Doepfer A-151v Quad Sequential Switch Vintage Edition

Module A-151 (Quad Sequential Switch) is like an electronic four-position rotary switch.
It includes trigger and reset inputs, four in / outputs, and a common out / input. Each time a pulse is received at the trigger input socket, the common out / input is connected to the next in / output. After the fourth in / output, the next trigger makes it step back to the first again, and so on. A positive pulse at the reset input switches the out / input immediately back to the first in / output.

Voltages in the range -12V...+12V at the O/I resp. I/O sockets can be processed by the module (not only control voltages but also gate, trigger or clock signals provided that they are in the -12V...+12V range).
By means of a toggle switch the number of steps can be limited to 2, 3 or 4.

Four LEDs indicate the active in / output (ie. the on that is connected to the out / input at any particular time).

Similar modules:

- A-150-1 Dual Voltage Controlled Switch

- A-150-8 Octal Manual/Voltage Controlled Programmable Switches

- A-152 Voltage Addressed Track&Hold / Switch (Multiplexer) / Digital Outputs

Technical notes:

- To protect the electronic switches in case of an unsuitable patch (e.g. connection of two outputs) a 1k protection resistor is inserted into the O/I line. If control voltages used for VCOs are switched this may cause a small voltage drop and lead to undesired audible detuning. For this application we recommend to insert a CV buffer between A-151 and the VCO(s), e.g. the modules A-180-3, A-180-4 or the Precision Adder A-185-2. Integrating the buffer into the module A-151 is not possible because this would ruin the bidirectionality of the switches.

- For modules manufactured before spring 2005 the voltage range at the in/outputs was limited to -8V...+8V. From spring 2005 the revised version of the module was available. With an additional switch the number of steps can be set to 2, 3 or 4 (thanks to Peter Grenader for this idea). Moreover the revised module allows to process voltages in the full A-100 voltage range (i.e. -12V...+12V). The limitation to -8V...+8V is no longer valid.