x0xi0 Full Kit - Install & Troubleshooting Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

[bcbox]

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?

[phono]

stickied

[lord.bix]

Hi Brian,

i have tested it tonite. The VCO Out is fine, the VCF out is fine as well. Than i tested the gear within my studio and figured out, that the noise is only on headphone outs. So it seems to be a headphone problem. I only have a clicking sound, whic is issued by VCA i guess. Is that sound normal? I will check with headphone out.

Another question i have is, the assembled devices has not the power in bass frequencies like my other xox'es. It misses a bit the pressure from the down.. what might be the reason for it? (May be its because i stuffed it fully with AP's? the others only have P's with only a gain of 260)

(one other small problem i have, but it has nothing to do with xoxio.. lol.. i loose a bit from the rotary switch, so that only activates every second selection..)

/Marco

[bcbox]

I only have a clicking sound, which is issued by VCA i guess. Is that sound normal?

There is a normal amount of clicking from the VCA that you can get with a normal x0xb0x or TB-303. However, I did get some excessive clicking on one of my x0xi0 boxes that I did not figure out yet (I'm in the process of moving and my studio is all packed up!). You can tell this because you can still hear the clicking when the volume is turned all the way down.

Another question i have is, the assembled devices has not the power in bass frequencies like my other xox'es. It misses a bit the pressure from the down

I haven't had this problem. Did you replace C20 and C21 with the 0.1uF caps? It should actually have an octave more bass than a stock x0xb0x.

[lord.bix]

Hi Brian,

regarding the VCA, its not there if i turn down the volume.

i soldered the 0,1 red caps in for c21 and c20. My xox has 0,1 caps in that place as well. If the resonance is turned all way down, it sounds good, but if i go with resonance over 25% its like all bass signal is killed. I know its designed like that, that xox/303 looses bass signal with turned up ressonance.. but this sounds like its totaly gone. I even miss the pumping sound i usually get with accented notes and a high ressonance and cutoff quite down...

Could this resulted by a el-cap i soldered in the wrong direction?

EDIT:

Do you have a idea how to fix the noise on the headphone plugs? I will check with oszi today.

/Marco

[lord.bix]

Hi Brian,

i have recorded the following sound sample to show what kind of noise i mean.

sorry for the sendspace link, have no idea where else to upload. http://www.sendspace.com/file/ngupe3

I recorded in the following steps:

- turn all values to original xox. cut 0, res 0, decay 0, env 100, acc 0
- turn vco1 and vco 2 off
- start xox
-> now you hear the clicking and noisy sound i mean.. (i have used prfessional devices for analog digital conversion, so its not the ADC)
- turn on vco1
-> now you hear that there is almost no sound.. no pumping bass

*1
- go with cutoff to 100
- go with accent to 100
- go with cutoff to 0 again
- put accent and env fast to 100, and go down with cut to 0 and back to 100
- turn all values back to start
*1end

- turn off vco1 and turn on vco2
- same procedure as *1

-> you can hear that vco2 is even more silent in bass section

- turn both vco and compare it.. vco2 is the more edgy one.. it does not sound so smooth like vco1

- turn all vco's down.. play with xmod, vco fm and track knob..
-> noise changes. so i gues its somewhere a leak

So now my questions:

- How i get rid of the noise?
- Why i dont have the pumping bass like i expect from xox (its not the vcf tune pot, i have checked it)?
- Why vco1 and vco2 sound that different? Its the AP's i have installed? or a tuning issue with the width?
- where this edgy distorsion effects, which sound like bad ADC xould come from?

So many regards

/Marco

[bcbox]

- How i get rid of the noise?

I just listened to the sample but only on my crappy laptop speakers so couldn't hear everthing. The clicking noise sounds like the VCA, you can try to trim it out by adjusting DC offset. I will listen again tomorrow on a real system. It sounds like you have enough experience with other x0xb0x's to say that this noise is worse or different than other ones.

