The conclusion is that everything is very similar and my control signals cover the Jove signal ranges - but it is worth mentioning that the cutoff maxes out at around 23kHz on the Jove.
Here are my findings in detail:
Resonance
My simulation doc says the following about calibrating resonance CV:
Tune U30 until you get -125uA Reso I_abc per OTA (or to freq response is OK)
Tune U31 until you get -25uA or -4uA Reso I_abc per OTA (for similar response to 5 or 10V CV on the JP6)
Comparing to the Jove reso circuit, this is exactly what you get from trimmer extreme, -120uA to -4.2uA, so a range of -120uA to 0uA is what we want to be able to trim from software
In the following, the three lines correspond to min, center and max trimmer settings:
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| Jove resonance - voltage seen at expo converter input |
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| Jove resonance 0-10V - I_abc in single 18k resistor |
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| Jove resonance 0-5V |
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| Jove resonance 0-5V, center trim only |
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| Jove resonance response, 0V but trim min center max |
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| Jove CV response 0, 5 and 10V CV |
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| My own JP6 filter resonance I_abc. It has the same range as the Jove one but is of course not exponential, as this happens in software instead. |
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| My resonance CV circuit |
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| The Jove resonance circuit |
Cutoff
Untrimmed, Jove maxes out I_abc at -600uA with a CV of 7V approx.
This gives a cutoff of around 20-25kHz.
The lowest current is -15.6nA
My trimmed version gives 169nA to 1.06mA, max is at approx 6V CV which gives a cutoff at 25khZ, similar to the Jove.
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| Jove expo converter input vs input CV |
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| Jove I_abc in single 18k resistor |
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| Jove I_abc for center only, shows max I_abc at approx 7V |
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| Jove cutoff with CV 7.5V (center trim) |
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| My version, I_abc from 0-10V CV |
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| My version cutoff at around 6V CV |
Buffer
Jove uses a transistor (J112, N-channel FET) as a buffer, with a 33k to gnd. Replacing the opamp buffer in my circuit with a nmos in the simulation gave a slightly lower gain out. Changing the 33k to 22k or 47k didnt affect the amplitude.
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Input vs output of first cell using op amp buffer
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| Input vs output of first cell using nmos-buffer |
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| N-channel Mosfet buffer, pretty similar to what the Jove uses |
