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Buchla Source of Uncertainty 266
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vtl5c3



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PostPosted: Sat Dec 13, 2008 11:06 am    Post subject: Buchla Source of Uncertainty 266 Reply with quote  Mark this post and the followings unread

A few years ago I realized that it would be possible to build my own Buchla 266 Source of Uncertainty. I took the schematics that were online and laid each one page out on a separate press n peel pcb layout. When I started putting it together, I exchanged a few emails with Scott Stites who pointed out some useful mods, which I will include here.

Today I will start things off by posting the first board layout and some sound samples that were created with it. I will post the remaining boards and samples to go with them as time permits. The original layouts have a few errors, so I'm going through each one to correct them before sharing with the public.

So, here goes: the first board, which is based off this schematic:

http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2660_1_200.jpg

I will post the sound files later today.

[edit]

updated the pcb layout and parts overlay. Found a small mistake in the n+1 output section. [/edit]

[edit2] Another quick update. Added comments on which resistors to swap out if you plan on triggering the 266-1 with 5 V pulses. [/edit2]

[edit3] fixed 2^n outputs [/edit]


266_1_revised_09112010.pdf
 Description:
266-1 (QRV) PCB w/parts placement. Fixed 2^n outputs 09/11/2010.

Download
 Filename:  266_1_revised_09112010.pdf
 Filesize:  2.09 MB
 Downloaded:  651 Time(s)


266_1_revised_09112010_PCB.pdf
 Description:
266-1 (QRV) PCB layout. Fixed 2^n outputs 09/11/2010.

Download
 Filename:  266_1_revised_09112010_PCB.pdf
 Filesize:  1.05 MB
 Downloaded:  484 Time(s)


Last edited by vtl5c3 on Sat Sep 11, 2010 11:02 am; edited 7 times in total
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cbm



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PostPosted: Sat Dec 13, 2008 11:49 am    Post subject: Reply with quote  Mark this post and the followings unread

 
Cool project. For the uninitiated, this is the Quantized Random section from the 266. There are several other sections involved in a Buchla 266.

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

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Luka



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PostPosted: Sat Dec 13, 2008 3:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

great, i just bought a mfos quantiser and was regretting not buying a second


quick question, does anyone know how similar is the noise section in the SOC to the cgs digi noise? by description it sounds exactly the same

im looking forward to the sample and hold and stored random voltages

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cbm



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PostPosted: Sat Dec 13, 2008 4:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Luka wrote:
quick question, does anyone know how similar is the noise section in the SOC to the cgs digi noise? by description it sounds exactly the same


I imagine that they are fairly similar. There were only a couple of digital noise chips made.

I'm not that big a fan of the digital noise chips, fwiw. A transistor or zener based noise circuit sounds better, IMO. Or even a fancier (than the noise chips) digital pseudo-random shift register approach.

-C

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Scott Stites
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PostPosted: Sat Dec 13, 2008 4:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yep - the reason I never finished my SOU is the Quantized Random Voltage - the shiny that distracted me from it was the first Klee sequencer. It was based off of the QRV, used a CD4006 and replaced the resistors with pots (using four of the outputs of the CD4006). IE, the Klee is a direct descendent of the QRV and Ken Stone's gated comparator.

And (yep again), the CGS digital noise would work in place of the IC. A noise transistor would work pretty well also. Noise is used for the noise outputs, and it also modulates a slow moving triangle, which is the sample source of the fluctuating random voltage section, which is my favorite (along with the cool S&H) part of the 266.

Best digital noise circuit I ever heard is Thomas Henry's design in the 21st Century book (available at Magic Smoke). Digital noise tends to suffer from chug-chug as the pseudo-random pattern repeats. This design by TH will chug in, what, two hours? IE, you will never hear any periodic element in the noise.

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vtl5c3



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PostPosted: Sat Dec 13, 2008 5:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

The CGS noise module is better, imho. For the simple reason that the clock speed can be changed, both manually and with voltage control. The MM5837 is pretty lame, but I guess it was adopted by synth mfgrs since it was simpler to implement than having to hand select noise transistors/diodes.

Luka wrote:


quick question, does anyone know how similar is the noise section in the SOC to the cgs digi noise? by description it sounds exactly the same

im looking forward to the sample and hold and stored random voltages
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vtl5c3



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PostPosted: Sat Dec 13, 2008 6:05 pm    Post subject:
Subject description: Quantized Random Voltage Samples
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Here are some mp3s that demonstrate a bit of what the 266 QRV can do. It's like a really unusual sample and hold. In two of the samples I fed in a VCO sine wave, both at audio and sub-audio rates. The third features the CGS VC noise as the input voltage.


266_1_01_Sine_in_2VCOs.mp3
 Description:
Sine wave VCO, audio rate fed into the QRV CV input Clocked by LFO square wave. Each output fed into separate VCO. Mix between the two with VCO at audio rate, then at 01:20 I drop the input VCO to subaudio.

