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Buchla VCO
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Tue Feb 27, 2007 10:58 am    Post subject: Buchla VCO
Subject description: Mark Verbos/ Buchla 258 style oscillator
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Did anyone try Mark Verbo's adaptation ?

Can anyboby explains to me why there is no vactrol in the oscillator core circuit ? Wink


http://www.simple-answer.com/DIY.html
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toppobrillo



Joined: Dec 10, 2005
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PostPosted: Tue Feb 27, 2007 11:40 am    Post subject: Reply with quote  Mark this post and the followings unread

heya-

haven't made it like Verbos', but i did build a version with a discreet OTA and NPN expo built with a transistor array IC. It works pretty well.

Quote:
Can anyboby explains to me why there is no vactrol in the oscillator core circuit ?


I wouldn't use one anywhere in the core circuit. The only place you'd use it, maybe, is for cross-fading between waveshapes. The original circuit uses a FET. I had decent luck with the MPF-102 here.
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andrewF



Joined: Dec 29, 2006
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PostPosted: Tue Feb 27, 2007 4:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

I built mark's version.
at the time, it was the biggest p'n'p board i had tried and it took 3 goes before i got a working VCO. I still have the 2 stillborn PCBs in a box somewhere.
My plan had been to build two, a square and a saw version, as you can see on the panel. but, in the end there was just one.

That being said, this VCO is well worth having. its character is very different from anything else i have tried

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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v-un-v
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Joined: May 16, 2005
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PostPosted: Tue Feb 27, 2007 4:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Beautiful front panel Very Happy
_________________
ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN.
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andrewF



Joined: Dec 29, 2006
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PostPosted: Tue Feb 27, 2007 8:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

v-un-v wrote:
Beautiful front panel Very Happy

Thanks -but it was a shame i made the panel before the circuits, all the 258 Saw sockets are unconnected.....sigh! finish it one day...
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mosc
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PostPosted: Tue Feb 27, 2007 8:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

You did the right thing. Buchla always designed the front panel before the circuits.
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mono-poly



Joined: Jul 07, 2004
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PostPosted: Wed Feb 28, 2007 5:04 am    Post subject: Reply with quote  Mark this post and the followings unread

I heard this vco isn't that good.
His vcf is a nice and good one!
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v-un-v
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PostPosted: Wed Feb 28, 2007 6:32 am    Post subject: Reply with quote  Mark this post and the followings unread

mosc wrote:
You did the right thing. Buchla always designed the front panel before the circuits.


A very wise move imo.

_________________
ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN.
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toppobrillo



Joined: Dec 10, 2005
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PostPosted: Wed Feb 28, 2007 4:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I heard this vco isn't that good.


you mean the Verbos version? in what terms?
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mono-poly



Joined: Jul 07, 2004
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PostPosted: Thu Mar 01, 2007 8:57 am    Post subject: Reply with quote  Mark this post and the followings unread

In terms that it doesn't sound as good as the orgional.
But his vcf is damn good!
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toppobrillo



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PostPosted: Thu Mar 01, 2007 11:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
In terms that it doesn't sound as good as the orgional.


it's basically the same.. the only difference is the use of an integrated OTA [as opposed to the discreet of the original, used here as a current-controlled current source] and an op-amp integrator. everything that contributes to what becomes audible sound is the same, including the sine shaper, which works well enough, in my opinion.
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23isgood



Joined: Nov 18, 2006
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Location: San Francisco, CA bay area
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PostPosted: Fri Mar 02, 2007 12:29 am    Post subject: Reply with quote  Mark this post and the followings unread

I agree really nice looking panel. How did you do it?
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andrewF



Joined: Dec 29, 2006
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PostPosted: Fri Mar 02, 2007 5:41 am    Post subject: Reply with quote  Mark this post and the followings unread

this description is on my homepage -

'The panels were cut from a sheet of aluminium and hand-drilled. i created the panel templates in Front Panel Designer, printed them out and used the prints as a drilling guide. The labels are a printable clear 'contact film' (some with inbuilt glitter). To get the image and labelling on i ran them thru the printer twice, 1st for the image, 2nd for the labelling. Then stuck the contact film to the panels and covered them with an 'industrial strength' (read - thick) contact as protection."

more pix of similar panels here too

http://www.sdiy.org/pinky/box/

I have only seen the printable clear 'contact film' on sale in Japan, needs a laser printer too. It isn't so strong on its own hence the extra layer of thick contact.

