DESIGN PHILOSOPHY
9
To maintain “Precision Bias” requires an advanced bias circuit that must have a very high
degree of stability under a wide range of temperatures and load conditions. The usual
bias network is of such high impedance and poor thermal regulation that at the extremes
of operation, bias currents are ineffectively controlled. Advanced tracking techniques
results in absolute control of bias currents under all conditions in the S12.5.
The main power supply of the amplifier consists of a 1500VA toroidal power transformer
with independent rectifiers to isolate the channels from one another. One hundred
fourty-four thousand microfarads of total capacitance provide effective filtering.
The above attributes result in a amplifier of such extreme linearity and bandwidth that no
overall feedback correction is required or used. One advantage of this is a high degree
of immunity from interactions with loads or cables and a superior transient response. An
extremely low nonreactive output impedance is maintained well beyond 20,000 hz. The
resulting uniform damping factor is not usually found in other designs.
The S12.5 has all structural parts made of machined aluminum which are milled
to very close tolerances yielding the seamless appearance characteristic of previous
products from Coda. As with all Class A amplifiers, heat dissipation is
important. The
S12.5 uses four massive heat sinks for efficient, noiseless, and clean thermal relief.
The thermal coefficient of the heat sinks is one of the lowest and most effective in the
audio industry.
I. Design Philosophy and Approach (continued)