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- Feb 12, 2006
- 60,978
- 5
- 220,734
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
For some tone shaping purposes, lower order filters can be useful, but not so much for the purposes we have been discussing.
I think it should also be stated, tone shaping, eq., will not likely be a good HPF. Or maybe I should say in most case would not be an HPF at all.
yes, there are many stupid people in this world......and the fact that they use our roads to display their stupidity makes me mad, cause I could be a victim
I was afraid to click it, for fear of the crack lurking behind the "play" arrow.
My pedalboard splits out the highs with a crossover after my octaver, which can't function without the lows. Highs goes through the rest of the effect chain. Reunification goes by way of a blender with phase 180deg optional footswitch which is good enough for jazz when the chorus is on but the distortion isn't, keeping the low mids from cancelling (per Agedhorse's post) in the crossover. Then the whole lot is high passed. No rocket scientists required.
A practical understanding of filters:
Filters are defined by their slope, which determines the attenuation of signals outside the 'pass' band. Most audio filters on mixing desks (and DAWs) will have a slope of 12dB or 18dB per octave, and in synthesizer filters the slope may be as steep as 24dB per octave.
If an 18dB/octave high‑pass filter is set to 80Hz, any audio an octave below that (at 40Hz) will be attenuated by 18dB, and an octave lower still, at 20Hz, it will be attenuated by 36dB... and so on.
Ref: Q. What are filters and what do they do? |
High pass and low pass filters attenuate all frequencies below and above the knee. So if you have a problem at 60hz for example, you need to set the knee of the filter at a higher frequency so that 60Hz is attenuated. A notch filter can be more surgical in attenuating specific frequencies.
Filters are defined by their slope, which determines the attenuation of signals outside the 'pass' band. Most audio filters on mixing desks (and DAWs) will have a slope of 12dB or 18dB per octave, and in synthesizer filters the slope may be as steep as 24dB per octave.
If an 18dB/octave high‑pass filter is set to 80Hz, any audio an octave below that (at 40Hz) will be attenuated by 18dB, and an octave lower still, at 20Hz, it will be attenuated by 36dB... and so on.
Ref: Q. What are filters and what do they do? |
High pass and low pass filters attenuate all frequencies below and above the knee. So if you have a problem at 60hz for example, you need to set the knee of the filter at a higher frequency so that 60Hz is attenuated. A notch filter can be more surgical in attenuating specific frequencies.
- Jun 6, 2012
- 4,837
- 6,859
- Disclosures
- I don't wait 30 minutes after eating, to go swimming.
It's a "no brainer" for you and others who feel the same. It isn't, for me and others who feel differently than you. Deal with it.
- Feb 12, 2006
- 60,978
- 5
- 220,734
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Iirc, Francis uses a 24dB/octave filter in his latest version, 12dB fixed and 12dB variable, as do I. This gives closer to the best of both worlds imo.
Link Removed
^ This has pictures for the text challenged like myself.
Probably more info than you wanted, but the drawings help show it getter, I think.
As others have said, it's a matter of how quickly things roll off.
They can achieve higher roll offs by "stacking" more filters one after the other.
So essentially, one filter section (Resistance/Capacitance aka RC) is first order, two sections are second order and on and on.
I'm pretty sure there is a diminishing point of return in that the slope will never be absolutely vertical.
There are probably other trade offs as well when stacking filters.
Each filter section will present some loss. A practical HPF would need some amplification to overcome the losses.
?please reveal which pedal that is?
I've spotted many summing pedals but don't think I've seen one with phase flipper. TIA
Comparo of three filters, all with the same 3 dB point of 35 Hz: N=3, 0.5 dB Chebyshev, N=4 Butterworth, and two cascaded N=2 Butterworth.
This illustrates why slope alone only shows part of the picture. Notice the attenuation at 20 Hz. The N=3 Cheby has more attenuation than the N=4 BW, though the Cheby has less ultimate slope. The cascaded BW has about 14 dB attenuation, though it has the same ultimate slope as the N=4 BW.
The cascaded case will happen in a bass amplifier that has simple AC-coupled stages. It does create a high-pass filter. However, even if the 3 dB points of the stages were the same, it will result in less attenuation at frequencies below the cutoff frequency than would result from a properly designed high-pass filter.
This illustrates why slope alone only shows part of the picture. Notice the attenuation at 20 Hz. The N=3 Cheby has more attenuation than the N=4 BW, though the Cheby has less ultimate slope. The cascaded BW has about 14 dB attenuation, though it has the same ultimate slope as the N=4 BW.
The cascaded case will happen in a bass amplifier that has simple AC-coupled stages. It does create a high-pass filter. However, even if the 3 dB points of the stages were the same, it will result in less attenuation at frequencies below the cutoff frequency than would result from a properly designed high-pass filter.
- Jun 6, 2012
- 4,837
- 6,859
- Disclosures
- I don't wait 30 minutes after eating, to go swimming.
