x0xi0 Support

The Build manuals for the x0xi0 kits are very detailed. However, they are advanced kits and it's not uncommon to ask for help. If you are stuck and need help you can contact BC Audio at the email address below.
user support also takes place here on the x0xb0x forums. Below is a summary of the support history for the kits that I have been tracking on the x0xb0x forum. If you have general questions or need support you can contact me

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Installation Step 14 show the wire connected to the wrong side of R60
[first posted July 25 2008]
please note that I have found an error in the Install Manual Rev1.01.

The sympton would be a non-working slide in circuit.
I will update the install manual as soon as possible. I will also include a revision history so in the future everyone can see what has changed.
I will also be emailing everyone that has purchased a kit as of today.
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Checking resistor values
[first posted July 26 2008]
[Computer Controlled]
Finished soldering all the resistors, except the ones in the variety packs. I don't know what each one is... Could someone type up a diagram so i know what resistors are what values?

[phono]
http://www.dannyg.com/examples/res2/resistor.htm

you can use this, look at the resistor, put the colours in and it will match it up for you, however its probably better to double check with a multimeter (if you are colorblind like me)
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Checking capacitor values
[first posted July 26 2008]
[Computer Controlled]
Now, I don't know what ceramic caps are what! I can't read the writing on the heads.

[bcbox]
yeah, you need really good eyes or a magnifying glass, and make sure you're looking at the right side.

47pF says 470 or 47J (blue color)
100pF says 101 (yellow color)
270pF says 271 (yellow color)
680pF says 681 (this one is yellow color and has the bigger lead spacing)
100nF (0.1uF) says 104 on it (blue color)
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Tantalum capacitor orientation - Error in 1st run pcb legend
[first posted July 27 2008]
[Booster]
Hi Brian,

Great kit, well bagged/organised.

Just one quick question:-
Can you please confirm the orientation of the tantalums please, in particular C329. I think the polarity mark for this is obscured a little by the silkscreen for R350.

Thank you.

[Computer Controlled]
I couldn't tell that either, I just guessed that it was the same as the other one.

[booster]
I have a feeling the positive for C329 is that little line you can see across the silkscreen for R350. Which would make it opposite to the other tantalum I believe.

[bcbox]
Booster you are correct. The (+) side of C329 is towards the top of the board.

However I see that the legend for C330 is backwards. This is a mistake, the (+) side should also be towards the top of the board.

This error exists in all kits up to serial #042.
I will update the docs again. It is important to get those correct or it could burn out. Sorry for the trouble guys.



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TM302 Calibration
[first posted July 28 2008]
[Computer Controlled]
I got it all built, and i'm trying to calibrate it. But the voltage is slowly dropping as i try to adjust TM302. As of right now, the voltage is 11.7 with the trim pot at fully CCW, and 11.6 at fully CW. I can't even get to 11.9 anymore. Any ideas why it should be dropping like this?

When i turn it on, and have the trim pot at full ccw, it read 13.9v, then quickly starts dropping from there. It's almost like a cap isn't holding it's charge. Also, the trim pot has almost NO range when sweeping it. like .1v range. So i can sweep from say 12.5 to 12.4 at most. Is this the way it should be?

[bcbox]
The range of TM302 is +/-0.2v
It's just to fine tune the supply voltage
The supply voltage should always be in the range of 11.7V to 12.1V.

[edit] TM302 give a 0.8v range
The supply voltage should generally read bewteen 11.4v and 12.6v assuming worst case tolerances of parts. TM302 should definitely allow you to calibrate to 11.9v. I've built seven or eight of these so far

and haven't had a problem. We'll have to revisit this, check out out the voltage from the x0xb0x diode bridge, power supply rating etc...

A few things to check.

1. orientation of C329, C330 (you probably checked this already).
2. orientation of IC301-IC304. Don't forget to check IC303 the small TO92 package.
3. verify pad BB is concected to the correct place on the x0xb0x I/O board.

- does the voltage remain stable once it reaches final value? (how long does it take to get there)
- does the voltage regulator get hot?
- what are the ratings of the power supply are using for you x0xb0x?

[Computer Controlled]
It seems to steady out at around 11.6v. Takes a few mins to reach, but appears to stay there. I'll check those measurements in a while. I put it together to make sure everything works. All works and sounds fine. Just a bit of harmonics in the sawtooth that wasn't there before. That back panel is a tight squeeze in that slot! =o]

Takes a few mins to reach, but appears to stay there

[bcbox]
that's a problem. Should settle immediately, few mS at worst.

[Robert Lowell]
just built mine and i am doing the calibrations. i am getting a 12.2v - 14.6v reading from pad C + D. so far everything looks fine i've done the updates & i'm using the power supply that came with the kit from ladyada.

[bcbox]The stock x0xb0x power supply is fine.

Ideally you should be able to adjust the voltage to 12V. I've done about a dozen now and haven't had any problems.
I'm assuming one of the 1% resistors is out of tolerance, either R350 is a bit high or R351 is a bit low. These set the output voltage of the LM317.
You could pull one end of each resistor and double check the value if you want to be sure. Adjusting it to 12.2V is not a problem though.

[Robert Lowell]
nice. i've adjusted it to 12v now. looking good so far. going to put it together and test it out.

[Computer Controlled]
So i got the box open replace that diode, and i notice C329 looks fried. I've noticed no odd behavior at all. Maybe it;s still good? It's all brown on the top. C330 looks fine... maybe i'll run to Rat Shack and get new caps just to be sure!

[bcbox]
I bet it's fried. I remember your supply voltage was off. It'll still work without the cap but it'll be unstable, so you should replace it.

If you go to radio shack this is the part you need...
1.0F 35V 20% Dipped Tantalum Capacitor
Model: 272-1434 | Catalog #: 272-1434

you can also use a 22uF electrolytic instead if you can get one to fit ok. The one below may work but may be too big to fit without getting in the way.
22 uF Electrolytic Capacitor
Model: 272-1026 | Catalog #: 272-1026

[Computer Controlled]
Cool. I'd go tomorrow, but i work an open to close shift. Yay
[cc] Go figure, the radio shack by has NO caps at all! Useless store on this useless island!

