Living VCOs

dingebre · Posted: Sat Dec 05, 2009 11:39 am Post subject:

Thanks JH and Dave. I'm just happy to know I didn't screw up something else when building (I assume you read my post about wiring the frequency pots...). I might try the 10K resistor.

Happy holidays to all, and a special and big thanks to everyone on this list who takes time to help and share their experience.

JH, a big thanks and Merry Christmas to you for making your designs not just available, but for all the support and patience.

David

Girts · Joined: Aug 21, 2009 Posts: 8 Location: Latvia

I have found better Depth response with a 300 ohm resistor between CW pin and center pin. However, I am using a 10K pot and VJK is shorted with jumper for now.

btw, I wonder what control voltage is usable for the VJK (Vibrato depth CV)?

jhaible · Posted: Sat Dec 05, 2009 11:55 am Post subject: Re: Vibrato Depth Sensitivity

Girts · Joined: Aug 21, 2009 Posts: 8 Location: Latvia

Thanks for warning, JH!

I will try external modulation to see how the Depth control will act without added resistor ...
and I will check if that potentiometer is still OK Smile

/mr · Posted: Sun Dec 06, 2009 4:07 am Post subject:

Haha, wonderful... we're all here because synthesizers are our lives, but now suddenly it's all about life or death! Laughing

Anyway, shunting potentiometers with a resistor to ground is a habit we should practice more often. There are many occasions where lin/log responses are not the optimal, and there is a lot tweakability to gan from adding some resolution to one end of the pot. Or to the middle of the pot, if it's bipolar. Smile

Though, to get a large change in pot curve, the shunting resistor value often needs to be quite small compared to the pot value, and problems can arise with varying impedance issues or lethal currents as in the above example. Increasing both the pot and resistor values might be a solution in many cases. Stay alive! Wink

dingebre · Posted: Wed Dec 09, 2009 12:11 pm Post subject:

I am happy to announce I finally got the first of two VCO's done.

After tracking down TWO bad panel pots (I did NOT overheat them and you can't prove I did Smile

) it all seems to be working. I have never struggled so much with a module. I damaged more parts in this build than in every kit I have ever built combined, One multiturn frequency pot, two other panel pots, two or three transistors, mis-wired all three frequency pots, installed the wrong values for the high frequency trim pots, and could have labeled my panel mount trim pots better on the panel. So, that said the VCO's are humming along and I'm going to start the second board soon.

Merry Christmas, Happy Holidays, whatever you celebrate this time of year to you and yours.

Thanks again JH for your designs, very, very cool stuff.

David

Funky40 · Posted: Sat Dec 12, 2009 4:51 am Post subject:

here are fotos of how i wired the fine tune ---> i solder a 3-pin header directly to the ICs.
Thatway i have the whole Board disconnectable whta is a good thing.

my camera is fucked up, shots from short work now ( in the past they didn't ) but modules i get very blurry.

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header for finetune wiring attached to the IC

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two JH living VCOs in euroformat. sorry is blurry

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dingebre · Posted: Fri Dec 18, 2009 11:49 pm Post subject:

OK, here are some photos of my first "Living VCO's" finished and a shot of the second PCB populated ready for its panel. I know the wiring is very dense, but it really is organized deep inside the rat's nest...

The Euro format panel is tight, but it all fits. I panel mounted the v/oct scale and high frequency scale (I have no idea why I labeled them the way I did). As soon as the second one is done, tuning is next.

Thanks J.H.

(EDIT) took down some of the photos to reclaim space. See below for both VCO's in the rack.

dmi

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Varoudis · Joined: Dec 03, 2009 Posts: 31 Location: London

where can I get the PCBs (if i can)?

thnx
tasos

EDIT! Sorry .. im stupid Smile

neandrewthal · Joined: May 11, 2007 Posts: 672 Location: Canada

Cool stuff! Might as well throw up a pic of mine too:

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

As you can see, it's on 2 separate panels since I don't have the equipment to make panels that large by myself. They are attached together by the PCB bracket. I also added a fine tune for each VCO, multiple outputs and a mixer.

The Bad Producer · Joined: Mar 08, 2009 Posts: 282 Location: The Manhole

Wow, really nice work from everyone, those Euro ones are tempting me back to that format from Frac, hmmmm.......

With bananas obviously....

