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any leads on techs who could replace the curtis filter

any leads on techs who could replace the curtis filter
« on: May 29, 2021, 07:30:07 PM »
as DSI's idea of "acceptable" oscillator bleed levels is much different from my own, I was wondering if anyone has attempted to replace the filter or knows of any techs who have the ability to replace it.

I don't know about anyone else but trying to gain stage a filter like this is a nightmare. you either have to record super bright sounds and filter them outside of the rev, or you have to record soft stuff that has a shitty amount of the unfiltered oscillator coming through.



Re: any leads on techs who could replace the curtis filter
« Reply #1 on: May 29, 2021, 11:11:29 PM »
It is a all in one chip, there is no way to isolate the filter AFAIK. If you were to mod the machine you would need an access to the firmware as all the auto running options would be affected.

Re: any leads on techs who could replace the curtis filter
« Reply #2 on: May 30, 2021, 11:03:47 AM »
Yeah, as Tugdial mentioned, the Rev 2 chips are not discreet. 

They are PA397 ICs based on CEM3397...   each chip has two Osc Waveshapers, the VCF Filter, and VCA amp mixer.

It not really feasible to swap filters.

If you're trying to get the filter to close down completely, you can try to route a Mod Slot with:
Source:  DC
Destination:  Cutoff Frequency
Amount: -24 (or somewhere around there)

I do this sometimes on Pro 3 to close down the SEM filter completely.   Not sure if it will have the same effect on Rev2, as haven't tried it, but thought I'd mention it.

Sequential Pro 3 and Rev 2, Deepmind, PolyBrute - Sound Sets, Patch Banks - Available on Sellfy: https://sellfy.com/sounddesign/

Re: any leads on techs who could replace the curtis filter
« Reply #3 on: May 30, 2021, 07:58:04 PM »
Nop, offsetting the cutoff with a DC source doesn't change the bleeding on my REV2.

I think that the oscillator bleeding is internal to this DSI120 or PA397 chip (crappy CEM3397 to begin with), and is probably coming from the VCA rather than the filter.
Minimoog D (vintage), OB6 (Desktop), Oberheim Matrix-6 (MIDI Controller), Prophet REV2-16, DeepMind 12, VC340