Built Xoxbox // NO SOUND

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sequentialmood
 
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Built Xoxbox // NO SOUND

Post by sequentialmood »

Hello Guys,

I've finished to build my first xoxbox bought from xoxshop.de.

Unfortunatly, i don't get any sound from mix out or headphone outputs.
The digital part seems to be ok.

I tried to test different parts (Power supply & VCO) to identify where the problem would come from.

Power Supply
It is correctly outputting 5,33V and 11,8V on J4.

VCO
With the 3V test and cheap headphone test:
- i do have buzz sound on SW1, but when I change its position, the buzz seems to drop in pitch...
- voltage on IC11 pins are the following: 4,64 - 5,33 - 5,33 - 0 - 0,02 - 0,64 - 0,64 - 11,75
- pitch knob seems to work

VCF
The Resonance knob test fails, no sound...

To be honest, i'm pretty lost and don't really know from where to start debugging the whole stuff.
Could you please guys , drive me in the first step to find where the problem (the first) might be ?

Thanks a lot! :D

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mmm
 
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Re: Built Xoxbox // NO SOUND

Post by mmm »

First of all, if the digital side seems to work we'll use this to debug from now on.

Second, do you have an oscilloscope (or can you borrow one)?

At the moment let's try the following: Switch the xoxbox to keyboard mode. Play the low and the high "C" and measure the voltage on pin7 of IC11.

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

Hi MMM,

Thanks for your rapid answer, really appreciate it.

I don't have an oscilloscope, but a multimeter. (i guess i'll have to buy one soon...)

Anyway, here are my voltages on Pin 7 of IC 11 when i tap on keyboard's note (keyboard mode).

Note -- Voltage (V)
C -- 1.99
D -- 2.16
E -- 2.33
F -- 2.41
G -- 2.58
A -- 2.75
B -- 2.92
C -- 3.00

#/b notes seems to works too.
No sound, but from time to time, low and thick bleep sounds when a key is pressed.

Thanks for your help.

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mmm
 
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Re: Built Xoxbox // NO SOUND

Post by mmm »

This shows that the digital side and the DAC are working fine - the oscillator will get a proper CV this part.

Next thing to determine is if the oscillator itself works. Have you tried the "cheap headphone" procedure described in the online build manual? (I don't know if this is also in the xoxshop building instructions.)

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

Hello,

I did the test with the adjustable 3V power supply.
On the switch (SW1), i can hear a buzz (Square, i guess) with the cheap hearphone. Its pitch changes when i play with the pitch pot.

Thanks

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pulsar256
 
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Re: Built Xoxbox // NO SOUND

Post by pulsar256 »

x0xsh0p had problems with fake transistors. Please check the label on the 2SC2291, if it says 89C you'll need to ask for a replacement.

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

Thanks for the info, i've already verified that issue, my transistor is labelled "7ZG".

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

Hi,

I've just redo the VCO test with the "soundcard Oscillo" trick. Here are the screenshots:

Sawtooth on R105:

Image

Square on SW1:

Image

THANKS! :)

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mmm
 
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Re: Built Xoxbox // NO SOUND

Post by mmm »

That means the oscillator is working as it should (and the soundcard oscilloscope is performing well). So let's continue: Measure with the oscilloscope the output of the filter (C14). Set Cutoff to max and Resonance to zero for now. Is there any meaningful signal? It will be much weaker though.

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

Thanks for your great help, MMM!

It seems that i don't have any signal on C14:

CutOff -> Max
Reso -> Min

Image

:(

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mmm
 
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Re: Built Xoxbox // NO SOUND

Post by mmm »

Well, the vertical resolution looks comparatively coarse (looks like a 1V grid); you might want to try this again with a smaller grid (like 100mV or so - if that's possible with this software).

I would also like you to measure (with a voltmeter) the voltage on all pins of Q12 and Q22; and you could measure with the oscilloscope the signal on the "-" side of C17 (again, this is going to be a very weak signal).

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

Here are my voltages:

On C14, with a finer resolution, i still have no signal:
Image

On C17, on the negative leg, i have a really weak signal...
Image

On Q12:
5.33 V
9.83 V
6.12/6.24 V
9.83 V
5.33 V

On Q22:
11.2 V
11.6 V
11.6 V
11.6 V
11.2 V

Thanks!

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mmm
 
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Re: Built Xoxbox // NO SOUND

Post by mmm »

Please check (with the oscilloscope) both sides of R62. The signal should have a very different amplitude on both sides.

sequentialmood
 
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Re: Built Xoxbox // NO SOUND

Post by sequentialmood »

On both sides of R62, i've the same signal amplitude (pretty weak one):

Side 1:
Image

Side 2:
Image

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mmm
 
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Re: Built Xoxbox // NO SOUND

Post by mmm »

That's odd - one side of R62 connects directly to the waveform switch. Please check the signal at the middle pin of the waveform switch (and recheck signal at R105).

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