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The LED meters (cont.)
This way the user has a rough idea of how much power
the amplifier is putting out IF the impedance was 8Ω or
4Ω. Since the amplifer is meant to drive various load
impedances, and the impedance of the speaker changes
depending on the frequency being reproduced, the
meters are never actually calibrated "power meters."
Secondly, most audio amplifiers (including this one) use
unregulated power supplies.
Unregulated power
supplies do not output a fixed voltage.
Instead, the
output voltage of the power supply will vary based on the
input voltage to it.
The output voltage of the power
supply will also vary based on amplifier load impedance.
These types of supplies are commonly used because
they are more efficient than a regulated power supply,
and arguably produce a more dynamic sound by offering
more headroom than a regulated design. This can be
problamatic for typical output meters.
Example, an
amplifier with a unregulated power supply might clip at
42V RMS output when connected to a 8 ohm load, but
35V RMS when connected to a 4 ohm load. So a typical
output meter might indicate clipping when it is not, or
vice-versa (worse!)
The solution -
In order to avoid the issues outlined
above, we have designed our meters with a dynamic
maximum. That is, instead of the maximum end of the
meter scale being set by a fixed voltage, our meter's full
scale position is relative to the power supply's high
voltage rails. In this way they will much better indicate
that the signal is close to clipping no matter the load on
the amplifier or the input voltage to the amplifier. An
industry first as far as we know .
7
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