My 207 #2

Through a series of trades, I ended up with a front panel from a 207 module. I had to clone the PCB in order to make it into a finished module. The module is mostly finished now, it simply awaits the microphone transformer. I have one lined up, I'm just waiting to get my filthy hands on it. Anyway, someone asked how the PCB I made looks, so here it is blank.




Here it is with some parts stuffed. Notice I went with film caps in the audio path instead of the 1uF electrolytics. I just felt like it was a good idea. I don't know if I'm making the world a batter place, but I'm trying, one capacitor at a time.



I did that messy kludge just like the original ones have too, but I didn't take a picture. it's in the cabinet now, so that will have to be shown off some other time. I don't know how much crosstalk would have been added by placing the resistors on the PCB, but I figured it wasn't worth tempting fate.

Mixers Mixers Mixers

With the release of the Buchla 206e, there's been some chatter about mixers. Evidently some people wanted to have the patch storage, but not the MIDI control for their 200e. But people more like me said they would like a 1 space all analog mixer for their system. This got me thinking, "what have the mixers been so far?"

206 "elegant" 2 x 3 channel mixers that are also summed to operate as a mono 6 channel one. It has mute and monitor switches on all channels.

205 2 x 5 in 4 out matrix mixers that also sum to make a simple 10 in 4 out one. Monitor switches on each input channel. Not exactly small at 3 panel spaces.

207 jam packed 6 input stereo mixer with manual pan on 4 channels and CV pan on 2. Pre amp. Monitor and mute switches on all channels. Monitor output on the front.

The 226 and 227 are quad interfaces that for the purpose of this discussion are irrelevant.

I think it would be nice to have a 6 channel, stereo mixer with CV controlled level and pan on each channel. I love sliders too. I don't know if anyone besides Grant uses the monitor system, so that might be eliminated.

The 207 uses a pair of Vactrols to do the panning, but because of the way the equal power curve is implimented, I don't think I could just send the level CV into the bottom of the differential pair. I could put basically a lopass gate in gate mode on each channel before the panner. The parts count could add up REALLY fast. That's 18 Vactrols! That's a lot of board space.

I'm thinking about solutions that are more elegant, like how the Serge Universal Audio Processor works. It's just 2 VCAs per channel that are controlled for the gain and panning. It would be nice to get a fast moving VCA in the equation, for the times when you want a snappy percussion sound. Three SSM2164s could do it.

I'm studying up on equal power voltage controlled panning circuits now.

Unearthing Greatness

In the last trade I did, I ended up with 2 modules that seem to be very early examples. The first is a 292B labeled "Prototype" on tha back of the panel. It's written in pencil, funny enough. This one worked well and matches the 292B I already had here.


The front panel was dirty, I had to take all the parts off to clean it up.




The other, a beat up old 207, has "Model" on an orange sticker, stuck to the back of the panel. I believe this means that Don built this up for the assemblers to use a reference while they were hammering them out. This thing had a few broken sliders, so I decided to replace all of them, since I was ordering a set for the 207 I was building from scratch. Synth Restore in the UK has re-manufactured sliders for ARP synths, and these were CTS too, so they work for Buchla stuff. To my horror, the inside of this thing was filthy! Balls of hair at the top and bottom of each slider and crumbs were everywhere.


I took out the sliders and blew out the crap to get started.


The sliders went in really nice and even though the shafts are shorter than Buchla used, they look great. Now, I just have to finish his buddy...