hp/bp/lp resonate filter with cv control

[rnilson]

Hey Guys,
The title says it...
I want to know my options for a hp/bp/lp resonate filter with cv control over the frequency cutoff/range.

Right now I got.....
Out of Production
1.) Frostwave Resonator
2.) Alesis Philtre

In production (Robot Factory)
1.) Meatwad
2.) Photron

What else is there?

[bongomania]

Electrix made a rack unit that can do that; I can't recall ATM whether the Akai rack unit had hp/bp/lp switching.

In the land of modular synths there are several options, but of course then you're in for a larger and more complex piece of kit.

The Waldorf 4-pole desk unit might work... *curses aging memory*

Also there are some boutique desktop units (essentially pedals with no footswitch) that I've seen on web stores that cater to the modular synth and boutique drum machine crowd. Drawing a blank on specific brands or stores ATM, but they're out there.

[rnilson]

Originally Posted by bongomania

Electrix made a rack unit that can do that; I can't recall ATM whether the Akai rack unit had hp/bp/lp switching.

In the land of modular synths there are several options, but of course then you're in for a larger and more complex piece of kit.

The Waldorf 4-pole desk unit might work... *curses aging memory*

Also there are some boutique desktop units (essentially pedals with no footswitch) that I've seen on web stores that cater to the modular synth and boutique drum machine crowd. Drawing a blank on specific brands or stores ATM, but they're out there.

Thanks Bongo,
I think you are talking about the Electrix Filter Factory.
I guess I should have stated that I would like it to be in pedal form. (I guess the alesis is not a pedal.) I have access to a rack mount filter and several soft-synth filters, but it just adds to the crap I have to carry to a gig.

[kevteop]

Originally Posted by rnilson

1.) Meatwad

And the Barge Grinder of course.

Weird, I can't think of any others.

[idoru]

I've seen a schematic and finished build of the filter & distortion section from the old Wasp synth, adapted for guitar/bass/misc.

Helpful only if you or someone you know is willing to build it for you, of course.

[bigchiefbc]

Originally Posted by kevteop

And the Barge Grinder of course.

Weird, I can't think of any others.

According the Barge's manual, out of the 3 exp jacks, none of them control freq cutoff. They control blend, depth, and decay. The only reason I know this is that I thought of that one to recommend it as well

[fightthepower]

The Decay and Cutoff inputs on the Grinder and mf101 respectively, are functionally almost the same with an expression pedal- the MP201 included. I think the combonation of 'Depth' and 'Decay' = Cutoff on the mf101.

For instance; To use the Grinder like the moog lpf, pick the lpf and lowest frequency settings. Then plug into the decay input and turn the decay and attack knobs full clockwise for instant response, and set the depth knob to taste-- full clockwise provides the highest sweep when rocking the exp pedal forward. 'Filter Color' = 'Resonance' on the mf101, and the 'Envelope Level' on the Grinder = 'Envelope' on the moog lpf.

To use it as a wah or highpass, just click into lp/bp/hp and pick the desired frequency range, and then repeat the above steps. It took me a little while to figure it out, but it works great.

[dannybuoy]

Originally Posted by idoru

I've seen a schematic and finished build of the filter & distortion section from the old Wasp synth, adapted for guitar/bass/misc.

Helpful only if you or someone you know is willing to build it for you, of course.

Have you got a link to that please?

[kevteop]

Originally Posted by bigchiefbc

According the Barge's manual, out of the 3 exp jacks, none of them control freq cutoff. They control blend, depth, and decay. The only reason I know this is that I thought of that one to recommend it as well

Isn't 'depth' the filter cut-off?

They wouldn't build a filter with every control possible and then decide not to bother with exp. control over the cut-off. It must be 'depth'

[fightthepower]

Before buying the Grinder from the classifieds, I emailed Barge Concepts asking asking if it was possible to control the cutoff with an expression pedal, and they basically told me 'no', but that I could get close... at the time that answer confused me more than it helped me, but I eventually figured it out hehe. This excerpt is from their email:

"First off, thank you for your interest in Barge Concepts.

The FILTER FREQ and FILTER TYPE (LP/BP/HP) switches have the most direct control over the cut-off/operating frequencies of the Grinder and is not expression controllable. That being said, as all of the controls are interactive, depending on your other settings, frequency response can be manipulated via the DEPTH and DECAY expression inputs for some wah-like results. Depending on what you're looking for, the BLEND expression control also comes in to play - letting you vary between your clean/dry Input signal and the filter (set up as Low Pass, High Pass, etc).

If you have any other questions or need anything else, please let us know. Thank you for your interest in Barge Concepts.


Geoff Bryant.
Barge Concepts"

[JohnDavisNYC]

wow... that seems incredibly stupid to me, to build an amazing filter that cannot be swept via CV/expression...

finding a good HPF is tough... I am on the hunt.

John

[dannybuoy]

Well that's a major bonus for the Meatwad then which I think does exp controlled cutoff if you set the full/half/static sweep switch to static.

Since I've been meaning to build up a few circuits myself, I'm gonna try out some Wasp / MS20 / Moog lowpass filters. All I want is an expression controlled lowpass in a tiny enclosure and the Moog is too big and expensive for me!

[basscheez]

Originally Posted by dannybuoy

Have you got a link to that please?

I found this so far:
http://jhaible.heim.at/tonline_stuff/hj_wasp.html

[fightthepower]

Originally Posted by JohnDavisNYC

wow... that seems incredibly stupid to me, to build an amazing filter that cannot be swept via CV/expression...

finding a good HPF is tough... I am on the hunt.

John

It can! They just made it confusing as hell with their answer and labeling. The MP201 works great with it as a lowpass, sample&hold, highpass, etc.

