[sdiy] Sequencer Idea

[James Husted]

on 10/2/01 11:16 PM, John L Marshall at john.l.marshall at gte.net wrote:

> I just bought 288 BCD thumbwheel switches for $20. I figure that I can build
> a really big, easy to program, sequencer using the thumbwheel switches. Here
> is the plan:
> 
> Build a 48 step sequencer using 48 thumbwheel switches. The thumbwheel
> switches point to a 4x10 bank of pots. Four control voltages are available
> but there will only be ten unique sets. My experience is that longer
> sequences often repeat sounds. Ten unique sounds for a 48 step sequence
> probably works.
> 
> 1. Clock drives usual divider chain.
> 2.  Divider chain drives 3 each 74x159 (open collector) four line to 16 line
> demultiplexer.
> 3. Each demux output connects to  it's own BCD thumbwheel switch.
> 4. The BCD lines are all tied together and routed to an open collector BCD
> decoder.
> 5. The BCD decoder is connected to a 4x10 bank of pots.
> 6. The rest is the usual analog stuff.
> 
> Comments?
> 
> 
Here's a different idea I was going to try once. In this one you just dial
the notes up. I also have a bunch of BCD switches, enough for each step of a
sequencer. I was going to clone the control voltage producing part of the
Sequential Pro-one synth. If you have a copy of the schematics, you can see
a D/A converter hanging off of the keyboard's diode matrix (The AD558). It
gets 6 bits of data on this buss from the CPU. The D/AC also gets a D/AC
enable line. If you own a Pro-one, all these lines show up on a 14 pin dip
socket at the rear corner of the PCB (accessable with a ribbon out the back,
notch provided!). Wire the Switches to these lines, and build the part of
the circuit from the D/AC on to the V out jack. Provide the gate from the
gate in section, and keep the enable line in the state it want to be in (the
10k to ground on the schema R1182). This circuit would give you glide and
transpose inputs. All this with 4 ICs, 2 transistors, and a hand full of
other parts. Look for the schematic on line or I can scan it for you.
-James 

-- 
James Husted                        The ErsatZ Planet
james at ersatzplanet.com           www.ersatzplanet.com

"Welcome to the first day of the rest of your money."