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Tiptop Audio Buchla Model 257t Dual Voltage Processor

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The 257t Dual Voltage Processor

Tiptop Audio and Buchla team up to continue production of the iconic 200 series designed by Don Buchla and reformat it to Eurorack Modular standards. The 257t Dual Voltage Processor provides any system several essential functions to eurorack modular synthesis: offsets, attenuation, crossfading, attenuverters, and more. Full control over positive and negative voltages routing in and out of the 257t at your fingertips. Modulate your modulation. 

Model 257 Dual Control Voltage Processor consists of two identical sections, each of which permits several applied control voltages to define a single output voltage according to the equation:

(Va * K) + ((Vb * (1-M)) + (Vc * M)) + Voffset = V_out

The algebraic manipulations possible with this module include addition, subtraction, scaling, inversion, and multiplication. Also incorporated is the capability of using one control voltage (M) to transfer control from one applied voltage (V_b) to another (V_c).



Va is the voltage input a for attenuverter (left jack on the panel)

K knob can scale the incoming Va voltage either positively or negatively


Vb is the voltage input b for the left side of the crossfader (second jack from the left)

+.5 switch adds 5 volts to the input of Vb

Vc is the voltage input c for the right side of the crossfader (fourth jack from the left)

M scales Vb from 1 to 0 based on the position of M knob

M scales Vc from 0 to 1 based on the position of M knob

The middle CV input at M/M can crossfade between Vb and Vc (third jack from the left)

The M knob and M CV added together to control crossfade position


Voffset Adds 0 - 10 volts to any combination of Va + Vb + Vc


Vout is the combined voltage of the attenuverter, crossfader and offset (right jack on the panel)


Size: 14HP - Depth: 25mm Power: +12V 45mA / -12V 22mA

type ["Offset","Attenuation","CV Effect"]
_hp 14