Re: CV

[Richard Zvonar <zvonar@zvonar.com>]

At 2:37 PM -0600 12/13/01, jim palmer wrote:
>anybody really think this is off topic?
>i would like to hear about your use of cv.

Back in the early 1980s I was touring with the singer Diamanda Galas, 
performing in quad with backing tapes and live effects processing. I 
had a pair of DDLs, a Harmonizer, and a digital reverb at the mixing 
console, and she sang into a collection of mics that were routed 
variously to the quad system and to the processors.

Since she wasn't too thrilled to surrender all control over the 
effects processing to me, we started developing ways for her to 
control the levels of the effects returns. At first we did this with 
just the reverb, by sending the reverb output signal down the 
microphone snake to the stage, through a pedal, and back to the 
mixer. This was problematic due to degradation of the signal and 
pickup of noise, so we had a VCA box made. This meant that just the 
supply voltage went down the snake, through the pedal, and back. No 
noise problems. Unfortunately this device wasn't too road-worthy, so 
when it came time to replace it we did a deluxe version.

I approached SMS, a synthesizer company in San Francisco known for 
their high-quality analog modules (As Chris Muir liked to say, "SMS - 
When you don't care how much it costs"). Using their 6-channel VCA 
circuit as a basis, we designed a 12-channel VCA array in a solid, 
2-rack box, along with a small remote that could be mounted on a 
microphone stand and operated by Diamanda as she performed. The 
remote had six knobs and six momentary buttons, each of which 
controlled a separate control voltage signal. As in the prior device, 
the common source voltage was sent up the mic snake, where it was 
split into twelve branches that were scaled or gated and then 
returned through the snake to the VCA box. This meant that 1 + 12 = 
13 control voltages were routed through the snake, and we used seven 
channels of the snake for this purpose. The VCA box and remote each 
had a short multi-cable with seven XLR connectors on the end, so the 
connections were both robust and standard, AND we didn't have to 
schlep our own proprietary snake around on tour. The VCA box also had 
some nifty features such as manual override, LED displays of the 
current CV levels, and very flexible patching of the control voltages 
(which allowed ganging together of multiple channels and inverse 
control inputs to allow crossfading).

The system worked flawlessly most of the time. The two notable 
exceptions came during what was perhaps our most over-the-top gig, in 
London during the winter of '85. We'd been performing throughout 
Holland and in Rome without a problem, but when we got to the venue 
in Deptford the VCA box simply did not work. Naturally I had no 
schematics, nor did I have much skill as a repair tech, but I popped 
the lid and peered inside. I didn't see anything obviously burnt out 
or flopping around loose, but I did notice a single IC, all alone on 
a daughter board sitting above the main VCA cards. "Hmmm" I thought, 
but closed up the unit in momentary despair. Fortunately the venue 
was within a quarter mile of one of the primary electronics repair 
shops used by major British bands, so we brought the box to them. 
Within an hour or two they had it working. Despite the lack of 
schematics, they had simply popped the lid, had seen the lonely IC, 
said "Hmmm," and and replaced it.

The second problem came during the performance itself, a 
collaboration between Diamanda and the percussion ensemble Test 
Department (sort of left-wing political punk predecessors to Stomp). 
Acting on her usual premise that more is always better, the diva had 
rented an additional four effects processors and wanted eight 
microphones. I did manage to convince her that more open mics meant 
more feedback, especially in the sound field produced by five 
muscular skinheads pounding on oil drums with axe handles and 
whalloping a huge boiler suspended by chains, all of which junkyard 
instruments were also miked. We pared it down to the usual four mics 
and set up the remote to act as a crossfade controller for pairs of 
channels on the VCA box. This worked fine in principal, but the 
microphone stand we mounted the remote on turned out to be a very 
flimsy boom stand and the boom (with remote) went flopping over in 
the middle of the performance. This was especially hilarious because 
Test Department's record company Some Bizzare [sic] had rented a 
remote truck to do a multichannel recording intended for album 
release. The subsequent mix session is an epic tale unto itself, but 
suffice to say the performance was unsuitable for commercial release.
-- 

______________________________________________________________
Richard Zvonar, PhD
(818) 788-2202
http://www.zvonar.com
http://RZCybernetics.com
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