The MBL Noble Line preamplifier N11 incorporate a new technology developed by MBL called “UNITY GAIN” which provides a clearly audible and measurable sound enhancement.
In a typical music system, the preamplifier
has the task of receiving the music signal originating
from the source device, preparing it, and forwarding it to the power amplifiers
. The power amplifiers expect the preamplifier to relay the signal to them with a maximum of 2 volts RMS. They are designed to deliver their full rated output at 2 volts input level (this value varies within limits, depending on line voltage and rated load, and applies to all output stages of MBL’s and most manufacturers’ amplifiers).
Analogue source devices, such as turntables
, with the associated equalizer pre-amplifier, or tape
decks, provide a voltage of 0.5 volt maximum (tuners and turntables) to 0.75 volts (tape decks).
Nevertheless, in order to achieve a maximum voltage of 2 volts at the amplifier input, the signal
must be "pre-amplified" before being passed on to the output stage. This is the responsibility of
the preamplifier, hence its namesake.
Today's preamplifiers typically amplify the input signal by 12 dB before delivering it to the
amplifier’s input. This corresponds to gain by a factor of 4, making it possible to achieve the
required 2 volts at the output even at input levels of only 0.5 volts.
In a source device with a voltage of 0.75 volts, for example, a voltage of 3 volts would already be
reached at the power amp input and the volume potentiometer would have to be reduced to
about 67% in order to not exceed the maximum level.
In the majority of cases, today's source devices are digital sources and the music signal supplied to
the preamplifier comes from a D/A converter
. These are standardized to the extent that they
deliver a maximum output voltage of 2 volts RMS (+/- 5%) and all D/A converters from MBL strictly
adhere to this requirement (although other manufacturers sometimes exceed this value to sound
Pre-amplification of this signal is not necessary, since the output voltage of the D/A converter
corresponds exactly to what the output stage expects from input voltage. Nevertheless,
manufacturers of preamplifiers have adhered to the system of amplifying a signal originating from
a D/A converter.
In this situation, with the volume turned up fully, a voltage of up to 8 volts (!) would appear at the
output stage’s input, and in order not to exceed the 2 volts, the potentiometer would need to be
turned down to a maximum of 25%.