Hey all,
I have a 70's analog synth that's got a bunch of BA662's in it (Roland proprietary OTA chips used for various voltage controlled stages), and i'm looking to more or less clone a couple sections of the synth to make a simple single channel drum module.
These chips are unjustifiably expensive to get original, although there is a clone that's more affordable which i've purchased several of already for starting to make said channel. The maker of the clone has also kindly displayed the fact that 2 resistors and 11 carefully chosen transistors can recreate the BA662 as well.
However there is ONE chip that's OTA still in manufacturing today, which is the National LM13700. http://www.mouser.com/ds/2/405/lm13700-452966.pdf It's dual channel as well, which could make life even easier here.
Does anyone have enough familiarity with OTA topology to see if this LM13700 could replace a BA662 or a BA6110 electronically? Pinout arrangement is irrelevant here.
The datasheet for the BA6110 can be found, where as the BA662 can't. However Roland once used the BA6110 as nearly a drop in design replacement for the BA662. I think there was one minor addition or subtraction to the surrounding circuitry with instruments using the BA6110 instead of BA662, but it was close. Anyways here's the BA6110 datasheet http://www.firstpr.com.au/rwi/dfish/TT-303/click-fix/BA6110-datasheet-with-SIP-9.pdf
I have a 70's analog synth that's got a bunch of BA662's in it (Roland proprietary OTA chips used for various voltage controlled stages), and i'm looking to more or less clone a couple sections of the synth to make a simple single channel drum module.
These chips are unjustifiably expensive to get original, although there is a clone that's more affordable which i've purchased several of already for starting to make said channel. The maker of the clone has also kindly displayed the fact that 2 resistors and 11 carefully chosen transistors can recreate the BA662 as well.
However there is ONE chip that's OTA still in manufacturing today, which is the National LM13700. http://www.mouser.com/ds/2/405/lm13700-452966.pdf It's dual channel as well, which could make life even easier here.
Does anyone have enough familiarity with OTA topology to see if this LM13700 could replace a BA662 or a BA6110 electronically? Pinout arrangement is irrelevant here.
The datasheet for the BA6110 can be found, where as the BA662 can't. However Roland once used the BA6110 as nearly a drop in design replacement for the BA662. I think there was one minor addition or subtraction to the surrounding circuitry with instruments using the BA6110 instead of BA662, but it was close. Anyways here's the BA6110 datasheet http://www.firstpr.com.au/rwi/dfish/TT-303/click-fix/BA6110-datasheet-with-SIP-9.pdf