[issue still open]
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Rear panel fit
[first posted July 28 2008]
[Computer Controlled]
That back panel is a tight squeeze in that slot!

[bcbox]
yeah it worked out pretty good. It's definitely a tight fit and won't rattle.
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Overdrive not active through Headphone output
[first posted September 8 2008]

[rarara]
overdrive makes no difference (i take it the on/off is off in the down position btw?) that i can tell. using the 'low freq' option creates a very tiny bit of crackle. this may be related to the other issues...
i didn't realise the main out and the phones out would be different where the overdrive was concerned, so once i connected things up to my mixer things were looking a lot better

[bcbox]
The overdrive is on the main output, after the headphone out, so the headphone out does not go through the distortion circuit, so you can have both clean and distorted signals. When the Overdrive is OFF the
main output is exactly the same as the headohone out (minus any distortions in the headphone amp) so if it if sounds different there is most likely a problem.
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Filter Hi Range Switch
[first posted September 8 2008]

[rarara]
filter range button seems to make a difference. subtle though

[bcbox]
It increases the maximum cutoff frequency of the filter so it's more noticeable with certain settings, generally with higher settings of cutoff or when using a full range signal to the VCF Input (external input).
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VCF & VCA Input and Gate Signal
[first posted September 8 2008]

[rarara]
i ran a signal from a minidisc into the audio in (vca?) and the signal seems to be getting processed. should i only expect to hear the audio in while a note is being played on the x0xb0x since this is whats happening?

[bcbox]
yes this is correct, the gate must be on for the VCA to be open. You can do the gate on mod for unused slide switch and it will keep the VCA open.

[rarara]
gate-on slide mod - it does seem to work when playing a pattern as switching between the two states produces a change in the slide length. with this switched, should any signal coming into the vca-in be
played fully? i can still only get this to occur if i have say a pattern of the same note playing with each note set to slide - then i hear all of the vca-in i thought any signal through the vca-in would get processed/mangled by the x0xb0x to a degree, but i only seem to hear an unaltered version. and i am confused about the practical use of this when you need a
pattern to be playing for vca-in to be heard. is something wrong here?

[bcbox]
I'm not sure I understand exactly. Is this the mod for the unused rear panel switch to keep the VCA envelope open? If this is the case then notes will play for as long as the gate is on. A good way to check
this is to put the x0xb0x in keyboard note and hold a note down - it should play forever and not decay.

[rarara]
i thought any signal through the vca-in would get processed/mangled by the x0xb0x to a degree, but i only seem to hear an unaltered version. and i am confused about the practical use of this when you need a pattern to be playing for vca-in to be heard. is something wrong here? [/quote]
What you are saying is correct. You need to keep the gate open in order to hear sounds through the VCA. This is done with a front panel switch on the full mod but with the I/O only mod you have three options to keep the Gate open.

[bcbox]
What you are saying is correct. You need to keep the gate open in order to hear sounds through the VCA. This is done with a front panel switch on the full mod but with the I/O only mod you have three options to keep the Gate open.

1. Input a control voltage to the Gate In jack. This would typically be the Gate Out from another device, but any 3-10V signal will do.
2. Put the x0xb0x in Keyboard mode and hold a key down. If you don't want to hear the x0xb0x VCO plug a cable into the VCO Out jack - this interupts the signal from the VCO to the VCF.
3. Install a Gate On switch which connects 12V to the cathode of D35 (the full mod uses a DPDT switch which turns the Gate On [i]and[/i] keeps the VCA open). Now, when the switch is ON the Gate is held open.

If you're playing another synth in to the VCA input and you want the gate to stay open you should connect the Gate Out from the other synth to the Gate In on the x0x. If your other synth or other sound source (minidisc)doesn't have a gate out you'll need to do option 2 or 3 above.
Another thing a lot us do is use the VCA Input in tandem with the x0xb0x Gate Out so the other synth is being triggered by the x0xb0x and also playing through it at from the VCF In or VCA In at the same time. This is different from what it sounds like you're trying to do, which is simply play a sound source through the filter, VCA, and Distortion (which can be done by doing what is described above).
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Keeping the Gate and VCA open while paying through VCF In or VCA In
[first posted September 8 2008]

[rarara]
the gate on mod for the unused rear switch seems fine. i would think this might be more useful it it could also keep the vca open at the same time. is there any way i can connect this switch to achieve this (you say "full mod uses a DPDT switch which turns the Gate On and keeps the VCA open" but can this be done with what i already have, rather than a dpdt?)

[bcbox]
you're screwed there because it's a single pole switch.
One thing you could probably do is mod the filter high range switch (which is DPDT). If you think you can do without this feature let me know and I'll sketch out how to mod that switch for gate on & vca on.
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Adding a VCA on/Gate On Switch
[first posted September 8 2008]

[rarara]
i still see a vca-on mod as being most useful option to have. you say that the current single pole switch for the gate-on mod is no good - is it possible to replace this switch with something else more suitable which would fit into the already created hole? it would be nice to use whats already there. it would also be ideal if the high range filter was left untouched (or at the leat, 2 out of the 3 options on this switch still being available?)

[bcbox]
I didn't find any DPDT slide switches that will fit.
A couple were close.
CW Part# GS-113-0512 is the DPDT version of the one that is used. It has a different hole spacing and also a bit more travel so it won't fly.
E-Switch part #EG2202 looked like an OK candidate the switch shaft is too wide.

I think you may be able to retrofit a toggle switch in there without messing up the clean fit & finish. I'll test it out tonight if I have a few minutes and see if it's do-able.
I haven't looked yet - this will be update
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Removing old components
[first posted September 8 2008]

[rarara]
the build itself seems straightforward, apart from the removal of old components on the mainboard (r47, r61, r62, r121, r122, r155, c20,21, remove c17). could any of these replaced components be causing a
problem?

