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The input stage and Output 1 are transformer-balanced. Output 2 is electronically balanced and can not be equipped with a transformer. Output 2 is de-coupled actively to allow splitting the input signal over Output 1 and Output 2. Channel Split Since the Premium Mic Pre provides two independent outputs, it always offers you two routes for one input channel. If, for example, a RackPack is configured as a channel strip, one pre-amp output can feed the next module while the second output is used to record the direct preamp signal. Another exemplary studio application is to send one signal directly into the A/D converter to be recorded in your DAW while the second signal is used for latency-free monitoring (e.g. cue mix for the singer). In live applications output 1 can be routed to the Front Of House (FOH) while output 2 feeds the monitoring mixer. Pad The Pad function allows you to attenuate the input signal by 20 dB so that you can process even very high levels, i.e. from drums or brass instruments. If the VU meter shows levels above +3 dB even while Mic Gain is set very low (and the -10 dB button deactivated), the time has come to press the Pad button. It illuminates when it is activated. Phase Reverse With the phase reverse button you invert the polarity of the microphone signal. When not pressed (button is not illuminated) the polarity is in phase. After pushing the button (button is illuminated) the polarity is inverted. The phase reverse feature comes in very handy if you have to switch the polarity of the XLR input according to the polarity of the microphone or the microphone cable. The pin wiring of the XLR sockets are as follows: Pin 1 = ground, Pin 2 = hot (+), Pin 3 = cold (-). Sometimes it is useful to switch the polarity of a microphone, for example in the case of M/S miking. A second classic application is the miking of a snare drum with two microphones that are placed above and below the snare: Since both drum heads move in the same direction when the drum is played, the microphones are out of phase. Switch the polarity of the bottom mic and you avoid any cancellations when you join both signals in the mix. High-Pass Filter The high-pass filter, also known as rumble filter, helps to eliminate any interferences within the lowest frequencies. The first order filter operates smoothly with 6 dB per octave, starting from 75 Hz with -3dB. This characteristic usually helps in most cases and has the least sonic disadvantages. If you need to filter on a more extreme scale, even second order filters (12 dB/octave) are overstrained frequently and sonic disadvantages become more and more apparent. In those cases a variable filter is the means of choice. Triple Stage PreAmp The preamplifier circuitry of the Premium Mic Pre is composed of three stages: a transformer, a discrete differential amplifier stage and an instrument preamplifier all contribute (in different shares) to the main amplification. The three stage setup firstly ensures a load distribution that minimizes the risk of overloads. Secondly, each stage can be optimally configured through select components and sophisticated circuits – a decisive advantage over single IC circuitries where the main amplification is achieved by just one stage. In addition, the potentiometer (as the control element of the differential amplifier stage) only has to cover a range of approximately 68 dB while the maximum amplification is at around 80 dB. In practice this means that even very high amplification values are still outside of the extreme control range positions - which are critical for any potentiometer. Stage 1 - The Input Transformer Inherent part of the Premium Mic Pre design are the input and output transformers of the High Performance Series by Lundahl. These transformers are lavishly handcrafted. They replace common input and output balancing stages. These classic components offer a very high sound quality and common mode rejection but they are also very reliable and provide connections and signals of superior quality. Lundahl transformers have a very high reputation in terms of manufacturing quality and the resulting longevity as we have seen proven impressively throughout many years of experience. In any microphone preamplifier the input transformer is of special relevance as it is an integral part of the preamp circuitry: it contributes to the main amplification through a passive and permanent boost of, in this case, 6 dB. The advantage of passive amplification over active amplification is that it does not add any noise. A second advantage of integrating this passive amplification is a signal processing that is, as a matter of principle, lower in overdrive and noise throughout all following