5 band EQ IC - LA3600 or BA3812?

Started by blackieNYC, December 21, 2015, 06:35:29 PM

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blackieNYC

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http://29hourmusicpeople.bandcamp.com/
Tapflo filter, Gator, Magnus Modulus +,Meathead, 4049er,Great Destroyer,Scrambler+, para EQ, Azabache, two-loop mix/blend, Slow Gear, Phase Royal, Escobedo PWM, Uglyface, Jawari,Corruptor,Tri-Vibe,Battery Warmers

R.G.

As noted here: http://www.geofex.com/article_folders/eqs/paramet.htm , why bother with a special purpose chip? A dual opamp and five high gain NPNs does the same, and is remarkably similar to the circuits inside those "EQ ICs".

I did dueling layouts for the opamp/transistor approach and the IC approach with another similar chip, the KA2223, and they were the same size. Resistors are about $0.01 to $0.02, and the number of caps are remarkably the same.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

blackieNYC

Thanks RG. I've built your single band parametric and I use it a lot. 
I was playing with my boss eq and decided I would build a metal pedal with an eq built it. I thought this would be a low parts count option. And small. A one-off build.
Someone posted a graph of the graphic eq with op amps vs transistors, which were very slightly broader in bandwidth. A functional toss-up, IIRC.
(BTW If I leave the parametric's Q very narrow and boosted, the thing will oscillate on power up. It can be heard somewhat when bypassed - a multi-pedal.  I simply remember to roll back the settings when I set up and it goes away. I suppose I should limit the Q somewhat.)
  • SUPPORTER
http://29hourmusicpeople.bandcamp.com/
Tapflo filter, Gator, Magnus Modulus +,Meathead, 4049er,Great Destroyer,Scrambler+, para EQ, Azabache, two-loop mix/blend, Slow Gear, Phase Royal, Escobedo PWM, Uglyface, Jawari,Corruptor,Tri-Vibe,Battery Warmers

blackieNYC

RG's layout with a similar chip, from deep within Geofex. About the same size
http://geofex.com/Article_Folders/EQs/greqs.gif. I do perf so I might get it smaller.
  • SUPPORTER
http://29hourmusicpeople.bandcamp.com/
Tapflo filter, Gator, Magnus Modulus +,Meathead, 4049er,Great Destroyer,Scrambler+, para EQ, Azabache, two-loop mix/blend, Slow Gear, Phase Royal, Escobedo PWM, Uglyface, Jawari,Corruptor,Tri-Vibe,Battery Warmers