[bcbox]
It sounds like you have everything correct up to the point of the overdrive circuit, which is taken from the output of the x0xb0x.
R47 & R62 are simple changes to increase the range of cutoff and env mod.
R62 is part of the VCO to VCF circuit, so if there was a problem you would not have any sound.
R121 & R122 are at the VCA input, so if there was a problem you would not have any sound at the VCA Output or Main Output.
R155 is in the output 'mixer'. If there was a problem with that one you would not have sound at the Headphone Output or Main Output.
C20 & C21 are just for used for extending the low end freqeucny response of teh x0xb0x. If one or both was installed badly the sound from the Headphone Out and Main Out would not sound right.
C17 is removed and used as a patch point for the mod. That component is relocated to the new rear PCB. If it wasn't installed correctly you would have no sound from the VCO, VCA, or Main Output (Mix Out).
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Orientation of IC304
[first posted September 8 2008]

[rarara]
IC304 - tlc2272. this had no notch to correspond to the one on the pcb, therefore i may have put it in backwards. i used the same orientation as on the mainboard though. so if looking at the instruction diagram as a guide, the writing on the IC would read top to bottom.

[bcbox]
It sounds like you installed it correctly. If there isn't an actual notch it shoud have a circle on it to indicate the orientation - it serves the same purpose as a notch. That part is used for the VCO Frequency Modulation input circuit and the Accent Sweep Output circuit. If you were able to calibrate the Acc Swp output (TM301) then it is installed correctly.
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Using the rear panel Slide Switch for VCA On
[first posted September 8 2008]

[rarara]
for step 18 of the instructions i added the vca-on to the slide switch. would it make an difference if i attached d36 to the wrong side of this switch?

[bcbox]
This wouldn't be a problem, it would just change which position of the switch corresponds to turning the mod on.
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Completing step 12 regarding pads Q & R
[first posted September 8 2008]

[rarara]
step 12. its not clear what "installing the I/O kit only" means. is this seperate to the overdrive kit? i didn't add the jumper to Q and R. should I? would this explain much of the above?

[bcbox]
This is referring to the Full x0xi0 mod that is not available yet. Since you're installing the Rear kit only you should jumper Q & R.
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What's up with all the different pad's labeled C & D?
[first posted September 8 2008]

[bcbox]
Those are all the same connection. D is the new 12v supply, C is analog Ground.
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Overdrive Amount & Tone controls?
[first posted September 8 2008]

[rarara]
with 'tone' and 'amount' of the OD turned a fairly small amount things do seem to get quite noisy. i think i will have a look at some previous suggestions for reducing noise, as the sound is far from 'clean', even without distortion, and hiss is very noticeable. are there any sound clips of boxes with just the IO mod that i can listen to? brian, your myspace site sounds very impressive but those clips are no doubt for the complete mods.

[bcbox]
With the distortion in the OFF position the noise level is the same as a stock x0xb0x. If there is a difference there is most likely a problem. The overdrive/distortion circuit itself has huge amounts of gain, even more than a typical stomp box . So when the overdrive is ON it can certainly get noisy. As stated in the Users Manual I gave it more gain so it can get really filthy ;) To avoid this keep the volume at max and turn the overdrive amount down, and you will find the Overdrive/Distortion character remains the same but the noise level decreases. The Overdrive and Distortion both allow for much more high frequency to pass through versus typical distortion boxes, and there's a lot of noise up in the high frequencies. If you want it to sound more like a typcial distortin box you will need to turn the Tone control down, this will also filter out a lot of noise/hiss like a typical distortion box.
The samples on the myspace site are the same circuit as the Overdrive type in the x0xi0 I/O kit, the Amount and Tone controls are turned down
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Filter Cutoff Range
[first posted September 8 2008]

[rarara]
cutoff. now i need to have cutoff at least half way or there is very little sound. i can't remember needing as much cutoff pre-mod. what could be the cause?

[bcbox]
The minimum cutoff frequency has been lowered by a few octaves. Check out the users manual for actual frequency response measurements showing how much the minimum cutout freq has been extended. This is done on purpose so the cutoff can be lowered to a much lower frequency so that you can can bring in a bass line from almost inaudibility to get those low burbling sounds. Certainly if you don't like the extended range you can replace R47 with 10k and you'll be back to stock setting.
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VCF Input impedance
[first posted September 8 2008]

[rarara]
vcf-in - if i use the same signal signal (minidisc oputput) as i connected to the vca-in and put it into the vcf-in then i hear nothing, even if a pattern is also playing. i may be missing the point here, but what should i expect to hear? should it work? i was hoping that vcf-in and vco-in would both be put through the distortion, OD, filters etc but thats not the case.

[bcbox]
You should hear the minidisc material coming through. Assuming it's preamp level stuff (100mV to 500mV is fine) you should be hearing a healthy signal level into the VCA. If you're playing a x0xb0x pattern
it will get chopped up as the VCA opens and closes (unless you hold the VCA open just as above). If you want to test it try this.

1. plug a cable into the VCO (don't route it anywhere). This opens the connection from the VCO to the VCF so you can use the VCF Input without hearing the x0xb0x VCO.
2. Turn the Cutoff knob to max.
3. Put the x0xb0x in Keyboard mode and hold a key down, this will hold the gate open and trigger the VCA. The VCA will decay in 3 seconds unless you do the VCA Envelope mod described above (sounds like you
did) in which case the Gate [i]and[/i] VCA will be held open indefinitely.
4. Now play the minidisc and you should hear it playing through the filter and the rest of the signal chain (through VCA then Overdrive to Main Output).

[rarara]
the vcf-in seems to work too, but only when i have the x0xb0x volume near max (and i need to plug something into the vco-out since the sound of the vco hides anything from the vcf-in). is this normal? with the vca-in the same signal (minidisc) is fairly good in terms of the level it plays at.

[bcbox]
The deal there is that the output of the minidisc is pretty low level, probably between 100mV and 250mVrms. The VCF Input is primarily designed for an instrument level input, say 2-10V peak to peak, like
from a synth or synth module. The input impedance of the VCF Input is 22k. This is designed to work well with levels from synths. It's a catch 22, if I make the input impedance any lower the signal from synths will overdrive and distort the VCF even when the volume control from the source instrument is turned way down. On the other hand it doesn't allow a low level source like a minidisc or ipod to drive a healthy amount. When I designed it I decided to stick close to the standards of a modular synth.
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TM301 Adjustment problem
[first posted September 16 2008]

[Robert Lowell]
i'm getting .990v when i turn tm301 clockwise it lowers to .986v and not really making a difference. pin c to tip of j306. i'm wondering if i screwed up a resistor somewhere or could it be another issue. does someone have a high res. picture of the finished board to match resistor bands.

