Pedal simulation?

[hanumanlangur]

I've been wondering if other DIY people here use SPICE (or other circuit simulators) when making their pedals? I've been starting out on my first pedal, and have been using Gnucap (similar to SPICE) to test it. For the input signal, I use a sin wave that varies between 50mV and 2V. Would this range cover most guitar input signal levels?

Also, have others noticed that when using diodes in an inverting op-amp feedback loop, a smallish (~22k) resistor can be added in series with one of the diodes to add uneven clipping and second harmonic distortion? Have other pedals done this before? I stumbled across this when I was watching the different harmonic levels using Gnucap's Fourier analysis.

[barry]

I use spice often in work and play. My hands down favorite is LTSPICE, a free simulator from www.linear.com. The learning curve may be steep (it has been a while so it is hard to remember), but I can do everything I used to use Microsim for and more. In addition, there are no limits on how many components you can use. It does accept most SPICE statements.

I am also running it successfully under kubuntu and wine if that helps you.

I think your input range is reasonable. There is a huge variety in pickup/effect output levels in my experience. I have seen the resistor/diode series combination before.

Hope that helps,
barry.

[frank.clarke]

Yup, I find it useful, although not 100% accurate. It is a great way to learn and to design new things. I find Circuitmaker and Simetrix reasonable. LTSPICE, I couldn't get the hang of. There are several free windows programs around.

[rocket]

I think 2V peak to peak is quite alot for guitar. On the other you might want to go lower than 50mV - you will have alot less as the tone decays.

Also I would suggest to use a triangle or sawtooth instead of the sinus - you will see the nonlinearity muich better.