> On 11/29/2023 3:09 AM EST Jens Johansson <[email protected]> wrote: > > > Been lurking for 20+ years off and on :D > > I would finally like to ask for some advice. I have this idea to simulate a > guitar stomp box (a Morley JD-10). Most of the filters are simple RC type > circuits which I think (hope) that I can figure out by analyzing, farting > around in LTSpice, and then using some of the formulas from the Audio EQ > Cookbook. >
Audio EQ Cookbook is limited to about seven different classes of second-order filters that are commonly used. Not every possible frequency-response is covered, but you might be able to cascade or parallel a few sections to approximate a given frequency response. You might be able to cascade a low-shelf, peaking EQ, and high-shelf to get pretty close to your BASS, MID, and TREBLE frequency response you want. Perhaps even the two shelving filters can be simpler first-order. > However, there is an EQ section which doesn't quite fit into those molds. Or > does it? > Probably not exactly, but it should be possible to cascade a couple second-order biquad filters to get it. It appears to have 5 capacitors (but what precedes the input on the left is possibly important and what comes after the output on the right might also be important), so conceivably it's a 5th-order filter, which can be broken down into a couple second-order filters and *maybe* you'll also need an additional first-order section. But you need to figure out what the poles and zeros are. > What would the esteemed mailing list's advice be, is it even possible to > analyze Yes it is. You use circuit analysis (like Node-Voltage) that EEs learn in college. > and simulate the below circuit just with simple(r) feed-forward and feedback > algorithms, or is it so complex that I would have to take the step how to > learn to deal with those "Wave Digital Filters"? I am curious about C6. What does that "4n7" mean? Is that just a typo and it's just another 47 nanofarad cap? And what does R7 connect to? What is "N"? Is it another kind of ground? Or is it some buss somewhere? -- r b-j . _ . _ . _ . _ [email protected] "Imagination is more important than knowledge." . . .