[bcbox]
do you have the schematic? It'll help with troubleshoothing.

The parts that make up that circuit are:
R333,R334,R336: 22k
R335,R337: 100k
TM301: 20k
IC304b

The resistors may be 1% or 5% (the 22k's in the pic below are 5%):
22k 1%: red/red/brn/red/brn
22k 5%: red/red/org/gold
100k 1%: brn,blk,blk,org,brn
100k 5%: brn,blk,yel,gold



[Robert Lowell]
thanks so much, i will have a look at it tomorrow. i do not have the schematic though.

edit: i found the problem. works like a charm. thank you.
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Slide In not working with external CV
[first posted November 14 2008]

[crx091081gb]
I bought and installed the xoxio back panel mod but I'm having a little difficulty with the slide cv input, when I send it 5 volts it holds the gate open but the pitch cv isn't slid (no portamento).

[bcbox]
I took a look at it tonight and have confirmed your problem. After staring at the schematics for several minutes I realized it's pretty trivial. The slide happens when the cv is slewed by component C35 and the resistance seen from the CV input. This is the equivilent resistance seen from the DAC (the internal CV generator). This is around 100k. When using an external CV input from most gear the slide circuit is going to see a minimal impedance, so the resistance is pretty much just R327 from the x0xi0 CV input circuit. There is a slide time but it's so fast you can't hear it. The solution is to replace R327 on the x0xi0 PCB with 100k, this will give you a slide time equivilent to what you get when using the internal CV. Let me know how it works.

The full x0xi0 mod includes a slide time control which consists partly of a 500k pot in series between connections Y & Z of the x0xi0 mod. This gives a full range of slide times from stock to several times greater than stock. The resistor R327 that's part of the I/O & Overdrive mod is simply for protection to current limit whatever may be plugged in to the CV input, and not high enough value to slew the pitch long enough. When making the I/O only kit I overlooked the fact that there's no slide time pot in series. If you're only installing the I/0 & Overdrive kit and won't be upgrading to the full kit you should simply replace R327 with 100k and you will be good to go.

[crx091081gb]
Just swapped the resistor for 100K and slidey slidey. Wahey.
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Overdrive circuit is not working
[first posted December 29 2008]

[kartoshka]
when type switch activated up, i'm having no sound at all. When switch is down, distortion works smoothly and sounds sa-ha-weet! I hear sound both in headphones and main out, unprocessed and processed respectively as explained earlier.
Overdrive outputs silence.

[bcbox]
This is the order to check things..

1. Make sure you are getting power to right places...
IC303 Pin1 = ~12V
IC303 Pin3 = ~6V (make sure IC303 is in correct orientation)
IC301 Pin8 = ~12V
SW303 Pin2 (SW303/C304) = ~6V

2. Check that you have signal at SW302 Pin1 (SW302/C301)
3. Check for signal at IC301 Pin1
4. Check for signal at IC301 Pin7
5. Check for signal at SW302 Pin4 (SW302/R325)

With the x0xb0x volume all the way up the signal should be greater than 2V peak to peak (regardless of the setting of the overdrive amount control). If you don't have an oscilloscope try using earbuds as described in the x0xb0x build manual.

[kartoshka]
Ok, I (hopefully) identified the prob. it's in the amount pot. it's somewhat failing (it didn't work before, i did not touch soldering iron at all - it just began to function, absolutely spontaneously).
first i play the sequence with xoxio on, type (up on) overdrive, tone and amount all the way down.
then i turn tone up, full way up.
then, i touch amount and turn it all the way up too, later playing with it.
then both of the controls go down - to their initial state.

second, i switch the type (down to) distortion, and execute same procedural cycle.
tone to full on, then amount up to full and playing with both.
then, both controls go back down again.

third, i turn xoxio module off and hear xoxbox naked.
no xoxbox controls were touched during the recording.

So, amount pot needs to be replaced.
I can't find it locally (local ratshack refuses to stock ANY dual pots, been in this story before - with effects pedals for synths)

[bcbox]
The pots are dual gang and the overdrive and distortion circuits are completely independent. One section of each pot is for the overdrive circuit and other section is for the distortion circuit, so it's possible for the distortion circuit to work and the overdrive to be faulty as you describe.

[kartoshka]
fixed!
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All notes Accented problem
[First Posted Nov 17, 2008]
[crx091081gb]
After replacing the resistor I seem to have a reoccuring problem of every note being accented. This doesn't occur with the sequencer triggered notes, just the ones from the cv ins even when only the gate is being used. I fiddled about this morning resoldering any part around that bit of the board (r329, q302) and checked x's connection to whichever diode its wired to on the xox - and it went away but now its back. Dry joint?

[bcbox]
sounds like there's some interaction between gate in and accent. check again the connections AA and make sure it's not touching conneciton X somewhere. Also check connections Y or Z andmake sure they're not touching connection X somehwere. Connection X should go to the base of Q35.

[crx091081gb]
Cheers, Brian. I took it apart and checked it, fiddled about a bit, applied desolder braid, reapplied solder, etc, etc, etc. And now it's gone. x0x sounds better than ever. Cheers I've now realised that my resoldering wasn't what fixed the accent problem. The x0x sequencer leaves the accent on or off depending on the last note it played. If you go to pattern edit and set a sequence with all accents and stop it and then play the x0x with the cvs then all notes will be accented regardless of the accent in voltage. This drove me insane this week as I thought I'd messed up my installation. Something to be aware of.
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Overdrive not working
[First Posted Dec 29, 2008]
[kartoshka]
hi Brian and other fella xoxers!

i am having problems with overdrive circuit. everything else seems working (i did not test it throroughtly 3.5 jacks), main switches/pots/buttons work and f.

when type switch activated up, i'm having no sound at all.
when switch is down, distortion works smoothly and sounds sa-ha-weet!
i hear sound both in headphones and main out, unprocessed and processed respectively as explained earlier.
Overdrive outputs silence.

rechecked it triple-twice to watch for soldering faults, bad joints, etc. none found.
pls help!

