ARP 1023 Dual VCO Module
ARP Production 1023

Inside a stock 1023 module - The 1023 uses 2 modified boards from the 1004 VCO module. Each board has 2 potted submodules. As with the 1004, it uses a unusual method of generating it's primary triangle waveform. 1023's are great for stuffing many VCO's into a 2500 system. Since they only use 6 of the 10 matrix switches available in each slot, they are useful for filling up 2500 slots that lack matrix switches. You just rewire the empty matrix switches over to the next slot. On the minus side: The concentric fine tune knobs are difficult to tune. As with the 1004, stock units have CV linearity limitations. This can be corrected, but it is expensive. There is no PWM.


ARP Experimental 1023
    Inside the ARP experimental VCO module - Years ago, I tracked down ARP's former service department manager Clark Ferguson. As it turned out, he now lives in my home town. I went over for a visit, and over his workbench was sitting this gem. "Oh, it's just something me and Roger Powell were messing around with". It uses a stock 2600 submodule for the primary ramp waveform. The pulse and triangle are shaped similar the the 2600. The sine shaper is from the 1004 VCO. The square wave has its own independent circuit and output. By the looks of the old submodule hole pattern, it originally utilized the 4011 VCO from the Blue Marvin 2600.    
CMS Replica 1023
    A peek inside the CMS 1023 module - A couple of years ago I made some 1004 PCBs with this strange notion that I could reissue several ARP 1000 series modules. My first attempt was the 1023 replica. The conclusions: It's a very complex and expensive oscillator to build. It's difficult and time consuming to calibrate, requiring the selection of many components. It's a great sounding and unusual design, but very difficult to produce with any consistency. The fact is, there are not many 2500 cabinets out there needing modules to begin with, and most ARP 2500 owners will only buy OEM ARP modules.