Boss DR-55: fodder for an easy DIY drum machine?

[bobbletrox]

I was the proud owner of a Boss DR-55 until recently, when I had to sell it to raise funds for a holiday.  It was a really nice sounding analog drum machine, so I got to thinking how about how hard it would be to make a simple DIY version that would let me sequence it's few drum sounds: BD, SD, & perhaps rimshot.

When I tracked down the schematic, I found that the actual drum sounds themselves are produced by really simple discrete designs.  Each drum is no more complex than your average fuzz circuit!  (pay no attention to the hi-hat because it sounds like crap). That got me to thinking...

Would it be possible to use a simple sequencer like RG's to cycle through toggle switches that would trigger the drum sounds?  

This is the schematic:
Boss DR-55 Schematic (140kb)

The Service Manual that contains a detailed parts list and a supersized schematic is available here:
http://www.colinfraser.com/misc/BossDr55SM.zip

[lightningfingers]

this is actually exactly what i'm looking for, is it feasible to build the little drum making circuits by themselves and trigger them with a switch?

[toneman]

several folks have cloned Roland drum machines.
search for TB3030...
Tony Allgood(UK) used to offer a DIY pcb.....
google around.....
T

[Nasse]

Looks like this person is serious analog drum enthusiast

http://www.electronicpeasant.com

http://www.electronicpeasant.com/projects/ssdrums/ssdrums.html

[Paul Perry (Frostwave)]

Those small 'kiddie' keyboards you get at yard sales sometimes have a drum section that you can access by pushing buttons, it should be pretty easy to mod one of those.

[keko]

Looks like this person is serious analog drum enthusiast

http://www.electronicpeasant.com

http://www.electronicpeasant.com/projects/ssdrums/ssdrums.html

That is soo cool. did you see the ring modulator on that site?

[hair force one]

paia electronics offers kit ant shem for simple drum synth tones too...

->http://www.paia.com/syndrum.htm

[Mark Hammer]

Although you can use RAM and that type of sequencing, it was common to find simple drum machine projects in magazines in the late 70's and early 80's that used something a little more physical.

Essentially what you had was a master clock (usually 555-based) that stepped a bank of 4017 counters through their paces (these can be cascaded for more than a 10-step limit).  The output of the various 4017 pins would then be enabled by means of dipswitches, and routed to drum voices awaiting a trigger pulse.  This would let you physically SEE a sequence by noting whether the dipswitch for step N was in the on or off position for the bass drum.

While entirely non-volatile and not requiring anything terribly extensive with respect to digital circuitry, programming, or interfacing, it's obviously a crude system, and cumbersome to reprogram.  On the other hand, can be built quite simply and if you're nimble in such matters, can also be designed to have alternating patterns.  ETI had a few projects of such a nature.

There are lots of resources on the net.  Those projects may be among them.  Midwest Analog Products (http://www.midwest-analog.com/bass.html) has some stuff.  PAiA also produces their little "Finger Drum" unit which is kinda nifty and modable.

[bobbletrox]

Thanks for the replies guys!

Mark Hammer: thanks for the suggestion of using a 4017 decade counter combined with a switch matrix.  That looks like the solution -except- is it possible to only use 8 stages of the 4017?  10 isn't a very musical number of beats for a drum machine!