A-151 modification - you might like it!
2002-12-13 by (i think you can figure that out) <petergrenader@hotmail.com>
I just picked up an A-151 because of Milton, a 16 x 4 voltage controlled sequencer I'm designing so I can construct these humungus 32, 48 and even 64 step sequences. Kewl. Not thinking about it clearly enough when I bought it, I figured I would just use the NEXT step of the A-151 to reset it to anything shorter than it's maximum range, much like you would with a pulse sequencer. Once I got it however, I realized how stupid this was. In a pulse sequencer, you have pulses coming out of each of the outputs. With this baby however, you have only whatever is on the I/0 port coming out, and unless you've arranged it to be high like a pulse at that specific moment, it don't reset. Blast. But it does have LEDs.....ahhhhhh ...and they take a high signal from the mutliplexer to turn on...ahhhhhh....so I did the obvious and it works like a charm. There is 1 empty space below the last I/O jack which will (barely) accept a hole and a switch to be installed. On the wiper, I have a diode leading into the backside of the reset jack, to each of the other contacts of this ON-OFF-ON three position switch I have 1Ks which connect to the step 3 and step 4 mutliplexer outputs. You switch it up, and a two position sequence is selected. You switch in downward, and a three step sequence is set. In the middle, you have an open through the switch and the resets are bypassed so it counts threw to four. Because there's diode protecting this, the external reset jack can still be used whenever you wish. Sorry for the long post. I thought some of you might benefit from this. I have a schematic posted for this on my site. Go to: http://www.allegrobikes.com/synth.html and click on 'Son of Frankensynth" scroll to you see the link on the word modifications, and when the new page loads, scroll down to Doepfer A-151. enjoy (or not), Peter