BA6110 / Boss CS-2: any experience?

[Zero the hero]

Hi breadboarded the Boss CS-2 circuit yesterday and I have many issues mainly because I did not used the factory chip, the rare BA662 (manufactured by Rohm for Roland and unavailable on the open market, as far as I know, and soon discontinued).
The BA662 was used on some 80's synth such as the TB-303 and many synth people who cloned this famous bassline synth used the BA6110 VCA as direct replacement for the original VCA, although not being pin-2-pin interchangeable.

The synth people claimed that one should swap pin 2 and 3, and use a current amplifier for supplying enough current on the control pin (1). That's how it's used on some TB-303 clones I found on the net (as well as in the Boss VB-2 clone).
This is AGAINST the official Rohm datasheet I have, since pins 1, 2, 3 and 4 are all inverted!
I double checked the schematic where the BA662 are used (Boss VB-2, Boss CS-2, Roland TB-303, Roland SH-09, Roland TR-808) and the all show this discrepance.

Moreover I have both the service manual and the Steve Cerutti schematic, and the only difference between them is the biasing network; the service manual wiring does not work, and the Steve C does.

So far, I tried both solutions and the synth-world suggestion seems not to work (no sign,al passes through the VCA). Wiring the BA6110 as the datasheet returns a working compressor, at least the sound passes through the VCA, the envelope follower reacts well, both attack and sustain controls work BUT the VCA catches RF interferences...

Anyone experienced with this chip?

[Mark Hammer]

The BYOC folks use the BA6110 to replace the BA662 in their clone of the Boss VB-2.  They used to have the schematic posted, which included pin connections, but I can't find it at the moment.  You can reverse engineer the connections using this document:  http://buildyourownclone.com/vibeinstructions.pdf

Now that Behringer is supposed to release their VB-2 clone this summer (if it isn't already out), I wonder how long the BYOC clone will continue to be sold.  On the other hand, I suppose there are some possible merits to making a through-hole version in a Hammond chassis, with separate bypass and ramp-up switches.

[Zero the hero]

Thanks Mark!
I had a look at that PDF, but unfortunately they show the solder side of the BA662 version only. I however noticed that the output of that small amplifier section (4 transistor) goes to pin 4 of BA6110, consistent with my breadboarded version.
That's pretty much I needed to know!

[mudmen]

I found this thread on BYOC forum. I hope it'll be helpful
http://board.buildyourownclone.com/viewtopic.php?t=6064

[zeta55]

well, I did manage to get a VB-2 working with the BA6110 chip. I used the schematic posted by BYOC here on the forum.

It does not look like the schematic posted here:

I found this thread on BYOC forum. I hope it'll be helpful
http://board.buildyourownclone.com/viewtopic.php?t=6064

I got the trasnsistor array connected to pin1 of the BA6110, depth pot through R42 to pin2, my R44 goes to pin3.

/Krister

[mudmen]

I had a look at that PDF, but unfortunately they show the solder side of the BA662 version only. I however noticed that the output of that small amplifier section (4 transistor) goes to pin 4 of BA6110, consistent with my breadboarded version.
That's pretty much I needed to know!

Zero the hero, any updates on this project? Your previous post looked very promising!