An 8HP wide Eurorack module that adds an extra column of eight control voltages to the Behringer 1027 Sequencer. There are outputs for both 2V and 10V ranges and green LED’s indicate the step position. The module is connected internally to the Behringer 1027 using a 12-way IDC ribbon cable. There are eight rotary potentiometers for setting the voltages. Multiple AM1028’s can be chained together.
Overview I revisited the ARP 2500 in the Spring of 2024 and designed a set of ten “lost modules” that ARP mentioned in 1970 but never manufactured. These Eurorack modules are commercially available from the AMSynths webstore here. The ARP 1028 “Slave” module was announced in the Tonus August 1970 catalog but never made it into production.
The original ARP design provided three channels of 10x control voltages, the levels being set by the front panel potentiometers or controlled by a 1027 sequencer. The module was probably intended as double width and there were preset cards with trimmers that could be used.
There were probably indicators for each of the stages and it looks like ARP used LED’s rather than bulbs in 1971 (as the 1026 module does). The steps can be sequenced by the 1027 gate positions via an external RS232 cable at the rear of the modules, and this is typically how the 1028 would have been used as an expander module, where it proves very useful in increasing the sequencer functionality of the ARP 2500.
AM1028 Module I revisited the 1028 module in 2024 as part of the “lost ARP 2500 modules” project. There are no ARP schematics for the 1028, but the module uses a similar design approach to the 1027. The AM1028 has just one column of 8 steps, to make it inexpensive and easy to locate close to the module it is controlling. There are control voltage outputs for both 2V and 10V ranges. The 2V output is designed to be used with VCO’s, as its much easier to set the pitch correctly. The 10V output is duplicated with two jack sockets, which enables the same CV to be patched to two downstream modules.
There are green LED’s mounted in the front panel to indicate step position, they are low current consumption SMD types. The module is connected internally to the Behringer 1027 by a 12-way IDC ribbon cable. There are eight high quality rotary potentiometers for setting the control voltages. Multiple AM1028’s can be chained together using custom made 12-way cables or by plugging each module into the AMSEQBUS PCB (which has eight 12-way sockets).
Availability & Outcomes Prototypes of the AM1028 module were demonstrated at SynthEast 2024 and production versions were released in the summer. The delay enabled real ARP 2500 coloured control knobs to be used, and the design was updated with LED light pipes, ,which give a better colour rendition. The module is available in four versions with different coloured control knobs; Green, Gold, Blue, Red.
Firstly I wanted to congratulate you on these amazing Arp 2500 re-creations. I have purchased a number of the Behringer modules, but hav found a imitation in the 1027 that I wanted to ask about. Regarding the Behringer 1027, I would like to clock the oscillator from an external system so that it can be in sync with the rest of my rig. While the “Step” input allows me to clock the sequencer, this doesn’t faciliate a consolidated gate output, I would like the ability to externally clock the oscillator so to maintain the the PWM gates available at the “CLK OUT”. I wanted to ask if you have a modor solution for this?
Hi, Many thanks for the positive feedback!
The STEP input goes straight to the 4017 decade counter, and there is no gate summing as it does not preserve the pulse width – it would be one continuous +5V when running. The 1027 does have a sync feature which is used by the ON/OFF controls and inputs. Try putting the external clock input into the ON input. Pulse width adjustment will work but only within the limits of the external clock PW ratio. The CLOCK OUT will now correctly follow the external clock PW and and adjustment on the 1027 PW. Hope this works and helps! Must try it on mine… Rob