jonathan.heslop wrote:

> Do these three filters contain similar chips as they all share the 106 Is the A-106.6 just an "expander" version of the A-106.5

No,

106-1 is an MS20 VCF adoption (as far as I know using a combination of
three transistors and an opamp as kind of OTA).

106-5 is the 12db/oct state variable filter from the Oberheim SEM module
(or Formant 12dB VCF) and uses CA3080A

106-6 is an adaption of the Oberheim Xpander Filter which uses a CEM3372
(different possible slopes 6//12/18/24dB)

Florian