Madrigal Imaging BPA 2, BPA 3 manual Special Design Features, Multiple monaural design

Multiple monaural design

Low impedance power supply

Balanced inputs

Robust output stage

Extensive protection

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.

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).

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.

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.

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.

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.

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