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Building Sasha's x0xb0x


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I might just hacksaw off that corner of the subpanel

Don`t cut it out it, just file it down a bit at the top and bottom and it will fit. I draw the opening hole according to the switch, but there is another diagram in datasheet with dimensions of metal part that goes out of the switch. I draw the openings on panel without a part so I made that mistake. I didn`t mount the metal part on my x0x. The palel and sub-panels holds it in place firmly.

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Hi Sasha,

I enlarged the hole for the toggle switch with a Dremel.  Now the sub-panel touches the Panasonic pots before it reaches the spacers.  I just looked more closely at your first x0xb0x and I see that the black keys don't stick out from the panel as much as the white keys ... it's because your panel is doing exactly the same thing.  It is bending a little.

I think the solution would be to either use larger spacers (but then the pot shafts are too short), or else enlarge several holes in the sub-panel to accommodate for the taller housings on the Panasonic pots.  I'm going to think about it.

Please let me know if I'm missing something.


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I just looked more closely at your first x0xb0x and I see that the black keys don't stick out from the panel as much as the white keys ... it's because your panel is doing exactly the same thing.  It is bending a little.

??? I don`t know where did you look but that is NOT the case with my x0x. All the keys sticks evenly.

I think the solution would be to either use larger spacers

If you cut pot shafts as suggested on ladyada instructions and use 10mm spacers everything fits perfectly. I also shorten the Grayhill shaft some 1-2mm to have the same space from the panel to the knob as it is on other knobs.

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I should be clear here:  I'm not upset or anything like that, and I'm not pointing fingers ... I'm just trying to find the solution for my problem.

I looked at this pic:


Maybe it's just me, but it seems to me that the black keys look like they don't stick out as much as the white keys.  Am I wrong?

I have used shorter spacers than you, maybe because I trimmed the shafts too short.  But my black keys stick out less than my white keys, and it's because I can't get the top part of the panel to sit as low as the bottom, due to the height of the Panasonic pots.

I am sure I can remedy this by enlarging the holes in the sub-panel.  I am only posting to see if anybody else is having the same problem.

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:) Steve, look at the enlarged picture. You`ll see it is reflection. Why black keys are not reflecting the same, I really don`t know. but I ensure you they are all sticking out the same distance. There is no way PCB can bend just where the black keys are. The PCB is fixed to the panel in 3 positions very well and there is no any bending. Also I wouldn`t advise you to widen the screw holes on panel. Please think twice before you do that because in that case you will screw the PCB directly to the panel whish is NOT good idea. It will brake! Sub-panel is not there without a reason. I`m sure you can find some spacer closer to 10mm in US. Also, I don`t think you are pointing finger at me. I would really like to help you to make it right as you shouldn`t have any problems fitting it together. I did it with my 2 boxes and also unit-sound did it on his without much effort.

EDIT: check out the marked edge on the picture in full size, and ignore what you see on the panel. ;)



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Hmmm ... Now that I look at it more closely, I guess you're right about the reflection.

I'm not proposing enlarging any screw holes.  I think I trimmed my pot shafts a little too short.  To compensate, I can use shorter spacers, and then just enlarge the holes in the sub-panel around the Panasonic pots.  It should make no difference, because those areas are generally covered by knobs anyway!

Also, on closer examination I see that the Grayhill encoders have a little "nub" that sticks up, which I can also file off.  I'll try that first, but I'm confident now that I can work around this.

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Hmmm ... Now that I look at it more closely, I guess you're right about the reflection.

If you know my work bit better you knew that I couldn`t ever lived with such imperfection.  :P

...just enlarge the holes in the sub-panel around the Panasonic pots.

Oh, that holes... that`s fine to do it. Just take care if you don`t have experience working with acrylic as it can crack.

Also, on closer examination I see that the Grayhill encoders have a little "nub" that sticks up, which I can also file off.

The Grayhill shaft is fairly soft and don`t need to have exact length as you fix knob with the screw... so, I just cut it off with wire cutters after I mount it to the PCB.

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I now have a working x0xb0x!  Peeeeeeooooooowwwww!!!


1. I had 10 mm spacers.  I filed them down to 8 mm.  They are not perfect, so it my panel is still slightly uneven.  It's hardly noticable, but it is there when you look for it.  I'll be buying some new spacers.

2. I think my square wave is a bit too sine-y.  Back when I built the VCO the square didn't have that nice sharp point at the beginning of the cycle, it was slightly more rounded than the Ladyada oscilloscope screen shots.  My square doesn't sound as bright as I think it should, and this is probably why.  I'm going to look at Q8, C11, and some stuff around there.  I don't remember right now, but I may have subbed a Tantalum in for C11 and some of the 1 uF caps instead of electrolytic.


1. First, let me repeat: MULTI-TURN trim pots.  Next time I have my x0xb0x apart I am going to replace the VCO calibration trimmers and the power supply trimmer.

