#stereoping

IT. IS. DONE. Took fucking forever and a year and a half and three weeks to do. Well, not really. I guess I got the thing maybe late November or early December so it’s not even taken a month in all. Feels like forever though, maybe that’s because I’ve had about eleventeen different projects going on at once, with a few non-noise-making-projects thrown in as well. Anyway...

Yeah so there it is. Lemme back up here a sec and start at the beginning. I think I posted about the KPR but lately my memory has been absolute shit, so just to be safe I’ll say some things about why I got one and decided to mod it. I’d never actually seen a KPR in real life, I think. I saw one on the auction for cheap and thought “well, why the hell not?” Sounds like, I dunno, what, a real cheap version of a 606? It’s a weirdo in any case, Like a cross between a 606 and a 707 (sounds of the former, sliders plus the LCD (kinda sorta) of the latter). Pretty bland overall actually. Volca Beats DNA can be found here for sure though.

I was fucking around looking at useless shit online when I thought “Hey I wonder if anyone has modded a KPR.” Sure as shit, the answer was yes. CircuitBendersUK has, but they (as usual) went full-fucking-freakout-mode and as opposed to a ‘mod’ their end product was an overhaul-slash-total-makeover-transformation type deal. Fucking thing looked like a modular almost. Anyway I wasn’t about to go that far with it. I saw that who of all people but the guy behind Stereoping had modded a KPR in the past, and even put up a spreadsheet with the components he replaced with pots, their original values and part numbers and which PCB they can be found on (with photos too!!!), and the types and values of pots he used in his mod. AND did I mention he has photos of the whole deal! SO helpful!!!! In his versions, he used a ribbon cable between the KPR and the breakout box, but I thought that looked a bit delicate and prone to being damaged, so I wondered what the hell to do. There are 17 knobs. Each knob needs two wires. That’s 34 fucking wires in all (Hey I can do basic math! Damn well better be able to, been teaching the shit to the 4th graders this school year). Hmmmm. In the end, the best option seemed to be a 37-pin d-sub connector and associated cable, though the actual cable I ended up with is a bit large and unwieldy.

Breakout box. You can read what the knobs are ‘supposed’ to control... I say ‘supposed’ to because some of them don’t behave as I expected they would, and there is a lot of interaction between certain knobs. 

In a nutshell, here’s what I noticed about the knobs, per instrument. The Bass Drum Tune and Decay knobs interact with each other to produce sometimes unpredictable results. The Tune works more like a lowpass filter than a pitch control. Decay will self-oscillate when set fully clockwise, but that stops at about the 3 o’clock position. You can get some LOW kicks with real THUMP behind them depending how you set these two knobs.

The Snare has three controls: Tune, Decay and Snap. Tune will self-oscillate when fully clockwise. Decay works but interestingly will produce a very pronounced POP (sounds more like BUMP though) when fully counterclockwise. Snap is a noise amount control, and boy is that an apt description—when fully open there’s more hiss than that roomful of snakes Indiana Jones dealt with in Raiders of the Lost Ark. That control is more like a lowpass filter than an 808-style ‘snappy’ deal, but it’s close. Some very interesting snares can be cooked up with these controls.

The Toms... I’m not sure the info I referred to was totally correct here. The reason I say so is because the controls sorta work as labeled but not always, and sometimes the effect is not what I expect. The Tune controls work, and at low settings produce a VERY 808-like bass drum sound. Decay... well... first of all, these controls interact with the Tune knobs, sometimes quite noticeably so. Here the mod is very much like the BD Tune and Decay mod on the DR-110.

There’s some mischief going on with the hats/cymbal/noise section, in general. It isn’t always obvious what the Noise Color and Noise Level controls are actually doing. You get an audible high-frequency whine sometimes when the Color knob is fully clockwise but it depends on what a few other controls are set to. HH Tune works more like a bit reducer the more counterclockwise you go, and it seems to lower the volume of the hats as well. CY Tune is sweepable but there’s an almost continually present audible high-pitched whine which goes away with the knob fully counterclockwise. I wired the CH and OH Decay knobs in reverse (meaning the CH controls the OH and vice versa). Oops. But, those work as expected. CY Tune works as expected, but also controls the tuning of the hats. CY decay works normally too.

Last but not least, Clap and Noise controls. CP filter is exactly that—a lowpass filter. This is VERY hissy when set fully clockwise, more so than the SD Snap even. Maybe I need a fucking Dolby NR system on this motherfucker. Hahaha! The NZ (Noise, not New Zealand, duh) Color whines when fully clockwise. I think this actually is the tuner for the square wave of the hats & cymbal. The NZ Level doesn’t seem to affect anything in an overly obvious manner. Now, the biggest conglomeration of mischief makers in this mod is the malicious gang of the following members: NZ Level, NZ color, CY Tune, CP Filter, and HH Tune. All of these interact with each other.

Impression. As I said above, the KPR at factory settings is rather unremarkable. On top of that, it is also a real bitch to program, so unless you’re trying to be some throwback we-can’t-afford-anything-else-at-all-so-there-80s-proto-goth band, I can’t really say this machine has a place in a studio, which may sound like a pretty goddam harsh judgment. And it is, to be sure. Now, in this day and age you can go online and find sample packs of just about any drum machine ever fucking made, so if you WANT the sounds of the KPR, they are out there, and it is arguably more practical to load up an MPC with those sounds, and far, far easier to program too, so that’s why I say what I said. But having said that, after doing these mods, well, it sure isn’t an 808-killer (maybe not even a 606-killer either, hehehe) but it sure does have character. Very reminiscent of the drum synth modules I’ve played with. But if that’s what you’re after, there’s the DrumBrute and DrumBrute Impact (the latter of which I was really, REALLY thinking about buying but then the KPR happened). Like the KPR, neither of those remember the knob settings per pattern. Coincidentally, the MFB-503 DOES, though, and it’s an analog drum machine, and that memory deal is a huuuuuuge reason I still have the thing though it is collecting dust. The Arturias are not that much more expensive than the KPR plus the cost of parts and time spent modding (though if you asked me to do the same thing for you I’d stick you with at least $400 for labor because it took damn near for-fucking-everrr to wire up those 37-pin d-sub connectors. It wasn’t easy to cut a hole in the side of the casing for the connectors either, on both the breakout box and the KPR itself. Wiring the thing up was an adventure with spaghetti too. Here have a look:

Desoldering the resistors and trimmers took a bit of time, and then measuring the resistance on the original trimmers for something I’ll talk about below was a pain because I didn’t mark which trimmer came from where (dumbassssss). Sourcing a cable wasn’t easy either (Yahoo Auctions to the rescue). Speaking of desoldering and stuff, look at how this electrolytic cap was originally done (it’s the orange on in the lower right of the photo above):

Dayum look at those legs! Seriously Korg, what happened here? I trimmed those off so now they’re flush to the PCB.

Tried to make the inside of the breakout box tidy. Not bad. But since I wired the OH/CH Decay pots up to the wrong destination, I’ll have to open it up and take care of that (those are the bottom two pots on the second row over from the right side, white & black wires to the CH Decay, red & brown wires to the OH Decay. Those need to be switched. Since I turned the bottom row so the solder lugs face inwards it should be an easy fix.

I also thought about not being able to use the thing unless the breakout box is plugged in, which can be a hassle. So the idea hit me to make a SCSI Terminator type thingy to jam into the connector on the KPR side, with wee resistors soldered across the relevant legs, set to original values. That way, you can return it to ‘factory’ settings if need be (it also saves space). So I did that.