- Why i dont have the pumping bass like i expect from xox (its not the vcf tune pot, i have checked it)?

I'm not sure about this one. The whole sample doesn't sound right so there's definitely problems. How does it sound if you listen to the VCF out? does it sound better/correct? Double check R121 & R122 and make sure that the resistor values are correct and were not swapped by accident.

Why vco1 and vco2 sound that different? Its the AP's i have installed? Where this edgy distorsion effects, which sound like bad ADC xould come from?

The VCO's should not sound very different. At most the square wave may have a slightly different character. From listening to the sample there is something wrong. There is also a lot of distortion as you mentioned (is this the headphone output only?) Listening to the VCO Out and then VCF Out the sound should be very good, clean with no noise at all. If the VCO's still sounds very different, distorted or funny check to make sure C405 & C406 are installed with correct polarity. Also check pad 6 and pad 9 on the x0xi0 Top pcb and make sure they read ~5.33V and ~11.9V (these pads are connected to the stock x0xb0x power supply) [Note: you can use any pad C for ground - all pad C's on x0xi0 pcb's are analog ground] Also check pad D on the x0xi0 Top pcb and make sure it reads ~11.9V. This is taken from the new 12V power supply that powers the whole x0xi0 mod except the VCO2 core circuitry (it does power IC401 in the VCO circuit).

the chirping at the end of the clip is just the filter self-oscillating. This can happen when resonance is close to max. You should not be hearing that much if the resonance control is less than 75% or Hi Resonance is turned on. The high-rate modulation you hear when VCO FM pot is adjusted (and VCO's turned off) is also just the filter cutoff being affect by the VCO waveform while the filter is self-oscillating. Also the filter tracking knob also effects the filter cutoff and will be audible when filter is self-oscillating.

I'll listen to the sample again tomorrow on real system and I'll be able to hear the problems better.

[lord.bix]

Hi Brian,

thank you for the fast post. I will check all these comments by you, but i am not sure if i can make it today. I am on a business trip. May be i can do tonite.

I am realy impressed by your responsivness and your dedication to help. This is outstanding, dude!

/Marco

PS:And yes, i have more xox than these at home.. lol 3 plus one 303. So i know how it should sound.. :D

[xjn]

I'm having a problem..

I can't find the 1n5232B called for in the parts list on page 3 of the install manual.

I have a single diode in a bag all by itself, suspiciously singular like the 1N5232B, but the part number on that seems to be something more link 237B... I'm pretty sure that really is a 7 there and not a messed up 2...

is this the same part, am I reading it wrong? a sub maybe? Confused and only on the first page of assembly...

thanks.

[bcbox]

I can't find the 1n5232B

yes, the part in the bag by itself is a 1N5237B or 1N5238B. It's spec'd for either one that's the zener you want.

[xjn]

excellent, thank you very much... tried to look up the subs for it, put in the part # and came up with some voltage regulator and got confused.. probably read the B as an 8 off the part...

thanks again.

now what do these little stripey color things on the blue thingies mean? jus kiddin..

[lord.bix]

- How i get rid of the noise?

I just listened to the sample but only on my crappy laptop speakers so couldn't hear everthing. The clicking noise sounds like the VCA, you can try to trim it out by adjusting DC offset. I will listen again tomorrow on a real system. It sounds like you have enough experience with other x0xb0x's to say that this noise is worse or different than other ones.

The record sample came from the mix out output. Distorsion was turned off.

- Why i dont have the pumping bass like i expect from xox (its not the vcf tune pot, i have checked it)?

I'm not sure about this one. The whole sample doesn't sound right so there's definitely problems. How does it sound if you listen to the VCF out? does it sound better/correct? Double check R121 & R122 and make sure that the resistor values are correct and were not swapped by accident.

As mentioned, record from mix out. The sound is not much better from vco out.

