Octave wrong CV Offset.

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mtz
 
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Joined: Fri Jun 19, 2015 6:10 am

Octave wrong CV Offset.

Post by mtz »

Hello everyone,

i just build an XoX and almost everything has gone fine.
The Filter sound very good and the Sequencer is working fine as far as i can see. Yay!

Except that i have an wrong CV Offset for the whole Octave
and there is a Jump down between G# and A.

Don't have a clue if its a Problem of the digital side or in the VCO or probably IC9 that is fried....

Here are the CV Outputs and here you can hear how this sweet Thing sounds :)
https://www.youtube.com/watch?v=9xEcGEGpIU0

C - 4,59 V

C# - 4,67 V

D - 4,75 V

D# - 4,83 V

E - 4,92 V

F - 5 V

F# - 5,08 V

G - 5,17 V

G# - 5,25 V

A - 2,68 V

A# - 2,77 V

B - 2.85 V

C - 2,93 V

I hope that the solution is not too far because i cant wait anymore to let it scream and growl the whole weekend long... :)

Thanks for any Tipps in aDvance!!!

Mattes

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mmm
 
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Joined: Tue Apr 24, 2012 1:51 am

Re: Octave wrong CV Offset.

Post by mmm »

The problem is somehow related to the highest bit; this becomes active with A.

My guess at the moment is that the highest bit is always active and hence is added to the lower notes too (the CV for the notes from A an upwards looks more or less normal).

Measure IC9, pin 11 and pin 10. Probably one of them is high all the time (also for notes G# and lower) while it should only be high for notes A and higher.

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mtz
 
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Re: Octave wrong CV Offset.

Post by mtz »

Hey thank you for your tip!

You`re right. PIN 10 of IC9 (output, if i read correctly in the data-sheet) is always high.
PIN 11 only high from A up.

So now i have to replace the 74AC174

- can you confirm it?

Mattes

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mmm
 
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Re: Octave wrong CV Offset.

Post by mmm »

You may want to check first if there is some kind of bridge or short at pin 10 which pulls it high. If there is none then probably IC9 is faulty.

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mtz
 
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Re: Octave wrong CV Offset.

Post by mtz »

Thank you. It was the IC9 that was faulty....

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