Bass Bot.mod with BA662

video upload by Alexey Taber

via AMSynths:

"The BA662 is a custom made DC controlled variable transconductance amplifier (or OTA) that Roland had manufactured by Rohm from 1978 and is now obsolete and very expensive. There are two types of chip with different suffices; the A version has been selected for lower offset than the B version. They are further classified by gain/gm. The BA662B can only replace another BA662B, whilst an A can be used in either application.

To quote Roland from the 100M Service Manual: 'color has great importance in the circuits of some models'. However there is nothing mystical about the sound of the BA662, it is just a reasonable good OTA chip which is often carefully matched and selected."

And via Sunshine Jones:

"The Roland BA662A VCA chip is the Voltage Control Amplifier IC from the Roland SH-101, TB-303, Juno-60, JX-3P etc. which is a part of what makes it sound so wonderful. These can also be found in the Jupiter-4, the Jupiter-8, and MKS-30,50 and 80. They have counterparts – The Roland BA662B (B stock versions of the A) and also a cousin IC the BA6110 which is similar, and looks virtually identical under a scope, but the power comes from negative rather than positive, and so it won’t work exactly the same way."