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Approximating a High Pass Filter in Prophet '08?

dsetto

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Approximating a High Pass Filter in Prophet '08?
« on: January 20, 2017, 08:29:01 AM »
Hello. Is there a way to approximate a high pass filter in a Prophet '08, within the instrument itself?


My thoughts are:
- One can always add a high pass filter to the output of the Prophet '08.
- I suppose the closest one could get is to use thinner pulse waveforms. ... But, it's not the same result. Nor is it the immediacy of the HPF button and convenience of a modulation destination. 

 

Re: Approximating a High Pass Filter in Prophet '08?
« Reply #1 on: January 20, 2017, 10:26:08 PM »
The high pass filter really is the most obvious component missing from the Prophet '08 design.  If you wanted that distinctive HP gradual removal of lower frequencies until the sound disappears into thin air, then the P'08 can't help you.  But if you wanted merely to eliminate some of the lowest frequencies, say, to reduce boominess, you could always use the 2-pole filter, some resonance, a very narrow pulse width (as you mentioned), and even a graphic equalizer.  But these would be no substitute for sweeping a patch with the real thing.
« Last Edit: January 20, 2017, 10:27:46 PM by Sacred Synthesis »
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Re: Approximating a High Pass Filter in Prophet '08?
« Reply #2 on: January 22, 2017, 12:23:28 AM »
The high pass filter really is the most obvious component missing from the Prophet '08 design.

Agreed with Sacred Synthesis.  In fact, I think if I was looking at a Rev2, I would be willing to give up the effects and some of the mods in trade for a HPF.
Jim Thorburn .  Toys-  Dave Smith: Prophet 08;
Pro 2; Prophet 12; EastWest Orchestral soft synths; Yamaha S-90; Yamaha Montage 8, Yamaha DX-7; KARP Odyssey; Ensoniq ESQ-1.  All run through a Sonar DAW with a Tascam DM-24 board.

Re: Approximating a High Pass Filter in Prophet '08?
« Reply #3 on: January 22, 2017, 10:36:32 AM »
The high pass filter really is the most obvious component missing from the Prophet '08 design.

Agreed with Sacred Synthesis.  In fact, I think if I was looking at a Rev2, I would be willing to give up the effects and some of the mods in trade for a HPF.

Ditto.  It's easy enough to add offboard effects.  But an offboard high pass filter?  I would be willing to sacrifice all the REV2's effects for a HPF.
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dsetto

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Re: Approximating a High Pass Filter in Prophet '08?
« Reply #4 on: January 23, 2017, 06:46:55 AM »
Me three

Re: Approximating a High Pass Filter in Prophet '08?
« Reply #5 on: January 24, 2017, 11:52:32 AM »
I've used a Vermona Lancet filter (which is mono) on one of the PO8 outputs.  This allows some of that HP sound to be incorporated into a patch and still preserve the stereo.  Then I run it thru a reverb which more or less blends the stereo signal anyway (so that the HP is not just all in one speaker).  It's a work around but it's somewhat satisfying.

Re REV HPF:    me four ;)
DSI Equipment: Poly Evolver Keyboard, Evolver desktop, Prophet 8,  Pro-2, OB6, P-12
 

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Re: Approximating a High Pass Filter in Prophet '08?
« Reply #6 on: January 25, 2017, 12:04:15 PM »
I haven't tried this, but I think you can approximate a sweep removing low frequencies by using a small amount of resonance and then raising the LPF frequency. The Prophet '08 filter loses its lows with a little resonance added. With another layer to provide the highs in you might be able to approximate this behavior. I'll try it next time I get some keyboard time.

Re: Approximating a High Pass Filter in Prophet '08?
« Reply #7 on: January 25, 2017, 01:03:19 PM »
I haven't tried this, but I think you can approximate a sweep removing low frequencies by using a small amount of resonance and then raising the LPF frequency. The Prophet '08 filter loses its lows with a little resonance added. With another layer to provide the highs in you might be able to approximate this behavior. I'll try it next time I get some keyboard time.
That's generally how I subtly thin out the lower frequencies. The effect can be a little like the Juno 60 HPF.

Re: Approximating a High Pass Filter in Prophet '08?
« Reply #8 on: January 25, 2017, 01:08:26 PM »
I haven't tried this, but I think you can approximate a sweep removing low frequencies by using a small amount of resonance and then raising the LPF frequency. The Prophet '08 filter loses its lows with a little resonance added. With another layer to provide the highs in you might be able to approximate this behavior. I'll try it next time I get some keyboard time.

This does work, but in the smallest way.  So, too, does using the 2-pole filter setting and turning up the resonance all the way.  These are two useful approaches for reducing just a tad some of the lower frequencies that can cause a "boominess," but still, they're a far cry from having an actual high pass filter.
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dsetto

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Re: Approximating a High Pass Filter in Prophet '08?
« Reply #9 on: January 26, 2017, 09:50:04 PM »
This sounds useful. Thank you.

Re: Approximating a High Pass Filter in Prophet '08?
« Reply #10 on: January 27, 2017, 01:51:03 AM »
Moinmoin,

as all "user interaction" may be read out via MIDI out, You could add a MIDI controlled high pass filter (HPF), or a voltage controlled HPF with a programmable MIDI to CV converter. Both things are available.
Main issue will be to insert it into the sound chain:
  • HPF will sit after the VCA and therefore prone to noise, as it will not always get the optimal input level.
  • HPF will need at least two (stereo) or even four (stereo, layers A and B) inputs.
My personal solution:
  • I use my old monophonic synth, originally equipped with LPF/HPF/BPF capacity, and pre VFC audio input.
  • Prophet outputs are fed into a mixer (I do this anyway in order to add effects and control layer volumes) and routed through a pre output into the mono synth with its internal sound sources switched off and VCA bypassed.
  • The mono synth's output is fed back into the mixer (I do this anyway, as I also use it just the normal way...).
Pre out is used in order to get the HPF-sound only if I want to. Volume control "original" vs. "HPF" is done by main faders. The whole arrangement surely is somewhat "knob-intensive" and not easy to dial in quickly, but rewards with quite some flexibility.
If the general sound and operation of prophets is just the holy grail for You (as it is for me) and You really want or even need a HPF just now, this or a similar approach may be a quick solution.

BTW: As the mono synth also features a pedal control for VCF frequency, I can even use it as a "very flexible nerd Wah" for all audio input fed into the mixer.

HTH

Martin

dsetto

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Re: Approximating a High Pass Filter in Prophet '08?
« Reply #11 on: February 10, 2017, 10:38:47 AM »
Neat approach, Martin. ... I've found myself doing intricate routing things like that to get what I need.