PD HD500X - Difference between physical EQ knobs, and EQ stompbox fx? in POD HD Posted March 9, 2016 Yes, the physical EQ knobs equate the the knobs you would normally find on an amp. There are a number of reasons why you would use digital FX EQ's depending on the effect. For example, the EQ knobs for the amp are somewhat wide scoped in frequency range and vary from amp to amp. In some cases you may want to accentuate or deaccentuate a certain specific and tighter range of frequencies within the frequency range than what's set by the amp, so you might appy one of the many, various parametric or graphic EQ FX at the end of the signal chain. In another case you might want to change the tone when you kick into a lead, so you would adjust the EQ knobs on a boost or overdrive pedal to get that effect. Basically the EQ settings on many of the FX are there for fine tuning, but they will all be subject to and affected by the base EQ set on the amp. Thanks for the reply, that is good information.