J.Haible's Living VCO for Eurorack [Build Thread]

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audiohawk
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Post by audiohawk » Sat Jun 06, 2015 9:24 am

leterell wrote:
It turns out that the holes for the resistors are a little too small, and most brands physically won't fit.
i cant find the info on tayda's site what the lead diameters there are, they dont give that info on the resistors.
Answer from Tayda...

What is the body lenght? ( about 5.70 mm.)
What is the legs diameter? ( about 0.40 mm.)

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Siri
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Post by Siri » Sat Jun 06, 2015 11:17 am

elmegil wrote:presumably somewhere here

http://www.oldcrows.net/~jhaible/living ... _vcos.html
How did you know? RandomSource should put a link to this site while they are rebuilding the site ...

Concerning the resistors i got mine from tayda too, works nice.

Also the resistors sold at dipmicro fits. Cheap price & cheap delivery (1 week). I don't know if they carry all the values though.

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qfactor
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Post by qfactor » Thu Jun 25, 2015 5:41 am

So....with the announcement of the "official" LVCO pcb being able to do Sync'ing of its 3 Oscillators, I was wondering, would this be something that can be modified on our version of the LVCO as well?? :hmm:
"The 'clockwise' end is the pin that the center wiper connects to when you turn the pot shaft clockwise." - daverj

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Altitude909
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Post by Altitude909 » Thu Jun 25, 2015 5:49 am

I've decided to pass on this project so if anyone wants my kit, send me a PM. I have one stuffed board and all correct size resistors, some other parts for the other boards, pots, and panel. Will sell everything at what I paid for it (~$100)

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Post by Grumskiz » Thu Jun 25, 2015 6:18 am

qfactor wrote:So....with the announcement of the "official" LVCO pcb being able to do Sync'ing of its 3 Oscillators, I was wondering, would this be something that can be modified on our version of the LVCO as well?? :hmm:
BLASPHEMY!

Just kidding, I actually think this would be a great addition! I might leave out the Sine wave outputs to have individual sync inputs if that is in fact a possibility

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Post by leterell » Wed Jul 01, 2015 7:49 am

so, i finished my build, got all 3 cores plus the driver going. :hyper:

HUGE thanks to everyone sharing information in this thread, and to the people who did all the hard work to make the PCB's happend!

the sounds that come out of this thing are pure gold. when they come out. osc 1 is still weather-dependent or something on the pulse, just puts out -5v on some days.

so i can definitely recommend this build! i have a year of SDIY experience, no scope (ableton + line in for tuning duties) and a 10€ multimeter and i managed to pull it off.

Image

here's a pic (please excuse the horrific quality, my htc is 4,5 y old :deadbanana: ) of my custom panel (works great, even the 3590s's fit back there, although not even a millimeter between the top rail and them), decided to attach a noise source and a mixer on the panel. i really like the MFOS noise cornucopia, with the options i crammed on the panel especially. and the RYO ampmix brings a nice grit to things when needed. might change up for the newer version tho, that seems to work more versatile.

the rotary switches for waveform selection are a personal preference, i really do that rather than repatch a cable each time.

i flew the v/oct and hi-freq trims to a separate stripboard, and this i can highly recommend. i did this after i had assembled and trimmed everything, only to note that there was prob a quarter of a semitone discrepancy in the oscs over 2 octaves. i mean i want it to 'live' but that was too much for playing anything. after retuning it kept in tune nicely for 3-4 hours of playing yesterday evening, i mean over 4-5 octaves with 3 parallel oscs.

also, the pw goes from what sounds like 10% to 90% in 1/10 the pw pot's movement with osc 2 and 3, go figure... but i like the 50% pulse the most anyway...


would have some questions tho:

1. i get out a very nice sine shape optically, but it always has a sharp peak at one end, cannot get rid or that on any of the converters. could i trim something to iron this out?

2. is there a simple way to bias the sawtooths even a bit? getting any volume out of them is quite hard mixing all 3... of course i could just ass a -v from my MVP in the mix but that's also omitting one of my sources from the mix :waah:

3. the vibrato depth pot starts to work at 12 o'clock, ccw from that no effect. any easy way to try to trim this down? i played with the resistors close to the pot to no effect, not even magic smoke.

4. how could i go about setting the rate of the vibrato lower or increasing the range? it's now 1-2Hz at its slowest, i'd like something like 0,1-0,2Hz for the low end.

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Post by Randy » Wed Jul 01, 2015 9:06 am

leterell, impressive build, congratulations! I need to get back into mine and trim the v/oct again, but unlike you, I left the trimmers on the board so I need to take it apart to do it. Argh!

