ba662

[WeAreAs1 at aol.com]

Hello Dave,

In a message dated 2/19/00 6:00:04 PM, you wrote:

<<     I'm currently working on an tr808 clone, and hopefully then on to the

tr909 and tb303... I've struct a problem though. I'm up to building the hand

claps and have noticed that they use a BA662. I was wonder how I could

replace this chip with something else or if it could still be purchased???

Also for the opamps in the tr808 I've used LM324's these seem to be working

fine, I was just wonder if these opamps cold be improved on?>>

You can use pretty much any OTA in place of the BA662 (for instance, half of 
an LM13700, or a CA3080 would probably do the trick.  However, you can still 
get Rohm's newer version of the BA662, the BA6110.  Its pinout is slightly 
different, but it sounds and works almost identical.  

LM324's should work just fine in most of the 808 voice circuits, however, 
some of the "opamps" found in the 808 handclap circuit are not really opamps, 
but rather are comparators (I think Roland used the AN6912 there?).  I'm talki
ng about the four stages that create the multiple delayed/staggered handclap 
trigger pulses.  You can (and should) use a readily-available quad comparator 
such as an LM339 for that part of the circuit.

One of the list members, Trevor Page <trevor at resonance.fsnet.co.uk>, was 
recently working on cloning that circuit (as well as some of the other 
808/909 drum voices).  You might contact him for further advice.

Best regards,
Michael Bacich