AM104 Analog Sequencer – Steel City


104 Sequencer

Overview The AM104 (Steel City) is a replica of the Roland analog sequencer from the System 100, the  104. It was introduced in 1975 as part of the System 100 and sold around 1500 units. It is a basic analog sequencer that provides 12 steps in 2 banks. Whilst it sold well in 1976 and 1977, by 1978 it was looking increasingly obsolete and expensive at US$495. Roland took CV/gate sequencing much further forward in the late 1970’s, using the newly available microprocessor (MC-8, MC-4 and CSQ range).

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.

All the electronics around the Sanyo chips is discrete, with no CMOS chips at all! This makes for quite a bulky design and CMOS chips would eventually be used in the Roland 100M sequencer and the ARP Sequencer (1976). The 104 and 717 designs are actually identical, except the 717 adds more features per step; including 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 many years ago. 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 metal work 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 analog clock. There is a large amount of discrete logic on the MAIN PCB. The expensive 2P12W rotary switch has been replaced with a cheaper 1P12W rotary switch, and CMOS logic and analog switches (4532 and 4067).

The project was paused for many years, especially after Behringer released the Roland 182 and Moog 960 clones, which are low cost analog sequencers. I restarted the project in 2022 and completed the design in November, with the two PCB’s (MAIN and PANEL) and a 60 HP aluminium front panel. The four large control buttons have been retained, using MX1 switches and coloured caps (white, yellow, orange and red).

The AM104 has the same features as the original, but with the addition of a CMOS quantizer on CH-A for just the 2V setting,  so that CH-A can be used for driving VCO’s with accurate note values over 2 octaves.

Outcome & Availability The AM104 is currently in development.

 

 

 

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