[sdiy] Behringer Cybermix CM8000

[Ullrich Peter]

Hi Batz!

>If you take a look at the photos on that site I posted, you'll notice that
>the only ICs adjacent to the VCA chip are a couple of Op Amp packages. A
>TL074 and some kind of 8 pin device. (Might even be a dual sample/hold
>chip) Each channel seems to be accompanied by a pair of trim pots. I can't
>see anything that suggests any further switching components per channel.
>Which is what threw me about the extra jacks. I would have expected there
>to be some kind of switching on the Mo-Bo but there was none.

I don't think that there some switching elements. Switching off the channels is
simply done via the VCAs that are good enough for this job.

>So all I can glean from these photos is that it's got MIDI and RS232. It
>also seems to have SMPTE I/O of some kind. And is powered by a HC11.

Yes, as far as I remember this little beast normally works synchronzed via SMPTE.
But you can also use it without (unsync'ed) via starting the software clock on the PC program.

>I need to make a decision whether to make a play for this thing within the
>next day or two. I know I could sum the outputs fairly easily. But I guess
>now it seems I have to find some kind of special software to run it.

I can give you the original Behringer software... Different version.
Should run up to WinME but with additional tools it should also run on Win2000
and WinXP but I haven't tried that yet. But I could test it in a few days when I have
more time (hopefully).

>At it's most basic, I just need to mix a bunch of incoming stereo sources
>from Analogue synths etc. Each synth has it's own autonomous mix/FX chain.
>The only thing I need to do is adjust each synth's level to normalize them.

Should be no problem.

>But if I could also use it like an automated noise gate, where I only have
>to have them in line as needed, then that would be a bonus. This is where
>this behringer box and it's VCAs would come in.

Also for that it should be OK - maybe a bit "overshot".
A few years ago I built a 48 channel MIDI-MUTE automation for a medium studio
mixer and the mute circuit was very primitve but worked fine. We added the circuit directly
into the mixer and swithced the audio signal right before the summing resistor (when I remeber
correctly) via a simple MOSFET to GND. I think we used the BSS98 MOSFETs.

They did not disturb or make noise when open but grounded the signal line so that no
further noise came to the summing line. I controlled this mute circuit via MIDI that was analyzed
by an 8051 microcontroller that controlled the MOSFETs via 8255 IO circuits (24 lines per chip).
This system worked very nice and could be upgraded to a lot more channels. You just have
to think how you will control it via MIDI. I controlled it via MIDI note on/off commands...

>I've tried various methods of doing this in the past but none of them have
>been quiet enough. OTAs are too noisy outright. The digital control blocks
>have zipper noise. Just plain switching causes pops and sudden introduction
>of noise. And to build something like this from scratch would be both
>prohibitively expensive and time consuming. And there-in lies the rub.

If you want to use it a realtime noise gate that switched during your music than my solution is not
perfect - but with an addition we added later (RC filter for soft switching) it was also useable.
The main task for this tools was to make unused mixer channels silent. So if the parts of that
channel ended we sent MIDI note off for that channel ansd it was muted until the next
signal should come - then we switched on via MIDI note on again.

>I don't want to find myself having to learn and write HC11 code.Or any code
>for that matter. I now just need to know that I can slot it in with some
>mods and tell it to behave and it will. So I'm a bit concerned about this
>RS232 notion and getting whatever software is required. More to the point,
>that means it's not platform independent and likely to become redundant.

So you could only use the Behringer software.
If you could write a program then the analysation of the serial data stream would be possible.
I have done this for some gadgets in the past but not for the CM8000...

>But from the general consensus here it seems like it's worth making a play
>for. And If so, I'll take you up on that offer Peter. You can always use my
>FTP and I'm happy to host some files there if anyone else needs this stuff.

Give me your FTP access data and I will upload the files.
It would be nice if other users could have read access too.

Ciao
Peter

http://www.ullrich.at.tt