Download
 Filename:  266_1_01_Sine_in_2VCOs.mp3
 Filesize:  2.5 MB
 Downloaded:  922 Time(s)


266_1_2_2VCOs.mp3
 Description:
Same patch as last one. Input VCO at subaudio rate.

Download
 Filename:  266_1_2_2VCOs.mp3
 Filesize:  1.79 MB
 Downloaded:  627 Time(s)


266-1_NOISE_IN_1.mp3
 Description:
Same patch as before, except that the input voltage is CGS noise source. I played around a bit with attenuating the noise input and varying the manual control.

Download
 Filename:  266-1_NOISE_IN_1.mp3
 Filesize:  3.92 MB
 Downloaded:  628 Time(s)

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ericcoleridge



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PostPosted: Sat Dec 13, 2008 9:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very Happy Very Happy Very Happy Very Happy Very Happy Very Happy
Last edited by ericcoleridge on Sat Dec 13, 2008 9:32 pm; edited 1 time in total
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ericcoleridge



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PostPosted: Sat Dec 13, 2008 9:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

I see that futurlec has the 2n1711 general purpose NPN for .80, in case anyones looking.
Last edited by ericcoleridge on Sat Dec 13, 2008 9:30 pm; edited 1 time in total
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ericcoleridge



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PostPosted: Sat Dec 13, 2008 9:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is such a great project VTL5C3, thanks for posting it here. I'm really looking forward to building the whole module! I have a few questions if anyone here could answer:

Scott Stites wrote:

And (yep again), the CGS digital noise would work in place of the IC. A noise transistor would work pretty well also. Noise is used for the noise outputs, and it also modulates a slow moving triangle, which is the sample source of the fluctuating random voltage section, which is my favorite (along with the cool S&H) part of the 266.


The noise circuit is not part of *this* pcb though, right? I didn't see a Noise output on this project. I'm guessing it's probably part of the Fluctuating Random Voltage circuit.

On the SOU module, is the noise source sent to the QRV or the SRV circuits? Or do they just use CV inputs for input signal?

Last question, what does 'quantized' mean in the context of this module? I'm assuming it's not quantized to intervals for a volt/octave VCO, right? Or is it?
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Luka



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PostPosted: Sat Dec 13, 2008 9:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

no this pcb above is just one section of the SOC module
it is the quantised random voltages

the SOC includes (from top to bottom)

digital noise
fluctuating random voltages
quantised random voltages
stored random voltages
integrator
sample and hold

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vtl5c3



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PostPosted: Sat Dec 13, 2008 9:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Eric,

You must be excited, with your reply in triplicate! Laughing

I'm not sure that I can explain what is meant by Quantization, but this module does take the input signal and chops it up, sort of like a sample and hold... but only sort of.

I was going through my 266 dossier and came across an old email that Steve Ridley had sent me back in '99. In it he analyzed the 266 and did a great job of making it easy to understand. I'll post the part relevant to the QRV section here:

"The "Quantized Random Voltages" section is based around a fairly standard gpseudo-random sequence generator, using a 4006 and an EXOR gate. The 4006 is clocked by input pulses from the top left 4mm socket. The next bit is clever. Various taps of the 4006 are taken through 4016 switches and suitable scaling resistors into a mixing op-amp - a sort of analogue/digital filtering. There are two different mixes to give diferent noise distributions. The 4016 switches are driven by comparators from a resistor ladder and a CV, so increasing the CV or turning the pot brings in more switches, mixes in more stages and changes the distribution. Each output has a 4mm sockent and an LED."
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ericcoleridge



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PostPosted: Sat Dec 13, 2008 9:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

vtl5c3 wrote:
Hi Eric,

You must be excited, with your reply in triplicate! Laughing


Sorry about, I guess I got a little over zealous! Tried to erase, but couldn't. Embarassed
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Scott Stites
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PostPosted: Sun Dec 14, 2008 2:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey VTL - did Steve happen to discuss the 266 Stored Random Voltage function? That's the one that I still have trouble getting my head around. I breadboarded the thing, but it still mystifies me, what with that diode ring and all. I'd love to see Steve's take on that!

Bitchin' samples, BTW. Very Happy

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numbertalk



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PostPosted: Sun Dec 14, 2008 9:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Luka wrote:
no this pcb above is just one section of the SOC module
it is the quantised random voltages

the SOC includes (from top to bottom)

digital noise
fluctuating random voltages
quantised random voltages
stored random voltages
integrator
sample and hold


So there are 6 boards in total? Will you show how to wire them all together when you have them all sorted out?

Thanks for the great projects recently! They're all going in the queue.
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vtl5c3



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PostPosted: Sun Dec 14, 2008 9:35 am    Post subject: Reply with quote  Mark this post and the followings unread

No, there's four boards in my version (2 in the original). Each of my layouts was based on one of the 4 pages of schematics.

