mandag 31. desember 2018

A closer look at responses for the Jupiter 6 filter

NB: This post was written before i discovered a missing 33k feedback resistor. Results are not correct

To make a good state variable filter with 12/24dB HP, LP and 12dB BP I simulated the JP6 filter and tapped it at various places to look at the responses.

For my simulated circuit, setting cutoff CV to 0.2V (this has nothing to do with 1V/oct CV btw, look at the circuit to see exactly how it is wired) and Resonance CV to 10V (=off, see this post for details), gives the following results:

24dB LP:
- Cutoff: 507Hz
- Resonance (3V CV): 14dB at 953Hz

24dB HP:
- Cutoff 2kHz
- Resonance (3V CV): 13.7dB at 1.05kHz

12dB HP + 12 dB LP
- LP cutoff: 1.77kHz
- HP cutoff: 574Hz
- Center: 1kHz
- 10dB attenuation on top
- Resonance (3V CV): Top has 13dB amplification

12dB LP + 12dB HP
- LP cutoff: 1.77kHz
- HP cutoff: 574Hz
- Center: 1kHz
- 10dB attenuation on top
- Resonance (3V CV): Top has 13.5dB amplification

12dB LP with connection to second stage
- Cutoff: 666Hz
- Base attenuation 1.35dB
- Resonance (3V CV): Top has 6dB amplification over base at 885Hz, base is -1.26dB

12dB LP without connection to second stage
- Cutoff: 666Hz
- Base amplification 1.6dB
- Resonance (3V CV): Top has 7dB amplification over base at 885Hz, base is 1.6dB

12dB LP with connection to second stage
- Cutoff: 1.38kHz
- Base attenuation 1.2dB
- Resonance (3V CV): Top has 6dB amplification over base at 1kHz, base is -1.18dB

12dB HP without connection to second stage
- Cutoff: 1.4kHz
- Base amplification 1.7dB
- Resonance (3V CV): Top has 7dB amplification over base at 1kHz, base is 1.7dB


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