Coda Stereo Amplifier 40.0 - Manual (Page 10)

I. Design Philosophy and Approach
The subtlety of the design process at this level of performance makes it impossible to
easily explain all of the advantages inherent in the 33.0. However, we present here an
overview to give you an understanding of some of its unique features and an idea of
the listening experience you can expect. Often a particular technique has numer-
ous unrelated advantages and possibilities. We make every effort to exploit these
advantages with the final result being an amplifier that performs better than the
sum of its individual features suggest.
The topology and component selection is built on the foundation established by
the Coda System 100. Balanced interconnections are provided to take advantage
of their greater noise rejection. Differential voltage gain throughout provides excep-
tional rejection of external noise and contributes to the inherent DC stability of the
circuit. This allows direct coupling without servo circuitry. The unit also uses output
followers operating without feedback.
Excellent high frequency design insures linear operation at high speed, and trans-
lates into a sonic reproduction which is extremely transparent in character. The power
supply takes a very direct approach to high performance. First, top quality toroidal
transformers and over 184,000uf of capacitance with very low ESR and inductance are
used. For optimum performance and reliability all circuitry remains continuously
powered.
The specifications are consistent with what would be expected in a high current ampli-
fier design. In this design , however , an unusual degree of attention has been paid to
sonically meaningful parameters.
For example, the current stage is capable of producing peak currents in excess of
100 Amperes with a degree of linearity and speed unmatched by other designs
producing only a fraction of of this current. This is achieved by the implementation of
several distinct circuit features.
Extremely wide bandwidth transistors are used in the output stage instead of the usual
TO3 devices used in other output designs. Each channel uses 30 individual output
transistors with a combined power rating of 1500 Watts and 120 Amperes with a
bandwidth of 50 Mhz.
The 33.0 uses bias voltages and component values which have been specifically
selected to produce a precision transition with no abrupt changes in distortion or
output impedance. This “Precision Bias” technique yields seamless performance
regardless of the complexity of the load impedance and is particularly effective at
eliminating IM distortion which often occurs in these instances.
DESIGN PHILOSOPHY 9