Low Pass & High Pass Filter Thru-Sound

[Boricua]

Hello,

I am completely new to the Polybrute and have spent the last couple of days getting acquainted with this amazing device.  As I went through the manual to learn a couple of items, I noticed that that I would hear sound coming through when placing the unit on the Init patch with the Low-Pass (Steiner Filter) or the High-Pass while having the Cutoff at Min/Max (16 Hz & 26.57 KHz) respectively.  The manual indicates that "NO" sound should be heard with such settings.  Thus my question.  Is this normal, or, could there be an issue with the unit? 

Thank you.

p.s. I performed a voice auto-tuning, yet, with same results afterwards.

[larioso]

The Init preset sends oscillators only to Ladder filter.

Did you change this, or?

The Steiner setting should have no impact at all.

If you send oscillators to Steiner what manual states should be correct.
Just press buttons in mixer until only upper led is lit.

[Boricua]

Yes, that is exactly what I did.  Following the Manual instructions (pages 15-17), I hit the VCO1 (Mixer) selector pad to only have the "Orange" circle lit, thus, only the Steiner Filter would be accessed.  Then proceeded to move the Cutoff knob (of the Steiner Filter) to Min/Max while using either "LP" or "HP.  I could still hear sound through my headset (running through external mixer ProFX) at those extremes.  The sound was much lower, yet, still there.

p.s. The lower notes come through stronger when using LP, and, the higher notes when using HP as expected. So, can hear sound when (per manual) I should not be.

[larioso]

Don't think it is faulty unit, I get the same thing.
Tested in daw -42 dBFs fully open to closed cutoff, and noise floor is -54 dBFs.

Ladder seems to be quiet at left most cutoff, below noise floor.

Maybe there should be calibration of Steiner to do, so no leakage at end positions.

I tested on my Prologue.
Fully open to closed cutoff just -33 dBFs, but noise floor is -62.4 dBFs.

For me it is not a problem. It's an analog thing.
Remember what cutoff means 3 dB drop, 70%, not quiet - for Steiner 12 dB/octave,

[DrJustice]

...Then proceeded to move the Cutoff knob (of the Steiner Filter) to Min/Max while using either "LP" or "HP.  I could still hear sound through my headset (running through external mixer ProFX) at those extremes.  The sound was much lower, yet, still there.

p.s. The lower notes come through stronger when using LP, and, the higher notes when using HP as expected. So, can hear sound when (per manual) I should not be.

The Steiner has a slope of 12dB/octave whereas the Ladder's slope is 24dB/octave. I.e. neither are brickwall filters, and with the Steiner's relative shallower slope, it will be heard several octaves away from the Ladder. This is what the numbers look like:

- for the Ladder, 1, 2, 3 and 4 octaves away from the center frequency will give attenuation of  24dB, 48dB, 72dB and 96dB.
- for the Steiner, 1, 2, 3 and 4 octaves away from the center frequency will give attenuation of  12dB, 24dB, 36dB and 48dB.

That is quite a difference and should explain why the ladder sound goes away (-96dB, below the noise floor) already after 4 octaves, while the Steiner is til audible (-48dB, high above the noise floor) after 4 octaves. I just did a listening test, and it all checks out here :-)

[Boricua]

Don't think it is faulty unit, I get the same thing.
Tested in daw -42 dBFs fully open to closed cutoff, and noise floor is -54 dBFs.

Ladder seems to be quiet at left most cutoff, below noise floor.

Maybe there should be calibration of Steiner to do, so no leakage at end positions.

I tested on my Prologue.
Fully open to closed cutoff just -33 dBFs, but noise floor is -62.4 dBFs.

For me it is not a problem. It's an analog thing.
Remember what cutoff means 3 dB drop, 70%, not quiet - for Steiner 12 dB/octave,

Thank you very much for the insights. Not much technical details in the manual, so, these inputs certainly come in handy.

.

[Boricua]

...Then proceeded to move the Cutoff knob (of the Steiner Filter) to Min/Max while using either "LP" or "HP.  I could still hear sound through my headset (running through external mixer ProFX) at those extremes.  The sound was much lower, yet, still there.

p.s. The lower notes come through stronger when using LP, and, the higher notes when using HP as expected. So, can hear sound when (per manual) I should not be.

The Steiner has a slope of 12dB/octave whereas the Ladder's slope is 24dB/octave. I.e. neither are brickwall filters, and with the Steiner's relative shallower slope, it will be heard several octaves away from the Ladder. This is what the numbers look like:

- for the Ladder, 1, 2, 3 and 4 octaves away from the center frequency will give attenuation of  24dB, 48dB, 72dB and 96dB.
- for the Steiner, 1, 2, 3 and 4 octaves away from the center frequency will give attenuation of  12dB, 24dB, 36dB and 48dB.

That is quite a difference and should explain why the ladder sound goes away (-96dB, below the noise floor) already after 4 octaves, while the Steiner is stiil audible (-48dB, high above the noise floor) after 4 octaves. I just did a listening test, and it all checks out here :-)

Thank you very much for taking the time to perform these tests, much appreciated.  Does Arturia have a Technical Manual for the PolyBrute?  I am used to seeing such in many other products, and, with the amount of features these device has, it would certainly help all the newcomers (as well as experienced folks).
.

[DrJustice]

...
Does Arturia have a Technical Manual for the PolyBrute?
...

No, there's only the single user manual. It does mention the 12dB and 24dB filter slopes, but does not go into what the different slopes entails.

[Boricua]

...
Does Arturia have a Technical Manual for the PolyBrute?
...

No, there's only the single user manual. It does mention the 12dB and 24dB filter slopes, but does not go into what the different slopes entails.

Thank you for letting me know!