Buchla Model 185 - help with wiring

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lasesentaysiete
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Buchla Model 185 - help with wiring

Post by lasesentaysiete »

I am trying to wrap my head around how to wire up 2 x 196 phase shifters (dome filter), 1x 111 dual ring mod, and 1 106 mixer. Most of it makes sense to me, I think, except when it gets to the mixer.

Below is a modified version of a block diagram I found on Guitarfool.com. How do the outputs of the 2 ring modulators get mixed in order to get the "sum" and "difference" outputs on the 185?



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diophantine
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Post by diophantine »

I seem to recall a photo floating around of a 185, showing the stacked boards. I couldn't find it... also, not sure if it shows any of the wiring related to the 106 PCB.

Since the 106 stages are (IIRC) inverting, I'd imagine that it is:
RM1 out -> MIX input 1
RM2 out -> MIX input 2
MIX out 1-3 -> "sum" out
MIX out 1-3 -> MIX input 4
RM2 out -> MIX input 5
RM2 out -> MIX input 6
MIX out 4-6 -> "difference" out

So:
"sum" = -(RM1 + RM2) = -RM1 + -RM2 .... effectively RM1 + RM2 for audio
"difference" = -(-(RM1 + RM2) + RM2 + RM2) = -(-RM1 + RM2) = RM1 - RM2
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Post by lasesentaysiete »

diophantine
thanks for the algebra!

how does this look?

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diophantine
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Post by diophantine »

I think that looks right!

Did you end up finding a schematic for the 196?
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Post by lasesentaysiete »

diophantine wrote:I think that looks right!
There is something about RM 2 going twice into the second mixer that I do not understand.
diophantine wrote:Did you end up finding a schematic for the 196?
check it out:

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Post by guitarfool »

I see you found my Klangumwandler page. I took it apart to mount on a proper silk-screened panel, but didn't finish cabling and adjusting it 'cause I got distracted by all this Buchla 100 clone stuff :picard:

What Diophantine said is right. You just invert one of the 2 inputs for the difference, so if Don just used an off the shelf 106 board, that's what he must have done. It would be simpler to just make a one transistor inverter and 2x 2 input mixer, but who knows?

The critical part is balancing the inputs on the 2 mixers - take a look at Harald Bode's schematics, or Board 1 of Jurgen Haible's FS-1.
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Post by guitarfool »

lasesentaysiete wrote:diophantine
thanks for the algebra!

how does this look?

Image
Makes my brain hurt. I guess it works because you are mixing -RM1, -RM2 and +2RM2 for the difference output...
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lasesentaysiete
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Post by lasesentaysiete »

so the second output from RM2 going into mixer 2 is inverted. Like this?

EDIT: probably not
Last edited by lasesentaysiete on Wed Jan 09, 2019 7:20 pm, edited 1 time in total.
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Post by diophantine »

lasesentaysiete wrote:
diophantine wrote:I think that looks right!
There is something about RM 2 going twice into the second mixer that I do not understand.
Having RM2 go into the 2nd mixer twice means that you're doubling the amplitude of that signal, as it adds the inputs.

If we were to just have RM2 going once to Mix2, it would cancel out the inverted RM2 signal from Mix1, and the output of Mix2 would just be the original RM1 signal. So we cancel out the inverted RM2 signal and add the original RM2 signal back in.
lasesentaysiete wrote:
diophantine wrote:Did you end up finding a schematic for the 196?
check it out:
Yay!!
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lasesentaysiete
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Post by lasesentaysiete »

diophantine wrote: Having RM2 go into the 2nd mixer twice means that you're doubling the amplitude of that signal, as it adds the inputs.

If we were to just have RM2 going once to Mix2, it would cancel out the inverted RM2 signal from Mix1, and the output of Mix2 would just be the original RM1 signal. So we cancel out the inverted RM2 signal and add the original RM2 signal back in.
great! I understand. Thanks :tu:

Words work better than algebra for me, I guess :)
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Post by diophantine »

lasesentaysiete wrote:great! I understand. Thanks :tu:

Words work better than algebra for me, I guess :)
Haha, cool, glad that explanation worked better!
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Post by diophantine »

guitarfool wrote:It would be simpler to just make a one transistor inverter and 2x 2 input mixer, but who knows?
Yeah, it seems like a rather odd decision to use the 106 board as opposed to building a small new circuit. Obviously the 106 was a very early 100-series module; I wonder if the 185 came out a lot later and there were a lot of 106 boards left over? (I don't think I've ever seen a picture of an SFTMC-era 185.)

