Re-Bop Pattern Sequenser

[oskar]

Hi!

I tossed up a pattern sequencer. I only had the demo version of electronic workbench so I can no longer
simulate digital circuits, I haven't taken the time to figure out how to do it in LTspiceIV. It hasn't been
verified in no way whatsoever. If you feel like killing some time by bugghunting you're most welcome to
just go crazy...
I don't intend to re post new revisions (current is rev. 3) but to just update the original file.



It is based originally on the dbop drummachine from EFM, a very special thanks to Tom G for long and
faithful diy service!   
He/ they seem to have stopped selling pcb's      ...I had been planning to just buy like 2 of each of what they had!
Dbop is currently hosted at the synthdiy
synthdiy.com homepage. However I don't see how the sequencer
part could possibly work. If your interested in dbop please take the following notes into consideration.
These aren't verified mods but some of them are obvious wrongs, some possible errors and some just
plain paranoia from my side...   
dbop

Sequencer
------------

Add diode from pin 9. Now it's shorted to V+ through the 2n3904
Add diode from left NAND(and in drawing) output. Now it's shorted to V+ through the 2n3904.
Add diodes from the AND outputs which now grounds the high 4017/AND output.
Lfo should be NAND gates (4011), not AND.
Most LED's are turned the wrong way.


Generators and switches
---------------------------

Switches should be NAND gates! (4011)


PS. Generators not tested!!!
To also take into consideration is the length of the trigger signal which in present is set by the clock
and the 4017 output AND gates. Normally analogue drummachine triggers have lengths of a couple of
ms. Like the DR-55's 8ms.

Re-Bop's only concern however is the sequencer.
I have kept all features of dbop and added a few. What is kept from the original circuit is basically the
R/C values in the LFO and the bop in the name. My late father was a jazz composer/pianist so keeping
the bop is also in loving memory of him!
PS. He wasn't very fond of drummachines though, just bebop!  You swing it daddy!   

I could perhaps put together a complete project file as pdf if someone would be interrested but I only
did this for fun and I plan to do one or possibly two more sequencers. One AVR version which I intend
to give the programming interface of the DR-55 and eventually an arduino version just to try it out...
PS. I have seen arduino based sequencers elsewhere and at www.sequencer.de they have really advanced
diy sequencers. This stuff however will be kept at a minimalistic level.

Re-Bop!
--------------------------------------------
In short...

You have the option to have three patterns and an extra feature to use both patterns at the same time.
This is a feature from the 4019 chip that performs a logic OR function if both control pins are low. You
can just omit this part of the circuit. It was added because the 4019 had this function and also because
an early drummachine, I can't remember which, had this function as the result of a construction error.

To add both a play/pause and a stop button is completely redundant on an 8-step sequencer (probably,
I don't see any way I could use it personally) I just wanted to try it out. Also the switches could just as
well, and perhaps "weller" be implemented with ordinary switches. I just happen to like the CMOS 4k
series of IC's     

For clarity I have only showed one row of switches. You can add 4 rows for each pattern and each row
should have it's own pull down
resistor.
IC3E,F is a delay circuit. It is there to, hopefully, make IC2b shut off Q0 from the 4017 before resetting.
I haven't finally gone through the logic of all functions so I give you the sweet pleasure of finding my errors
of the pain of total failure should you go ahead with this.   
Hey, it even could work!   

To keep with the theme of the forum you can off course control any patterns and also add pots for pattern
controlled effects such as a wha or anything your heart desires off course. The 4019 is a digital switch only
and if you wish to switch controll voltages you must change to an analogue switch of some kind. 4053, for
instance, could switch 2*3 rows of switches or pots. I have also an earlier version of the Re-Bop without
proper logic. For just trying out the concept of a pattern sequencer it will probably work just fine but you
will find problems when starting and stopping such as starting from the wrong position...
PM me if you want the simpler version. I don't intend to post it.
All IC's are in current production.

Have fun!



Oskar

[oskar]

OK!

Just updated to rev.3

-Changed IC2 to AND package. I had misinterpreted the symbol on the controlpins as inverters for some reason...     
Logic one turns on the corresponding output according to the harris cd4019 datasheet.


-------------------

I'm uncertain about C2,C5 values. They should probably be 1-10n.
Also C4 is not decided upon 10-50n?
The square to trigg converter after the LFO (which starts with C4) is from CMOS cookbook but I take it from memory only.
I'm not sure about R3 value but R3 and C4 is a basic highpass filter and 100k/10n gives a cutoff of 160Hz. I don't know what the corresponding pulsewidth would be but 10n is probably a good starting point.

[oskar]

Rev.4

IC4A introduced to delay the onset of the clock so the sequenser don't skip to Q1 at start possibly triggering two pulses.
The clock is now off course half the tempo. What is worse is I had an idea to introduce a swing function and that isn't
possible if you divide the clock. At least not the way I had intended to implement it quite simply by making the LFO a
variable triangle (~KORG MS10 MG) and then adding a frequency doubler (XOR).

I think it's ready for breadboard now. (famous last words...)

[oskar]

Rev.5

Much cleaned up construction.

Removed the pause function. Resets at every stop.
A+B button removed. Press of both A and B sets both high.
Pattern indicator LED's now work on A+B setting.