Symmetrical Pure Class A microphone preamplifiers. The AD2022 is Avalon's fourth generation of fully discrete, Switched 2dB, high-gain preamplifier to +66dB High quality transformer input & isolated output This feature empowers the V5 with a new scale of sonic character.įorward musical detail and sonic excellence Two alternate solid-state topologies are cascaded to provide a rich, low midrange harmonic content not offered in other Avalon preamplifiers. The V5 includes the best of the Avalon U5 DI functions with a studio quality preamplifier and "a new sonic addition". They have found their way into the world's leading musicians rigs and recording sessions and have been featured on thousands of the best selling (and sounding) albums, downloads and live performances. The Avalon DI-preamplifiers have been in use around the world since 1985. This will change the lower limit of the dynamic range of the microphone/preamplifier combination, thus limiting the ability to measure very low sound pressure levels.ĬCP (Constant Current Power) is the same as IEPE (Integrated Electronic Piezo-Electric) and CCLD (Constant Current Line Drive) and is compatible with many other constant current driven products such as Deltatron®, Isotron, etc.V5 Pure Class A DI-RE-Microphone Preamplifier The only effect of elevated temperature is a slight increase in inherent noise level. Special versions for use at temperatures up to 120☌ (248☏) are available on request. They will work within their specifications up to a temperature of 70☌ (158☏). The casings are made of stainless steel for maximum strength and durability with minimal sensitivity to vibration and microphonics. They are all compatible with measurement microphones as defined in the international standard IEC 61094 “Measurement Microphones, Part 4: Specifications for working standard microphones”.Īll GRAS preamplifiers are built around a small, thick-film precision amplifier with very high input impedance. GRAS microphone preamplifiers are all small, robust units optimised for acoustical measurements with condenser microphones. The range of available prepolarized microphones is still not as wide as for externally-polarized microphones, although GRAS was the first in the world to introduce 1/4” prepolarized microphones and have also released a 1/8” prepolarized microphone. This is traded off by accepting a lower upper limit in dynamic range (due to the lower driving voltage of a constant-current source) which limits the maximum output signal to approximately 8 Vpeak, and the necessity of having to use prepolarized microphones. This means that simple co-axial cables can be used instead of the more complex 7-core cables used with the voltage driven LEMO types. The great advantage of CCP preamplifiers is that they use a two-wire system, where the signal is superimposed on the wire through which the current is kept constant. The output signal from the microphone superimposes fluctuations around this DC level. A CCP preamplifier uses a Constant Current Power supply, which must be between 2 mA and 20 mA (nominally 4 mA), to produce a constant nominal voltage level of 12 Volt DC (referred to as the bias voltage). Before that, the quality of CCP preamplifiers was not as good as the voltage driven LEMO types, but this is not the case today. The other principle uses a Constant Current Power (CCP) supply and was introduced around 1996 to the world of high-precision acoustics. It is voltage driven and can handle high voltage signals up to 50Vpeak. One is the traditional type for externally-polarized microphones often referred to as the “LEMO” type because of its 7-pin connector and has become an industry standard. There are today two different preamplifier principles in the world of acoustics. The highest level is related to the preamplifier’s supply voltage, whereas the lowest level is related to the electrical noise generated by the preamplifier itself. The dynamic range of a preamplifier is defined as the range between the highest level that the preamplifier can handle without distortion, and the lowest level it can measure. High microphone capacitance gives a low cut-off frequency. The lower end is determined by the input impedance of the preamplifier and the capacitance of the microphone. The frequency range of a preamplifier is determined by its electronic circuit and is typically more than 200 kHz at the high end and 1-10 Hz at the lower end. This makes it necessary to introduce a driver with high input impedance and low output impedance. The output from a condenser microphone is a very high-impedance signal and is therefore very sensitive to the capacitive loads of cables.
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