[bcbox]
This is the order to check things..

1. Make sure you are getting power to right places...
IC303 Pin1 = ~12V
IC303 Pin3 = ~6V (make sure IC303 is in correct orientation)
IC301 Pin8 = ~12V
SW303 Pin2 (SW303/C304) = ~6V

2. Check that you have signal at SW302 Pin1 (SW302/C301)
3. Check for signal at IC301 Pin1
4. Check for signal at IC301 Pin7
5. Check for signal at SW302 Pin4 (SW302/R325)

With the x0xb0x volume all the way up the signal should be greater than 2V peak to peak (regardless of the setting of the overdrive amount control). If you don't have an oscilloscope try using earbuds as described in the x0xb0x build manual.

[kartoshka]
Ok,
i (hopefully) identified the prob.

it's in the amount pot.
it's somewhat failing (it didn't work before, i did not touch soldering iron at all - it just began to function, absolutely spontaneously).
So, amount pot needs to be replaced.

[bcbox]
The pots are dual gang and the overdrive and distortion circuits are completely independent. One section of each pot is for the overdrive circuit and other section is for the distortion circuit, so it's possible for the distortion circuit to work and the overdrive to be faulty as you describe.

[kartoshka]
fixed!
http://believe.mytinydream.com/x0xIO-38/amount-pot-fixed.mp3
recorded from cheap mic, otherwise same cycle, same pattern, same bpm.
thank you for prompt help, BC.
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Main output is low
[First Posted Mar 14, 2009]
[kroutshev]

Hi Brian,
i've got some problems after x0xi0 build ... The volume of main output is very low, distorsion doesn't work, no sound and phone output is mono and not stereo.
Overdrive is ok and filter too.
What i have to test please ?
Thanks.

[bcbox]
1. Sound output is low:
How quite is it? is it about 3dB quiter than normal or is much lower?
What is value R155?

2. Distortion doesn't work.
First thing to check is to make sure the L-bracket on the far left is not shorting out the circuit.
If you look at the bottom of the x0xi0 PCB you will see that the screw for the third L-bracket
goes over a PCB trace. This is a design flaw I didn't catch. If the screw is tightened too much it may cut through the soldermask and short out the circuit since the L-bracket is connected to the rear panel, and the rear panel is grounded. Unscrew it and see if this is the case. If so you can insulate it first by adding a plastic or fiber washer underneath the screw, or by putting a piece of electrical tape between teh L-bracket and the rear panel.

3. Headphone output is mono.
Did you install the optional Accent Out circuit? See page 22 of the Install manual for details.
If you did install Accent out it uses the Ring of the headphone output so you'll only get output on the right side of your headphones. The headphone output is mono but the same signal is fed to both sides. If you install the accent out circuit and also want the headphone output to both ears you'll need to make an adapter that feeds the Tip of the headphone jack to both left and right sides of the headphones.

[kroutshev]
Hi Brian,
Thanks for your quick answer.

1. Sound output is low:
How quite is it? is it about 3dB quiter than normal or is much lower? it's very much lower !!
What is value R155? it's 100 K like in manual.
In this post
2. Distortion doesn't work. i've made a mistake when type is down i have sound but type up no sound ... it's overdrive which is failed ....
After remove far left L-bracket i've got the same problem, i've checked pcb and circuit isn't cut.

1) The signal is coming in good at pad B
i have 0V and on mainboard J7 pin 1 = 0 V. Pin 2 and 3 = 0 V
On J4 it's ok 5.33 V and 12 V.

3. Headphone output is mono.
Yes you're right i have installed Accent out circuit.

[bcbox]
1. You may have a bad solder joint somewhere along the way. Here's what to do to find out what section has gone bad...
a) take the signal from the VCO Out jack and send it straight to your mixer. This is the output of the VCO. Chances are it's good good and loud.
b) take the signal from the VCF Out jack and send it straight to your mixer. See if the output is still good level.
c) If it still sounds good and loud then the problem is after the VCA. If you have an oscilloscope check the signal at pin 3 of the volume pot. With the volume turned all the way up it should be greater than 2V peak to peak.
d) If you think all is good up to this point the problem could be a bad conection from J7 pin1 on the x0xb0x mainbard to Pad B on the x0xi0 board, or from Pad A on the x0xi0 board to J7 pin 1 on the x0xb0x I/O board.

I noticed in your comments you mentioned the signal is good at pad B on teh x0xi0 board but 0V at J7 pin 1 o the x0xb0 mainboard? The signal from J7 pin 1 on teh x0xb0x mainboard goes to Pad B so something is not right there. Make sure thsoe connections are correct.

2. Overdrive doesn't work. You may have seen the comments already but I'm pasting these from Alex's post from a few months earlier..
a) The signal is coming in good at pad B (since distortion works). Check it there and see what you get. With x0xb0x volume turned mostly up it should be greater than 2V peak to peak. If you're just using earbuds to test you'll hear it.
b) Test it again at pin 1 of SW302. This is before distortion so should sound same as 1). If OK go to step 3)
c) Test it again at IC301 pin 1. It should now be distorted depending on setting of Amount pot. If ok,
d) Test it again at IC301 pin 7. It should sound nice and overdriven, adn quite loud. If ok,
e) Test at SW302 pin 4

see at what point you lose signal.

[kroutshev]
Sorry Brian, i'm not very clear, i think i've lost my brain into x0x pcb ...

The main problem is there's no signal on J7 on mainboard. I have copy previous Alex's post and that's why you see "1) The signal is coming in good at pad B =>" but it's not true in my case.
I have begun to make these tests and i have 0V on J7 of the mainboard Pin1, Pin2 and 3.
That's why it's normal that overdrive doesn't work there's no sgnal to PadB obviously. I think it's not a problem from x0xio board but into my mainboard and near J7. Because in troubleshooting post Phono had same problem with low output and problem with J7. I think that i have the same problem between low output and overdrive failed.
I'll try with VCO and VCF jack out tonight !!
Thanks.

