chip, and then they both worked... must have been a temperemental connection i guess.

anyway, this thing sounds massive.

jhaible · Posted: Mon Jan 25, 2010 2:06 pm Post subject:

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

jhaible · Posted: Sun Jan 31, 2010 1:08 am Post subject:

jhaible · Posted: Sun Jan 31, 2010 1:14 am Post subject:

Here's an idea what might have happened: You may have created a short between pin 3 pof the 3046 and -15V on one channel (lower picture), killing that chip. Swapping chips between channels, you would then have killed the other chips as well. Inserting such a chip into an otherwise good channel would then produce the strange voltages shown in your upper picture.

JH.

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

i dont have any IC in the circuit as of yet, just transistors and passives
should i pop one in to try stir up some current?

jhaible · Posted: Sun Jan 31, 2010 12:04 pm Post subject:

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

before i insert IC into pcbs i usually go around and check to see if all voltages look correct. since there was such a drastic difference between the voltages at the lm3046 between the different vcos i decided to ask why to see if it was a problem

jhaible · Posted: Mon Feb 01, 2010 12:53 am Post subject:

Luka · Joined: Jun 29, 2007 Posts: 1003 Location: Melb.

i loaded all the IC in and im getting 3 tri waves
i guess i got a bit ahead of myself with the testing process Embarassed

thanks jurgen

2thick4uni · Joined: Feb 20, 2009 Posts: 113 Location: UK

How can I get hard and soft sync on my Living VCO's?

I've built my Living VCO PCB and everything is working as it should, however as this is going to be the only (three) vco's in my modular I'd like more waveshapes and hard and soft sync. Sin and Tri waveshapes are easy, I'll just use MFOS VCO pcb's with just the waveshaping circuitry in place to get the full complement of waveshapes as per Bill and Will's Dragonfly Alley mods.

I'd really like to have hard and soft sync for the living VCO's, I've had a look at the schematic and as it is based on a standard integrator / comparator sawtooth oscillator so it should certainly be possible, however I do not have sufficient knowledge to implement it. I'd guess I need to apply sync to pin 2 of the LM311, however I don't know the implications of this..........

Has anyone done this already or can anyone give me some ideas to start experimenting?

Cheers,
Allan

bennethos · Joined: Apr 18, 2009 Posts: 31 Location: Belgium

Hi all,

I finished the soldering part and wanted to start the calibration part.

I connected the :

- Lin detune
- Freq
- Pulse Width

But I noticed the saw waveforms has minor problems. it basically looks like half a trapezium Very Happy

I took some pics of my saw out with the 10 turn freq dial at max and at 5 turns.

It also has a weird start, a little bump in when the waveform begins.

any idea's ? (this is my first project :p, thx to Juergen who got me into this Smile

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10 turn @ max

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10 turn freq @ 5 turns

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decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

Hi Folks,
Wanted to check in with those who have ordered PCBs recently. Did you use the email form several pages back that JH posted? From what I can tell this seems like the mechanism for ordering JH designed PCBs.

jhaible · Posted: Mon Feb 08, 2010 12:10 am Post subject:

bennethos · Joined: Apr 18, 2009 Posts: 31 Location: Belgium

I've been troubleshooting VCO1 for a couple of hours (see pics in my previous post).

I've changed all ic's --> same problem
Ive changed all small ceramic caps --> same problem
checked all diodes --> they were OK
checked all transitors --> they were OK
changed my 10 turn dial --> same problem

Still have this little bump when my sawtooths starts, and at 3/4 my sawtooth flattens, it becomes worse when I increase the freq range.

I can't compare the other 2 vco's as they all have different kind of problems :p... I don't have a single one that is working...

One thing I'm concerned about, the tiny caps on the back of the pcb, I think I heated them too much when soldering them on the board...

Could you guys give me some advice ?

thx
Ben

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA