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Scott Stites/Buchla 291 adaptation
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Sun Feb 04, 2007 3:45 pm    Post subject:
Subject description: about the CV response...
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Fernando wrote:
about the CV response... I think the Buchla uses 10V for CV, are you using this range?


yes, 10V PP signals, we use stantard Oakley, CGS modules.

Sometimes I find myself boosting some external signals before feeding the 291 VCF control inputs.
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Scott Stites
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PostPosted: Sun Feb 04, 2007 9:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey Funkyfarm,

I've downloaded the first sample, still working on the second (dial-up, I live in the sticks). It's sounding pretty good!

About the external range (drum roll please....)

Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed

There was one leeeetle eensy weensy l'il mod I plum forgot about. It was the first thing I did when I built it, and promptly forgot it:

I changed R39 from 68K to 33K.

You see, I'd just built it and the control signals from my synth weren't.....um, you know the rest of the story.

You can either take out the 68K and replace it with a 33K, or you can just piggyback another 68K on top of the one you have (parallel) if it's lying down and 'easy'.

BTW, I did the same thing with the bandwidth input resistor, R43.

I left the FM input resistor at 47K.

Sorry about that - I'll have to note that on the schematic. It's been a few years since I rode that pony.

Congrats on the build, it looks and sounds great!

Take care,
Scott
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Scott Stites
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PostPosted: Sun Feb 04, 2007 9:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Second sample just downloaded - now that's rock'n'roll!
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synth_ollie



Joined: Sep 11, 2006
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PostPosted: Mon Feb 05, 2007 10:55 am    Post subject:
Subject description: 291 styro caps
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funkyfarm wrote:
By the way, I have here 100 encumbering pieces of 900pF Styroflex caps.

I will throw them soon !

If anyone is interested for this project, only shipping fees...



I may need a few ! Very Happy
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vtl5c3



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PostPosted: Mon Feb 05, 2007 2:06 pm    Post subject: Re: 291 samples Reply with quote  Mark this post and the followings unread

That's a very tasty nugget!

cyclops

funkyfarm wrote:
And another interesting sound from "the other 291 french adaptation"...
with AD633 ring modulator from here


633_291shining.wav
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funkyfarm



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PostPosted: Wed Feb 07, 2007 2:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
About the external range (drum roll please....)

I changed R39 from 68K to 33K.

Take care,
Scott




That is the SCOOP i was looking for !

I put 33K on CF and 47K on BW as "it was all that was lying around"... Wink


FM's 47k is associated with a 470pF cap, no ?

Lowering it to 33K implies to put a 330pF cap with ?
(have big holes in my electronics skills !)

Cheers

Last edited by funkyfarm on Wed Feb 07, 2007 11:22 pm; edited 1 time in total
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funkyfarm



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PostPosted: Wed Feb 07, 2007 2:51 pm    Post subject:
Subject description: RING MOD BATTLE : Papareil vs. Moogerfooger
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The track is mono but :

"On my left, the Moogerfooger 102 RM" (alone the ten first seconds)

"On my right, the Papareil AD633 RM"

291 BPF is the referee...

RING MOD BATTLE

Isn't that rock ?

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



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PostPosted: Wed Feb 07, 2007 3:21 pm    Post subject:
Subject description: 291 styro caps - End of out topic
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funkyfarm wrote:
I have here 100 encumbering pieces of 900pF Styroflex caps.


Okay !!!

900pFpix

[edit]
I have 3 "customers" for now

So there will be about 30 items each
Lucky you ! Wink
[\edit]

I guess I will have to charge (packing/shipping)
1€ to france,
2€ to barcelona and europa,
3€ to the rest of the world.
Don't know exactly for U.K. ! Let's say 2.50€ Cool
Only via Paypal (sorry)

You would be pleased to PM me for this.

[edit]PS : 4 of them are needed in the Quad 292 LPG... Cool[\edit]

Last edited by funkyfarm on Mon Feb 26, 2007 5:02 pm; edited 2 times in total
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Blue Hell
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PostPosted: Wed Feb 07, 2007 3:47 pm    Post subject:
Subject description: RING MOD BATTLE : Papareil vs. Moogerfooger
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funkyfarm wrote:
Isn't that rock ?