2. Don't spend too much time on VCO calibration when you're still at the VCO building phase.  Get it close and move on, you'll need to calibrate it later.  Ladyada's build site would have you inject 2V and 3V to get the VCO calibrated.  The problem is, your actual CV generated might not be exactly 2V and 3V.  My x0xb0x generates 1.98, 2.98, 3.97 and 4.95 on each "C".  You'll never know the precise voltage you'll see until you fire it up with the atmega.  I suppose you could remedy this somewhat by hand-matching all those 1% 200K resistors, which actually form the DAC in this project, but it's not really necessary unless you also want to interface with other 1V/oct control voltage devices.

3. If you use spacers under 10 mm (3/8") long, you will need to cut or file off the little protrusion on the side of the big encoders, or else they will get in the way of the sub-panel.  Similarly, you will need to enlarge the holes where the toggle switch and Panasonic pots poke through.  I used a machining bit on a Dremel and it made short work of the job, although it does of course make a mess :)

Now, if I may ....

HUGE thanks to Sasha and The Prof.  You both remained dedicated to this project and made it really easy for a dolt like me to build this thing.  Thanks for being there to support us, the builders too. 

I decided to get in on this project only because I had a few extra bucks to burn.  I have a pretty nice little home studio, and usually any time somebody came to visit they'd say something like "oh, wow! do you have a 303?" ... I would usually just sort of mumble some story about how the TB-303 was overrated in the first place, and it's played out ... and then show them something else I have that's more interesting.  So the x0xb0x wasn't even really on my radar, until Sasha announced a pretty good price for boards and panels, with Dr. Pepper taking all the headache out of finding the rare parts.  I figured "what the hell" and bit the bullet.

Am I ever glad I did!  I have always thought the TB-303 to be more of a toy than a serious music machine.  Now that I have had a x0xb0x for about 13 hours, I can honestly say that it's a surprisingly versatile instrument - not just for cheesy acid sounds!  It also does really solid sub-bass parts, screaching leads, and other stuff too. 

The really cool part the x0xb0x is that it can be sequenced via MIDI, so if you want swing timing, or just tighter DAW integration, it's there.  I think I want 2 more.

Pics to follow.

EDIT: one thing I forgot to add... at first I thought Sasha's layout changes weren't all that important.  Now that I'm using it, and I have this gorgeous front panel when compared to the adafruit x0x panels, I can honestly say that Sasha's changes are a significant improvement, and worth the deviation from Limor's design.  Great job, Sasha!

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  • 2 weeks later...

still not tested! or, only on breadboard up to now.

i make my x0x along xoxio mod, and now i'm exactly before interconecting between them all altogether.

still unsoldered tactiles, led-resistors and leds.

i see the progress as this:

(soldering in order)



sticking leds in their places (one led roughly soldered)

installing i/o board (attaching the board)

installing xoxio mod (attaching the board)

final frontpanel fit

leds fit into the frontpanel (hard-sticking, tough!) and soldering them to allign nicely.


boom.  ;)

on a breadboard, i see 22K-33K-47K as most comfortable resistance i find.

probably 33K is to be used (47 is too much and 22 is very bright yet).

How do i test the leds in their places before i go on and finish the unit? i never turned on x0xb0x before.

the software is from ladyada directly - so atmel is programmed, already.

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Vlad, I`m really not sure what exactly are you trying to do, and why. If you satisfied with brightness of your LEDs with whatever value of resistors, just solder it all on their places. That is last step in building the x0x, so you will see if there are some problem with LEDs or not when you start it, but as the sequencer is fairly simple I wouldn`t expect any LED problems. Just build it, man!

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i managed to get it working yesterday. everything worked from scratch, except one faulty led and x0xio overdrive circuit.

what a killa machine! i still have to tune this beast, the tm4-tm5 chapter, but hey...  :P

it sounds incredible.

thanks for people involved. Without you this project would not be possible.

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  • 1 month later...

Yey, finally got my x0x emitting sounds! Swore to myself that Acid Trax would definitely be the first tune I'd make a cover off after getting the device in a fully operational state, so here it is! Not a 100% match, but maybe I'll refine it later ;)

As far as the device itself is concerned, now there's only the casing left to build, the design for it is maybe around 70% complete. For me, this x0x-project has had plenty of "two steps forward, one step back" type of progress (keyboard/mcu/cabling problems), so it's fun to see it finally ending up to this stage.

ANYWAY, I did have a question in mind.. Has anyone added the muffler distortion mod to their x0x? If so, could you report the signal levels on your unit? Scoping the output of my unit I'm seeing a 500-600 mVpp signal, so using a LED for clipping the output hardly works. This mod is however mentioned to work at the x0x forums so I'm left wondering, is the output level on my unit too low or are the people reporting this mod as a working one completely deaf? :). I already decided that I'll just not include this feature on my final x0x (stick with guitar pedals etc. for distortion), but it would be good to know if the output is really too low so I can fix that bit.

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I like the both, distortion and overdrive. That is part of I/O mod? What have you tested from it by far and what do you think of it?

I see some very small and nice looking power switch... do you have where it is from and do you have some bigger picture?

What I don`t like is that Re`an knob. Being red in B/W world isn`t very nice.

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