I'm also curious if the unnecessary parts (like the parts for the 3rd mixer) were omitted on the 106 boards in the 185?
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Post by guitarfool »

ImageImage

Okay, maybe this is a clue? The 111 panel shows holes for the 2 trimmers for the 2 ring modulators. The 185 panel shows the same 4 holes (for the 2 ring modulators?) and 2 more (panel mounted?) trimmers. I'm guessing these are the 2 balance adjustments for the SUM and DIFFERENCE mixers.

So maybe he just used a 106 PCB to kludge up an inverter and the 2 2-input mixers (no pots) and wired up the 2 balancing circuits?
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Post by lasesentaysiete »

Mr. Buchla appeared to me in a dream and reminded me that each ring modulator in the 111 has 2 separate outputs, the secondbeing the inversion of the first.

So there you have it!
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Post by lasesentaysiete »

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Post by lasesentaysiete »

guitarfool wrote: Okay, maybe this is a clue? The 111 panel shows holes for the 2 trimmers for the 2 ring modulators. The 185 panel shows the same 4 holes (for the 2 ring modulators?) and 2 more (panel mounted?) trimmers. I'm guessing these are the 2 balance adjustments for the SUM and DIFFERENCE mixers.
I am pretty sure that you are right about the trimmers holes being for the 111 circuit, but it looks like the 2 white bits below are jacks. But what for?

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Post by diophantine »

lasesentaysiete wrote:Mr. Buchla appeared to me in a dream and reminded me that each ring modulator in the 111 has 2 separate outputs, the secondbeing the inversion of the first.

So there you have it!
That's interesting... I never noticed it before!
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Post by guitarfool »

lasesentaysiete wrote:Mr. Buchla appeared to me in a dream and reminded me that each ring modulator in the 111 has 2 separate outputs, the secondbeing the inversion of the first.

So there you have it!
Doh! Sometimes it helps to glance at the schematic.
lasesentaysiete wrote:... but it looks like the 2 white bits below are jacks. But what for?
And if so, they look like pin jacks, not bananas. Test points? Or the sum and diff outputs for displaying on an oscilloscope? (Lissajous figures)
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Post by diophantine »

I always assumed they were some sort of test outputs, since in the CBS manual they very clearly look like 1/8" jacks.
Page 27: http://synthpalace.com/SynthPDFs/Buchla ... Manual.pdf
Though, for all we know, this could have been a mock panel.

Not a great pic, but this system has two 185s, one with white jacks(?), and the other with black ones, it would seem:
https://i.ytimg.com/vi/yaQJvHysWwU/maxresdefault.jpg

Also an interesting/odd find... a Buchla 165 with 1/8" jacks in the same location:
https://i.pinimg.com/originals/ee/e0/13 ... c80fe0.jpg
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Post by lasesentaysiete »

diophantine wrote:
Also an interesting/odd find... a Buchla 165 with 1/8" jacks in the same location:
https://i.pinimg.com/originals/ee/e0/13 ... c80fe0.jpg
those could be direct outputs for the noise generator, maybe?
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Post by diophantine »

Does the 165 use a noise generator as the sampling source? Seems like it would be overkill - noise generator + scaling it to 0-15V. Nyle Steiner used a 12kHz sawtooth wave as the "random" source in his S&H.

Anyhow, back on topic...


It now occurs to me that those "mystery things" are most likely the outputs of RM1 and RM2. Stick a probe in there & calibrate the ring mods appropriately with their panel trimpots. I can't imagine trying to calibrate the RMs based only on the FS output!

That would also make sense if sometimes they were jacks, and sometimes pin tip jacks (or similar). Maybe they switched to the pin tip jacks so people wouldn't get two free ring modulators? :razz:
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Post by sempervirent »

lasesentaysiete wrote:Mr. Buchla appeared to me in a dream and reminded me that each ring modulator in the 111 has 2 separate outputs, the secondbeing the inversion of the first.
I have nothing to add other than to say: that was really funny. I can picture this clearly.

Nice to see someone diving into the esoterica of the 100 Series.
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Post by Isaiah »

Presumably the 185 and 170 would make a good standalone Frequency Shifter, right?
Or would the Haible FS-1a be a better choice for someone without any Buchla (or plans to build any)?
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Post by lasesentaysiete »

Isaiah wrote:Presumably the 185 and 170 would make a good standalone Frequency Shifter, right?
Or would the Haible FS-1a be a better choice for someone without any Buchla (or plans to build any)?
I have not heard the 185, but the Haible would be easier to build. It is a more flexible and modern design, too.
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