[bigchiefbc]

Originally Posted by fightthepower

The Decay and Cutoff inputs on the Grinder and mf101 respectively, are functionally almost the same with an expression pedal- the MP201 included. I think the combonation of 'Depth' and 'Decay' = Cutoff on the mf101.

For instance; To use the Grinder like the moog lpf, pick the lpf and lowest frequency settings. Then plug into the decay input and turn the decay and attack knobs full clockwise for instant response, and set the depth knob to taste-- full clockwise provides the highest sweep when rocking the exp pedal forward. 'Filter Color' = 'Resonance' on the mf101, and the 'Envelope Level' on the Grinder = 'Envelope' on the moog lpf.

To use it as a wah or highpass, just click into lp/bp/hp and pick the desired frequency range, and then repeat the above steps. It took me a little while to figure it out, but it works great.

I'm sorry that doesn't really make a lot of sense to me. Decay is essential a speed control for the filter sweep, and Depth is simply how far the filter sweeps up or down from the cutoff. I don't see how manipulating either/both of those will effectively move the cutoff itself. I'm not trying to be argumentative here, it just doesn't make sense to me and I want to understand.

[rnilson]

Just talked with Mario from Robot Factory. He is said he can build me a switchable HP/BP/LP filter with a resonance knob, a frequency knob, gain and master output. There will be a true CV input for the frequency control. It will be using the circuit from the Photron (ms-20).

Now I can move my moog lowpass filter between my OC2 and LS2 to add oscillation to my low end fundamental and use this new filter for sweeps of my fuzz/oscillators with the various modes. With an LFO running the cutoff on the moog and another LFO or expression pedal running the Robot Factory filter I should be able to do some sick stuff.

[fightthepower]

Originally Posted by bigchiefbc

I'm sorry that doesn't really make a lot of sense to me. Decay is essential a speed control for the filter sweep, and Depth is simply how far the filter sweeps up or down from the cutoff. I don't see how manipulating either/both of those will effectively move the cutoff itself. I'm not trying to be argumentative here, it just doesn't make sense to me and I want to understand.

I have a hard time understanding myself, but it works. I'll do my best job of explaining it in relation to the Moog LPF:

When using the moog lpf as a lowpass filter, I turn the envelope level off, or way down, so that I have full control of the sweep when I use an exp pedal with the cutoff-- hit a note and there is no envelope/sweep unless I rock the pedal.

To do the same thing with the grinder, I turn the 'envelope level' off as well-- When I do this, the Decay knob is rendered useless and there is no change in the sound whether full CCW or full CW. Now if you plug an exp pedal into the decay input and rock the exp pedal back and forth, then decay knob controls how fast the filter closes in relation to the exp pedals movements; Set it to full CCW and toe down with the exp pedal, and then quickly rock the pedal to heel down and the filter will slowly close, but at full CW, the sweep is locked on to your foot movements; ie when you go heel down the filter moves at the same speed as the pedal. The attack knob does nothing with the envelope level knob turned off. If you switch the filter selector to BP or HP, this process works the same for using the Grinder as a wah, sweepable highpass, etc.


When using the MoogLPF as an envelope filter with the envelope level full CW, the filter cutoff control's the filters sweep/effected range. With the Grinder, you can control that by picking one of the 4 frequency selectors for the effected frequency range, and then use the 'Depth' knob/exp pedal to fine tune the range of the sweep, starting from the selected initial frequency. The sweep will start from one of the 4 positions, and the depth controls how far it sweeps from that point.


Basically, you can't specifically control the 'cutoff' with one knob/exp pedal, because I guess it's broken up into a few switches and knobs. But you can zero in on the frequency range that you want to control, and by using either the decay input for static lp/bp/hp, or the depth input for envelope following, get essentially the same functionality as plugging an exp pedal into the cutoff of the Moog LPF. With such a high level of control with all the knobs, there are many settings that make no sound, do nothing with exp pedals plugged in, etc. That coupled with the labeling of the knobs and the email response from Barge, made it take me a while to figure out how to use an exp pedal with it, but it does indeed work. They have a 'coming soon' section that is supposed to have a guide to using expression pedals with the Grinder, and I'm sure that if they ever release it, that it will explain this stuff a little better than I can.

Anyway I hope that helps, I really had to pick my brain and go through it all with both pedals again to put it all together, but this stuff (effects) is all pretty new to me so I have a hard time explaining it in the proper terms. At some point I'll do a review of the pedal now that I'm finally comfortable with it (took a while), but if I get a chance later tonight, Ill record a quick clip of the MoogLPF and Grinder in a couple settings with the mp201 plugged into the Cutoff on the Moog, and Decay on the Grinder.

[fightthepower]

So here we go: with the envelope off, and an exp pedal in the decay input:

With decay at full and envelope off, the exp pedal controls the sweep (otherwise its fully decayed/closed, and moving the pedal forward opens it to the cutoff), up to the cutoff point set by the one of the 4 frequency selectors and fine tuned to a specific point by the Depth. Or something like that.. It's a cool pedal and I'm learning more about it all the time, but that's the best explanation I can give,. hope it helps!

[idoru]

Originally Posted by dannybuoy

Well that's a major bonus for the Meatwad then which I think does exp controlled cutoff if you set the full/half/static sweep switch to static.

Since I've been meaning to build up a few circuits myself, I'm gonna try out some Wasp / MS20 / Moog lowpass filters. All I want is an expression controlled lowpass in a tiny enclosure and the Moog is too big and expensive for me!

I'm so over wah, and all about resonant lowpass these days. You WILL let us know how you get on

c-

[dannybuoy]

There's been a few threads around here asking about which expression controllable LPFs are out there, I just found out about another, similar to the Frostwave Resonator:

http://thesquarewaveparade.com/MoleS20r.html