Nice ring mod thingy Cool

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funkyfarm



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PostPosted: Wed Feb 07, 2007 11:21 pm    Post subject:
Subject description: Homework
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Isn't that freak ?

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



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PostPosted: Thu Feb 08, 2007 10:47 am    Post subject: Reply with quote  Mark this post and the followings unread

is this our own layout, whats different from mark v´s ?
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Fernando



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PostPosted: Thu Feb 08, 2007 12:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott's LP and HP output buffers were added, as far as I see

original here:
http://www.simple-answer.com/DIY.html
http://www.simple-answer.com/291.pdf
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janvanvolt



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PostPosted: Wed Apr 18, 2007 5:43 pm    Post subject:
Subject description: Homework
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funkyfarm wrote:
Isn't that freak ?


Oh hell yeah! Do you have the BOM available ? If yes, i'd like to get the pcb etched as i got spare vactrols.
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funkyfarm



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PostPosted: Wed May 16, 2007 5:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

no bom, mark's plus one tl072 and 47k resistors for inverting buffer !

Quote:
I put 33K on CF (cv in)
FM's 47k is associated with a 470pF cap, no ?
Lowering it to 33K implies to put a 330pF cap with ?



What the difference between these two inputs ?

just a cap to block dc signals ?
intended for audio signal ?

and at least, "Lowering FM to 33K implies to put a 330pF cap with ?" Wink

291 schematic
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Scott Stites
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PostPosted: Wed May 16, 2007 9:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, the FM input is specifically for audio inputs - I didn't increase the cap value - (it's 470 nF, BTW). It didn't seem to make a whole lot of difference.

The slew of the Vactrol really limits how much FM you can put on it past a certain frequency - the higher in frequency the modulation, the less effect it has other than to change the passband. The attack is fairly quick, it's the release time that gets ya. In the frequencies where it is responsive, it's a very nice effect. My favorite thing to do with that input is to 'thwip' the passband with LFO range pulse or sawtooth waves - the fast transient makes it on through the capacitor and really plays well with the natural response of the VTL5C3. It's a great effect, it almost sounds like a slapback echo under certain settings - I've found myself reaching for the delay control before, only to realize I don't have any delay on the signal Very Happy

Cheerio,
Scott
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janvanvolt



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PostPosted: Thu May 17, 2007 5:04 am    Post subject:
Subject description: Homework
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funkyfarm wrote:
Isn't that freak ?


Yeah, looks like though! Do you have a schema or diagram ? i'd like to etch one of it, but i need the part list/placement ...
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funkyfarm



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PostPosted: Sat May 19, 2007 9:18 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
what about mark verbos's adaption:
http://www.simple-answer.com/291.pdf


Scott Stites wrote:
Yes, the FM input is specifically for audio inputs - I didn't increase the cap value - (it's 470 nF, BTW). It didn't seem to make a whole lot of difference.

The slew of the Vactrol really limits how much FM you can put on it past a certain frequency - the higher in frequency the modulation, the less effect it has other than to change the passband. The attack is fairly quick, it's the release time that gets ya. In the frequencies where it is responsive, it's a very nice effect. My favorite thing to do with that input is to 'thwip' the passband with LFO range pulse or sawtooth waves - the fast transient makes it on through the capacitor and really plays well with the natural response of the VTL5C3.


Cap is involved in filtering high frequencies (not sure but this makes sense).

Maybe swapping VTL5C3 for another type of octo-coupler could increase FM process. The new one should be faster for FM, isn't it ? Or maybe there is just no link...

anyway it would also affect CF response...


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vtl5c3



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PostPosted: Sat May 19, 2007 9:43 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:


Maybe swapping VTL5C3 for another type of octo-coupler could increase FM process. The new one should be faster for FM, isn't it ? Or maybe there is just no link...

anyway it would also affect CF response...


