City Mouse Meets Country Mouse

What happens when the Good meets Evil? East meets West? Then meets Now? Can't we all just get along!?

I had an original Buchla 288 in my shop. I got it working and was able to introduce it to my 288v. A good time was had by all. It's a cool module and a very powerful piece, even if it is noisy.

1.2 volt per octave input

Pictured is the 258v with the addition of a trimmed 1.2 volt/octave CV input (the grey banana jack on the left). I have decided to go with this system because it gives the trimmed CV in I want, but doesn't take away any other inputs or outputs. The fine tune control for the left most CV in, I believe only was useful when scaling that input for a keyboard.

I'm working on them, and still waiting on the Selco knobs...

Gentlemen, I give you the 258v

This is a clone of the Buchla 258 oscillator. Despite what some people might tell you, it is totally true to the original in sound and response. I made all the electronics fit between the panel controls on a single PCB, as opposed to wiring to it like the original. I replaced the obsolete heated transistor pair with a modern matched pair and a tempco. The CV inputs respond exactly the same as a 258c. This one has the CV input fine tune control on the left, but I will be doing them with a grey banana jack in place of that. It will be trimmed to 1.2v/octave, but the other CV inputs are unaltered. Now I just have to build the rest of these....

Verbos' little workshop

I have a full on production line going here. I <3 my new Swiss Assembly Jig!

Holding Pattern

As I wait for my silkscreen guy to come back into town and the rest of the back-ordered parts to arrive, I give you a picture of a 258 clone with no front panel legend.

funny waveshapes

Some people think that a good waveshape is one that looks like what is printed in a textbook. A clean SAW wave is not always the best sounding one. Buchla 259s do not address the waves at the main output by the way they look, but rather by their harmonic content. Sure, there's a square and sine output, but the main output is a blend between even and odd harmonics, between hi and low order harmonics and between lo and high timbre. This always seemed, to me, like the better way for a musician to deal with oscillator output. The 258 claims to have a saw and square wave, but I feel that the spirit has always been about even or odd harmonics. They crossfade from sine to saw on the top oscillator and square on the bottom. The waves never look perfect, but they sound so good that the oscillator has a cult following. People clone it left and right. The above 'scope pics are from the prototype of my clone.

Here you will find some scope shots from an actual vintage Buchla 258C:

http://www.synthtech.com/pix/buchla/b258/b258_w1.jpg
http://www.synthtech.com/pix/buchla/b258/b258_w3.jpg
http://www.synthtech.com/pix/buchla/b258/b258_w4.jpg

Looking good. Sounding good. Feeling good.

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.

getting my modules together

After a month of downtime, I am back in the saddle. I got tonsillitis and had to go to the hospital, then my grandmother died. It's been a bummer, but I've done a little bit of work on a couple modules that I'm ready to show. These pictures are just the panel designs on paper with knobs laying on top, but they give a suggestion of what the finished modules will look like.



The first is a clone of an oldie. I don't care too much for the idea of cloning old modules (I'd rather do something new), but people keep asking me about 258 oscillators. It makes sense that some 200e users would crave the raw analog sound of the classic 200 sound source. There are a couple things that make this a funny one to re-do in modern times.

The first is that it used a µA726 matched transistor pair. That transistor is heated to maintain a constant operating temperature, so the scale doesn't drift as it heats up. This part is long obsolete. Although I could buy NOS ones on ebay, I have decided that this is not the best idea. Since the 259 uses a regular matched pair and a tempco resistor and the 208 switched from a µA726 to a regular matched pair and tempco in one of it's design revisions, I figured it would be ok to do this one with an LM394 and a tempco resistor. I also have redone the PCB so that all the panel controls mount on it. It makes the module much cleaner looking and less prone to failures. If the pots fail 20 years from now and nobody is making the same ones I have used, one could always panel mount some and wire to the PCB like the original design. It could be built up using the original knobs, blue knobs (if I can get the big blue ones!) or the ones Don is using now on the 200e modules.

The second thing is that the 258 has no keyboard input. Don decided to put a fine tune on the left-most CV in instead. I have never cared much for this and have entertained several other options. The first idea was to put a push/pull pot in the left-most position and when it is pulled engage a trimmed CV in rather than the scalable one that is normally there. Grant Richter told me he had done this on an actual Buchla 258. The problem I have with that is the depth of those pots would require really long stand-offs and panel mounted pots. The second idea I had was to put a gray banana jack in the hole where Don put the fine tune control on the left. This would work, but I don't know that I like having a banana jack in the area where the knobs are, call me weird. The final idea I had was to put a toggle switch where the fine tune was. If it's up, the input is trimmed 1.2volts/octave or whatever and if it's down, the CV goes through the control. I have set up my PCB so that the original fine tune control, the banana jack or the switch are all possible. I plan to try them all out and decide which suits best.

Although I did a couple 258 clones a few years back using a CA3080 instead of the discrete transistors in the core, I found the triangle symmetry to be imperfect and the whole exponential converter had to be changed to use a PNP pair, hence this module will be true to the original design using discrete transistors.


The second module I have ready to order parts for is the Quad Voltage Processor I wrote about last month. I thought I could get all the parts between the controls on a single PCB, using SMT, but I found that it was more parts than I anticipated. It is a motherboard with all the panel controls and a second board with the actual circuit. Since this is essentially 2 whole 257 modules, each with an extra CV input, I think that is respectable enough. I'm really looking forward to getting this one built up. This will be a boon to small 200 systems, where it will solve many control voltage situations.

Anybody interested?