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Grounding multiple Buchla boats & using Negative voltage
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge  
Author Grounding multiple Buchla boats & using Negative voltage
musicalfungus
Hello fellow wigglers!

I have 2 questions for the forum today. I have been using an Easel for a couple years now and have decided to finally expand my Buchla setup! I just recently purchased a 257r and I am in the process of acquiring a 6U boat. (weedywhizz/samodular)

Here are my questions.

1. When using the 6U boat with my Easel (in BEMI suitcase) Do I need to ground the two cases together? And when using in conjunction with my Eurorack and the Syunovatron CVGT1. Would I just ground the Easel to the 6U boat and then stack a banana from the boats ground to the Synovatrons ground? I feel like this is the correct way to do it. but just wanted to confirm as I have never used multiple Buchla boats at the same time. Ive only ever had to ground the Easel to the Synovatron in order to play nice with Eurorack.


2. I have heard in the past and read on this forum a few times about negative voltages and Buchla. Specifically the BEMI Easel. Seems to be that some people said its ok to route negative voltages (specifically to the pitch cv on the oscillators). But others seem to say its not good and can cause issues or even break something. I often like to use the Synovatron CVGT1 to use an analog Shift Register and send the cv pitch sequence to the Easel. My shift register has an ability to transpose and shift octaves as well and can push voltages into the negative range. Ive been scared to do this when hooked up to the Easel due to various people stating it cant take negative voltages. The Synovatron has the handy LED to tell you when voltages go negative. But just curious if ive been given false info and if I can go ahead and send both positive and negative voltages to the Easel. I ask because now that I have ordered the 257r. I noticed its attenuverter can go into negative voltage range. So It made me think that if the 257r can send negative voltages. The 208 should be able to accept negative voltages.

Any help or knowledge you mighty synth wizards could provide would be greatly appreciated. Thanks!
ArguZ
You need a common ground in order for the voltages to make sense.
The closer to 0 the more reliable it is.
And if your ground is +5V then you have only half the control voltage if you use something that can produce +10V

If you send +10V into the 257r it can attenuate that down..
So you can invert a curve for example...
But it does not go lower than 0V
dkcg
I don't know about 3rd party modules, but i believe 200e modules will safely clip all negative voltages. I can't verify for sure, but I believe all 200e modules are diode protected against negative voltages.

It's been a few years since I sent my 200e modules any negative voltages, but I seem to recall the Zeroscillator's banana outputs being clipped at 0V before the V2 came out which offset and scaled the banana outputs to be all positive voltages.
Drillionaire
dkcg wrote:
I don't know about 3rd party modules, but i believe 200e modules will safely clip all negative voltages. I can't verify for sure, but I believe all 200e modules are diode protected against negative voltages.

It's been a few years since I sent my 200e modules any negative voltages, but I seem to recall the Zeroscillator's banana outputs being clipped at 0V before the V2 came out which offset and scaled the banana outputs to be all positive voltages.


OEM Buchla modules have negative (and over-) voltage protection on tini-jax modulation inputs (think FM on 285e/oscillators, mod inputs on 291e, etc). There is no negative voltage protection on any 200e CV input.

The 208, on the other hand, is fine to accept negative voltages, or any voltage between its power rails (±15v). This does not apply to the 218e. It falls into the same category as described above about 200e modules.
solaris
Drillionaire wrote:
There is no negative voltage protection on any 200e CV input.


uhm, but a module like the 254v produces negatives votages - or am I wrong?
Drillionaire
solaris wrote:
Drillionaire wrote:
There is no negative voltage protection on any 200e CV input.


uhm, but a module like the 254v produces negatives votages - or am I wrong?


It's been a while since I've worked on one of those, but I believe that's correct.
solaris
now that I think about, what about the 255 and 256e?
never had those but I had a 254v and it worked without problems in a 200e.
Kent
254V does generate negative voltages. 255 and 256e do not.

Caveat: see Drillionaire’s post below.
Drillionaire
solaris wrote:
now that I think about, what about the 255 and 256e?
never had those but I had a 254v and it worked without problems in a 200e.


