A-184-1 Ring Modulator/S&H/T&H/Slew Limiter
The small module combines three functions already available in Doepfer's dual modules: ring modulation, sample & hold and slew limiting.
The same three functions are actually already available in other modules (e.g. A-114, A-148, A-170). But in many systems it's not necessary to have two ring modulators (A-114) or two S&H units (A-148) or two slew limiters (A-170) available. That's why we have compiled these function in one small 4 HP module.
The upper section is nothing but half of an A-114, i.e. a ring modulator with the usual X/Y inputs and the X*Y output. Inputs and outputs of this sub-unit are AC coupled, i.e. suitable only for audio signals. A detailed explanation of a ring modulator can be found on the A-114 info page.
The lower section is the combination of a Sample & Hold (S&H) / Track & Hold (T&H) unit and a Slew Limiter. The S&H/T&H unit is identical to one half of the module A-148. The slew limiter is the same as the upper section the A-170. The S&H/T&H unit and the slew limiter are internally connected and cannot be used separately. The max. slew time is about 10 seconds.
A toggle switch is used to set the mode to S&H or T&H. In S&H mode the unit picks out a sample from the voltage at the SH input at the rising edge of the trigger signal input. In T&H mode the output follows the input voltage as long as the level of the trigger signal is high. As soon as the trigger signal turns low, the last voltage is stored. The trigger input is internally normalled to high, i.e. the unit works just as a slew limiter in T&H mode when no trigger signal is applied.
Detailed explanations of S&H/T&H and slew limiters can be found on the info pages of the modules A-148 and A-170.
- required min. trigger signal level: +5V
- 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.
- The S&H/T&H unit and the slew limiter are internally connected, i.e. they cannot be used separately. If only the S&H/T&H unit is required the Slew Time control has to be turned fully CCW. If only the slew limiter is required the switch has to be in position TH and the Trig In socket has to be left unconnected. With these settings the S&H/T&H unit is bypassed.
- The S&H/T&H/Slew Limiter unit is not suitable for the processing of audio signals but only for slowly changen signals in sub-audio range (e.g LFO, envelope, random voltage).