The Roland CR-5000 and CR-8000 drum machines, both released in 1981 (around the same time as the TR-808, TB-303 and TR-606), are very closely related; they share the same chassis, boards and general design, the sound generators are identical for both units, except the 8000 has twice the amount of presets, and also programmability. So basically the 5000 is a more affordable version of the 8000, with some features removed. It’s also very similar to the Korg KR-55 series of drum machines (the first one released a couple of years earlier), although with a few distinct features.

Control of the cymbals and hi-hats is extremely versatile, as there are five switches to select various combinations (4ths and 8ths ride, 4ths and 8ths hi-hat, open hi-hat) and these can be used in any combination with any of the 24 presets. There is also an extensive mixer section, with 5 pots for setting individual voice levels.

There are 8 fill patterns (actually 7, one of them is silent) that can be triggered every 2,4,8,12 or 16 bars, a “crash” button that allow a (rather wimpy) crash to be heard on the first beat returning from a fill, a “shuffle” switch that turns on a preset “swing” feel (which isn’t adjustable like on the KR-55/55B drum machines), a “register” switch that allows to register two beats (including cymbal/hi-hat settings) and alternate between them manually every time the button is pressed, an “accent” knob for volume variations within the pattern, and finally a trigger out for external sequencers.

The unit’s main drawback, apart from an obvious lack of programmability, is the single output for all the sounds. But it didn’t take me too long to solve that problem… Below are some instructions on how to modify the unit for separate outs, a copy of the owner’s manual and the CR-5000/CR-8000 service manual.

Technical Info / Service Notes

CR-5000/8000 Separate outputs modification

One of the main problems with this drum machine, like many others from that era, is that all the sounds are bundled into one mono output. Fortunately, it’s not too hard to modify the unit in a completely reversible way, with minimal work. I haven’t done this mod on the CR-8000, but I see no reason why it wouldn’t be exactly the same, as the voice board, mixer and output stage are identical.

Most vintage drum machines have many jacks at the back: one or two outputs, plus various jacks for foot switch control, so the quick and easy way to add more outputs is to use these jacks. Personally, I have no use for foot switch-controlled interfaces, so I really don’t mind sacrificing them if it means I’ll get separate outs without having to drill holes in the chassis…

The CR-5000/8000 have six jacks: output, start/stop, restart, intro/fill in, register and trigger-output. The only one I don’t want to touch is the trigger output jack, because this one I use frequently. So, that leaves five jacks, which will give great separation of the various voices. Voice assignment is a no-brainer, since there are also five volume pot on the top of the unit!

A peek inside the unit reveals that, on the board with the mixer pots, each voice’s location on the PCB is clearly indicated. It doesn’t get easier than that! So it’s just a question of running wires from those locations to the jacks at the back, after having disconnected them from the circuit… which proved to be the only challenge to this project, since the jacks were soldered directly on the PCB.

The jacks, before modification (bottom)

Fortunately, I found that it was farily easy to unsolder them, and then simply flip them 180 degrees in order to disconnect them from the board and make them available for rewiring. Unsoldering was a little tricky, because three pins were lodged deep in the PCB, and I couldn’t heat all of them at the same time. But two of them were near each other, which allowed me to heat them up at the same time, and then pull them out. After pulling out the third pin, the jack came loose. I did this for the four “footswitch” jacks, leaving the trigger out and output jacks connected normally. For each removed jack, I also had to solder the PCB points where the two closely located pins used to be, in order to emulate an unused, shorted jack for the circuit. Without that, some buttons on the front panel would probably have stopped working.

After removal of the jacks.

Next, I flipped the jacks and fixed them back on the chassis. I was then ready to wire the individual sounds to them. You might have noticed that I didn’t change the “output” jack, and here’s why: by keeping it intact, it still functions as a regular, “all voices” output, and the drum machine’s mixer still works for it. So, by turning down all of the voices except one, say, the bass drum, you can get an insolated bass drum output for this jack. All you have to do then is route the four other voices, and all voices are separated. And if you ever want to use the drum machine as a one output unit again, just turn up those mixer pots and all the voices are back in one jack…

Now, which voice you choose to keep on the main output and not reroute is your choice. The only real impact this choice will have is that the “accent” control only works with the main out, so choose the voice that you think will profit the most from keeping the “accent” feature. Due to the nature of the circuit (the accent control momentarily modifies the amplification ratio of the very last output stage, when all voices have been combined already), it’s not really possible to keep the “accent” control working on individual outs tapped before the last output stage…

Here was my test setup with crocodile clips, and finally the finished modification:

Test setup

After modification

That’s it! Close back the unit, and there’s no way to tell visually that it’s been modified. Remember that, with this mod, you can’t use the drum machine’s mixer pots to control the volume of each output (they’re still wired to the main, original output jack). You have to do that outside the unit, perhaps with a mixer or straight into a computer. Everything else works just as before.

>>> Update, December 2009:

After plugging in my newly modified CR-5000 into my sound interface’s input, I quickly realised that the signal level coming out of my tapping points for individual sounds is EXTREMELY loud. Higher than line level for sure. So you might want to tone it down with a resistor or a pot, because at this level it will probably overload most devices you send the signal to.

>>> Update, January 2010:

A reader has contacted me with some tips regarding the signal levels, and great advice and ideas regarding CR-5000/8000 modifications. Here’s an excerpt from our email discussion:

“You state on your site that the output of the individual outs is very hot, requiring a resistor or additional pot to bring the level down when connecting to an external mixer, interface, etc. If you tap the center pin on each of the voice pots (instead of the pin labeled with the voice group as you have), you can still get the individual output but with the additional level control provided by the original pot. This means you can reduce the level of that voice group before it exits the CR5000 and no other components are required to get a direct recordable signal level. Also (and you probably already know this), if you isolate the hot pin on the pot, you can connect the pot to the closed circuit jacks (the ones you salvaged from the CPU board; BRILLIANT idea btw) in such a way that the signal is cut from the mixed mono output when a cable is inserted, and the voice is only output through the individual output jack. I’ve found the well documented TR606 modifications to be very useful as well, as the circuits are very similar to the CR5000/8000: http://www.synthdiy.com/show/?id=224.”

“Oh, and a couple notes to add about the individual outs:
1) I had to isolate the closed circuit jacks from the chassis, otherwise the open hi hat wouldn’t trigger. I haven’t been able to figure why this is the case exactly, but it might be due to the Elby trigger units rather than the CR circuit. Anyway, I did this by wrapping the outside of the jack threads with electrical tape (only where the threads could make contact with the inside of the hole on the chassis) and placed a strip of electrical tape on the front and rear of the panel where the washers/nuts could make contact with the chassis. Of course a much easier method would be to use isolated (plastic) jacks, but then you wouldn’t be using the CR’s original jacks. Not green!
2) I still get some bleed through to the main mono output even with all the voice signals cut from the main mix via the closed circuit jacks. I’ve been over the schematics again and again, but I can’t figure out why this is the case, as I don’t see any other connections going to the main out amp. The bleed is pretty quiet and sounds like it has a high pass filter applied to it, but it’s enough to drive me buggy.”

Many thanks to Josh Gumiela (GumiElectronic) for the help and great suggestions.

Specifications

Gallery

After removal of the jacks.

The jacks, before modification (bottom)

After modification

Test setup