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I am wanting to know what the typical frequency cut-offs are for the bass/mid/treble controls on a pre-1990s guitar amp. I want to simulate them in Java. So basically I have

bass = 20 - 250 Hz
mid = 250 - 650 Hz
treble = 650 - 4000 Hz 

But I have no confidence in these figures. References would be great!

EDIT: Got a great algorithm from David Yeh's paper .... once you work out that the H(Z) transform is not really an algebraic expression, and how to turn it into code.

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2  
Sounds like this might be a better fit for music.SE. –  Jason R May 18 '13 at 0:17
    
I think if he wants to know the cutoff frequencies, this is a good place. For help programming ii dsp.SE or StackOverflow. –  Bjorn Roche May 18 '13 at 2:21
    
Is there a reason you are set on using Java for signal processing? –  ObscureRobot May 18 '13 at 5:18
    
I'm on Android and its just not worth moving the data down to c for a few nano seconds speedup. But its easy to translate either way. –  hack_on May 18 '13 at 6:26

1 Answer 1

up vote 6 down vote accepted

The classic "tone stack" or three band EQ found on many guitar and bass amps is not usually implemented as three separate second order filters, but rather one third order filter with three parameters. As a result, the various "bands" aren't shaped and defined in the way you'd like. In particular, there is no "flat" setting and the range around 1kHz is effected by all knobs.

For a nice overview of this, along with some matlab code implementing a classic Tone Stack, see Chapter 12 of DAFX. (The matlab file is bassman.m)

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1  
OK thanks. Things are never as simple as they seem at first. I'll go elsewhere and ask for a java tones-tack emulation. –  hack_on May 18 '13 at 3:50
    
On the second look I saw the link to the code at the top-right corner :) Thanks. –  hack_on May 18 '13 at 13:22

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