Vertex user tip Sep 2012 - amplifier feedback

Firstly, apologies fo no user tip in August - we were on holidays!

This month the tip is about the amounts of feedback in your choice of power amps. Many times in the past this topic has come up with customers, and what choice they make. Is feedback an important consideration, or should they just look at the power and frequency responce figures alone? 

Well in our view feedback figures are much more important than power or frequency response. If power is reasonable for the system, then its often the amount of feedback in an amplifier design that really influences the musical presentation. 

When designing an amp, we can increase the amount of feedback in the circuit in order to produce a wide overall bandwidth from the design. When its measured and tested with simple sine wave signals we appear to get a better amp. But what we have learned from the mathematics of the systematic approach, is that feedback increases tracking error. Or in other words, greater feedback reduces the system's ability to rapidly respond to complex music. Of course, with lower feedback you may get an amplifier who's specs might not show as much bass or treble extension - but usually this is not a significant sacrifice in musical terms. But amps with lower feedback seem much more responsive, lifelike and transparent.

We suggest you read round the web and lots of reviews on amplifiers - and specifically look out for other people's opinion on the sound quality aspect of low feedback designs. These types of amplifiers might not be what you're after, but if you are one of those who is working towards a good 'low tracking error' system, then you should include the debate about feedback levels in your thinking.