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Problems with CV feedback to LPG's on BEMI Easel
MUFF WIGGLER Forum Index -> Buchla, EMS & Serge  
Author Problems with CV feedback to LPG's on BEMI Easel
musicalfungus
I own a 2016 or 2017 BEMI Easel. Purchased in early 2017 but probably made in 2016. It was before they switched over to using the newer 200e style rogan knobs so its got the classic amazing big red and blue knobs.

My issue is as follows. I am at work but will try to post a video example later and provide a link to better help demonstrate if needed.

Best way to describe it is to provide a patch example.

1. EG to either LPG1 or LPG2 CV in. (or both)
2. EG to Timbre CV in.
3. Any of the 4 Random Voltage outputs to Timbre CV in.

The problem here is that the random voltage should only be modulating the timbre. Yet somehow it is also effecting the LPG. The same thing happens if the EG was going to LPG2 as well. For some reason the random voltage is feeding back through the EG cables and going to the LPG's.

My initial thought was grounding. I tried several different plugs and power strips through my home but the issue persists. I have also tried grounding the Easel to my Eurorack via the Synovatron CVGT1. But even then it still happens which makes me think maybe its not a grounding issue. I still need to take it to a different house or my office to fully rule out the grounding possibility.

Now maybe I am crazy and this is how its supposed to work. But I feel as if it just started happening a few days ago. Anyone else have a similar issue? Or maybe can confirm if this is standard behavior? Other than this 1 issue. The Easel seems to operate correctly. I feel as if I used to patch EG and random to Timbre, and EG to the LPG with no bleed through of the random voltage to the LPG's. Hopefully one of you Buchla experts out there can help me. I contacted the authorized BEMI dealer I purchased the Easel from and they provided me with Alex Sifre's contact info. I left him a voice mail and I am waiting to hear back.

Thanks in advance for anyone who may be able to help as I await a response from Alex Sifre at BEMI.
vgermuse
If I read you correctly you're stacking EG output and Random output into the single Timbre input. I'm not near my easel just now either but stacking on to a single input has varied and unexpected behavior in my experience.
Drillionaire
vgermuse wrote:
stacking on to a single input has varied and unexpected behavior in my experience.


Definitely want to reiterate this.

The colored output bananas of the same color on the 208 are all connected to each other passively in parallel. If you connect two modulation signals to a single black CV input, you're also connecting each modulation source to all other output jacks of the other modulation signal(s).

The only exception to this rule is the random outputs, which are four separate random voltages, each with their own connection to the random daughter card PCB.

As an example, if you were to modulate any parameter with the sequential voltage source and the pulser, the voltage resulting as a combination of the two signals will be present on all the yellow and blue bananas at the bottom of the 208. This is because the signals are connected together at the input banana jack, and therefore all the output bananas for the sequential voltage source and pulser are now connected.

One could make custom banana cables with schottky diodes in series that would allow for stacking multiple signals on a single modulation destination (if they are connected in the right polarity) with only a minimal voltage drop. Alternately, the diodes could be installed between the motherboard and the output banana jacks themselves.

Hope this makes sense.
papz
The 208 ToolBox offers a useful CV mixer. cool
Tropic Al
papz wrote:
The 208 ToolBox offers a useful CV mixer. cool


A fantastic mixer it is!
vgermuse
Tropic Al wrote:
papz wrote:
The 208 ToolBox offers a useful CV mixer. cool


A fantastic mixer it is!


+10 nanners
musicalfungus
vgermuse

Thanks for the info! I was hoping you would chime in here. Thanks Todd!
musicalfungus
Drillionaire

Your explanation was exactly what I wanted to hear. Glad to know this is normal operation due to the passive connections. Completely makes sense! I am very grateful for the knowledge you just provided me. Thank you very much!
musicalfungus
papz

I hope to one day own both the 208 toolbox and a Bob expander!
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