Buchla 218 VC-able Portamento - Works!

vtl5c3 · Last edited by vtl5c3 on Tue Dec 30, 2008 11:19 am; edited 5 times in total

Last night I finally tested the slew circuit that I cloned from the Buchla 218 keyboard. I'm happy to say that it works. I've posted the schematic and a couple of sound samples below. I may have to do a bit of fine tuning... if nothing else I will try smaller cap values, since it's pretty easy to get way too much portamento going.

Update: I've uploaded the PCB layout, for those who like to roll their own.

218_slew_01.mp3

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218_Slew_02.mp3

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Buchla_218_Portamento.jpg

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buchla_VTL_slew_PCB.jpg

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PCB Layout. Works!

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buchla_218_Slew_parts.pdf

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Parts layout. Corrected diode part number.

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buchla_218_Slew_parts.pdf

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StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

Interesting - I was waiting for Jeff Beck to crash in! Have you heard him make similar sounds!

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

Here's a sample of Jeff Beck doing just that
http://www.4shared.com/file/18815193/15b17a7/JBeck.html

His fingers, a whammy bar and a Rat distortion!

bubblechamber · Posted: Thu Jun 28, 2007 10:16 pm Post subject:

thanks for posting

krisp14u · Joined: Nov 11, 2006 Posts: 206 Location: uk

Cheers for that vtl5c3 I will have a go at this 1 over the weekend

paul D

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

I'm not quite sure if I needed to have bothered (subjunctivo!) with the Jeff Beck sample - a lot of synth players would give their right arm to play like that!!

Quad · Joined: Dec 30, 2006 Posts: 18 Location: Stockholm, Sweden

Thanks for posting!

What is the difference between Ground and N Ground? and what is L1 & L2?

thanks!

vtl5c3 · Posted: Sat Jun 30, 2007 8:53 am Post subject:

Fernando · Posted: Tue Jul 10, 2007 7:30 am Post subject:

I missed the thread.

wow, thank you so much!
(actually the "wow" was a "fantastico" before being slewed)

Is the 4.7uF capacitor that you are refering to?

maybe is the control of the LED's vactrol what should be finetuned...?

_

Dave Manley · Posted: Sun May 04, 2008 9:25 am Post subject:

I was looking for the 218 schematics yeseterday and couldn't find them in the usual places. Are they online somewhere?

-Dave

P.S. Is there anything Buchla couldn't (wouldn't?) do with a vactrol? Very Happy

cbm · Joined: Oct 25, 2005 Posts: 381 Location: San Francisco

vtl5c3 · Posted: Fri May 09, 2008 10:59 am Post subject:

Did you need the entire 218 schematic set? I don't think it's online, but I have them. Could have sworn I got them off the web at some point.

R.

cbm · Joined: Oct 25, 2005 Posts: 381 Location: San Francisco

Quite a few older Buchla schemos:
http://rubidium.dyndns.org/~magnus/synths/companies/buchla/

Dave Manley · Posted: Sat May 10, 2008 12:12 am Post subject:

I was studying the Easel and the 218 is a key part of it. The 216 and 217 are online at Magnus' site, but the 218 is absent. It would be a good addition to his pages if available.

How many pages total are there in the 218?

CJ Miller · Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1

Cool... I was just looking over slew/portamento ideas, and I was surprised how few are VC-able.

In the schematic, it calls for a 6V Zener diode. But on your PCB diagram it says 1N5224. Isn't this a 2.8V Zener? What Zener did you use here? I don't know how crucial it is, as I have neither anyway. I'm a vactrol n00b and I don't want to fry them.

Nice efforts studying Buchla's work! Most of his stuff makes my head spin.

vtl5c3 · Posted: Tue May 27, 2008 8:51 am Post subject:

Good question. I'll have to check my work when I get home. You're correct that the 1N5224 is a 2.8 Zener. It should read 1N5233. Thanks for pointing it out.

R.

haxster · Posted: Sun Nov 16, 2008 12:21 pm Post subject:

Is the type of vactrol used critical? Would a VTL5C4 be okay to use. I am new to vactrols.

doctorvague · Posted: Sun Nov 16, 2008 1:52 pm Post subject:

The VTL5C4 would be slower than the usual VTL5C3 that Buchla uses. It's not spec'd here but I'm assuming it is a VTL5C3 in this circuit. The 'slower' would just be response to control changes, not the portamento itself. IOW, if you wanted quick turn-on and turn-off of portamento via control voltages it will have more lag time, especially the turning off or quick turning down of the portamento. Kinda like portamento'd portamento. Shocked

Cheers
Phil

vtl5c3 · Posted: Sun Nov 16, 2008 3:25 pm Post subject: Schematics

Forgot that I was gonna post them, but here they are.

Buchla218-1.jpg

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218 Schem Page 1

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Buchla218-2.jpg

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Buchla 218 Page 2 Schem

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Buchla218-3.jpg

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Buchla 218 Board Part Placement

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probablyjoel · Joined: Aug 31, 2008 Posts: 11 Location: Seattle

What type of offboard components are you using for the control inputs? Just standard 1/4" jacks?

vtl5c3 · Posted: Sun Dec 07, 2008 10:07 am Post subject:

I'm using 1/8th inch jacks. Nothing fancy.

probablyjoel · Joined: Aug 31, 2008 Posts: 11 Location: Seattle

Thank you! One more question...I'm not so familiar with the buchla... how do the control inputs differ from the input? If i use it for my 4017 step sequencer, would it work through the normal input or through the control input?

vtl5c3 · Posted: Sun Dec 07, 2008 11:39 am Post subject:

Whatever CVs you'll be processing go into the normal input. The CV input controls how much portamento is applied to the processed voltage.

probablyjoel · Joined: Aug 31, 2008 Posts: 11 Location: Seattle

So i would need another CV control to control the level of portamento? What types work best as controllers? Sorry if this is super obvious... I'm still a newbie:).

vtl5c3 · Posted: Sun Dec 07, 2008 2:58 pm Post subject:

You can use the manual control to set a portamento amount, but the value only changes when you turn the knob. To CV control it, run an LFO into it, have a second analog sequencer control it, or even aftertouch from a keyboard... really any CV source will work.