x0xi0 IO & Overdrive - Install & Troubleshooting
Moderators: Altitude, adafruit_support_bill, adafruit, phono, mome rath

x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Thu Sep 25, 2008 5:11 pm

I merged several old posts into one thread here to make it easier to access Q&A and troubleshooting information on the x0xi0 installation. If your kit is not working or you just have questions please post in this thread. Once the issue is solved I will archive in this first post.
-------------------------------------------------------------------------------------
[first posted July 25 2008]
please note that I have found an error in the Install Manual Rev1.01.

Installation Step 14 show the wire connected to the wrong side of R60

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.
-------------------------------------------------------------------------------------
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)
-------------------------------------------------------------------------------------
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)
-------------------------------------------------------------------------------------
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.

all links have been updated to link to Install Manual Rev1.06

Image
-------------------------------------------------------------------------------------
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...
1.0µF 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]
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
Audible noise/buzzing with kit Installed

[first posted July 28 2008]
[Computer Controlled]
There's just a bit of harmonics in the sawtooth that wasn't there before.
Sawtooth = some odd harmonics that are in the back ground. Maybe noise, i'll make a recording so you can hear. It's REALLY slight, barely audible.

[bcbox]
it's probably noise - which we should able to reduce.
a sample would be great help.

[Computer Controlled]
Here ya go.
http://acid.experimedia.net/x0xb0xsawtoothoddness.mp3

It's more audible in the higher note. I switched to squarewave as well, so you can hear it's only on the sawtooth.

[bcbox]
For the extra bit of noise you're hearing with the saw wave it's definitely a bit of noise buzzing through. I just listened to it again at home on my studio monitors.

[phono]
sounds like some leakage to me, must be before the filter also since its doesn't seem affected by the cutoff, also theres some nasty random pops (or is that the recording)

[rarara]
hopefully either brian or someone else who has done the mod can help me get to the bottom of my problems.
there is a slight high pitched buzz which acompanies the saw wave. i have added another ground to the free 'c' pads but that didn't make a difference. its not that bad to cause me to worry about it (no idea if it was there pre-mod) as its really only been noticed when i have been using keyboard mode to test that gate open mod

[bcbox]
I've had two other people point out the same thing and I've had a couple x0xb0x's I did where I found the same. It vary's somewhat, and can also be present in a stock x0xb0x, but the chances of it happening with the mod is greater because the VCF Output is sent to the new PCB and then back to the VCA input. What you're hearing is technically capacitively couple noise being induced to the input to the VCA, since it has a very high input impedance and then the signal is amplified. You basically hear sort of higher harmonics of the saw wav creeping in. I've written what I guess what you would call an addendum to decribe how fix this, but I'll describe as briefly as I can below.

You can do a simple test to confirm the noise is coming at the input of the VCA:
Take the VCF Output and plug it into your mixer. I guarantee you there's no extra noise or buzz there. Try it ;)

This verify's it the VCA. To fix it you need to use a guarding technique (like shielding). The thing is figuring out where to do this and how to do it. Here's what you want to do.

1. Take a 7" piece of single conductor shielded cable. A typical crappy RCA cable works well because they're generally small diameter and not too bulky and you can get the wires where they need to go [edit] I am now shipping kits with a specifc shileded cable (Mogami W2330) that works excellent, better than typical low grade shielded cable. See further down for more details.
2. Strip both ends about 1/2" or so, so you have the single conductor and the shield to connect.
3. Cut the shield on one end of the cable at the base of the insulator because it won't be used - a shield is only connected on one side. Like this pic below:

Image

4. Remove the 7" piece of white wire from Step 9 in the Install proecedure. This is the wire going from Pin 3 of IC15 to pad J on the x0xi0 PCB.

5. Now you're going to connect the single conductor from this new wire to pin 3 of IC15 and the shield to pin 2 of IC15, like this pic below:

Image

...and closer up
Image

6. Then connect the other side of the wire to pad J on the x0xi0 PCB.

This may look funny at first but what it's doing is eliminating the noise from being picked up by that cable run. The x0xb0x is run off a single supply so there is a bias voltage used through out, and there is a certain voltage at the inputs the VCA that's not equal to 0V. Also, both inputs of the VCA, the inverting and non-inverting, are ideally at the same potential since it has such a high input impedance (basic op amp principles). So you're guarding that cable run from picking up any stray apacitance. You should find the high frequency buzz goes away.