I have checked R122 = 64,1 k (why ever this is 64,1k instead of 68 i dont know, should i fix it? But there is no 68k left)
R121 = 150k
R59 = 100k

I have made an oszi pic on the poti for vco1 and vco2. The signal looks little bit strange as soon as the sqr signal has the step in the beginning. Even the VCO2 has a lower signal as i recognize it from listening and the level.
EDIT:
The signal comes out of the VCO on the xox mainboard is fine and undistorted btw.
EDIT END:

EDIT2:

Just have checked the signal again.. Its undistorted as soon as the vco1 level stays down.. as more as volume is getting up, as more distorsion and lower level it gets. Same for VCO2. So there is a shortage or a something wrong behind the pot.

EDIT2 END:

VCO1 sqr / saw (Voltage per oszi step are 5V)



VCO sqr/saw (Voltage per oszi step are 5V)

Why vco1 and vco2 sound that different? Its the AP's i have installed? Where this edgy distorsion effects, which sound like bad ADC xould come from?

The VCO's should not sound very different. At most the square wave may have a slightly different character. From listening to the sample there is something wrong. There is also a lot of distortion as you mentioned (is this the headphone output only?) Listening to the VCO Out and then VCF Out the sound should be very good, clean with no noise at all. If the VCO's still sounds very different, distorted or funny check to make sure C405 & C406 are installed with correct polarity. Also check pad 6 and pad 9 on the x0xi0 Top pcb and make sure they read ~5.33V and ~11.9V (these pads are connected to the stock x0xb0x power supply) [Note: you can use any pad C for ground - all pad C's on x0xi0 pcb's are analog ground] Also check pad D on the x0xi0 Top pcb and make sure it reads ~11.9V. This is taken from the new 12V power supply that powers the whole x0xi0 mod except the VCO2 core circuitry (it does power IC401 in the VCO circuit).

the chirping at the end of the clip is just the filter self-oscillating. This can happen when resonance is close to max. You should not be hearing that much if the resonance control is less than 75% or Hi Resonance is turned on. The high-rate modulation you hear when VCO FM pot is adjusted (and VCO's turned off) is also just the filter cutoff being affect by the VCO waveform while the filter is self-oscillating. Also the filter tracking knob also effects the filter cutoff and will be audible when filter is self-oscillating.

I'll listen to the sample again tomorrow on real system and I'll be able to hear the problems better.

I have checked the voltage on PAD6 = 5.33 V and on pin PAD9 = 12,09 V. The C405 and C406 seem in the direction its printed on board and in documentation.

Additionally i recognized that the IC305 gets very hot.. not burning hot but hot enough thatit hurts on fingers.. i guess temprature of 55-60° Celsius.
I have made a pic of the xox build, that you may have a look if i made a general error while building it.

a higher resolution pic is found here: http://www.sendspace.com/file/dmvnyi


Thank you in advance.

1000 Thanks and Regards

/Marco

[bcbox]

The waveform problems should be fixed first. The noise problem is coming from the VCA that can be fixed as well after you get the VCO’s working.
The waveforms are not correct, so those need to be fixed before moving on to anything else.

Step 1. Test each waveform output.
1. Select VCO1 & VCO2 waveforms as saw.
2. Adjust VCO1 & VCO2 Level to minimum.
3. make sure VCO sync is off (switch to left).
4. Plug a cable into the VCO Out jack. This will open the circuit between the VCO’s and VCF.
5. check the waveform at pin 3 of VR405. This the waveform directly from VCO1.
6. check the waveform at pin 3 of VR406. This the waveform directly from VCO2.
7. Do the same with square wave selected.

Does VCO1 look ok?
Does VCO2 look ok?
If VCO2 still looks funny goto step 2.

Step 2. Eliminate VCO2 linear freq modulation inputs.
1. Remove wire from pad 1 on the x0xi0 top pcb.
2. make sure Xmod control is at minimum.
3. select Xmod source as “1-2”
(This removes all linear frequency modulation inputs to VCO2)
4. check the waveform at pin 3 of VR406.