stages simply because the rest of the electronic circuit is charged with 6 dB less at any setting of the amplification. In addition, transformers ensure a galvanic isolation, preventing any disturbing or damaging voltages from being carried in any of the two directions. Electromagnetic, high frequency or digital interference has no more influence. Problems with humming e. g. in a live environment that have been caused by differences in the potentials between the stage and the FOH do not occur. Even a voltage that has accidentally or through technical failure been connected to a ground line cannot be transmitted. So transformers can exclude even mishaps or problems in an installation reaching the categories "improbable" till "unbelievable" ... Further, the phantom powering of microphones does not require any condensers in the preamp socket which has further sonic advantages. From our personal listening impression we can recommend transformers in any case. The advantages in operational safety can not be over-estimated especially in critical or complex installations for studio, live or broadcast applications. Stage 2 - The Discrete Differential Amplifier From the input transformer, the signal is routed to a discrete differential amplifier based upon a quad parallel transistor circuitry. This parallel circuit of eight single transistors reduces noise remarkably through distribution of load. The discrete differential amplifier is the central amplifying stage; here the amount of the amplification is controlled by a current-carrying source. Control systems that are triggered by current rather than voltage have the main advantage that possible negative effects of the potentiometer will not affect the audio signal. The discrete differential amplifier offers a maximum amplification of up to 68 dB. A servo drive circuit actively eliminates DC offsets of the differential amplifier. Servo drive circuitry minimizes DC offsets more effectively than conventional solutions that utilize capacitors by setting the DC offset to almost 0 mV. In addition, the active servo drive solution has sonic advantages over passive capacitors as it tends to produce less distortions. Stage 3 - The Instrumentation Amplifier An instrumentation amplifier is following the discrete differential amplifier to produce the output signal’s voltage. Functionally a summing amplifier it eliminates possible disturbing voltages and also contributes to the main amplification with an additional +6 dB. Foil and Styroflex Capacitors Only the best MKP and styroflex capacitors are used in the various circuits. They sound more open and dynamic in contrast to the conventional ceramic capacitors. Output Stages The Premium Mic Pre offers two balanced output stages: a transformer output (Output 1) and an electronically balanced stage (Output 2). These output stages are capable of driving very long cables (up to a few hundred yards, depending on the capacity of the cables and the input stages on the other end). The maximum output level is +22 dBu. Channel Split Since the Premium Mic Pre provides two independent outputs, it always offers you two routes for one input channel. If, for example, a RackPack is configured as a channel strip, one pre-amp output can feed the next module while the second output is used to record the direct preamp signal. Another exemplary studio application is to send one signal directly into the A/D converter to be recorded in your DAW while the second signal is used for latency-free monitoring (e.g. cue mix for the singer). When playing live output 1 can be routed to the Front Of House (FOH) while output 2 feeds the monitoring mixer. Specifications Audio Frequency Range 10 Hz- 68 kHz (-3 dB) CMRR -87 dBu (at 1kHz with -30 dBu input level and 30 dB Gain) THD & N @ 1 kHz Input Level Gain THD & N -30 dBu 30 dB 0,0071% -60 dBu 60 dB 0,078% Noise Gain Noise Level (A-wtd.) 80 dB -48,3 dBu 60 dB -64,2 dBu 30 dB -89,0 dBu E.I.N. (Equivalent Input Noise) -128,3 dBu Dynamic Range 111,0 dB Input XLR connector, transformer balanced Impedance unbalanced ca. 2,0 kOhm Impedance balanced ca. 4,0 kOhm max. Input Level +10 dBu, +30 dBu with Pad activated Outputs Output 1: XLR connector, transformer balanced Impedance unbalanced ca. 60 Ohm Impedance balanced ca. 120 Ohm Max. Output Level +22 dBu Output 2: XLR connector, electronically balanced Impedance unbalanced ca. 75 Ohm Impedance balanced ca. 150 Ohm Max. Output Level +22 dBu Control Elements Mic Gain Range 12 dB – 80 dB Pad -20 dB High-Pass fg = 75 Hz (-3dB) Phantom Power Supply 48 V Dimensions & Weight Height x Width x Depth: 132 mm x 46,9 mm x 315 mm Weight 0,55 kg Note: 0 dBu = 0.775 V. Specifications are subject to change without notice. |
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