There will still be some noise since the signal to noise is poor in a x0xb0x/TB-303, but you should find the buzzing of the higher harmonics of the saw wave is gone.

This shielding technique can be improved even more by running a second shield from the analog ground connection pad C on the x0xi0 PCB (right next to pad J) to the other end of the cable, and leave the shield open on the VCA side of the cable. This would be a double shield technique. I left that extra ground pad there for this reason when I designed the pcb, I thought ahead that some noise issues might come up.
To do it this way you would most like use a cable with a twisted pair and a shield, using one of the twisted pair as the second shield. I won't get into it now, try what I describe above and let me know how it goes!

[ok gotta to go to sleep... yes I do sleep sometimes .. usually during the day........at work!]

[edit April 17 2009] Note that I started shipping kits with a specific high grade shielded cable, Mogami part# W2330. I did some further tests and found I got superior noise rejection with this cable, moreso than the typical low grade stuff I was shipping with kits #43 to #81. If you have a kit below #81 and want a piece of this cable send me an email or pm and I will send a piece out. This is a very sensitive input so it's good to do everything you can to eliminate any possiblity of noise.

[rarara]
brian, thanks again - brilliant stuff.
i added the shielded cable and the saw wave buzz has now gone, so that means everything is working as it should.

[Booster]
Hi Brian,
Will these new wires go into the same holes (2 and 3) on IC15B if you have a BA662A fitted?
EDIT:-
Just taken my x0x apart, the single conductor goes to pin 1, shield to pin 2. This has completely removed the light buzzing I was getting.
Nice one Brian.

[bcbox]
yes that's correct. good to hear it's fixed the problem for you guys.

[Computer Controlled]
Well, i replaced the diode, and installed a shielded cable. You were right, no more saw tooth fuzz =o]
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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).
-------------------------------------------------------------------------------------
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 and 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).
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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
-------------------------------------------------------------------------------------
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).
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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 and 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.
-------------------------------------------------------------------------------------
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

Image

[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.
-------------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------------
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!
-------------------------------------------------------------------------------------
Last edited by bcbox on Sun Apr 19, 2009 12:57 am, edited 4 times in total.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by crx091081gb on Fri Nov 14, 2008 8:07 am

Slide In not sliding

Hi Brian

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). I was looking at the x0x vco schematic on the wiki and noticed that slide in the x0x is normally high and brought low to allow analogue switches IC12C and D let the pitch CV across C35.

Reading the user manual I see the "The signal from the tip of the Slide In jack goes through R331 to the base of Q29".

Is this why slide isn't working, because the xox slides on low voltage rather than high? Or have I installed it in a retarded fashion, the other cv's (pitch gate and accent, haven't tried filter yet) seem to work as does the distortion.

I read the sticky about the install manual showing the slide in Step 14 black wire attached to the wrong side of R60, I assume that has been corrected in manual 1.05? That's what I used when I assembled the mod.

Help?

EDIT - I've just hooked up a volt meter to measure the voltage at the long leg of R60 where the black wire from W is connected and it's 0.64 for slides whether they're triggered by the x0x sequencer or from the cv in. The slide cv in can make the pitch slide when the pitches are from the x0x sequencer just not from the pitch cv in. Is this a fault or a feature, is the pitch cv in coming in after the slide circuit ? Gonna poke about more.