Does it look ok now? If not we’ll have to test the core of the VCO waveshaping circuits.
As for the noise that can be eliminated by making some minor changes to the VCF Out/VCA In circuits. We'll get that after we have the VCO's working properly.

[lord.bix]

Hi Brian,

have done the following steps:

Step 1. Test each waveform output.
1. Select VCO1 & VCO2 waveforms as saw.
2. Adjust VCO1 & VCO2 Level to minimum.
3. make sure VCO sync is off (switch to left).
4. Plug a cable into the VCO Out jack. This will open the circuit between the VCO’s and VCF.
5. check the waveform at pin 3 of VR405. This the waveform directly from VCO1.
6. check the waveform at pin 3 of VR406. This the waveform directly from VCO2.
7. Do the same with square wave selected.

Does VCO1 look ok?
Does VCO2 look ok?
If VCO2 still looks funny goto step 2.

Step 2. Eliminate VCO2 linear freq modulation inputs.
1. Remove wire from pad 1 on the x0xi0 top pcb.
2. make sure Xmod control is at minimum.
3. select Xmod source as “1-2”
(This removes all linear frequency modulation inputs to VCO2)
4. check the waveform at pin 3 of VR406.

I think i have run behind a phantom. The VCO's (both working properly). The curve i saw in low frequencies seem to be in design of them. I have x-checked with my other xox. Same behaviour. So the VCO's themselves are fine.

The problem starts after them =)

Somehow i got rid of the strange curve on the beginning.. I cant reprodue it. Still the sound is in bass octaves very thin.. like described already:

- turn on vco1
-> now you hear that there is almost no sound.. no pumping bass

It seems that the sound itself developed a few.

I have done something additional. I already reported the real heat on IC305. I removed PAD D from TOP pannel. The heat does not occur. So i guess a shortage or wrong soldered IC in that section.
EDIT: The resistance between PAD C and D is 500 Ohm if not connected an off. EDIT END

EDIT2: I have tested more tonite. Found out, that the sound seems pretty much comparable if filter high range is on (region like normal xox). I have checked all resistors and potis in the are, and did not found anything. Swapped Q11. Nothing. I have checked cabling as well. Found out, that PAD H on io is not attached.
EDIT2 END

Sumarize:
- thin sound, but VCO1&2 seem ok
- IC305 heat problem, reason in to pannel

/Marco

[bcbox]

OK, so from what I understand the VCO's sound ok, at least up until the VCF, and the two problems you are still having is...
1. noise (VCA)
2. weak bass in relation to resonance

Let's tackle the the first problem, the noise. it may improve the second problem as well.
Step 1. Change VCF Out/VCA In arrangement
1. Remove R344 on x0xi0 I/O board. Leave location empty.
2. Replace R345 on x0xi0 I/O board with a resistor value between 100k and 220k.
3. Replace R121 on x0xb0x mainboard with 220k (back to original value).
4. Replace R122 on x0xb0x mainboard with 100k (back to original value).
5. jumper the connection between R121/R122 and IC15 (this trace was cut as part of original x0xi0 install).
6. Connect pad K on x0xi0 I/O board to anywhere on the junction of C21/VR4.

This changes the VCA In arrangement so that the VCF signal does not loop back through the VCF Out jack before going to the VCA Input. This eliminates the potential of capacitive coupled noise coming into the VCA input. The difference with this setup is that the VCF Out jack no longer acts as a switched jack, so when you take the VCF Out signal the signal is not openend between the VCF and VCA so the x0x signal goes to the VCF Out jack and straight to the VCA.
I have started to built x0xi0 kits with this arrangement to decrease noise. I am going to be udating the install manuals to follow this new procedure.

Let me know if you have questions on this or need pics to follow.