Genelec ROSE Manual

ROSE
A Comparison of Modular State-of-the-Art Switch
Mode and Linear Audio Power Amplifiers
Darren Rose
Genelec OY, Iisalmi, Finland
ABSTRACT
Modern commercially available, compact, low power audio power amplifiers are mostly designed around one of
three main technologies. These are integrated circuit class AB, thick film hybrid class AB, and switch mode power
amplifier modules. The decision to use a particular technology is not only based on idealised performance
specifications, but also on the performance under realistic operating conditions, and cost-to-performance
considerations. In this study, the performance of each amplifier technology is studied in ideal and realistic operating
conditions with two amplifier designs for each technology category. Regulated and unregulated power supplies are
used, in combination with ideal resistive and real-life complex impedance loudspeaker loads. For a fixed nominal
supply voltage, the value of the different technologies with regard to noise, distortion and continuous output power
is discussed. This results in an analysis of the cost effectiveness, or value, of currently competing technologies for
high quality, low power, compact audio power amplifiers.
0. INTRODUCTION
Modular power amplifiers are almost universally chosen for low
power, compact, audio power amplifiers because of cost-
effectiveness and advantageous size-to-performance ratio.
The ever-growing list of modular power amplifiers makes selection
very difficult. Datasheets for available power amplifier modules
show the performance of the modules in various conditions, but do
not reveal the performance-to-cost ratio, or value. This paper stems
from the need to justify the choice to use a particular contemporary
power amplifier module, of a particular technology, when budget
restrictions are in place.
1. POWER AMPLIFIER CONFIGURATIONS
There are several classes of power amplifier configurations. The
configurations most commonly used in audio power amplifiers are
class AB and switch mode configurations.
TH
AES 112 CONVENTION, MUNICH, GERMANY, 2002 MAY 10–13
COMPARISON OF AUDIO POWER AMPLIFIERS
1.1. Class AB Audio Power Amplifiers
Class AB power amplifiers have been used for decades in audio
reproduction, and have become well accepted. They are relatively
easy to design for mass production, and can be configured to give
almost any required output power. The total harmonic distortion
and noise (THD+N) can be reduced to 0.001% or less below
10kHz at reasonable output levels [1, p. 290]. This remaining
THD+N is mostly noise and crossover distortion.
It is possible to buy class AB power amplifiers as nearly complete
modules. These fall into two main categories: integrated circuit
(IC) and thick film hybrid (TFH). The IC is a circuit made on one
piece of silicon, normally encased in plastic, with metal legs. The
TFH is constructed from small discreet components mounted on an
aluminium substrate, which is then fitted with a plastic cover and
metal legs.
ICs are generally smaller and cheaper, with less output capability
and lower maximum operating voltages. They also tend to have
more comprehensive internal protection functions.
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