EDIT AGAIN - The pitch in is connected to pin 8 of IC12 as per instructions and I'm flummoxed as to why I can trigger slides with the slide cv in when I'm using the sequencer to provide the pitch but not when I use the pitch cv in. I know it's going across C35 cos when I check the voltage at C35 and slide is on pitch drops due to the crappy input impedance of my meter (this happens whether I use the pitch cv in or the sequencer).
crx091081gb
 
Posts: 54
Joined: Wed Sep 17, 2008 1:50 pm

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Fri Nov 14, 2008 2:03 pm

I just took a look at the schematics & I don't see why this is hapenning. I don't believe I ever tested slide in with an external CV so it could be a valid problem. I'll try to recreate it tonight when I have a some time.
btw, you should have received the schematic for the mod when you bought your kit. If you didn't let me know your email and send it over. It'll make it easier to figure out what's going on.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by crx091081gb on Sat Nov 15, 2008 8:42 am

Hi Brian, yeah I never got the schematic so I emailed you my address.

I was wondering if the problem could be my pitch cv source, it's a custom made midi-dac that I've put together using the output of an analogue systems AD5668 DAC chip, the outputs aren't connected across resistors but straight to the chip so perhaps there's too much current flowing into C35 for sliding. Does that make sense? Probably not. I've got a kenton pro dcb midi retrofit for a juno 60 with an aux cv output which chucks out 11 mA out into my multimeter. My midi-dac puts out 28 mA. These measurements are made without the cable connected to anything other than the meter. What kind of current should an ideal cv supply?

I'm electronics literate only up to a point, this midi-dac is my first big circuit, it's eventually going to allow me to play my x0x on my double bass (using a pitch tracker based on a bass tuner schematic I dug up). I'd really like the slide to work with pitch cv input as the double bass being fretless is an inherently slidey instrument.

AD5668 link
http://www.analog.com/en/digital-to-analog-converters/da-converters/AD5668/products/product.html

I'm going to listen if using the kenton for pitch cv gives a better slide.

EDIT - The kenton pitch cv doesn't slide either. Has anyone else had the slide working with pitch and gate cv inputs being used at the same time ?
crx091081gb
 
Posts: 54
Joined: Wed Sep 17, 2008 1:50 pm

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Sun Nov 16, 2008 5:20 am

Robin,

I haven't taken the time to check it out yet. The current draw of the cv input is minimum, so your cv source is fine.
I'll most likely get to it sunday afternoon.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Mon Nov 17, 2008 4:13 am

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. 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.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by crx091081gb on Mon Nov 17, 2008 5:04 am

Cheers Brian, I'll be upgrading though looks too good to miss. I'll just swap the resistor to 100K till your kit comes out.

P.S. Am I on the list ? If not can you add me ? :wink:

EDIT - Just swapped the resistor for 100K and slidey slidey. Wahey
crx091081gb
 
Posts: 54
Joined: Wed Sep 17, 2008 1:50 pm

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Mon Nov 17, 2008 1:39 pm

P.S. Am I on the list ? If not can you add me ?

you are now!

Just swapped the resistor for 100K and slidey slidey. Wahey

nice. I'm glad you found the problem.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by crx091081gb on Mon Nov 17, 2008 4:17 pm

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?
crx091081gb
 
Posts: 54
Joined: Wed Sep 17, 2008 1:50 pm

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Mon Nov 17, 2008 5:17 pm

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.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by crx091081gb on Tue Nov 18, 2008 4:58 am

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
crx091081gb
 
Posts: 54
Joined: Wed Sep 17, 2008 1:50 pm

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Tue Nov 18, 2008 7:26 pm

great news.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by crx091081gb on Sat Nov 22, 2008 7:14 pm

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.
crx091081gb
 
Posts: 54
Joined: Wed Sep 17, 2008 1:50 pm

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by charlie_says on Sat Dec 06, 2008 6:27 am

I was just soldering in the diodes, and on close inspection the 1n5237 appears to be a 1n5238
I've looked at the datasheets and it seems like the difference is minimal (at least in number terms to my layman's eyes) but can anyone confirm that it's ok?
charlie_says
 
Posts: 214
Joined: Sat Jul 15, 2006 6:33 am

Re: x0xi0 IO & Overdrive - Install & Troubleshooting

by bcbox on Sat Dec 06, 2008 6:50 am

it's ok, I shipped the 2nd run with 1N5238.
It's just an 8.7v zener vs. 8.2v zener.
It's used for CV protection for the CV Input.
bcbox
 
Posts: 587
Joined: Thu May 25, 2006 12:30 am