which filter for ssl comp sidechain signal ??

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matthias

Well-known member
Joined
Jun 4, 2004
Messages
768
Location
germany / frankfurt
hi,

In the next days, I want to build a hipass filter into my ssl comp
to cut out the low frequencies from the sidechainsignal...

currently I don't really know which type of filter is better...


an op-amp based 12db hipass filter:

variablefilter.gif



or maybe a passive lc dip cut filter:

dipcutfilter.GIF



are there better filters out there for this type of application,
or does anybody have a schematic for a simple 24db hp filter ??

waiting for your suggestions....

cheers,
mat
 
Well, a dip-cut filter is not a high pass, so if what you want is a true highpass (and I think it is what you want) then you can rule out the RLC filter. For a sidechain filter, you want something smooth and predictable...a gentle highpass is nice as it de-emphasises the bass, and lets the compressor focus on shaping transients as opposed to riding low frequency notes.


24 dB/octave...cascade two two pole filters (like the schem you provided)together.

Personally, I'd start with just a small value coupling cap. It's 6dB/octave, but you might like it, and it's real simple.

Cheers,

Kris
 
24dB/8ve is going to give you a De-Esser, and not a very good one at that!

Just make the IC schematic that you posted, only lose one half of the input stage to give you 6dB/8ve, and something closer to useable as a compressor... not a permanent de-esser with a fixed threshold (not very useable for vocals, -will still be completely outclassed by a basic dbx 902)

Personally, I think that the preferred slope is usually less than 6dB/8ve... somewhere between six and three. I'm not ragging on the idea of modifying the unit, but the 'real' SSL outboard comp has a sidechain capability and it's basically never used. The original console version is considered a classic operating full-range, and anything 12dB/8ve or steeper will make it essentially useless on full-range music.

Keith

Keith
 

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