Ok Brian about mix out, from vco jack out i've got good level but vcf jack out is wrong, volume is very low.

[bcbox]
ok, I see, you just built the whole x0xb0x with the mod so you don't know exactly where it's gone bad.
Since you have the VCO up and running I would test the VCF next. Do the tests as shown in the x0xb0x build manual and see if you get the correct waveforms (do you have an oscilloscope?). When doing these tests you won't apply 3V to R90 because your x0xb0x is already asembled. Instead you simply put the x0xb0x in keyboard mode and play the high C note.

There are some posts in the Making x0x forum that tell you what the voltages are at various points in the VCF section. This helps tremendously in finding problems. See if you can find those posts, then you can just use your multimeter and probe around. It seems to me you probably have a bad connection somewhere.

[kroutshev]
Hi Brian,
i have resolved my low volume problem. It was R109 and R112 which had bad values, i have changed them for resonnance boosting but not as given in manual.
I have soldered 10 K resistors and my x0x have good volume now.

But overdrive still doesn't work. I have checked J7 and no signal ...
I will check schematics that you have sent me !

Thanks.

The thing that i don't understand that if there's no signal on J7, overdrive can't work ? the problem is before x0xi0 ? i have to look before J7 mainboard, isn't it ?
Thank you Brian.

[bcbox]
if you don't have signal at pin 1 of J7 then you shouldn't have sound at the main output of the x0xbox. Whether or not the overdrive/distotion circuit is working at this point is irrelevant.
For piece of mind you could do a quick test by hooking up J7 back to stock x0xb0x specs. Simply hook the wires from the x0xb0x mainboard to the x0xb0x I/O board as shown in teh x0xb0x build manual when buildinga stock box. This effectively bypasses the x0xi0 distortion/overdrive circuit. See if you have output.

[kroutshev]
Hi Brian,
configuration of J7 in mainboard : Pin1 => Pad B of x0xi0 board
Pin2 => nothing
Pin3 => Pin3 of J7 I/O board
Test1 => Effect Off Pin1 J7 mainboard => 0 V ; sound of mix output with right volume.
Test2 => Effect On Distorsion On Pin1 => 0.53 V ; sound of mix output higher with effect than test 1
Test3 => Effect On Overdrive On Pin1 => 0 V ; sound of mix output very very very low.

I have checked many times to be shure.

[bcbox]
It sounds like you have everything working except the overdrive.
If you could record a few seconds and post the results I can confirm if it's sounds correct.

As for the readings at J7 Pin1 are you using a voltmeter? I know you said you don't have an oscilloscope. Since the audio signal is AC and pretty low level I think you're readings are not accurate. The signal at J7 Pin 1 should be exactly the same regardless of whether the effect is on or off, or which type of effect is selected. This is because this connection point is before the effect. Just to verify recheck the two points below to make sure you don't have these hooked up backwards.

1. x0xb0x mainboard J7 Pin 1 goes to x0xi0 board pad B.
2. x0xb0x I/O board J7 Pin 1 goes to x0xi0 board pad A.

If this is OK here's what to check next.

1. Make sure IC301 is installed in correct orientation.
2. Check voltage at IC301 Pin 8. Should be ~12V.
3. Check voltage at IC303 Pin 3. Should be ~6V.
4. Check voltage at the connection of SW303 Pin 2 and R307. Should be ~6V.
5. Check or listen to signal at Pin 1 of IC301. You should have a loud distorted signal.
6. Check or listen to signal at Pin 7 of IC301. You should have a loud distorted signal (similar to step 6 but some high frequency now filtered).
7. Check or listen to signal at Pin 4 of SW302. It should sounds exactly same as step.

The pin configuration for the toggle switches is indicated on the PCB by a '1' next to pin 1 on the PCB.
As viewed on the last page of the install manual it looks like this....

1 4
2 5
3 6

[kroutshev]
Oh yes i have to mesure in Ac voltage ... ok i understand !! Thanks for your patience and sorry for my lack of knowledge ...
I check that ...
Thanks Brian !

ok this is that i have tested =>

1. x0xb0x mainboard J7 Pin 1 goes to x0xi0 board pad B. OK ~ 3.08 V
2. x0xb0x I/O board J7 Pin 1 goes to x0xi0 board pad A. OK ~ 3.18 V

If this is OK here's what to check next.

1. Make sure IC301 is installed in correct orientation. OK
2. Check voltage at IC301 Pin 8. Should be ~12V. ~3.63 V
3. Check voltage at IC303 Pin 3. Should be ~6V. ~2.80 V
4. Check voltage at the connection of SW303 Pin 2 and R307. Should be ~6V. ~1.20V
5. Check or listen to signal at Pin 1 of IC301. You should have a loud distorted signal. Nothing.
6. Check or listen to signal at Pin 7 of IC301. You should have a loud distorted signal (similar to step 6 but some high frequency now filtered). Nothing
7. Check or listen to signal at Pin 4 of SW302. It should sounds exactly same as step. Nothing

Every functions are working correctly appart overdrive. As you can read, Voltage are not good :-(.

[bcbox]
OK, at least you know there's a problem and we can troubleshoot it. You'll appreciate it more when it's all done and working. :wink:

If the 12V supply is not good then the distortion effect is problably not right either.
Check the voltage accross pad D and pad C.

pad D is the output of the 12V power supply.
pad C is ground.

it should ready ~12V.
if it doesn't check and make sure the following capacitors are in the correct orientation and value:
C329 1uF, (+) towards top of pcb
C330 10uF, (+) towards top of pcb

check to make sure TM302 is the 100 Ohm trimpot (it says 101 on the side of it).
check to make sure R350 (150 ohms) and R351 (1.24k ohms) are the correct value.
check to make sure the connection sis step 6 of teh install manual are done correctly.

