Noticed something funny...

[suryabeep]

Hi everyone,
>I was searching for good 3 band eqs to build when I stumbled across this: https://www.electroschematics.com/6201/3-band-equalizer/
>Downloaded image, went on searching.
>Came across the guitarpcb website: http://www.guitarpcb.com/apps/webstore/products/show/5883546
>The guitarpcb circuit was published around Apr 2015 from the youtube demo. Their site claims: "Interestingly a commercial company released a similar circuit (5) months after the Tone TwEQ release."
>Now I'm thinking wait a sec that circuit looks similar to that one i just saw at electroschematics, I wonder when that version was published? I go check the earliest comments on the post: December 2012.
>
Correct me if I'm wrong, but is guitarpcb rippin on madprofessor for releasing a circuit that they themselves ripped off?

[PRR]

> is guitarpcb rippin on madprofessor for releasing a circuit that they themselves ripped off?

That plan is VERY much older than 2012. 1980s at least. ISTR it being in LM833 documentation, though it is not in the current '833 datasheet.

Here (circuit 2) is a copy of an old, obviously hand-drawn, implementation with the chip the LM833 was supposed to replace. There are differences, yes. But clearly your "2012" plan was not done on virgin paper.

[Digital Larry]

I'm surprised there is even a concept of "ripping off" an EQ circuit based on on op-amp. 

[ElectricDruid]

I agree, Larry. I don't think there is.

It's a basic Baxandall 3-band circuit. I think Baxandall's original 2-band implementation even pre-dates the op-amp. Looking it up, it was published in 1950 and then made popular in Wireless World in 1952. So we can call that "public domain" by now, I reckon...

Tom

PS: In fact, have a look at the original article. It makes fascinating reading:

http://www.learnabout-electronics.org/Downloads/NegativeFeedbackTone.pdf

[suryabeep]

ah thanks for the information guys!
However I still don't quite think it's fair for guitarPCB to be 'calling out' Mad Professor for using this schematic, especially seeing if it's old enough to be public domain

[Rob Strand]

I thought we narrowed the origin date for the three-band EQ back 1974 to 1976 based on the Jung's book and the National Semiconductor Audio handbook (1976).  Maybe in Ranko's bass preamp thread around Christmas.

[amz-fx]

[ElectricDruid]

I thought we narrowed the origin date for the three-band EQ back 1974 to 1976 based on the Jung's book and the National Semiconductor Audio handbook (1976).  Maybe in Ranko's bass preamp thread around Christmas.

I don't know, I don't remember that thread. I didn't know when the third band was added, so that's interesting. Amazing it took over twenty years for it to grow a third band!

I agree that no-one should be calling anyone out for using such a widespread and well-known circuit. More likely they were just miffed that someone else should be commercialising it too and stealing their sales. I notice they don't claim any originality.

T.

[Rob Strand]

I don't know, I don't remember that thread. I didn't know when the third band was added, so that's interesting. Amazing it took over twenty years for it to grow a third band!

Here's the thread.   I always assumed  the idea came from Dennis Bohn from Rane, and who wrote a lot of the  National Semiconductor Audio handbook.   However PRR pointed out it appeared in Jung's book Ed2.  We needed a copy of Ed 1 of Jung's book to resolve it once and for all.  It's all here,
http://www.diystompboxes.com/smfforum/index.php?topic=118943.40

As for some good ones.  Most are set-up for bass.   The problem with the three-band is a low Q for the mids and it's hard to increase the bass frequency if the mid frequency is too low.  The highs can get extra boost in the mid region which make the slope of the boost look low.  I've spent a lot of time tweaking those things over the years.

The Music-Man bass 3-band is OK but it has the high-pass filter (which helps push the bass frequency up through an indirect mechanism). 

Another one that looked OK was the G&L 3-band.
https://www.bassesbyleo.com/forum/viewtopic.php?f=28&t=2342

Personally I'd go for a 2-band with a separate peaking EQ (the common mid's version of the Baxandall, which was also in National Semiconductor Audio handbook (1976)).

[amz-fx]

I have Ed 1 (1974) of Jung's book and the bump equalizer is shown there in the same diagram as in Ed 2. PRR posted it in the other thread:


regards, Jack

[Rob Strand]

I have Ed 1 (1974) of Jung's book and the bump equalizer is shown there in the same diagram as in Ed 2. PRR posted it in the other thread:

Awesome Jack, thanks a lot!

I forgot the history issue was for the mid control not the 3-band.  Maybe the 3-band was Bohn.