If you read (backwards) through the thread you'll find fixes for some of the issues you are experiencing.

Randy

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Post by leterell » Wed Jul 01, 2015 12:07 pm

If you read (backwards) through the thread you'll find fixes for some of the issues you are experiencing.
thanks Randy. Yeah, i guess there are suggestions as to the vibrato depth will have to follow those.

but on the other issues i couldnt find fixes. only the mention that vibrato rate is deliberately limited to 2-12hz. well, with the vib depth pot i can live, but if someone could point me to a component it would make sense to tamper with to get slower low end, i'd be very grateful!

i have the feeling that if i go on my gut feeling on 'now this resistor seems like it'd have something to do with the LFO rate' i think i WILL see magic smoke :omg:

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Post by sammy123 » Wed Jul 01, 2015 12:43 pm

Nice build leterell. I love a shot of the backside if you have it out of the rack.

I would describe my sine as looking ok on the scope as well, but buzzy. Not that I mind that much. I actually was doing an experiment for a friend (more of a joke) and you can clearly hear the buzzy quality in the first three sines in this video.

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Post by leterell » Wed Jul 01, 2015 6:47 pm

I would describe my sine as looking ok on the scope as well, but buzzy. Not that I mind that much.
judging from the vid my sines are right in your ballpark. i also dont mind it that much, just thought about an easy fix, a couple of components or so.
I love a shot of the backside if you have it out of the rack.
will snap one for you the next days when i have to tune the thing up again =) judging from experience it wont be long haha

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Post by idealer » Thu Jul 16, 2015 11:24 am

Hi.. great to see all nice lvcos in this thread
But i bet no one have as cool waveforms as mine do :hihi:

The question is how i can uncool them a bit... seems like the saw is biased to about +0.5v and is a little triangular.. i post a picture and let you have a look at it
It applays to all three om my cores

The other waveform is the tri

I have been pooking around with r21 and r22 ..no change
So could it be crappy lm311... leaky timing cap?
Well i will turn every stone untill i find it but i find it a good idea to ask you guys for advise first

Ps ... it is the first time i publish a image here so it might not work

Image

idealer
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Post by idealer » Thu Jul 16, 2015 11:27 am

Image

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Zaibach
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Post by Zaibach » Thu Jul 16, 2015 1:18 pm

Finally I had the time to work on my Living VCOs a bit more... I installed all the mods and redid the panels. I desoldered all the trimpots (exept for the HF trim) and put them on seperate boards on the back (as recommended by someone on this thread), and moved the trimpots on the driver to the other side for ease of access. I leveled up my desoldering skills several times while doing this, because every single trimpot I desoldered still works :hyper:
Only a few pads lifted, but nothing serious. The only things left to do are installing 10-turn pots for frequency and kludging tempcos on the VCOs (and cutting out the normal resistors I put in there) ...

Hopefully I won't have to take this monster apart again after this...

Image Image Image

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qfactor
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Post by qfactor » Thu Jul 16, 2015 7:35 pm

Nice! :yay:

In case anyone is looking for alternative sources for the 10-turn pot, I found one on eBay that I bought from that is reliable (bought a few times from him alread and everything seems to work fine!)

Look for seller:michael99514
I've also ask him for components that he doesn't list and most of the time he'd be able to get it as well. They're all from China, of course!

Hope this helps! :tu:
"The 'clockwise' end is the pin that the center wiper connects to when you turn the pot shaft clockwise." - daverj

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Zaibach
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Post by Zaibach » Fri Jul 17, 2015 11:51 am

qfactor wrote:Nice! :yay:

In case anyone is looking for alternative sources for the 10-turn pot, I found one on eBay that I bought from that is reliable (bought a few times from him alread and everything seems to work fine!)

Look for seller:michael99514
I've also ask him for components that he doesn't list and most of the time he'd be able to get it as well. They're all from China, of course!

Hope this helps! :tu:
I just looked him up, he's got the 10-turn trimpots for 5$ plus shipping, which is not bad. Reichelt.de in germany has them for 6,99€...

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Siri
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Post by Siri » Sun Aug 16, 2015 9:47 pm

just to confirm that I am 15V version and i had to use, as logicgate suggested, 500k trimmers for OCTTUNE1 and OCTTUNE2 on the driver board.

I wish the linear detune knob was less subtle... On JH front panel you can see that his knob can go from flat to sharp. He even says "while the real interesting feature is the low range animation - the "linear detuning" stuff..

