x0x Heart

Anyone got an x0x Heart and Pacemaker going? I’ve finally got round to making mine up (it was actually the first Euro DIY project I bought boards for), and paired with my Turing Machine module (with Pulses and Voltages expanders), it’s a LOT of fun…

I have a couple of questions:

Is the VCA output supposed to distort heavily with the Volume control turned more than about 3/4 of the way?

How’ve you found tuning the thing? I’ve yet to attempt it, but given my previous form in breaking trimmer pots, I’m a little scared to start poking around with a screwdriver. Those teeny SMT trimmer pots look super delicate. It actually sounds pretty good, as is. It’s obviously not going to fit in with anything else though, tuning-wise.

Also, what knobs have people been using for the module? I have some white Davies 1900h clones from Thonk, which I’ve used on other DIY modules, but I’m thinking these black knurled aluminium knobs might look nice. Or, maybe these silver ones, for a more authentic look.


First test recording:


Nice! I think we’re in the same boat, though my experience is slightly different, I think. I can’t recall having any distortion when cranking up the volume knob. I’ll see if I can test that out tonight. I thought about tuning the module, but the instructions on the open music labs site were a little confusing to me. Like you, I think mine sounds fine as it is, and gives me all the wonderful x0x sounds I’m looking for. I probably won’t bother tuning it, until it seems absolutely necessary. As for knobs, I was trying to build up my modular on a bare bones budget, so I went with some orange davies clones from small bear. Here’s a quick video of a jam with my x0x heart. Sequence out of ableton using the cv-pal.


Nice. I was actually watching that video this morning, without realising you were a member of this forum!

I thought about writing some alternative firmware for the CVPal, with pitch and gate on the first two sockets, and two trigger outs on the other two. That way you could control pitch, gate, accent and slide via MIDI. You definitely need to trigger both slides and accents, for a truly authentic 303 sound.


The output is pretty hot… Cool thing Guest did was to keep all the part designators the same as the x0x/303 so it’s easy to mod. Mine was really clicky so I added the VCA DC offset mod as well as the D35 declick mod, both worked great. He used his BA662A clone for the VCA in this also which is available as a standalone device, I just built an x0x with one and its pretty spot on

The output on mine is pretty loud when turned up, but it also seems to be distorting internally when turned up more than about 75%. It sounds quite nice, to me, but I’m a little worried that I might damage something if it’s not meant to go that loud.


Good call on that firmware for CV Pal. Let me know how that goes. I’m not noticing a hot output on my x0x heart, but I’m still very much a noob in the modular world. I’m hoping to spend much of January (and 2015) getting more familiar with wtf is going on in my modular! Last night I noodled around with Tides, the x0x heart, Peaks and some other stuff. Tons of fun, although my wife would prefer more than an hour-long loop of a 4 bar sequence. How random/useful are you finding the Turing Machine? Are the expanders essential? Does it create decent “melodies” for you?

I really like the Turing machines. The pulses expander is essential in my opinion. The other expansion with the slider is great to, but not as essential imo.

+1 to what sammy said about the tm. it’s brilliant, and yes, pulses is a must-have.
but to get ‘decent melodies’ out of the tm, you’ll also need a quantizer.

Quantizer is a must. Barton DNQ for me.

@sammy: did you ever get the dnq to work properly w/o any issues? i built one to combine with my tm+pulses+voltages, but simply can’t get rid of those nasty fm artefacts. i tried all the tips from michael’s site, and contacted him directly, too. he was super-friendly and patient and gave me all kinds of tips, but nothing worked, so i gave up at some point. :frowning:

[edit:] hmm, now that i think of it again, there might be one last thing to try: i could exchange those reichelt quartzes for ones from tayda. think i read somewhere taht there might be some issues with quartzes from reichelt…

too bad i just placed a tayda order. will be a while till i’ll order anything from there.

I had an issue of it randomly freezing in a certain pitch. It was an issue with Michael’s code and he sent me a new pic. I have not had any others issues.

@cold_fashioned Turing Machine gets a thumbs up from me.

I think the Voltages and Pulses expanders are pretty-much a necessity. The only downside is they take up quite a bit of space, but I think it’s worth it. Thonk are still doing a bundle deal for the TM and expanders. I’d recommend the Grayscale combined panel over the acrylic ones, which I think look pretty tacky, but that’s just personal preference.

In terms of it generating melodies… dunno really. The only module with an oscillator I have currently is the x0x Heart. It sounds pretty cool with that, but I wouldn’t say it was producing anything you’d call ‘melodic’.

As you’ve probably gathered, Voltages isn’t a conventional step sequencer, so attempting to use it to produce a particular sequence you have in mind isn’t going to work. It’s not random, of course, and after a while, you do start to get a feel for how it operates, but its still more useful as a source of ideas than as a conventional compositional tool.

I find Voltages’ Inverted output the most useful for note CVs, since it benefits from both scale and offset controls. Of course, the sliders are reversed for this output, but it doesn’t really matter, given the obscure way it operates, anyway.

It’s pretty good for producing CVs to modulate stuff, too. With the expanders, you can get 3 different CV outputs, plus noise. They’re not completely independent, of course, but it’s still pretty cool, for modulating different things.


like i said, you need a quantizer for tm to play melodically. in this elements clip i posted in the new modules thread, all sequencing is done by a turing machine + pulses + doepfer a156.

The Grayscale Hybrid panel and the Bytes expansion, also with the Grayscale panel is the business for the TM. I need to get the Barton quantizer build done. It’s going to be interesting to get that show on the road.

I find the same with respect to the volume level: at 75% the level is fine, above that my mixer (Behringer RX1602) starts clipping. No internal distorion in xoxheart though, I think. I suppose it is useful to have some headroom with the volume: I just keep the level at 75% most of the time.

I’m feeding my xoxheart with Pacemaker (in the picture: bottom right in my Rast-based setup) with Hexinverter’s Orbitals, A Turing Machine (of course , and Hackme’s Vectr for some hand-wavy variation. Great fun )
The Turing Machine also drives a MI Peaks module (not visible in the image, sits in the second Rast on the right).

Wow… I think I’ve hit the power limit of my uZeus already…!

This (Freq. Central Ultra Wave, Turing Machine + expanders, x0x Heart + Pacemaker, unpowered Jack-O-Mix)


If I add any other module, the uZeus craps out. I’m not impressed…


The uZeus is not called so without reason…

Thanks for the info on the Turing Machine, gents. It sounds like I might need to invest in a quantizer as well. I need more hp! I’m trying to save room for an Elements, but the space is slowly disappearing.

@toneburst That’s interesting about the uZeus. I am powering 2 94hp rows. It doesn’t get too hot or anything. Could something else be wrong? I might be pushing mine too hard though.