Any hints on simulation of circuits (spice simulation)?

[slajeune]

Hi All,

I am trying to learn how to make my own pedals and effects.  I want to use something like spice simulation (with a software like circuitmaker).  Does anybody have any hints on using such a simulation?

I am looking for things like:

- What are the proper parameters for the signal generator?  The values that I am using are 0.43V and 440Hz.
- Any other hints in modeling and observing the wave patterns to guestimate the output of the effect.

Thanks,
Stephane Lajeunesse.

[Mike Burgundy]

Having a good feel of what a circuit does really helps when simulating. Guitar output varies from 10mV to 1V for hot pickups. A Low E has a fundamental of just over 80Hz, the A has a fundamental of 110 (so the tuningfork is actually two octaves up).
I use 100Hz to 1kHz for sims. You can see clipping waveforms that give an indication of clipping sound (hard/soft, symmetrical, asymmetrical). You can even do a fourier analysis to get an idea of harmonic content (asymmetrical clipping has more even order harmonic content and sounds smoother for single notes than symmetrical clipping (more odd order harmonics, harsher sound, BUT smoother ob chords). You can sim voltages, see if your biaspoints are ok, etc.
What it all *really* sounds like is an educated guess.
I do know Orcad can import a .wav as a source generator and put the output into a .wav, but this is an expensive professional package. Plus I've used it and reality sounds really different
I don't use sims to see what something might sound like, I do occasionally use them to check if a circuit "works" (biaspoints, power, component ratings, oscillation even - Orcad can do that!)

[slajeune]

Hi Mike,

thanks for your help!  it is very appreciated.  There isn't a lot of talk about 'circuit simulation' on the forums.  As I am just starting to learn some stuff, I like the immediate feedback that such a software can give you.  I fully understand that it is a simulation and it can be wrong.

Thanks!
Stephane.

[The Tone God]

I have to agree with Mike. Sims are good to test ideas and see if something will work. This can be especially nice if its a complex circuit that would take alot of time to breadboard and you not sure it will even work. Most of the circuits used around here are simple enough that breadboarding could be done quickly and you can the real results fast.

Beyond that I don't think simulators will give you a good idea of how a circuit will sounds. Various freqs, gains, amplitudes on both the input and output would be tough to judge based on resulting waveform. Unless you've spent time playing with things while staring at a scope you probably won't get much from the sim.

Also there is mother nature which a sim does not take into account. She always finds a way in if there is one.

This is probably why not many here use sims. It is another tool but you can't do everything in them.

Andrew