Coda 10.5 operation manual Design Philosophy and Approach

DESIGN PHILOSOPHY 9

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 Amplifier 11.5. 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 numerous unrelated advantages and possibilities. We make every effort to exploit these advantages with the final result being an amplifier that is greater than the sum of its individual features

The topology and component selection is built on the foundation established by the Amplifier System 100. Balanced interconnections are provided to take advantage of their greater noise rejection as in the 100. Differential voltage gain throughout provides exceptional 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.

The front end of the Amplifier 11.5 is designed to operate without ever entering Class B operation as is common in many other designs. This combined with excellent high frequency design insures linear operation at high speed, and translates into a sonic reproduction which is extremely transparent in character. The supplie take a very direct approach to high performance. First, a top quality toroid transformer and over 200,000 uf of capacitance with very low ESR and inductance is used. For optimum performance and reliability all circuity remains continuosly powered.

The specifications are consistent with what would be expected in a high current Class A amplifier 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 which is not matched by other designs when producing only a fraction of of this current. This is achieved by the implementation of several distinct circuit features.

In the Amplifier 11.5 extremely wide bandwidth output transistors are used instead of the usual TO3 devices which are used in other transistor designs. Each channel uses 24 individual output transistors with a combined power rating of 4800 Watts and 180 Amperes with a bandwidth of 10 Mhz.

The manner in which the Amplifier 11.5 accomplishes Class A operation is also different than that employed in conventional designs. All Class A designs leave Class A operation when they are operated into loads of sufficiently low impedance or power levels. Generally, this transition will produce a large and abrupt distortion increase.

The Amplifier 11.5 uses bias voltages and component values which have been specifi- cally selected to produce a precision transition with no abrupt changes in distortion or output impedance. This “Precision Bias” technique yields seemless performance regard- less of the complexity of the load impedance and is particularly effective at eliminating a form of IM distortion which often occurs in these instances.