255e is analog, with ±15v rails for the op amps, so it will output negative voltages if it is fed negative voltages. The front panel legend will not be accurate for the scaling if this is the case.
With no input CV, the scale knob outputs a 0 to ~10v DC voltage on the output.

The 256e uses a an ADC -> DAC signal flow, so it will not output negative voltages if it is fed them, and they can damage the ADCs and/or MCUs in the module.
ArguZ
Not that it matters much, but the Zeroscillator V1 also outputs negative... -5V/+5V
Pailo
really confused here. I thought my 254v
inverted. I didn't think there was any negative voltages in
the Buchla format for CV. Audio is different
cause its AC... the voltages are all DC I thought.

you can invert signal and you can use the attenuators to push voltage down
but....

and you can use diodes to rectify signals going tt-banana, but....

From the buchla manual
"Before getting in to the details of particular modules, lets pursue
some items that all 200e modules share in common. First the connections.
Like its predecessors, the 200 and 100, the 200e series differentiates
between control voltages, signals, and pulses. Control voltages are used
to specify parameter levels, range from 0 to 10 volts, and are
interconnected with banana jacks and cords. Pulses are used for
timing information, and have two levels. 10 volt pulses transmit only
transient information, while 5 volt pulses carry sustain information. Pulses
also employ banana interconnections."

I don't see anything about negative voltages....
Cobramatic
Pailo wrote:


From the buchla manual
"Before getting in to the details of particular modules, lets pursue
some items that all 200e modules share in common. First the connections.
Like its predecessors, the 200 and 100, the 200e series differentiates
between control voltages, signals, and pulses. Control voltages are used
to specify parameter levels, range from 0 to 10 volts, and are
interconnected with banana jacks and cords. Pulses are used for
timing information, and have two levels. 10 volt pulses transmit only
transient information, while 5 volt pulses carry sustain information. Pulses
also employ banana interconnections."

I don't see anything about negative voltages....


Well it does say the voltage ranges is always from 0 to 10v - so I guess the fact that no negative voltage is described implies that it is not expected.
(compare to Serge and Eurorack where the voltage range is usually described as -5v to +5v)

I think this description is also made without referencing or even contemplating using the Buchla with external gear other than via the specified 'entry points' such as Midi and the external signal processing module.
Pailo
I have a large amount of Eurorack too, and
it depends on what you are using but yea
those modules do the -5 to +5 bi-polar thing.

I use tons of caution when using the two systems together
to make sure I am not hurting a 1000$+ module.

I know with eurorack people have designed modules
to not take more than +5 and I have broke modules
hitting them with +10v. Eurorack is the Wild West.

Also with new companies making "Buchla adaptions"
I would always scope things before just assuming, to
protect your investment.
pre55ure
Pailo wrote:

I know with eurorack people have designed modules
to not take more than +5 and I have broke modules
hitting them with +10v. Eurorack is the Wild West.


Really? woah
Who would design a module like this?
IMO thats not a eurorack thing, thats just a bad design thing.

If you design a module that isn't tolerant up to the voltages used for the systems own rails... d'oh!
musicalfungus
Drillionaire wrote:

The 208, on the other hand, is fine to accept negative voltages, or any voltage between its power rails (±15v). This does not apply to the 218e. It falls into the same category as described above about 200e modules.


Thanks to Drillionaire for providing me with this info! That is exactly what I wanted to hear. I can now safely pursue my explorations of whacky shift registered Eurorack voltages (with possible negative voltages) sent into the Easel via the CVGT1.


I do still have one question that I don't think i've seen answered yet. What is the correct way to ground 3 separate boats?

Do I connect a banana from my easel the the 6u Buchla boat. And then stack another banana out of the same ground output and send it to the Synovatron CVGT1?

Thanks in advance for any help you can provide. It's peanut butter jelly time!
Pailo
You said it correct musicalfungus.
banana the back of the easel to the boat,
then do that same ground to the synovatron.
musicalfungus
Pailo

Thank you very much for confirming my question. I greatly appreciate it. I figured that was the way its done. But wanted to double check and verify. Thanks again!
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