Parametric eq

[dhuebert]

I have been trying without success to find a good schematic for a parametric eq. There is a lot out there but nothing simple to build with a couple of OP amps. Every mixer on the planet has one on it so you'd think there would be hundreds of schematics out there but there seems to be some kind of conspiracy to keep these things hidden away.

Don

[kheper]

Here is one from a forum post:



If you can find the back issues of Electronotes from the 1970s, there were many similar designs.

I may have one from an old synth construction book, but it'll take time to find it.

[jgf]

Just ran across one yesterday on the Nat. Semi. LME49720 datasheet.

http://www.national.com/pf/LM/LME49720.html

[jgf]

Just ran across one yesterday on the Nat. Semi. LME49720 datasheet.

http://www.national.com/pf/LM/LME49720.html

Oh, yeah, I should read the post carefully and look at the schematic...
PARAMETRIC eq. Cool! is Q equivalent to the frequency range (width) affected?

[dhuebert]

I didn't see a parametric eq in the TI datasheet, a couple of graphic eqs tho.

Don

[jgf]

I didn't see a parametric eq in the TI datasheet, a couple of graphic eqs tho.

Don

Yes, hence my d'oh! post following the first one.

[burnedfingers]

Just wondering why you would want a parametric as opposed to a 31 band.

I have one or two 31 band Eq's that I could send you for postage cost.

[Geek]

I know for recording, they are incredibly handy. And having played bass, they're unbeatable for that. Useful for PA too, or other places you have clue not one the acoustics of the venue.

Not sure of home playback use, though

Cheers!

[dhuebert]

The para eq is for a friend who plays harmonica thru a guitar amp and has a problem with feedback. As an interesting project I would like to see if a para eq can be used to notch out the feedback signal. Evidence so far is that it will work. The feedback frequency is far beyond the range of the harmonica and a graphic eq does the job somewhat.

Don

[battradio]

A bit of digital delay might also help .

[soundbrigade]

I remember an eq from Popular or Radio Electronics fram back in the good old stone age (silicon stone). It was much organized in octaves except för lower (?) or upper (?) ends, where it was constructed like an ordinary tone control "as that end didn't to be equalized in octaves - you didn't hear that".
Time for some googling.

[kheper]

Here's a notch filter. It is a passive device, using a mini-audio transformer.

[kheper]

I think this is the recommended transformer for the notch filter:

http://www.mouser.com/ProductDetail/Xic ... NCGw%3d%3d

[Ty_Bower]

Just wondering why you would want a parametric...

If you've ever used a parametric EQ, you'd probably never want to go back to the multi-band graphic EQ. At least, I know I don't. I picked up a DSP based parametric equalizer, and often wonder how I ever got along without it.

I believe they also offer some significant sonic advantages (wrt phase shifts?) when compared to graphic equalizers.

[burnedfingers]

I'm used to playing with Shure DFR22's ,DFR11's and other equipment that will make and install a feedback filter of the needed frequency.

The main thing I have against parametric EQ's is the notch filter is usually larger than what is needed to get rid of feedback.

Have played with a variety of different equipment from sound web devices to you name it. Unfortunately I am used to lugging around all the test gear to various sites. I can generally setup a 31 band faster than most can a parametric if eqing a system. Feedback is simple set a mic out and start turning up the gain slowly and start setting filters.

Quote:
The para eq is for a friend who plays harmonica thru a guitar amp and has a problem with feedback. As an interesting project I would like to see if a para eq can be used to notch out the feedback signal. Evidence so far is that it will work. The feedback frequency is far beyond the range of the harmonica and a graphic eq does the job somewhat.

I just happen to have two Shure DFR11's and a Shure DFR22 for sale if your interested. Both have the capability of immediately making feedback filters.