These days i use the same technique but just use photo quality paper, stick it to the panel with double sided tape and contact film over the top.
All the panel hardware helps keep it in place too.
my minisyn has such panels-

http://www.sdiy.org/pinky/MINISYN.html

its quick, cheap and cheerful but good enough for me.
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mosc
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PostPosted: Fri Mar 02, 2007 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Tell us about that mannequin... Very Happy

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

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andrewF



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PostPosted: Fri Mar 02, 2007 11:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very Happy meet pinky -

http://www.sdiy.org/pinky/pinky.html

"pinky has mostly CGS boards - gate sequencer, with preset and cv add-ons, analog shift register, digital wavetable with numitron display, Harry's morph lag, digital noise, 2 vcas, steiner vcf, 2 bandpass filters, passive ring modulator, envelope generator, joystick-nipple, super psycho lfo, psycho lfo and dc mixer. Also Paia dual VCOs and modulator"
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mosc
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PostPosted: Sat Mar 03, 2007 7:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, that has got to be the coolest synth construction I've ever seen. Seems relevant to this topic from long ago: http://electro-music.com/forum/topic-719.html

Congrats, AndrewF. Brilliant...

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Blue Hell
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PostPosted: Sat Mar 03, 2007 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

andrewF wrote:
Very Happy meet pinky


Right Exclamation

Pinky seems to have good set of controls to tweak Laughing

(and sounds good as well)

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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Sat Mar 03, 2007 7:48 am    Post subject: Re: Buchla VCO
Subject description: Mark Verbos/ Buchla 258 style oscillator
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Quote:
Can anyboby explains to me why there is no vactrol in the oscillator core circuit ? Wink



Vactrol ain't no accurate device ?
a VCO circuit design can't be designed around a single resistive element (for control) ?
expo response ?

Cheers
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Jerry L



Joined: Dec 13, 2006
Posts: 34
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PostPosted: Thu Mar 08, 2007 11:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi
Maybe I am confused, but isn't the matched pair(ssm2220)
in the wrong way round in Mark's layout?
By that I mean are not the collectors and emitters
reversed? Has anybody used this layout?
Jeri
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andrewF



Joined: Dec 29, 2006
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PostPosted: Fri Mar 09, 2007 12:29 am    Post subject: Reply with quote  Mark this post and the followings unread

yes he does, luckily I used a 2SA798 dual pnp.
I had some other issue with this board, can't remember exactly...

note- the component placement picture is viewed from the bottom. compress
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Jerry L



Joined: Dec 13, 2006
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PostPosted: Fri Mar 09, 2007 6:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi
Thanks!!!!!
The from the bottom component view sort
of put me off also. I have not found any other
obvious errors.
I was thinking of building one of these,
Any input would be appreciated.
Jeri
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tourist



Joined: Mar 15, 2007
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PostPosted: Thu Mar 15, 2007 3:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi everybody!!

I'm new on this site. looks great!

I finished recently one of M. Verbos adaptation of Buchla 258 (saw version).
Makes sounds but doesn't sound like i expected.
How does the waveshape control act? I think it must move from saw to sine.
Mine produces saw waves and i can distort it with waveshape control to produce something else (not sine). Of course, i tried many combinaition of trims but nothing like a sine.

Could anybody give me some audio samples of this VCO (for exemple A440Hz with waveshape control moving slowly from sine to saw/square)?

Thanks!!

Please don't pay attention on mistakes, I'm french and it's hard for me to write...
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toppobrillo



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PostPosted: Thu Mar 15, 2007 5:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

heya welcome tourist, this is about what the waveshapes are supposed to look like

[taken from http://www.hylander.us/images/schematics/buchla/Buchla%20200%20Photos.pdf ]

they look pretty close to that on mine- I didn't have very good luck with the 2n3958s here, for the sine-shaper i used a J201 and for the wave panning the MPF-102, although I'm sure alot of FETs will work well in both spots. experiment with resistor values. i changed them a bit.

ok good luck-

josh


258 wave shapes.JPG
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258 wave shapes.JPG


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mosc
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PostPosted: Thu Mar 15, 2007 6:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Topp, that is a GREAT link to old Buchla pics and schematics. Very Happy

thanks

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tourist



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PostPosted: Fri Mar 16, 2007 12:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot Topp...

I didn't use the pcb of M. Verbos. I did it by soldering components together.
So I made 2 or 3 errors during the manufacturing period. I must have burnt some key components of the sine shaping.

Now, I know how it is suppose to work!!
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