AM104 Analog Sequencer

Overview The AM104 is a project to build a replica of the Roland analog sequencer 104 that was introduced in 1976 as part of the System 100. It is a basic analog sequencer that provides 12 steps in 2 banks.  The driver for the project is two fold;

  1. Build a 12 step sequencer like the Synthanorma SQ312 that Klaus Schulze used.
  2. Subsequently build a replica of the Roland 717 sequencer, as the unusual chip set is the same.

Original Design Roland used a set of TV channels chips in the core sequencing of the 104 and 717, which was a very strange decision! The chips are the Sanyo LB1500/1501 and the LB1515. These are still available as NOS, as they must have been used in thousands of TV’s. The rest of the sequencer is conventional with a high quality analog clock with temperature compensation, and a simple flip flop circuit controlling STOP/START. There is a 12 position 2 pole switch to select sequence step  and two channels of unquantized control voltages.

The 104  and 717 designs are identical except the 717 adds more features per step; voltage controlled timing and individual gate outs.

Project Development I bought a set of LB1501 and LB1515 chips from UTSource, as  a starter for the project. In the winter of 2017 I laid out the main controller PCB using the same layout and dimensions as the original. Initially I planned to build a physical replica with custom metalwork but I moved to a 3U EuroRack design to reduce the costs for what is a simple sequencer.

There are two PCB’s; the PANEL PCB holds the switches, jack sockets and potentiometers and the MAIN PCB contains the control logic and clock. The DP12T rotary switch is going to be the expensive component to source, I use the Electroswitch C4D0212N-A.

The project was paused for many years, especially after Behringer released the Roland 182 and Moog 960 clones which are similar in design but with 8 steps (and low cost). In 2021 I reused the analog clock in my PPG 314 replica to provide a replacement for the limited CMOS based clock in the 314, which I could not get to provide the correct frequency ranges. This avoids an endless search for old CMOS chips that will behave as they did in the 1970’s.

To make the 104 project more attractive I have added some of the extra features from the 717, the manual step buttons and a third row of timing potentiometers.

Outcome In development.




Copyright AMSynths 2022