Strange detuning after not using my x0xb0x for a while
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Re: Strange detuning after not using my x0xb0x for a while

by guest on Thu Apr 19, 2012 2:34 pm

make sure you have a good 12v adn 5.333v on j4
before you reconnect anything
once you have those good powersupply voltages
then check the cv again
its possible chips were damaged by too high of voltage
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Re: Strange detuning after not using my x0xb0x for a while

by Apekooi on Tue Jul 03, 2012 7:00 am

Once again apologies for my delayed reaction, I was in my finals for uni. Again I took measurements for the C and F# of every octave and a chromatic scale from C1 to C2. The values marked with a * stayed the same for note on and off. Do you have any idea if, what IC might be broken? Is there a particulary vulnerable one?

Code: Select all | TOGGLE FULL SIZE
      Note on Note off
C0    .650    .635
F#0   1.461   1.461*
C1    1.987   1.987*
C#1   1.767   1.744
C2    2.96    2.96*
F#2   2.46    2.41
C3    2.88    2.86

C1   1.987   1.987
C#   1.385   1.337
D    1.490   1.463
D#   1.527   1.495
E    1.636   1.614
F    1.647   1.618
F#   1.756   1.736
G    1.796   1.772
G#   1.902   1.885
A    2.65    2.65*
A#   2.78    2.78*
B    2.84    2.84*
C2   2.96    2.96*
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Re: Strange detuning after not using my x0xb0x for a while

by MMM on Wed Jul 04, 2012 4:24 am

There are a couple of things that immediately become obvious:

1. The CV is way off near the bottom. C1 is pretty close to 2v, so that's ok. All other C's should be multiples of this; (C0 by 0.5 of course). So the proper value for C0 should be 1v. 0.65v is very far off.
On the other hand this may have something to do with your multimeter since the measurements of the resistors (while being roughly in the ballpark) did lack the expected precision. After all those should be 1% precision resistors and right now I can't see a scenario where all resistors would have roughly 2.5 precision instead. Do you have access to another multimeter?

2. The values shouldn't change for Note On/Note off at all. In fact there is no provision in the whole CV circuit to distinguish between those two states; the Gate circuit is fully independent from it.

Another test: Play the highest C (two octaves up) and measure the voltage on the following pins of IC9:

2, 15, 5, 12, 7, 10
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Re: Strange detuning after not using my x0xb0x for a while

by Apekooi on Tue Jul 24, 2012 7:00 am

I tried playing the high C today, and the button didn't work. I listened to the output and it seems the filter is very broken as well now and I have no idea why, and there still is no apparent solution for the detuning problem. I think this box might be broken beyond repair and it might be time to cut my losses and build a new x0x. I'm very sorry to have wasted you guys's time, and thank you very much for your help.
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Re: Strange detuning after not using my x0xb0x for a while

by MMM on Tue Jul 24, 2012 4:51 pm

Apekooi wrote:I tried playing the high C today, and the button didn't work. I listened to the output and it seems the filter is very broken as well now and I have no idea why, and there still is no apparent solution for the detuning problem. I think this box might be broken beyond repair and it might be time to cut my losses and build a new x0x. I'm very sorry to have wasted you guys's time, and thank you very much for your help.


What? Broken beyond repair? This is just a question of proper debugging - practically any xoxbox can be fixed (unless it was built really poorly).

Just send me a private message and I'll try to help you further. If everything else fails I could fix it for you.
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