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Project Specific Discussions => Filters/Equalizers => Topic started by: weiss on February 05, 2019, 02:22:41 PM

Title: Simple High Pass and Low Pass Filter unit for mastering
Post by: weiss on February 05, 2019, 02:22:41 PM
Hey guys,

i was wondering if anyone ever built like a hpf/lpf filter unit (like used in the bax eq for example) without any other filters involved. Preferably with switchable slope, 24/48db 6/12db (no idea if that's possible)?

Is it a complex task to build?

thanks for the input
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: john12ax7 on February 05, 2019, 06:13:25 PM
Is a super high slope that useful? Seems there would be more phase issues.
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: weiss on February 05, 2019, 06:36:29 PM
Is a super high slope that useful? Seems there would be more phase issues.

you are right, after reading some more, i gotta correct myself. probably 6 or 12 db is enough  ::)
Now i came across the harrison ford filters. seems to be most usable for what i had planned.
other ideas/experiences?

thanks  :)
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: john12ax7 on February 05, 2019, 06:48:02 PM
The harrison would do the job. Although for mastering you probably want stepped switches?  So you could go even simpler, passive RC networks  with a buffer.
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: weiss on February 05, 2019, 06:58:13 PM
The harrison would do the job. Although for mastering you probably want stepped switches?  So you could go even simpler, passive RC networks  with a buffer.

indeed i need switches only.
you mean something like that? how would i realize different frequencies?

LP
(https://www.electronics-tutorials.ws/filter/fil90.gif)

HP
(https://www.electronics-tutorials.ws/filter/fil92.gif)
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: john12ax7 on February 05, 2019, 08:05:53 PM
Those are the classic Sallen Key filters that the harrsion and others are based on. If you look at schematics usually the Cs are fixed and R3 and R4 replaced by a dual pot which then varies the frequency. So just use a switch to select appropriate R values instead of a pot.

Have you seen these? Maybe it could be modded for switched operation?
https://groupdiy.com/index.php?topic=68367.0
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: weiss on March 13, 2019, 05:09:21 PM
Those are the classic Sallen Key filters that the harrsion and others are based on. If you look at schematics usually the Cs are fixed and R3 and R4 replaced by a dual pot which then varies the frequency. So just use a switch to select appropriate R values instead of a pot.

Have you seen these? Maybe it could be modded for switched operation?
https://groupdiy.com/index.php?topic=68367.0

thank you! no, i haven't seen these, looking very nice!
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: Rocinante on March 22, 2019, 02:20:10 PM
I did the Harrison's with stepped switches. I never used them so sold them but I don't do nearly as much mastering as others
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: weiss on March 22, 2019, 06:56:45 PM
I did the Harrison's with stepped switches. I never used them so sold them but I don't do nearly as much mastering as others

nice. simple lorlins? do you remember the values used?
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: SKJGProject on March 23, 2019, 10:09:04 AM
http://www.bereich03-audio.de/mastering_filter.html
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: weiss on March 23, 2019, 10:37:52 AM
http://www.bereich03-audio.de/mastering_filter.html

I know the Filter but i find 500€ excl. VAT way overpriced in relation to the part costs.
Title: Re: Simple High Pass and Low Pass Filter unit for mastering
Post by: Rocinante on March 23, 2019, 11:24:57 AM
I used one of the regular contributors  calculater for rev pots (maybe Harpo or Jeff) ,and yes I used lorlins. I had to do them 3 times.