Doepfer A-148 Dual Sample&Hold / Track&Hold Vintage Black Panel
Module A-148 (Dual S&H) has two identical sample & hold modules, designed to produce 'staircase' voltages. The signal present at the sample input is sampled at a rate set by the signal at the trigger input, and held at that voltage at the S&H output.
The exact shape of the staircase depends on the sort of waveform at the sample input: NOISE or RANDOM signals produce random patterns; an LFO produces rising or falling staircase patterns.
Two LEDs for each S&H indicate the voltage (positive or negative) of the sampled signal.
For more detailed information please look at the English user's manual: A148_man.pdf on Doepfer's website.
Similar modules: A-152 Voltage Addressed Track&Hold / Switch (Multiplexer) / Digital Outputs
Since August 2005 an improved version of the module is manufactured: For each sub-module the operation mode S&H (sample&hold) or T&H (track&hold) can be selected by a jumper. In T&H mode the output signal follows the input signal while the trigger input is "high". As soon as the trigger input turns to "low" the last voltage is stored. The factory setting is S&H for the upper device and T&H for the lower device. At the bottom of this page the function of the jumpers is described. In addition the complete A-100 voltage range -12...+12V can be processed (no longer limited to -8...+8V as for the previous version).
The two versions can be identified by these details:
Version 1: four integrated circuits (2 x CD4053, 2 x TL064 oder TL084)
Version 2: three integrated circuits (1x DG442, 2 x TL084), see silk screen at the bottom of this page.
Technical note: The S&H/T&H function is realized by pure analog circuitry (electronic switch followed by a holding capacitor and buffer). Consequently the output voltage drifts a bit in the holding state because the capacitor is discharged by parasitic resistors. The typical drift we measured is about 30 mV/minute and depends also upon environmental conditions like humidity or temperature. For the storage of control voltages over a long time used to control the pitch of a VCO the module is suitable to only a limited extent.