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General Discussions => The Lab => Topic started by: TobWen on September 14, 2004, 02:33:04 AM

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: TobWen on September 14, 2004, 02:33:04 AM

Hi there,

I am looking for a variable Low-Cut/High-Pass for a mic-preamp project.

Since I don't have much time for the project at the moment, I have asked a friend to send me an idea.
He has sent me this one (it looks like something from RANE).
This is is about 12db (I think):

(http://tobwen.bei.t-online.de/preamp/filter.png)

My questions are now: Where do I connect this one and is it correct?
IMHO, I directly it after the amp-IC (INA217 for example).
Or can I hook up it on the main-output, which is line level?

Is this a good solution at all, or do you have some better ones?

Best regards,
Tobias

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: VacuumVoodoo on September 14, 2004, 03:02:57 AM

It can be placed after the first gain stage. Don't bother with the exact resistor values given to 2 decimal points, you would have to get capacitors with same exact values AND you'll never find a dual pot with that exactly matched tracking.
You'll do fine with nearest resistor values from the E96 series and 2% tolerance caps.
The pots could be substituted with precisiion dual stepped attenuators.

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: TobWen on September 14, 2004, 03:31:18 AM

Okay, thanks for help.

Is this filter okay or would you have another idea?
I don't know if 12db is enough?!?!

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: VacuumVoodoo on September 14, 2004, 08:05:16 AM

12db/octave is usually enough although i have seen up to 24db/octave filters being used.
The question that i feel is more important is whether to implement Butterworth or Bessel filter. Bessel filter is slower than Butterworth in reaching the asymptotic 12db slope but has linear phase shift  which IMHO opinion results in a "smoother" (for lack of a better word) sounding transient response.
The difference between these filters is in component values, ciruit is the same.

Your friend who gave you the original ciruit should be able to recalculate it for you, if not i can try to find a moment to do it - but no promises  :wink:

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: on September 14, 2004, 09:15:01 AM

Quote from: "VacuumVoodoo"

whether to implement Butterworth or Bessel filter. Bessel filter is slower than Butterworth in reaching the asymptotic 12db slope but has linear phase shift  which

Or to implement transitional thomson (bessel)-butterworth filter.
(TBT)
You have parameter which says simillarity to
bessel or butterworth.
These filter are known from television engineering as
Pelles-Murakami filters.

                                       xvlk

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: TobWen on September 14, 2004, 02:19:34 PM

does nobody else than me need a variable low-cut/high-pass? :-(

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: clintrubber on September 14, 2004, 06:06:24 PM

Quote

does nobody else than me need a variable low-cut/high-pass? :-(

I guess we all need them...
I forgot if it was here or at the old place, but there were some circuits posted quite alike the the Rane-circuit. Believe they came from a Drawmer DS201, which was recently posted here.

Peter

Title: Hi/Lo Filters
Post by: strangeandbouncy on September 14, 2004, 06:28:23 PM

I lerv the lo/hi cut filters on our SSL E series, they are very "musical" to trot out a somewhat Hackneyed expression . . . They are quite simple in design if i remember correctly. Unfortunately, we don't seem to have a Manual with the desk, but i am sure that quite a few people on this forum do . . . . .
i couldn't do my job without hi/lo cut filters of some kind. My favourites are the ones on Neve 33114 type eq's or even better on audix 33201's.

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: clintrubber on September 14, 2004, 06:31:00 PM

Quote

My favourites are the ones on Neve 33114 type eq's or even better on audix 33201's.

Let's have schematics !  :grin:    please

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: strangeandbouncy on September 14, 2004, 06:53:58 PM

Have Audix Schematics in storage due to recent flooding of my flat . . . will try to find when I go to storage at weekend . . . .sorry! Neve 33114 scematics must be around this forum, surely? Anyone?

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: clintrubber on September 14, 2004, 07:08:25 PM

Please no sorry and take your time. Could imagine you have other things to think about than quickly posting schematics... good luck with you flat.

   Peter

Title: Re: Hi/Lo Filters
Post by: clintrubber on December 31, 2006, 10:23:42 AM

Quote from: "strangeandbouncy"

My favourites are the ones on Neve 33114 type eq's or even better on audix 33201's.

Hmm, I saw those 33114 filters are even third order. I was just adding switches to my from-scratch-circuit to be able change 12dB to 6dB...

Quote

Have Audix Schematics in storage due to recent flooding of my flat . . . will try to find when I go to storage at weekend . . . .sorry! Neve 33114 scematics must be around this forum, surely? Anyone?

If you find a moment to post those Audix schematics I'm interested  :thumb:

W.r.t. 33114, all I was able to find was
http://www.danalexanderaudio.com/neveinfo/33114.jpg

Thanks,

  Peter

Title: variable Low-Cut, High-Pass & High-Cuts
Post by: Kit on December 31, 2006, 11:08:47 AM

Here is what ive been using,

http://munchenmotor.se/mickesbilder/tonkontroll.jpg

Slopes to infinity, though.