Fully parametric EQ schematics

[dogfaceaudio]

I'm looking for schematics for fully parametric EQ's from high end audio gear. I'm attempting to build a 5 band EQ with controls for frequency, bandwidth, gain and individual band bypass switches. Thanks!

 

[L´Andratté]

Check Steve Dove´s Studio Sound articles I think they are in the in the GDIY archive!

 

[iampoor1]

Fred Forssell has a paper on it, and the Urei 545 is a good state variable schematic to follow thats pretty easy to mod. Barry Porter
s Net Eq is fantastical as well.

 

[dogfaceaudio]

Grabbed the Steve Dove articles, that mostly appears to cover mixer design which is a useful subject to read about anyway. The Urei 545 schematic is a great resource. I can't seem to find a schematic of the Barry Porter NetEQ. I'd prefer to stay away from switched knobs and use a potentiometer instead for sweepable control over each parameter.

 

[bruno2000]

Grabbed the Steve Dove articles, that mostly appears to cover mixer design which is a useful subject to read about anyway. The Urei 545 schematic is a great resource. I can't seem to find a schematic of the Barry Porter NetEQ. I'd prefer to stay away from switched knobs and use a potentiometer instead for sweepable control over each parameter.

If you can't find the wonderful Barry Porter EQ schematics, you're not looking very hard. 
My $0.02.
Best,
Bruno2000
https://groupdiy.com/index.php?topic=33256.0

 

[abbey road d enfer]

I'm looking for schematics for fully parametric EQ's from high end audio gear. I'm attempting to build a 5 band EQ with controls for frequency, bandwidth, gain and individual band bypass switches. Thanks!

All good parametric EQ's use the SVF topology, with the exception of the GML/Sontec/MEP that uses bridged-T.
I suggest you have a look at the dbx 905 that solves elegantly the issue of RevLog pots, by usin law-steering on linear pots. Only the SVF topology allows that.
The only flaw in the 545 is the use of 4741's, which was all that was available at the time. Today there are much better opamps; noise is a serious issue in SVF filters.

 

[L´Andratté]

The Steve Dove articles contain exactly what you asked for: fully parametric five band eq schematic including individual i/o, based on negative impedance converters, which Fred Forssell also mentions in his paper.

 

[abbey road d enfer]

I'm attempting to build a 5 band EQ with controls for frequency, bandwidth, gain and individual band bypass switches.

I've always felt individual bypass switches to be useless in practice. EQ ON/Off is much more useful IMO.

 

[dogfaceaudio]

I found this page after a bit of looking around Google: http://sound.whsites.net/articles/state-variable.htm#s30
In figure 5 there's a schematic that would suit my needs, but I'm a bit unsure how to calculate the values for C2 and C3 to adjust the frequency range.

 

[abbey road d enfer]

I found this page after a bit of looking around Google: http://sound.whsites.net/articles/state-variable.htm#s30
In figure 5 there's a schematic that would suit my needs, but I'm a bit unsure how to calculate the values for C2 and C3 to adjust the frequency range.

the highest frequency Fmax (frequency pot Full CW) is governed by f=1/2.pi.RC (R being R9/10, C being C2/3).
The lowest frequency is a fraction of the highest frequency
Fmin=Fmax(R12//R9)/(R12//R9+R10), with R12//R9= (R12.R9)/(R12+R9)

 

[gyraf]

I think the Focusrite ISA's worth mentioning here, as she also uses linear pots for frequencies - https://groupdiy.com/index.php?topic=44818.0

The (attached here) Tantek (HomeStudio recording DIY rack module from late 1980'es) is on same principle..

Background: http://www.muzines.co.uk/articles/stack-in-a-rack/1949

Jakob E.

 

[echoplex]

Resurrecting this old thread becuase I'm looking for the Barry Porter Net EQ schematic or similar.
All links I find are down or invalid today.

 

[waltzingbear]

If they are old, try the internet archive, ie the way back machine

 

[peterc]

I have posted what I have of the Net EQ files in the Tech Docs section.

https://groupdiy.com/threads/barry-porter-website-and-articles.81558/