hi..i'd like to what does 'higher sampling freq' and 'a/d/a conversion' do to the sound of the multifx? what is it actually? does it play a big part in the sound the pedal makes?
AD/DA = analog-to-digital, digital-to-analog conversion. The better the quality of the hardware converters, the better the sound.

Sampling frequency = the number of times per second a source is sampled. The higher, the better, e.g., 96 kHz (studio-quality) is better than 44.1 kHz (CD-quality).
American HM Strat | LP Studio
Soldano Avenger w/DeYoung OT | Mark IV rackmount | DC-3 rackmount | Single-Recto

when an ADC converts the analog signal to digital, it's breaking it down mathematically into numbers. With a higher sampling rate, it uses more calculations to interpret the sound, so it's closer to the original signal. It's similiar to taking the area under a curve using integrals.

Picture this as a sound wave, and each of the little rectangles is the mathematical interpretation of the sound wave. The more rectangles you use to approximate the wave, the closer it is to the original signal.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
amp clips
amp vids
have you done integrals and limits in math? if yes, a higher sampling rate is like having the limit of the width of your sample decreased. means more samples, which is a closer approximation to the sound curve. an ideal sample rate would really be an integral, so it would basicly be infinitely small. we cant do that in practice, so a higher sample rate will have better quality. after a while though, the benefits of high sr are overshadowed by the fact that: a) we cant tell the difference in quality b) the cost and complexity of the sampler and c) the speed at which we can sample in real time.

so basicly you want a higher sampling rate, but only up to a point. i consider anything over 96 kHz to be overkill, but some people still use stuff higher than that.