Graphic Equalizer design HELP needed

[hrg2112]

Hello,
I'll attatch two circuits. The first is a bit of a classic
Graphic EQ design.
Q1 : I want to know if the secong circuit would work, using multiple resistors (EQ by increments :-) instead of potentiometers, and if I could use only one array of resistors to do the job. In this example, I drew multiple SPST switches, but it could be jumpers for example. In the two drawings, I put two stages of EQ, but there could be any number.
Q2: What are the best OpAmps (Quality + low power) for the job ?
Q3: If the design works, would the resistor values better be calculated in pseudo logarithmic fashion ?
Thanks !

[hrg2112]

[gmphadte]

LM4562, it is the best.

Gajanan Phadte

[moamps]

Originally posted by hrg2112
Q1 : I want to know if the secong circuit would work, using multiple resistors (EQ by increments :-) instead of potentiometers, and if I could use only one array of resistors to do the job. In this example, I drew multiple SPST switches, but it could be jumpers for example. In the two drawings, I put two stages of EQ, but there could be any number.
Q2: What are the best OpAmps (Quality + low power) for the job ?
Q3: If the design works, would the resistor values better be calculated in pseudo logarithmic fashion ?

A1:
Yes, multiple resistors would work. Some professional mixing consoles use such equalizers.
A2:
This is a tough one as the answer will depend on personal preferences and the budget available.
A3:
When potentiometers are used in professional audio, they are linear pots with center detent. When resistors are used (the way you are using them here), resistor values should preferrably model the S-curve. As an example, for attentuation values ranging from -10 to +10dB in 2dB steps, the following resistor string is used: 150, 180, 270, 270, 270, 270, 270, 270, 180, 150.

Regards,
Milan

[Nordic]

http://www.swtpc.com/mholley/Popular...PE_May1974.htm

You may enjoy this ancient article...