Ladder filter inverted polarity

Hi,

I’ve been just trying to get what different Ambika filters do with a scope. The Ladder by Tubeohm seems to have 180 phase shift on output.
Not an issue - maybe only when combining various voicecards-filters in one patch - just curious, is it by design?

Best regards,
Dzidek

Ooops, I’m sorry… 4P vs. SVF are inverted as well.
It’s not about voice sync as in this thread: http://mutable-instruments.net/forum/discussion/5522/voices-not-in-phase#Item_1
If I missed previous discussions on the topic sorry again, please point me to the right one.

Best regards,
Dzidek

Output polarity depends on the number of op-amp stages the signal goes through.

Since the oscillator phases are not synchronized, I did not bother making sure that each voicecard design had the same overall phase shift from oscillator to output. Especially since it could have costed additional op-amps and PCB real estate.

Olivier - clear, thanks!

Andre - sorry about the topic :slight_smile:

Best regards,
Dzidek