The digital noise is on the fluctuating random board. The integrator (slewer) is on the sample & hold board.

numbertalk wrote:
Luka wrote:
no this pcb above is just one section of the SOC module
it is the quantised random voltages

the SOC includes (from top to bottom)

digital noise
fluctuating random voltages
quantised random voltages
stored random voltages
integrator
sample and hold


So there are 6 boards in total? Will you show how to wire them all together when you have them all sorted out?

Thanks for the great projects recently! They're all going in the queue.
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cbm



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PostPosted: Sun Dec 14, 2008 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
I breadboarded the thing, but it still mystifies me, what with that diode ring and all.


Looking at your redrawn schemo, it looks to me like the diode ring is some sort of clamp, although what it's purpose is right there is slightly mystifying.

I would love to see some deeper analysis of this circuit.

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Luka



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PostPosted: Sun Dec 14, 2008 2:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

does the QRV need a 10v line?

and can you confirm the in/outs and pots are

clock
qunat cv in
quantisation pot
high out
low out

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vtl5c3



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PostPosted: Sun Dec 14, 2008 3:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

The 10V line is provided by the TL074 at the top left.

Inputs:

1) CV input jack with attenuator pot. The PCB layout has extra inputs in case someone wants to add them.

2) Clock input jack.

Manual control:

1) 1 Pot

Outputs:

1) n+1: 1 Jack & 1 LED

2) 2^n: 1 Jack & 1 LED

Scott's redraw of the 266QRV does not have the LEDs, but I do recommend including them. They put on a pretty show.


Luka wrote:
does the QRV need a 10v line?

and can you confirm the in/outs and pots are

clock
qunat cv in
quantisation pot
high out
low out
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Luka



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PostPosted: Sun Dec 14, 2008 3:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks vtl

wish i had room for leds
my panel design is choc-a-block a the moment

is your stored random voltage design similar to the verbos design?

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neandrewthal



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PostPosted: Sun Dec 14, 2008 8:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Luka wrote:
thanks vtl

wish i had room for leds
my panel design is choc-a-block a the moment

is your stored random voltage design similar to the verbos design?


There is always room for LEDs Very Happy You just have to get the small ones, and find a little crack between your panel components.

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ericcoleridge



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PostPosted: Mon Dec 15, 2008 7:03 am    Post subject: Reply with quote  Mark this post and the followings unread

vtl5c3 wrote:

The digital noise is on the fluctuating random board. The integrator (slewer) is on the sample & hold board.


Do you use the MM5837 in your Fluct Rand Voltage PCB? Just wondering if I should start hunting one down. I see that the are some 'pulls' for sale on e-bay now. $24 for 10, not too bad.
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vtl5c3



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PostPosted: Fri Dec 19, 2008 5:37 pm    Post subject: PCB Layout #2: Stored Random Voltages Reply with quote  Mark this post and the followings unread

Well, here's part two of this four part series. While cleaning up this layout I found one mistake that I have to fix on the actual module. I have sound samples of it in its current state, but I want to add the missing resistor to see if it's noticably different before I post any mp3s. Having used it, it seems similar to the QRV module in how it processes voltages. Anyway, here is the press and peel layout:

[Edit] I updated the parts layout to show which resistors to change if you plan on driving the 266 with 5V pulses. The actual Buchla design seems to call for 15V pulses, which is hotter than most other synths' output levels. It will still work with 15V pulses if necessary. [/Edit]

[Edit2]Removed a redundant 47K resistor in the CV2 rectifier[/Edit2]


266_2_PCB_Parts_revised_09112010.pdf
 Description:
266 SRV PCB + Parts (Edited 9/11/2010 - Removed a redundant 47K resistor in the CV2 rectifier)

Download
 Filename:  266_2_PCB_Parts_revised_09112010.pdf
 Filesize:  2.91 MB
 Downloaded:  387 Time(s)


266_2_PCB_revised_09112010.pdf
 Description:
266 SRV PCB. (Edited 9/11/2010 - Removed a redundant 47K resistor in the CV2 rectifier)

Download
 Filename:  266_2_PCB_revised_09112010.pdf
 Filesize:  1.71 MB
 Downloaded:  276 Time(s)


Last edited by vtl5c3 on Sat Sep 11, 2010 12:08 pm; edited 8 times in total
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funkyfarm



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PostPosted: Sat Dec 20, 2008 12:53 am    Post subject: Re: Buchla Source of Uncertainty 266 Reply with quote  Mark this post and the followings unread

vtl5c3 wrote:
A few years ago I realized that it would be possible to build my own Buchla 266 Source of Uncertainty.


THIS IS ABSOLUTELY AMAZING !?!

Thank you Romeo.
Thank you Scott.
(Thank God)
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BananaPlug



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PostPosted: Sat Dec 20, 2008 7:20 am    Post subject: Reply with quote  Mark this post and the followings unread

What a great distraction this is becoming. I guess I have to get up to speed on etching boards now or find somebody who's already got a setup. Many thanks for sharing this.
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