10
Special Design Features
Congratulations on your purchase of a Proceed BPA! While your new amplifier is
straightforward in its use, it includes several design features which are responsible
for its outstanding performance. A few of these are given below.
Multiple monaural design
Consistent with the finest amplifiers, your Proceed BPA is a true “multiple monau-
ral” design. Each audio channel has its own, dedicated power supply—including a
separate 300VA toroidal transformer for each channel. This approach reduces
crosstalk between audio channels for superior imaging and reproduction of
acoustic space. The demands placed on one channel have virtually no effect on
the performance of the other channel(s).
Low impedance power supply
A critical factor in the ultimate performance of an amplifier is its “power supply
impedance,” which can be loosely thought of as the freedom with which the au-
dio circuitry has access to the power it needs, when it needs it. The design of
your Proceed BPA has addressed this important characteristic in a comprehensive
fashion. For example, the power supply capacitors (which act as “reservoirs” of
power for the amplifier circuitry) are mounted directly to the printed circuit
board, immediately adjacent to the output transistors (which require the greatest
amount of current). The layout of the circuitry uses short, thick traces for high
current paths. Internal current capability is further enhanced with high purity
copper buss bars. This attention to detail yields an optimal environment in which
the amplifier may operate to its maximum potential.
Balanced inputs
Each channel of your BPA is individually configurable to receive either balanced
or single-ended inputs. This approach allows you to take full advantage of the
greater immunity from noise, RFI, and EMI which balanced transmission of audio
signals offers on any preamp-to-amplifier connection where it is supported. At
the same time, any or all channels of the amplifier may be configured for single-
ended inputs to maintain compatibility with the majority of preamplifiers avail-
able today. The gain structure of the BPA adjusts automatically when you select
different inputs to facilitate this “mix and match” approach.
Robust output stage
Each channel of your Proceed BPA uses eight 150 watt power transistors. These
transistors are all individually tested and sorted, and are used in matched sets to
ensure that no one transistor bears a disproportionate part of the overall load.
The combination of an “overbuilt” design specification and extraordinary attention
to detail in manufacturing improves performance, reliability, and longevity.
Extensive protection
Your Proceed amplifier will shut itself down if it senses either the presence of
DC (direct current) at the output or an unsafe operating temperature. In either
case, a power relay will cause the amplifier to be disconnected from the AC
mains. In addition, the AC input to each transformer is fused to protect against
excessive current conditions such as driving shorted outputs. Finally, inrush limit-
ing prevents premature aging of power supply components during power-up, and
switches off-line once the power supply has been charged.
