ShortCuts

The theory of the Otala amplifiers, and thus the basis for the Electrocompaniet amplifiers, has been detailed by many papers, mostly by Matti Otala, but also by several others.  At Electrocompaniet these theories were extended, and a theoretical framework for our amplifiers were established.  The following pages will give you an insight into both the original theories by Dr. Matti Otala, and also the theories built up in the first years of Electrocompaniet.  Some of the thoughts are solely mine, however.  Don't assume that Electocompaniet of today will vouche for all I say here :-)

	On TIM, DIM, Nonlinearity  and Distortion TIM   :::  This was the starting point of Otala's theories, and his own idea from the beginning.  Early seventies many people had already noticed that the sound of the new transistor amplifiers were inferior to the sound of the tube amplifiers.   How could that be, when the trans-amps had less distortion than the tubes ??? DIM - what it is and how it relates to TIM.  This was when everybody tried to find measurement   methods. The debates and the quarrels - but Otala was right ! "All distortions are equal, but some are more equal than others."  That was the feeling at Electrocompaniet at that time, and the beginning of an understanding of how these distortion mechanisms interacted, and how they affected the sound.  Also the understanding that the basis of all distortions are the nonlinearity.  The nonlinearity is the source, the distortions the symptoms.
	A theoretical framework for building good-sounding amplifiers A theory of single stages    A single stage is the basis for all amplifications, and at Electrocompaniet a model for the single stage and an "our way" evolved.  A theory of multiple stages    Multiple stages put together do not behave as N times a single stage, they interact.  In many cases they even counteract.   We explain how.  And how to design with multiple stages. A theory of feedback    Many people are either pro-feedback or fully against feedback.  At Electrocompaniet we learned to live with feedback in all forms, local and loop, and learned how to get it as a friend and not as an enemy. Output stages - that current - what does it do ?
	How do we calculate the nonlinearity Calculations of input stage nonlinerity    This is simple, when you know how, a table summarises everything Calculations of the nonlineairy of multiple stages.  This is more complicated, but by following a set of rules, and abiding by the general model we use, it is not THAT difficult. Calculations of distortions    One thing is the nonlinearity, another is how much distortion of the different types your amp will measure.  We explain how these are connected. Designing for lowest distortion    Here we tell you how to optimize your design to get lowest possible distortion.  Note that there very seldom exist one optimum point.  There are just too many variables, so you have to use som creativity and feeling for what's going on.
	Frequency response, rise times, slew-rate      What's the difference ? Open and closed loop frequency response How the frequency plane and time plane interconnects Time response behaviour Poles and zeroes Compensation of an amplifier
	Other factors The damping factor  - or output impedance, what is it ? Why there are no simple solutions Power supply interaction RFI - what can it do The importance of the components