10
Special Design Features
Congratulations on your purchase of a Proceed amplifier! While your new ampli-
fier is straightforward in its use, it includes several design features which are re-
sponsible for its outstanding performance. A few of these are given below.
Triple monaural design
Consistent with the finest amplifiers, each audio channel of your Proceed HPA 3
has its own, dedicated power supply—including a separate 663 VA toroidal trans-
former for each channel. The resulting reduction in crosstalk between audio
channels provides superior imaging and reproduction of acoustic space. Demands
placed on one channel have virtually no effect on the performance of the other
channel.
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 amplifier has addressed this important characteristic in a compre-
hensive fashion. For example, the power supply capacitors (which act as “reser-
voirs” of power for the amplifier circuitry) are mounted directly to the printed
circuit board rather than using point to point wiring. The layout of the circuitry
uses short, thick traces for high current paths. This attention to detail yields an
optimal environment in which the amplifier may operate to its maximum poten-
tial.
Balanced inputs
Each channel of your amplifier is individually configurable to receive either bal-
anced 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
available today. The gain structure of the amplifier adjusts automatically when you
select different inputs to facilitate this “mix and match” approach.
Robust output stage
Each channel of your Proceed amplifier uses twelve 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 atten-
tion 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
either DC (direct current) or a short circuit at the output, or any unsafe operating
temperature. In any case, a power relay will cause the amplifier to be discon-
nected from the AC mains. In addition, the AC input to each transformer is fused
to protect against any possibility of component-level failure that could draw dan-
gerous amounts of power. Finally, inrush limiting prevents premature aging of
power supply components during power-up. Once the power supply has been
charged, this in-rush limiting circuitry effectively defeats itself to allow unfettered
power supply access to the AC mains.
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