SV: [sdiy] Juno voice replacement!

[Oakley Sound]

 > Was the IR3109 a 3080 derivate or the reverse?

The SH-09 and others use a cascaded OTA filter made from BA662 using a 
single discrete expo convertor. These BA662 are matched for Gm. to 
ensure all stages track together. Remember too, that the BA662 actually 
contains an internal buffer as well as the OTA. It is possible that the 
buffer is different to the one used in the LM13700.

The IR3109 was therefore created for Roland to solve two issues. Firstly 
to get the expo on chip and thus save space. Secondly, by building it on 
a monolithic chip, one could get better matching between the OTA stages.

The IR3109 was made as both a DIL and a SO version. It is the SO version 
that is used on the Juno-106 VCF cards.

One has to wonder whether the LM13700 are matched on these new clones, 
or in fact, whether they actually need to be. Devices do seem to be 
better spec'd these days.

Tony

www.oakleysound.com