[kroutshev]
Ok, results of test :

it should ready ~12V. No ~0V but continious 12 V
if it doesn't check and make sure the following capacitors are in the correct orientation and value:
C329 1uF, (+) towards top of pcb; OK
C330 10uF, (+) towards top of pcb; OK

check to make sure TM302 is the 100 Ohm trimpot (it says 101 on the side of it); OK
check to make sure R350 (150 ohms) and R351 (1.24k ohms) are the correct value; OK
check to make sure the connections in step 6 of the install manual are done correctly; OK

But if i check on D42 and R179 i havn't ~12 V ! Is it normal ?
I continue my Grail Quest :-)

[bcbox]
About D42 and R179 those readings can vary somewhat. The voltage accross D42 (same as C5) could be anywhere between 10V and 15V DC. To test the x0xb0x power supply's you should check these points.

1. IC23 Pin 7: 5.33V
2. IC23 Pin 1: ~11.9V

OK, so it seems like the 12V supply on the x0xi0 board is working OK because you have 12V at Pad D.
Recheck the voltage again at IC301 Pin 8. This has to be 12V since it is connected directly to pad D which is the output of the 12V supply. Before you measured 3.63V at IC301 Pin 8, but this time you measured 12V at Pad D so one of them is wrong.

Can you upload a sample of what your x0b0x sounds like with the distortion on and then with it off?
If the x0xb0x sounds ok with the effect off and it sounds ok with distortion on then that will help with troubleshooting the overdrive.

[kroutshev]
Ok Brian, i've recorded samples as you ask me.
First one x0x without effect => http://dl.free.fr/t6Lb2DrPb
and second one with distortion => http://dl.free.fr/vuHhcvryc

I've realized that volume of mix out is higher without effect, there's a lot of noize in distortion mode and when x0x not start. Even distortion is working, i think that i have a problem with twice. Filter seems to be ok.
Another thing, when i measure voltage in alternativ mode i have to take ground, in C pad ? can you explain me with precision the method to mesure in alternativ mode.

OK, so it seems like the 12V supply on the x0xi0 board is working OK because you have 12V at Pad D.

I've got 12V but in continious voltage only not in alternativ.
But i'm afraid to make a mistake when i measure alternativ voltage, please specify me where i take the ground.

Thanks a lot.

[bcbox]
There's a lot of noise in the distortion. Yours does sound more noisy than typical. It can get very noisy if you have the Amount control and the Tone controls all the way up. When the tone control is at the maximum I have left a lot of high frequency content so the high frequency is not filtered much. Also, there is a lot of gain in the circuit. Try turning the Amount control and Overdrive control to 50% position and see if it's much better, this is equivilent to the max settings on typical distortion units.

Other than the noise the distortion sounds correct. It's a very compressed sound with a bit of a hole in the midrange frequencies. The overdrive is more gentle and more even frequency response.

About testing the voltages with DC or AC setting you should be doing all voltage measurements with your multimeter in DC mode. The only signal that you need to test that are AC is the actual audio signals, and this should really not be done with a meter but instead by using an oscilloscope or listening to the signal. I know you don't have an oscilloscope so you can actually make a cable to plug into your mixer and listen to the signal at various connections.

Do these tests first:

1. Put your multimeter in DC Volts mode.
2. Check again IC301 pin 8. it should be 12V
3. Check IC303 pin 3. It should be 6V.
4. Check SW303 pin 2. It should be 6V.

If this is OK then do this...
1. Get an extra cable and cut off the end so that you can plug one end into your mixer and use the other end to probe the circuit.



2. Connect a capacitor to the center conductor of the cable. Any capacitor will do, 1uF/10uF/100uF the value is not important. Connect the (-) side to the cable. You can use another type of capacitor too if that's all you have... tantalum or polyester type is ok. This is just to eliminate any DC bias from the signal. If you don't have an extra capacitor it is ok not to use it.
Next, connect a piece of wire to the shield...



3. Connect the wire from the shield to an extra pad C on the x0xi0 PCB.



4. Now you can use the other end of the capacitor to probe and listen to the audio signal.



Now you can plug the other end of this cable into your mixer so you can actually hear the signal as you probe around.

1. Listen to signal at pad B. You should have signal here because the Distortion works. This point is before the overdrive/distortion circuit.
2. Select Overdrive with 'Type' switch.
3. Probe the signal at IC310 pin 1. You should hear the distorted signal at high volume.
4. If you hear good signal in step 3 then probe again and listen for signal at IC301 pin 7. you should still hear distorted signal at good high volume.
5. If you hear good signal in step 4 then probe the signal at pad A. This is the output of the overdrive and you should hear the signal here too.

Let me know how this works out.

[kroutshev]
You're absolutly right :-) !! I have found the problem !! The bad guy is IC301, with magic probe i have tested as you've explained me and no signal on pin7 !! I have removed OP275 from his socket and replace by another one from 2nd kit and same thing :? !! Pin 1 ok but no sound on pin7 !! i remove part by the second OP275 of second kit and allelulia sound is coming :D ! I've got signal on pin7 and from mixer out too !!!
I'm so happy i have played a live perform with 303 and replace by x0xi0 and my machinedrum !! very good sound and wide sound range with your kit !! I'm very very impatient to have full kit :D !!
Now i havn't OP275 for second kit but we'll see that when you send me top panel kit !!
Brian a huge thank for your patience and your very good advises and debugging tools.
Bye, it's time for me to sleep !!
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Excessive noise
[first posted June 15 2009]
[lord.bix]
The noise seems to be a mixture of leaking noise comes from VCO and a realy silent noise of clicking or high lfo generated noise. Could be, that it comes from untrimmed xoxbox, i will trim it finally today (evening). [bcbox] The buzzy waveform noise is most likely noise coming in at the VCA input. The easy way to test is to take the VCO out and VCF out signal from the new rear jacks and listen. Chances are there is no noise. If this is the case let me know and I can help you eliminate it. For the clicking noise do you still hear it even if the volume control is turned all the way down? Does it seem to coincide with the gate signal going on and off?
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Excessive clicking
[first posted August 7 2009]
NOTE: This issue has been elininated by using the small 'mixer' PCB remotely located. If your kit didn't come with the small 'mixer PCB kit' contact me.
[dnigrin]
I *do* hear the clicks even if I turn the volume all the way down. I made some audio demos. This first one starts with all settings for "stock" x0xb0x. It's a square wave on VCO 1, and with resonance, env mod, and decay all the way down. Cutoff starts at its max, goes gradually down to its midpoint where I leave it for several seconds, then gradually all the way to its min. Once there, I then also turn the main volume down to min (from max where it started). You may have to turn your listening volume up at the end to hear the clicks, but they're there:
http://soundcloud.com/dnigrin/cutoff-range-and-clicks

