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Buchla VCO
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CJ Miller



Joined: Jan 07, 2007
Posts: 371
Location: 127.0.0.1

PostPosted: Fri Mar 16, 2007 1:30 am    Post subject: Reply with quote  Mark this post and the followings unread

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

thanks


Yes! I discovered those pictures last weekend! I was reading about Grant Richter designing a "MARF" and I knew I'd heard of such a thing before, so I did some searching. I found this link later, but they originate from here in case anybody wants the real directory and files.

http://www.synthtech.com/pix/buchla/

And big thanks to Paul Schreiber for having these up. I don't know if he was doing this restoration or if these are somebody else's - but these provide some beautiful pictures behind the panels of some amazing modules.
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Fri Mar 23, 2007 6:47 am    Post subject: Reply with quote  Mark this post and the followings unread

I've got three Oakley VCO (based on later minimoog design)

http://www.oakleysound.com/vco.htm

For me, they are superb sounding ! (don't know why...)

Apart from the waveshaper stage, what could be the sonic difference between my minimoog sawtooth waveform and BUCHLA 258 sawtooth signal ?


a sawtooth is a sawtooth, same harmonic content ?!


What's the number one modular VCO module ? and WHY ?!
I've heard something about the "colder" caracteristic of the MOTM vco...
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mosc
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PostPosted: Fri Mar 23, 2007 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:

a sawtooth is a sawtooth, same harmonic content ?!


Well, in the ideal, this is true. In the real world, virtually every sawtooth sounds different.

I first realized this in spades when I first got my Nord Modular (NM1). I was interested in comparing the filter with the LPF on my Moog Modular. I hooked up a patch on each - just a single sawtooth and a filter being swept with an LFO (Triangle).

Wow, what a difference. I couldn't get them to sound alike. Then I listened to just the sawtooth oscillators - very very different. On the scope, they looked different. The ramps on the NM were very straight and on the Moog there was a little wiggle. The snap part was instantaneous on the NM, but the MOOG had some perceptible slope and round off on the housetops.

I had to change my test setup to use a common oscillator for both.

So, a sawtooth doesn't always equal a sawtooth. When people say they like the sound of a particular oscillator, there is probably something differential in that sound. Even very subtle differences can "make a difference". Wink

FYI, the filters sound very much alike until you start using a lot of regeneration (raise the Q).

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ian-s



Joined: Apr 01, 2004
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PostPosted: Fri Mar 23, 2007 1:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
Apart from the waveshaper stage, what could be the sonic difference between my minimoog sawtooth waveform and BUCHLA 258 sawtooth signal ?


A saw core vco uses a narrow, constant time pulse to reset the capacitor on each cycle. This pulse time becomes more significant at higher frequencies. The reset slope is also limited to how fast you can completely discharge a cap through a fet.
The triangle core just switches polarity every half cycle so the reset time can be much faster and closer to an ideal sawtooth shape.


funkyfarm wrote:
I've heard something about the "colder" caracteristic of the MOTM vco...


The MOTM vco is ultra stable, if you want drift and jitter you need to patch it in. Trouble seems to be that nobody knows exactly what sort of drift/jitter/soft sync makes the (for example) minimoog vco sound "warm".

I think my ideal vco would be a triangle core made by MOTM.
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Ilanode



Joined: Sep 14, 2007
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PostPosted: Mon Aug 25, 2008 3:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd like to build the 258 clone by Mark Verbos however this thread is confusing me.

These "other issue" suggest trouble I won't be able solve on my own:
andrewF wrote:
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


But then this suggest it's just the view from the bottom which is confusing.

Jerry L wrote:
The from the bottom component view sort of put me off also. I have not found any other obvious errors.


Is the layout fine beside the view from the bottom?
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andrewF



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PostPosted: Mon Aug 25, 2008 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

From memory Exclamation
reversed pcb layout and pins mixed around for the transistor pair.
The other issue I had...well i could never get my tri version of the board to work, but the square version is fine. The components to change are not in the oscillator core but in the waveshaper section. The problem was almost certainly my own build error rather than a pcb/schematic issue.
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Ilanode



Joined: Sep 14, 2007
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PostPosted: Tue Aug 26, 2008 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks! However it seems to difficult for me then. A pity!

andrewF wrote:
reversed pcb layout

This could be dealt with by etching a mirrored pcb, right?

andrewF wrote:
pins mixed around for the transistor pair.

However, I'm not sure wether I'm able to solve this. The SSM2220 must be turned by 180 degrees?
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Luka



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PostPosted: Tue Aug 26, 2008 2:05 am    Post subject: Reply with quote  Mark this post and the followings unread

can you work out with these, or was the problem in the schematic too?

schematic
http://www.simple-answer.com/258mod.jpg
sssm2220 datasheet
http://pdf1.alldatasheet.com/datasheet-pdf/view/49084/AD/SSM2220.html

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andrewF



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PostPosted: Tue Aug 26, 2008 2:10 am    Post subject: Reply with quote  Mark this post and the followings unread

yes, just reverse the image (flip?)

it is not hard, to work out the pins, a bit of a pain if you are using a ssm chip. much easier to use a 2sc798, even easier with two regular transistors. just work out from the schematic which pin goes to which component, follow the tracks from the components back the the thru-holes and mark them, say 1e (transistor #1 emitter), 1b, 1c, 2e,2c, 2b.

