Korg KPR77 massive mod and rehousing

[Circuitbenders]

This is my latest creation. Its a Korg KPR77 analogue drum machine thats been rehoused in a desktop case with loads of mods, individual outputs, trigger inputs for each sound and a MFB SEQ-01 percussion sequencer module.









The mods consist of:
Bass Drum Level
Bass Drum Pitch
Bass Drum Decay
Bass Drum trigger adjusted for a more 808-ish attack
Accent Level
Snare Tone Pitch
Snare Noise Decay
Snare Noise Level
Tom 1 Level
Tom 1 Pitch
Tom 2 Level
Tom 2 Pitch
Closed Hat Level
Closed Hat Decay
Open Hat Level
Open Hat Decay
Hats Noise Mix
Ring Noise Frequency
Metronome Level
Metronome Decay
Clap Level
Clap Hi-Pass Filter
Clap Reverb On/Off
Clap Noise On/Off
Clap Noise Decay
Cymbal Level
Cymbal Ring Decay
Cymbal Hit Decay



Internally theres also a new +/-12v - 9v power supply for the MFB module and the KPR77 synth boards, a trigger interface board so the Korg will accept triggers from just about anything, and a small circuit to shape the accent trigger.

This took such a massive amount of work i nearly had a nervous breakdown. NEVER AGAIN!  

I'll try to get some audio up asap.

[Circuitbenders]

demos here:

http://soundcloud.com/circuitbenders-co-uk/sets/modified-korg-kpr77-drum-machine-demo-tracks

[Gordonjcp]

That is an astounding piece of work.  Well done!

[electoyd]

looks sweet defo one of the best things i've seen you do.  Funnily enough i've just finished a drum machine using drum synths in one of those boxes, i think they suit drum machines.  But i have to admit yours does look better, good work hope you recover from it.

[nochtanseenspecht]

wow that's ... incredible

[moordenaar]

Sweet ! Did you have a service manual for the KPR77 ? Because I got som old mini pops thing, but I simply cannot find any service manual for it. So I'm just probing around.

Also how much did you spend on the sequencer module ?

[Circuitbenders]

You can get the service manual here but theres a few pages missing http://saulihirvi.com/wiki/korg_kpr77

I do have the whole thing but someone 'borrowed' my scanner a while back.................

The guy that owns this thing bought the sequencer from Thomann i think, so i'm guessing it was about £130. It seems a bit expensive for what it actually is.

http://www.thomann.de/gb/mfb_modul_seq01_drumsequencer.htm

[moordenaar]

Yeah I found it on Thomann aswell, just wondered if somewhere was cheaper.

Oh and after some deep searching I found out that my mini pops thing is actually a

Donca Matic Minipops 20 S

aka. Keio
aka. Korg

And I've looked hi and lo for all variations of korg, keio and donca matic manuals but I can not find a service manual or a user manual. By the way the S stands for sterio.. How about that. A sterio Minipops.

[scrubber]

first off yo peeps! nice forum! lots of sick info and discussions! first post, straight in there..
sorry to drag up an older topic (which is sick btw! nice sequencer and mods!) but I'm in the process of trying to mod my KPR77 to add trigger inputs for each sound and can someone point me in the right direction please??
I'm not a total newb either, I've built and modded quite a few things now too
edit: just reading the service manual and theres a section headed KLM 448 with the snare, bass drum ect listed that routes to the TMS chip, am I right in thinking this is where I would need to be, to set up the trigger ins using an inverter like mentioned in the other post about the Korg Rhythm?

[Circuitbenders]

The trigger signals are shaped on the smaller KLM448 on the left. If i recall correctly the digital board sends very thin positive pulses to theKLM448 board via the wide connector, which are then converted into the correctly shaped negative going pulses by the circuitry on the trigger board, and sent onto the synth board.

For each sound theres a small cap just after the input to the board. I think you can inject inverted trigger pulses on the circuit side of each of these caps to trigger the sounds. Just shorting these points to ground with a wire should trigger the sounds. I wired up a load of separate transistor inverters to get the negative pulse, which you can see on the small board to the left of the green sequencer board on the bottom image.

I do have a vague recollection of having some trouble with the external trigger pulses only working when the digital board was disconnected, or that could have been the other way around. I've blanked the whole thing from my mind after the amount of stress it caused me  

Give it a go and see what happens.

[scrubber]

hey man! thanks for your help! will give the triggering a go tonight using your advice and let you know how it goes!
awesome work again man!
edit: you think it's worth trying a hex inverter or schmitt inverter?

[oryjen]

 

[scrubber]

hey yo man! been a while cos been on hols!
tried this and it does trigger just from ground everytime you touch the caps you mentioned on the klm448 board, made a small board with a negative inverter on to try the trigger in, just about to test using trigger out from boss dr110 and another kpr! keep you updated  

update: yo man! tried a negative inverter design off the net using a 2n3904, diode and 10k resistor....didnt work
what design did you use for your row of inputs man, please?

[M4RK]

This may be a stupid question, but did you make the labeling for all the parameter knobs yourself or did you buy those from somewhere? It's my biggest reservation with putting my instruments into a new housing. Excellent piece by the way.

[Circuitbenders]

On this one the label for the knobs was put together on photoshop and then printed out on some decent heavyweight sticky backed paper. I gave it a couple of coats of lacquer before peeling it off the backing and sticking it on the panel.

I would have done it differently now, as i've now got some clear adhesive sheet that you can print straight onto with an inkjet printer, and the ink somehow sinks below the surface to make a waterproof print.