But still I'm happy about it :banana:

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Post by Rod Serling Fan Club » Mon Aug 24, 2015 9:35 am

Possibly a silly question:

I believe I read that the synthi oscillators are tuned around .32 v/oct. At that tuning the voltage swing from another oscillator, trapezoid gen, etc. would be a lot more dramatic (approximately a 3 octave shift per volt rather than 1). It seems to me this is part of what is special about the way a synthi sounds. Just looking for other users thoughts on this matter.

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Post by bensaddiction » Mon Aug 24, 2015 6:14 pm

How about a decade counter on the Multi Turn.... Over kill? Would they fit?

Its only a buck more for the counter.

Like these:

Ebay Multi Turn

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Post by bensaddiction » Sun Oct 04, 2015 11:18 pm

Late start to my build. But its all done and its sounds amazing.

One thing though... Two of my oscillators tune and track well enough. But one VCO is out by 1 semitone. As in once its tuned to say C3 I don't get C4 unless I press C#4 on my CV keyboard

The scale trim pot doesn't fix the issue for this oscillator (it did for the others). The tuning gets closer part way through the scale trimmer's range (multi-turn) and then its starts opening up the difference again. I can't get vaguely close at all with VCO#1

This is with both the controller driver, and all the other possible v/oct inputs from . Does anybody know where I should look for a short or other error on the board?

The TL074 on that VCO was also a little warm. What would normally cause this and would that be the cause of the issue or its that chip for waveshaping for other wave forms?

The hardest solder points on the PCB have been the transistors which don't have the usual separated spacing you normally see on DIY boards and are easy to bridge, the pads for the SMT caps are also a little conservative and so I can't guarantee all of those connections.

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Post by billsship » Tue Oct 06, 2015 11:08 am

All I have left are the transistors, tempcos, and wiring it all up. I'm so afraid I've messed up one little part, but I've been thorough so fingers crossed.

Should I match the transistors? I didn't buy enough to match them, and the BOM doesn't say anything about it, so I'm guessing no. Although others in this thread have said it's a good idea.

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Post by Silesius » Sat Oct 24, 2015 3:01 am

Hi, I've finished my LVCO's with the Barcode boards. I've used some of the fixes found in this thread, so many thanks to everybody.
Surprisingly, everything seems to work fine: nice waveforms, the vco's track for about 5 octaves and the driver works as expected.

The only thing that bothers me is when you engage the "track" switch: even with the vibrato depth pot at minimum, you still can hear the driver modulation. It's subtle, but it's there. If you move the pot CW, the modulation increases (as expected), but you can never turn it completely off using the pot.

I've searched through this post and it seems to be a fix for the "vibrato depth problem", involving increasing resistors 158 & 160. But it seems that's meant to fix the pot when it has too little effect, and not the other way around.

Is anybody experiencing this? How about normalling my vibrato jack to ground so the circuit sees ground when nothing is plugged? Any ideas would be very welcomed...

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Post by unnu_ » Thu Jan 14, 2016 10:14 am

I am now building the Living VCOs following the schematics only, and from my readings so far some people noticed two differences between the original schematics and the pcb- variant:
1. R40 should be referenced to 0 and not to -vb;
2. there is an extra R6 from the junction of R30/R31 to 0; i would like to ask you what value is this mysterious R6...

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Post by qfactor » Thu Jan 14, 2016 10:43 am

unnu_ wrote:I am now building the Living VCOs following the schematics only, and from my readings so far some people noticed two differences between the original schematics and the pcb- variant:
1. R40 should be referenced to 0 and not to -vb;
2. there is an extra R6 from the junction of R30/R31 to 0; i would like to ask you what value is this mysterious R6...
From the BOM by Barcode, it says that R6 in the vco pcb is 10k.
Are you referring to this same one?

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Post by unnu_ » Thu Jan 14, 2016 10:57 am

thanks, qfactor, that's it. Somehow i've missed the BOM on the very first post of this topic :roll:

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Post by qfactor » Fri Jan 29, 2016 11:34 am

Hi,

For those of you who built this version of the LVCO, would you happen to know how much current it uses?

Today, I hooked up one (of 2) of my LVCOs along with 2 TH Mega Percussive Synth and used the LVCOs pulse wave (at its lowest freq setting) to trigger the 2 MPS and left them to "burn in" for a few hours. All went well.

Then I decided to hook up the 2nd LVCO. So had 2 LVCOs and 2 MPS powered up via a uZeus and this resulted in one of the LVCOs Not being able to work and when I touched the uZeus panel, it was burning HOT!!
This is the 1st time I'm experiencing a uZeus not being able to power up 4 modules (2 LVCOs and 2 MPS)!! I'm not powering any other modules but these 4 only.

Do the LVCOs take up so much current? :despair:

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