The next starts with the same settings. The VCA Attack is then gradually increased - I pause at about the midpoint of its range, then continue to the max setting. As before, you can hear clicks all the way though, but it seems that the behavior is not quite right:
http://soundcloud.com/dnigrin/vca-attack-increase

Thanks,
Dan

[bcbox] ok I listened to the clips and it sounds like you are getting the same type of clicking that I had on one unit and also two other guys have also had. I will add this symptom "clicking" to the top of my troubleshooting list so I can work on it very soon. Also, I have already been working on a test procedure for testing the Full x0xi0 x0xb0x. I won't give a date as to the completion of this file but it will be soon. This will help test a newly built x0xi0. About the white LED try 4.7k or even 10k if you find the supplied value of 1k is too bright. The color will get more yellowish as you move away from its max brightness but should look very good. [update February 2010]
I've finally got around to testing this elusive clicking noise problem that some of you are getting. I found that there can be a few different causes.

1. Gate on LED
The gate on led is tapped off of the gate signal and is not buffered by using a transistor switch like the other LED's. When orignally testing I found I didn't need to. However with the white LED and 1k resistor (R476) I found the low impedance can indeed affect the circuit and cause some very minor clicking. It's very minor and sounds similar to the usual VCA offset cicking. It is sovled by using a 10k resistor for R476. You want a 10k resistor for this white LED anyways to make it the proper brightness and current (~10mA).

2. Gate/Env trigger induced clicking in the VCA and especially the Mixer circuit.
There are a lot of triggers flying around the circuitry. I found that when the x0xb0x mainboard PCB and x0xi0 top pcb are mounted back to back during assembly some clicking can be induced. It happens at the midde/right area of the PCB's where the VCA is at (Note: actually it's the 'mixer' section that is much more prone). This clickign is just trigger clicking, sounds more like digital clicking, a more high frequecy annoying click..click....click; not really a pop per se. You can test this clicking by moving the right area of the x0xi0 top pcb away from the x0xb0x mainboard while playing a pattern during which you hear clicking. Also, this clicking remains regardless of the position of the volume pot, since it's coupling into the mixer stage which is after the volume control. As you move the x0xi0 top PCB closer to the x0xb0x mainboard all these triggers get closer to the 'mixer' circuit on the x0xb0x mainboard and the clicks begin.
Note: The installation of the foil shielding has been deleted as the new mixer PCB solves the issue
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Overdrive and/or Distortion not working, or general problems with x0xi0 rear PCB
[May 10 2010]
I have discovered an issue with the Alpha pots used on the x0xi0 rear PCB. The problem is very simple. The two outer pins of the pots can short to the body if too much solder is used when soldering in the two large lugs. Since the body of the pots are grounded there's the potential to short out those pins.


To check if you have a problem simply take a close look and see if it looks like the outer pins are touching the solder blobs from the legs, and test the resistance between these outer pins and the leg of the pots to verify they aren't shorted out (0 Ohms).
In retrospect I recall several issues from kit builders that I realize now were almost certaintly this problem.
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What are the different types of audible clicking I might experience?
[June 1 2010]
I'm adding this note to help distinguish the kinds of audible clicking.
There are two main types of clicking

- VCA offset clicking
- gate/trigger cicking

VCA clicking is the result of DC offset in the input of the VCA, either the BA662 or BA6110. The voltage of the signal into the VCA is small, so whem amplified this small DC offset can result in a click in the audio output. This is audible as a click or pop at the beginning of each note. This happens in the TB-303 as well as the x0xb0x and x0xi0 kits. Roland specified all BA662 with the best DC offset with the A suffix, so the BA662A are the better performing parts in regards to DC offset [They even further sorted the BA662 in other products with white dots, yellow dots etc]. Even still all TB-303 have this clicking to a varying degree. The range of DC offset in the BA6110 is similar to the BA662A. The clicking can be minimized by selecting a part with a very low DC offset or by minimizing the DC offset by biasing the input of the VCA gain stage (the custom x0xb0x mainboard adds a trimpot for this purpose). The sample below demonstrates this type of clicking at the beginning of notes. It is more audible with x0xi0 or x0xb0x's and TB-303 for which the filter range has been modified since the sound is band limited (low-passed) and the clicking is not masked by full range sound.

VCA Clicking

Gate & trigger clicking is the result of the fast switching times of the gate and trigger signals coupling in the analog audio circuits. This exists in all x0xi0, x0xb0x, & TB-303 but is more of a problem in the x0xi0 kits because of the proximity of the x0xi0 top PCB to the analog audio circuits on the x0xb0x mainboard. The only only significant problem area relates to the mixer circuit. This is the mixer stage after the VCA that mixes the x0x VCA output with the signal coming in from the Mix In jack. This problem has been solved by relocating the mixer circuit away all of the gate & trigger circuits. If you have a x0xi0 kit with serial number below #180 you may want to request the Mixer PCB Kit. Since the clicking is picked up by the mixer stage after  the volume control you will hear this even when the volume control is at minimum. In fact, you don't even have to have any audio from the VCO's at all, only active gates & triggers. This is a good way to determine the difference between this clicking and other types. Below are three samples. In all three samples the volume control of the TB-303 and x0xi0 is at minimum, and the output is recorded straight into a WAV editor through an audio interface with the same gain, so the levels are all the same and directly comparable. What you are hearing is essentially the noise floor of the TB-303/x0xi0 amplified several dB. The first sample is what this clicking sounds like in a TB-303. The second is the worst-case x0xi0 without the Mixer PCB Kit. The third is the same x0xi0 with the Mixer PCB Kit installed.

TB-303 Trigger clicking
x0xi0 Trigger clicking
x0xi0 w/ Mixer PCB Kit Trigger clicking ---

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