Yes, using faster vactrols, such as the silonex would result in faster response to CV. I think that's why Grant Richter used them in the Boogie filter. Fernando already posted the link below - it's for a 291 like filter using the above mentioned optocouplers.

http://hem.bredband.net/bersyn/VCBPF%20Bergfotron.png
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Peter Grenader



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PostPosted: Fri Jul 06, 2007 9:00 pm    Post subject: Samples and Holds and Buchla 100's Reply with quote  Mark this post and the followings unread

Someone said:

ll of the above were late 60's early 70's. Who pioneered Sample and Hold? Was it Buchla? Phillips??

The Buchla 100 didn't have a Sample and Hold directly. It had a random voltage genetator, which required pulses to advance (sample)...but it didn't have a voltage input. that was done via an internal noise source. So you could get stepped random voltages, which of course is a S+H, but a limited one.

The first 'classic' S+H DOn did was in the 200 system - the 264, which was quad , and also did track and hold (this happens when you're sampling signal has an on-time as opposed to a short pulse. When the sampling pulse if held hih, it passes the signal through and doesn't hold it until it's falling edge. This is why you have to keep those short in S+H's.

The real funciton for the 264 though, why it was quad, was it provided polyphony from the touch plates. You held down four keys, the pulse output of each going into one each of the S+H's, ran that voltage into four VCOs...you got a four voice keyboard. It worked great.

hope this helps,

- Peter Grenader
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Scott Stites
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PostPosted: Fri Jul 06, 2007 9:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey Peter,

I didn't know you were a member here! You slipped in under my obviously near-sighted radar, you sneaky guy. A belated welcome

Cheers,
Scott

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Randaleem



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PostPosted: Fri Jul 06, 2007 10:50 pm    Post subject:
Subject description: pro pcb's for the Scott Stites adaptation of the Buchla 291 will be available
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EDITed after reading Scott's follow-up Post.

I take great pains in securing permission from the appropriate copyright holder for anything I offer for sale.
It's the right thing to do; and even though US law does not require it for circuits and PCBoards which are only slightly changed; it's STILL the right thing to do. I have three boards right now that I cannot offer because the designer has held back permission unexpectedly. Which is his right.
(One will be changed to another design so it can be offered; the other 2 will lay dormant.)

I find it interesting that the general feeling seems to be that ripping off one is okay; (And even providing a circuit board layout so that others can more easily rip it off in the privacy of their own homes is welcomed and generally considered o-kay.

But if a person wants to make a better PCB available, which will take money and time to produce, and cost more, and require skill in layout and all the other business functions that go with presenting a product based on a design; then somehow THAT is not o-kay?

And then there's the oft-seen and common practice of using something somebody ELSE ripped off; and now we're one or two or more steps removed from the original. So that makes it okay?

As I said; I seek appropriate permissions; so for me it's academic. But I'd sure like to understand why it's okay to do one a hundred times behind closed doors. But not a hundred at once out in the open? [/rant]

Updated post below,

Hi,

Just want to mention that I talked to Scott about his mods to this Mark Verbos adapted design of Don Buchla's 291 a few weeks ago and he spoke well of it so it's in the works here. I hope to have pro PCB"s available before summer's out. Don't know yet about Kits and such until permissions are properly addressed.

FWIW, I'm also working on getting a few other things onto pro PCB's. I'll mention them briefly here but please keep replies to the 291 on this thread. We can start other threads to deal with these other projects?

a)The DImC TZ/Stereo. I'm in discussion with Roland to do this one legally. Seems that it will happen; but there's still a bit of ground to cover.

b)Scott's add-on to The MFOS/Ray Wilson ADSR. A re-trigger and input comparator (Add-on boards to use with RWSoft PCBs.) Soon 2B available.

c)Scott's add-on to MFOS/The Ray Wilson Triple filter coupling boards. Soon 2B available.

Note: Both of these planned RWSoft add-on PCB's were mentioned to Ray by Scott and I was told Ray had no objection.

d) A 4 pot Mini-Klee sequencer, based on Scott's orignal Klee experiments and the K2 development. (This is my main focus right now. It's really exciting; I've done a completely new fully Loaded LFO for it and the Super Klee2. More info soon in another thread.)

