QUAD SAMPLE AND HOLD MODEL 264
264 Panel Artwork, photo credit to Tom Rowlands
The 264 was a module that we originally thought was unobtanium in terms of being able to truly dissect and understand it. For a long time the only video of it’s operation was shot at very low quality, without much explanation as to how it worked or how it was to be used. Later iterations of the polyphonic array were utilized in the Buchla keyboards, such as the 219, 237, and 238.
Tom Rowlands of The Chemical Brothers was extremely kind to allow us to study his specimen, so the 264 became a reality.
We could wax poetic about how the 264 works, but the original catalogue entry does a fairly adequate job of explaining the functions:
242 documentation from the Buchla 200 Series Catalogue
NO HOLDS BARRED
If you’re here reading about these modules, we assume you might know the difference between the two flavors of held voltages that synthesizers utilize. A Sample and Hold follows the input signal of the module and will present an output voltage at every falling/rising edge of a pulse. A Track and Hold will track the input for the entire duration of the pulse, and present a held voltage when the gate is low. This will almost present itself as a slew effect.
POLYPHONY, IN MY BUCHLA?
Besides the flexibility of having four of these configurable sample/track and hold circuits, it contains a configuration that allows you to gain polyphonic output.
Dave Brown explains this quite well in his explanation of the prototype 264:
“The polyphonic support consists of two independent functions - a separate/common CV switch and 2 to 4 stage pulse generator. The switch simply disconnects the four CV input jacks and connects all four sample & hold circuits to the common CV input. The 2 to 4 stage pulse generator generates sequenced pulse outputs from a common pulse input. The Pulse Output jacks need to be connected to the Pulse Input jacks for the number of voices selected. With the switch in the Common position, the CV sampling is then sequenced through the number of stages selected.
For example, on the first pulse, the CV is sampled and held in the first channel. On the second pulse the CV is sampled and held in the second channel. When the maximum number of voices is reached, the sampling reverts back to the first channel. Thus a CV can be sampled and routed along with its associated pulse input to four VCOs and sustained over the number of voice pulse inputs. This differs from an analog shift register where the CV to a particular VCO is maintained only for the duration between common pulses.
When set to 2 or 3 voices the additional shift registers may be operated with their own pulse input but their CV input is common as controlled by the switch. Note also that the Common switch need not be used with the pulse generator. This allows sequencing of the sample & holds with separate CV inputs.”
It wasn’t long before we found some strange quirks with the circuit and gained knowledge of some “hacks” one could utilize to get the 264 to play chords with the aid of a 218. The video next to this text is from Kyle Swisher, who is “strumming” chords on his 218r. It’s a lengthy demo, but worth the time, Kyle is a master at his craft. Thanks Kyle!
REPLICATING THE 264
The 264 came a lot easier to us until we realized just how much WIRING we had to do. The 264 is a complex sandwich of boards, as exhibited by Chip’s build of his module.
