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kingdubrock
Posts: 32
Joined: Sun Jan 04, 2009 7:41 pm

SEM-like filter

Postby kingdubrock » Wed Jun 13, 2012 6:43 pm

Hi,

I'm trying to get ETCH to behave like the SVF on the Oberheim SEM (which can be demo'd with the trial download) or like the one on Reason Thor.
The main difference between Etch and the behaviour I am looking for is that with the SEM and the one on Thor, you set a LP state you like with one filter and then the SVF knob sounds more like it is "crossfading" rather than sweeping prior to the mid point, betwen the original state (as set by a first LPF) and a HPF. By this i mean that it gradually introduces the sound of an almost fully open HPF over top of the original sound up to a certain point and then it starts removing the low frequencies from around the midpoint to fully open HPF.

Is this possible and I havent figured out how to do it? If not, Id like to make this an official FR.

Thanks

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Rory_FX
Posts: 2495
Joined: Tue Oct 12, 2004 4:56 pm
Location: FXP:MCR

Postby Rory_FX » Thu Jun 14, 2012 10:07 am

Are you talking about Band Pass behaviour? Some filters BP modes are just a crossfade in disguise.

I couldn't really hear the behaviour you mean in Reason, however it should be easy enough to setup a crossfade between two filter types in Etch, just assign a modulation source (X/Y or LFO) to the output of each filter, one to increase the output, and one to decrease it. Make sure the filters are in Parallel.

kingdubrock
Posts: 32
Joined: Sun Jan 04, 2009 7:41 pm

Postby kingdubrock » Thu Jun 14, 2012 4:49 pm

Ha! Brilliant. X/Y'ing the outputs between the two filters seems to be the ticket. Better even because you arent stuck with a predetermined curve. I guess I didnt want to believe it was as simple as crossfading and didnt want to fake it. It will take some experimenting but Im on the right track now.
Thanks Rory.
This type of SVF was made famous as far as I know on the Oberheim SEM. If youre curious, download the trial of Arturias emulation.
As for hearing it in Thor (or in the arturia SEM for that matter) I find the easiest way to hear it is using a bass sound that has overtones.
Initialize Thor, set the Analog OSC to sawtooth and maybe tune it down a few octaves. Select the Variable state filter. Select "Notch" and move the LP\HP filter all the way to the left. Set the Freq knob to just shy of 9 o'clock (or 25% open). Now, while playing, slowly move the Notch dial toward HP.
I would upload a Thor patch to save you time but Im not sure how and it only takes a second.

Anyway, this all simply for interests sake now. (and of course being able to do it with Etch and a nice Cypher or Strobe patch is the way to go. I really dont like the sound of Thor.)
Thanks again

kingdubrock
Posts: 32
Joined: Sun Jan 04, 2009 7:41 pm

Postby kingdubrock » Thu Jun 14, 2012 5:07 pm

Btw, I have to confess That so far I have been totally sleeping on the X/Y pad.

Also, after some more fiddling I discovered I was approaching it totally backwards. I thought the secret was in having the HP up in the high freqs and moving the LP around. In fact, if you set both filters to SVF, F1 in LP and have F2 in HP and in parallel mode, set the LP down fairly low and just sweep the HP you get the effect as well. embarrasingly easy. The effect is a bit different from the XY/Output level approach alone, but whether you go with either or both combined, its like a whole new plug for me now.
Thanks again.

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Rory_FX
Posts: 2495
Joined: Tue Oct 12, 2004 4:56 pm
Location: FXP:MCR

Postby Rory_FX » Fri Jun 15, 2012 11:04 am

Nice to hear it's working for you :)


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