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Classic Buchla in Tiptop Form





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With Buchla’s official blessing, engineers and sound designers at Tiptop Audio have meticulously and faithfully re-created the vintage voltage of the West Coast synthesis pioneer’s 257 Dual Control Voltage Processor, with the 257t. Buchla’s iconic - and often esoteric - design ethos is now available in a fully-compatible, 14HP Eurorack module, uncompromising in delivering the full scope of voltage manipulation offered by the original 257, impressing Sweetwater’s premiere synthesists. Like its historic counterpart, the 257t utilizes two identical, independent sections of CV modulation, boasting a straightforward interface undergirded by complex mathematical equations to produce wildly compelling sonics. Voltages are blended into a singular output, with addition, subtraction, scaling, inversion, and multiplication processes, as well as voltage-controlled transfer between two CV inputs.





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You’ll have likely noticed that the face of the module indicates the mathematics being utilized through each port and pot to produce the output voltage: VaK Vb­M MVc Voffset = Vout. “Va,” “Vb,” and “Vc” comprise the inputs that can be added into the ports just below their respective positions. Voltage “a” is first multiplied by constant “K,” which is determined by the first pot. With a range of -1 to 1, this first pot can pass unaffected, attenuate, or invert the voltage present at the “Va” input. The next pot has a range of 0 to 1 and supplies our “M” variable. Voltage “c” is multiplied by “M,” whereas voltage “b” is multiplied by the complement of “M.” This means that when “M” equals 0, voltage “b” is added to the output and voltage “c” is ignored. When “M” equals 1, the inverse is true. Anything between those absolute values results in a mix of both voltages. Furthermore, the value of “M” can be voltage controlled through the middle jack between the “Vb” and “Vc” inputs. Lastly, there is an “offset” voltage, which is internally generated, with a value between 0 and 14 volts, and will be present even without any additional inputs in the chain. You’ll also notice the “ .5” switch ? this generates 6 volts to be used if voltage “b” isn’t present.





Tiptop Audio Buchla 257t Dual Control Voltage Processor Eurorack Module Features:


2 independent, parallel voltage processors enable a multiplicity of uses with input voltages


Linear transformations deliver mathematically derived changes from CV inputs to combine into a single output voltage


LED indicator displays when positive voltage values are detected


4 CV inputs on each processor allow for greater combinatorial capabilities