Funky40 · Posted: Sat Dec 26, 2009 6:06 am Post subject:

for many projects euro is just a perfect format,
for some i would prefer 4HE.

i tryed btw. different Resistor for the fine tune.
IIRC Jürgen was speaking from 1M5.
i used 2M2 on my first triple VCO, but was not fine enough for my taste.
so i tested 3M3 on my second which gave me a little less than 2 semitones, so i went then with 3M.
I would recommend 3M as the vaule to choose for the finetune

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

just doing some testing before i fully power my vco up

jurgen what should the rails see on the 3046?
my vco 1+2 have +/- 15 on pins 1 and 13 but my vco3 has about +/-5
i have +15 going to R83 but for some reason it drops to 5v
is that correct?

jhaible · Posted: Mon Dec 28, 2009 1:20 am Post subject:

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

cool thanks
i guess it is just a bad solder since i matched most of the components between the vcos

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

hi peoples, hoping one of you can help out a hapless rookie. Got my living vcos all set up again in situ... this time, I've got all three cores running well, I'd wired up one of the pulse outputs wrong before (doh!)...

But now, I have a problem I didn't have before, which is weird.

I can trace the signal for all 3 oscs all the way up to the amp section, into the TL072s and out the other side and up to the R135, R121 & R130 resistors on the output of the TL072s - but not on the other side of these three resistors (leading to the amp outputs which lead to my extra mixer board)... why is the signal not making it through? am I missing something obvious?

Many many thanks if someone can answer this for me!

Joe

dingebre · Posted: Fri Jan 01, 2010 7:17 pm Post subject: All done!

WoooHooo!

Got the second one finished and it fired right up. I'll post photos later.

Thanks JH, and Happy New Year to everyone!

[EDIT]
OK, here's a photo of the pair racked up. You see my Frac Frequency shifter above to the right and a spot for a TAU Phaser above it which will be my next project.

There are also some Blacet VCO's, Phaser, Mixer, and Splitter shown, as well as a Synthasonic produced MFOS Phaser.

I must say the Living VCO's calibrated easier than any other VCO I've tuned.

David

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Pair of Living VCO's built into a Euro Rack. The space to the right will house a Doepfer module. Above to the right is a JH frequency shifter and the space above is for a TAU Phaser.

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dingebre · Posted: Sat Jan 02, 2010 2:23 am Post subject: Detune

When I turn the detune knob, what sort of change in frequency should I hear?

I re-read the information on the website, and I think I am missing the point of the detune function and how it works.

David

jhaible · Posted: Sat Jan 02, 2010 2:34 am Post subject: Re: Detune

dingebre · Posted: Sat Jan 02, 2010 3:20 am Post subject:

Thank you JH. A couple more questions then please.

1. The detune pot is connected between the +/- 15 volt supply, so is "zero" detune when the pot is in the middle?

2. I think I still don't quite understand what detuning does. It detunes with respect to what? I know the answer is to experiment, but I'm not following what exactly this knob does. I guess I just thought is was just a fine-fine tuning knob, but clearly it is not that at all.

3. What is the most effective way to setup the detuing?
eg: CV into the driver
Set detune to "zero" (see question above)
Set desired frequency for VCO 1 through 3
Dial in desired detuning for VCO 1 through 3
Make wonderful music (or in my case, random, arythmic, atonal bleeps and burps)
Or is there a better way to setup the chorus of VCO's?

Maybe the best thing to do is just play with it...

David

jhaible · Posted: Sat Jan 02, 2010 5:36 am Post subject:

It's not complicated, once you figured it out. Smile

1. Set all the Linear Detune knobs to center position.

2. Tune the 3 VCOs with the multiturn pots, just like you would do with any other VCOs. Tune them to get slow beating rate at the upper end of the keyboard, to get a nice "phasing" sound that sounds rich, but not overly detuned.

3. You will notice, that with that setting (and carefully adjusted V/Oct tracking), you will get an almost beat-free and rather lifeless sound at the lower end of the keyboard. (The typical V/Oct VCO problem.)

4. Now, while holding a low note, turn one of the Lin Detune Knobs to the left, the next to the right, and leave the 3rd one alone. You can hear the magic happen immediately Smile

5. If you leave that setting from (4), and play a high note, it won't be much more detuned than before step (4). If you think it's too detuned, adjust it with the multiturn pot (not the linear detune pot).

6. With a little practice, this can be set up within a few seconds, and you have rich beating along the whole keyboard range, without sounding too detuned anywhere.

JH.

dingebre · Posted: Sat Jan 02, 2010 11:04 am Post subject:

Thanks JH.

David

[EDIT]

JH,

I tuned the way you described above and the linear detune worked perfectly and the "chorus" like sound at the low end was wonderful. Not too much so the "beat" was annoying, but enough to get a rich full sound with very little effort. I'm glad I built two...

David

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

right... I haven't had much luck with replies to my silly issues recently which is fair enough because i realise people are busy...

But i'm hoping as this is quite precise i might be able to get some response here...

I'm getting there, but one of my oscillators seems to be running at a very high pitch compared with the other two... (at the lowest frequency pot setting it's still very high pitch)

I've fiddled with the T trimmer but that doesnt have a huge range and cant be the problem... Ive also checked the components visually with the other two oscillators that seem to work fine, and cant see any discrepancies..
Is there a simple problem that could explain this issue?