Really these are not difficult problems, I was a newbie when i made this PCB....admittedly it took three goes to get it right Wink

isn't Peake planning to make a 258 PCB? or did i read that wrong? maybe that will be the easy path.
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Ilanode



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PostPosted: Tue Aug 26, 2008 3:02 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm bad in troubleshooting thus I'd like to reduce my possible errors. If I don't use a SSM220 I'll have to match the transistors?

Yes, Peake is planning a 258 clone but he's including hard to find parts as uA276 (hopefully correctly spelled). For me this little VCO would actually do the job, I think, since I'm basically looking for some nice lin FM-sounds.
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Peake



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PostPosted: Tue Aug 26, 2008 9:41 am    Post subject: Reply with quote  Mark this post and the followings unread

I've already derived artwork for the 258c off of an unstuffed board, but it uses the uA726, as you said. I'm in the slow process of transmuting it to a "b", and will likely offer a derivative using a THAT array in place of the 726 (or SSM, etc.). However, you might want to see if the "c" clone I'd heard about comes along, for your linear FM as well as to avoid the 726, and other added niceties.

If you're also just interested in linear FM and triangle cores, the Thomas Henry VCO-1 is a great home-etch project, and TOPP is shortly coming out with a through-zero triangle core oscillator...there is much to choose from, including Mark's "c" hybrid, the subject of this thread.

(I'm mainly interested in "the real thing" type Buchla cloning.)

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Ilanode



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PostPosted: Tue Aug 26, 2008 10:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Peake wrote:
(I'm mainly interested in "the real thing" type Buchla cloning.)

I'd love that, too! I'm sure that Buchla is doing not only electronically well layout instruments but extremly musical instruments as well. However, I've to take my lack of electronic skills into account. If the Mark's design would be fool proof it would be a fine project. Since it asks for some deeper understanding I'd probably better wait for another more precise layout.

So I might actually choose from your project, the one you've heard about and Topp's project. Crucial for me is the documentation especially if it's a bigger project.
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dar303



Joined: Jul 15, 2007
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PostPosted: Tue Aug 26, 2008 10:56 am    Post subject: Reply with quote  Mark this post and the followings unread

It is quite easy substituting the ua726 for a MAT02 and a tempco resistor like in the ASM1 and the likes. I have done this in a few Formant oscillators.


Peake wrote:
I've already derived artwork for the 258c off of an unstuffed board, but it uses the uA726, as you said. I'm in the slow process of transmuting it to a "b", and will likely offer a derivative using a THAT array in place of the 726 (or SSM, etc.). However, you might want to see if the "c" clone I'd heard about comes along, for your linear FM as well as to avoid the 726, and other added niceties.

If you're also just interested in linear FM and triangle cores, the Thomas Henry VCO-1 is a great home-etch project, and TOPP is shortly coming out with a through-zero triangle core oscillator...there is much to choose from, including Mark's "c" hybrid, the subject of this thread.

(I'm mainly interested in "the real thing" type Buchla cloning.)
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Peake



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PostPosted: Tue Aug 26, 2008 11:24 am    Post subject: Reply with quote  Mark this post and the followings unread

dar303 wrote:
It is quite easy substituting the ua726 for a MAT02 and a tempco resistor like in the ASM1 and the likes. I have done this in a few Formant oscillators.


I'm interested in modding the 258b design to do 1V/Octave tracking and to replace the 726 as well (but as it's a dual board and the MAT and SSM are expensive, will use a THAT array for the expo core of both, for $5.00 total). I have neither the skills nor the understanding to modify the design for 1V and for a Tempco (I'm not certain which resistor is the critical part- the 2K at the end of the CV summing?).

Might you be available to do this design work for my project? I'd certainly pay for an hour's time for a schematic alteration. No problem if not; it would only be for other people, not myself (I'd never use a tempco in a Buchla oscillator; wouldn't be the same).

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dar303



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PostPosted: Sat Aug 30, 2008 8:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

My best advise is to do what I did; just steal the cv-summing and expoconverter from a working and proven design!

Smile

Remove everything before the control current input to the oscillator core and replace it with the appropriate parts from one of these:

Thomas Henry VCO-1:
http://mypeoplepc.com/members/scottnoanh/sitebuildercontent/sitebuilderfiles/vco1_schem1.pdf

SAS VCO (ASM1):
http://www.jacek.nu/sas/vco_schema.pdf
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Peake



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PostPosted: Sat Aug 30, 2008 11:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks, but for my initial run, I'm not interested in anything so hybridized...
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verbos



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PostPosted: Wed Sep 03, 2008 6:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ilanode wrote:
Peake wrote:
(I'm mainly interested in "the real thing" type Buchla cloning.)