And Not by me; but I understand there will be a mutant filter PCB offered as well.

Randal

sine_wave wrote:
Coriolis wrote:
Well, Scott usually breadboards stuff (I think he actually had his entire modular on breadboard at one time), and then takes it to veroboard or similar, so there probably won't be a pcb-layout from him, but hey - if YOU need something to do over christmas...? Wink

I'm getting sorta ambivalent about making pcb's myself, because it means drilling a billion little holes, which I absolutely loathe...
Makes veroboard and a billion jumper wires look like vacation to me.

C


Hey C. Yeah it would be a good project. Problem is I'm still a beginner in regards to laying out PCB's from schematics, so the 291 adaptation looks a bit beyond my abilities unfortunately! Sad


.

Last edited by Randaleem on Sat Jul 07, 2007 9:58 pm; edited 4 times in total
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Scott Stites
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PostPosted: Sat Jul 07, 2007 12:09 am    Post subject: Reply with quote  Mark this post and the followings unread

I feel I should clarify things a bit.

The 291 Filter is Don Buchla's design. I did an adaptation of the design, which means I just added a few things to it (in addition to the op amp buffers Mark Verbos installed to replace the FETs). I did not design the filter, and would not presume to profit from it, and would prefer not to have my name on it.

Ditto the Dim C. The DC-2 (Dimension C) is entirely a Roland thing, save for some small things I added here and there. Again, I would choose not to profit from that design as well, and would certainly flinch at having my name attached to it.

The core of these designs, both of which I consider works of art, are far beyond my imagination or technical abilities to dream up. For any commercial venture, these two projects should be between Randaleem and Roland and Buchla.

The Mini-Klee was the first edition of the Klee sequencer I did, though from what Randal's mentioned to me in private, it's going to be considerably different and beefed up as well. Sounds like he's having a blast with it.

Cheers,
Scott

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Peter Grenader



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PostPosted: Sat Jul 07, 2007 2:28 am    Post subject: Being sneaky... Reply with quote  Mark this post and the followings unread

Yup, I'm a member! I don't have the time to contribute as much as I'd like, but do when I can.

That being said, I have been eyeing Macron's vactrols for some time, as I'm impressed by the On Resistance levels which seem to be much better than Perkin-Elmer's (probably due to using newer LED technology), and they're slower so they will (on paper, anyway) ring longer. But I have a way of tempering that if it becomes problematic. I've received quotes and they don't offer much of a cost advantage over P.E.'s, but if they would allow for a leak-less LPG, or DTG for that matter, i'd be one happy camper. This is the only thing about Vactrol-based sallen-key's that bother me. They just don't dip low enough for compete silence when used with rich signals.

I've also been working on another filter which uses twice the number of opto's as the Model 12, which I'm hessitant to release as doing so in the Eurorack format is always a tricky situation given the fact that Dieter has a huge selection, each at a price point I couldn't touch. Vac's aren't cheap...but too much of a temptation for me not to utilize because I think they make for the best sounding filters. You just can't get that brassiness with transconductance amplifiers.

- P
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Peter Grenader



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PostPosted: Sat Jul 07, 2007 2:39 am    Post subject: Buchla's designs.. Reply with quote  Mark this post and the followings unread

Regarding the 291's design... As with much of Don's work from that period, it definately sings of "add a bit more spice', as many of his solutions have stuff hung on them which indicates he got his decade box out and starting adding things to the soup until he got what he wanted, although some of it doesn't add up.

A perfect example is his method of biasing the drive transistors on the 291's vactrol drivers, all that jazz thrown in the feedback loop...totally wack and there are better ways of doing it, with less parts, and with the bracketing and response curves he was after.
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numbernone



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PostPosted: Mon Jul 16, 2007 7:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Lame question probably but...

What became of the Q pot found on the first schematic? This seems to be the only revision to the main body of the circuit.

Thanks.
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