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This is the coolest filter I've ever heard
MUFF WIGGLER Forum Index -> Modular Synth General Discussion Goto page 1, 2  Next [all]
Author This is the coolest filter I've ever heard
SynthBaron
http://forum.moogmusic.com/viewtopic.php?f=1&t=21274

CZ Rider cloned an extremely rare Moog Modular filter, the 902-A Bandpass Filter Adaptor, from just pictures and anectodal guesswork. It's basically a module that interfaces with a 902 VCA to convert some of the circuitry in it into a weirdly resonant and distorting (in a readly good way) voltage-controlled bandpass filter. There's lots of info in the above link, but I've quotef the sound sample srction below.

Someone should make this thing commercially, in any format.

MY ASS IS BLEEDING
CZ Rider wrote:
It looks like the original, but does it work?
And the million dollar question...What does it sound like?

Well it works and is quite unlike any filter I have ever used. Not sure if I have it exactly right because I do not have an original or any reference to compare it to. But it works as a filter, so it must be close? I subbed many parts experimenting and there is a feedback oscillation I was able to eliminate, but it would no longer sound like a filter, just a VCA. So this oscillation seems to be part of the design. Almost like a Minimoog filter at the brink of oscillation where the oscillation effects the tone. It is a constant tone though and not a wide adjustable range, but is seems to go away when the is a signal present. I discovered when processing audio, it helped to modulate via the CV input with a similar tuned source. This colored this oscillation and made it change with the note like a Minimoog filter would when set to track the keyboard.
The sound is raspy and has a grit to it. Similar to a violin bow scraping or throaty/buzzy sound from a brass instrument. Really unique the way the oscillation tone interacts with the audio signal.

Uploaded a few sond samples to give an idea what this filter sounds like.
First, what I would guess is a typical filtered 902A tone. It gets a different tone at higher registers and is somewhat smoother then the lower registers.
MP3 of typical tone

Can hear that constant tone and the raspy quality of the filter.
Tried using white noise and the oscillation can not be heard. Actually gets a pretty good hi- hat type sound
MP3 of white noise through 902A

Doesn't sound too bad and probably the best hi-hat I ever got from the Moog.
But these are the clean sounds it can do. The 902A gets this awesome dirt and grit when pushed in a different direction.
Here is a filter sequenced type patch. Sounds nasty, almost evil sounding.
MP3 of 902A filter sequenced

The resonance is somewhat a constant tone on the last clip. this is where I noticed if I modulated the CV input with an audio rate tuned oscillator, that static sounding resonance would now more closely follow the note played. Here is more of a lead tone with the modulated filter similar to using osc. 3 on the minimoog modulating the filter at a tuned audio rate.
MP3 902A lead with FX

Sounds bad ass! Getting the tracking modulation makes it less static and more like a traditional filter.
So this morning I was trying to get something completly different from the filter, when this scrapping violin sound comes out. The grit and dirt from the feedback oscillation turns into the "zing" sound similar to a bow scrapping.
MP3 902a bow sound

If this filter is broken, I will leave it that way. Some really strange tones this is producing. That type grit and dirt is missing from many electronic patches I get from the Moog. This is just the 902a in the samples and naturally in a modular system can be recombined with any other tone. But that was the best electric violin I ever got out of the Moog. Did this before and had to multi track a few passes for the strings and another few passes for the bow sound.
The best way to show the filter effects is to blend in each tone on the next sample. First just the feedback oscillation. A tiny bit of sequenced CV to give a slight difference between notes. Then I blend in the modulation oscillator that is in tune at audio rate patched into the 902 CV input but not the audio input on the 902A. Can hear how the oscillation morphs into the "zing" part of the bow sound as the oscillation fades away. (Could just use this method and skip the audio input.) Then I bring in the audio from two 901's mixed together in a CP3 mixer. Gets a bit gritty bacause the filter is being modulated at audio rate. Have to watch the levels but it sounds unlike anything else in that Moog system.
MP3 902a feedback sound blended in

This filter is wild!
So why did Bob and company discontinue this? Unknown. Perhaps because of the unstable nature of it. It is quite radical and not smooth like the ladder filter. But I like it and can see where this unstable filter will be usefull for adding that grit to patches. Like all Bob Moog designed circuits, this has a lot of depth and many uses.
So has anyone heard the original Moog filter much? I think so. Eric Siday more than likely used this filter on his early 1964/65 sound logos. They were all over radio and TV. One of the most memorable, the Screen Gems "S from Hell" sure sounds like that same filter and was produced at that same 1964/65 time period. I was always fascinated by that sound, and it has that same electronic yet gritty tone. As a kid I thought it sounded very futuristic.



So this was a fun project to try. Might be the only working 902A? Might be broken and way off the original, don't know. The most important part, it sounds unique and bad ass!
I'll put it next to the 904 filter combo. Module on the top right.
Badwhite
wow... just listeneed to the samples... It's cool, I wonder why no one else has cloned it yet!
M6live
Redacted.
brandnewmath
It's probably bias from knowing the source, but it actually sounds pretty Moog-y to me on some of those clips despite not sounding anything like a transistor ladder filter.
WhiteOut
Quote:


Someone should make this thing commercially, in any format.


Oh yes! I'd sign up for one! Regardless if this thing actually was meant to sound this way it's something I'd be using a lot I think...
GGW
What a great sound!
DIY ?
chamomileshark
interesting but not to my tastes - but then I'm always out of step when it comes to filters generally.
doctorvague
I like unstable. Great bow sounds- very cool!
mousegarden
thumbs up
ualslosar
Want one NOW !!!
strangegravity
This one sounds better

DougD
There's no info about the no pass filter or demos, so... seriously, i just don't get it

I think the 902a sounds spectacular, I want one in Euro!
loustic
I like very much the sound of this filter with white noise.
onthelees
strangegravity wrote:
This one sounds better



I understand the noise levels on this one are incredibly low! absolutely no bleedthrough!
Dcramer
onthelees wrote:
strangegravity wrote:
This one sounds better



I understand the noise levels on this one are incredibly low! absolutely no bleedthrough!

Pfft meh who needs one of those in their rack! It doesn't even have VC resonance twisted
obelisk
Nice. Love the sound of that.

I've been using an Asteroid VCF in my Eurorack as of late. Takes up a lot of space, but sounds super interesting and different.
SynthBaron
Sounds like another example where this filter was used:



https://www.youtube.com/watch?v=ZZP0Tbzqlwk

(two years and not even a Euro manufacturer has taken this idea to make a filter out of it, in this market? sigh)
abelovesfun
you have my attention...
SynthBaron
abelovesfun wrote:
you have my attention...


Dr. Sketch-n-Etch
The beginning of this sample:
MP3 902a feedback sound blended in
reminds me of a Chemical Brothers thing that I can't quite place right now.
Dave Peck
It sounds like the filter cutoff is being slightly modulated by an audio-rate osc, maybe an octave below the pitch of the main osc that is being sent through the filter.
abelovesfun
I am studying the filter and trying to determine how the CV could work, since it appears the filter is changes by varying different capacitor values. I contacted the poster there for more information.
_phibber
Dang that thing does sound incredibly nice.
SynthBaron
abelovesfun wrote:
I am studying the filter and trying to determine how the CV could work, since it appears the filter is changes by varying different capacitor values. I contacted the poster there for more information.


I think it uses a 902 VCA like you would a 3080 or 13700 OTA.
abelovesfun
@SynthBaron are you saying that you think the CV he is referring to is CV of the VCA it runs into?
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