If the Mark's design would be fool proof it would be a fine project. Since it asks for some deeper understanding I'd probably better wait for another more precise layout.


I feel like I came into this thread too late to be of any use, but for the record the "PCB is reversed" is not an error. That's just the way I drew them when I was working with Adobe Illustrator to lay them out. You'll be making the board from a transparency anyway, so I don't see why this should matter at all.

The layout for the PNP pair is an oversight. I never actually used one of those DIP pairs. I used a metal can PNP pair, where the layout was fine. I have built this design and it works fine. I will not be building them this way in the future because the 3080 is obsolete and not exactly symmetrical. It just makes more sense to me to build them as Buchla did for the 258c and change out the uA726 for a LM394 and add a tempco. It's just a few resistor changes and it will work fine. I don't believe that the sound will be changed, Mike may disagree. Buchla used tempcos in the 259 and they sound great. I'm not sure if the exponential converter in the 258c may make a difference, or I'd just use the 259 front end.

It would only make sense to add a 1.2v/oct trimmed input, since that's what Buchla's are using now, or a 1v/oct input for some other system. Before anyone builds this stuff they should be aware that Buchlas have a lower signal level than doepfers or whatever. They also expect a bigger voltage swing on the control inputs. My point being, you may want to add gain on the output and inputs to suit your modular. I only build for my Buchla, so I don't need to worry about that.

I think Mike is referring to my 258c project, but I will not ever make a PCB for sale. So don't hold your breath. I may also take down that DIY page I do have, since it keeps confusing everyone.


Mark
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Peake



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PostPosted: Wed Sep 03, 2008 6:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

verbos wrote:
I think Mike is referring to my 258c project, but I will not ever make a PCB for sale. So don't hold your breath. I may also take down that DIY page I do have, since it keeps confusing everyone.


I am really sorry to hear both of those items! I was trying to help drum up interest without naming names- sorry if I've had any unintended effect! I really appreciate what you're doing and wouldn't want it to ever change, except for the better.

Edit: Because I doubt that many others would take the trouble to do a commercial version out of love and reverence.

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loss1234



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PostPosted: Wed Sep 03, 2008 8:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

DONT TAKE IT DOWN!!!
i have it all printed out and am ready to etch and i love to be able to refer to the page when i get stuck and not only that but i LOVE your page.

I THINK the confusion has been made out to be bigger than it is (which is obvious from your answers)

from what you are saying, a CAN double PNP is the way to go eh?

thanks

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Peake



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PostPosted: Wed Sep 03, 2008 10:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
DONT TAKE IT DOWN!!!


Seconded! I love your page and your work. Your music ain't bad either Cool (remembering the message inside your CD: The future of modular synthesis is DIY).

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Ilanode



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PostPosted: Thu Sep 04, 2008 4:02 am    Post subject: Reply with quote  Mark this post and the followings unread

verbos wrote:
I may also take down that DIY page I do have, since it keeps confusing everyone.

Pls, don't do so. When I started out with DIY I could build Blacet kits while Ken Stone's design puzzled me for years even with the bought pcb in front. I'm happy that Ken's page is still up since by now his projects are those I'm happily building in a fly. (Well, most of them, I've to admitt.)

The solutions to allegedly confusing designs are: the noobs should be picky in what they attempt to build or they have to build up the necessary knowledge. To withdraw information from the public bcs. it's confusing to the noobs is definately a bad solution.

Even though I can't make the most out of your page I'm very happy it exists and then time will tell what I'm coming up with in the future.
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Jerry L



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PostPosted: Thu Sep 04, 2008 6:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi
Please take the Buchla page down Mark, I really like the thing.
I may have caused some of the confusion.
I built this and it works, it is only the pnp pair that is put
in the wrong way round.
Jeri
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Jerry L



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PostPosted: Thu Sep 04, 2008 6:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi
Damn!!!!
Need more java
What I meant to say was
Please DON'T take the Page down Mark!!!
It is a wonderful VCO
Jeri
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funkyfarm



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PostPosted: Sun Feb 08, 2009 3:42 am    Post subject: Reply with quote  Mark this post and the followings unread

mono-poly wrote:
I heard this vco isn't that good.
His vcf is a nice and good one!


Quote:
This is a clone of the Buchla 258 oscillator. Despite what some people might tell you, it is totally true to the original in sound and response. I made all the electronics fit between the panel controls on a single PCB, as opposed to wiring to it like the original. I replaced the obsolete heated transistor pair with a modern matched pair and a tempco. The CV inputs respond exactly the same as a 258c.


Ahh ! a long-awaited note.
Thank you mark.

http://buchlatech.blogspot.com/2009/02/gentlemen-i-give-you-258v.html
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neandrewthal



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PostPosted: Sun Feb 08, 2009 10:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hmm, now I`m temped to build a pair of these. What are the mini-dials for?
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