What this figure doesn't tell you is how well the mic amp performs at intermediate gain settings cheaper designs often produce the best 'paper' figures when used flat out, but in most practical situations you'll be using the Gain control somewhere in the middle. OK, so it's obvious that a great deal of care has gone into this mic amp, but does it perform any better than the one in your mixer? After all, the printed EIN noise figure is just 126.6dBu, which is more or less exactly the same as that boasted by most mixer mic amps. The mains power supply is integral and uses a toroidal transformer, while the audio circuitry conforms to a carefully‑designed grounding system and is built using very high‑tolerance 1% and 0.1% metal oxide film resistors. No two front panels are the same, so perhaps SPL should consider providing a photocopied 'fingerprint' of the panel as an aid to identifying stolen equipment. A novel cosmetic touch is the use of a special anodising technique on the front panel, which produces a random deep blue swirl pattern. The MikeMan comes in a 1U package which has been newly designed to conform to the impending legislation on RFI (Radio Frequency Interference) susceptibility. Additional smoothing circuits are also employed to limit the rise time of the phantom power voltage when it is switched on, so as to avoid disturbing thumps and bangs. The normally vulnerable input stage has an exceptionally high overload margin and is protected from DC offsets or damage from excessive signal level, while the phantom power circuitry uses precision components so as not to compromise the efficacity of the balanced input stage. A common mode rejection ratio of over 90dB is claimed, which basically means that the interference‑cancelling effect of the balanced input stage works rather better than most. The maximum gain of 72dB is 12dB more than is normally available from a conventional mic preamp, and has been achieved by using the amplifying devices in an instrumentation amplifier configuration - the same circuit topography as is used for ultra low noise, very low distortion measurement and calibration test gear. A Ground Lift switch is fitted for use in ground loop‑sensitive situations. A 10‑step bargraph PPM meter shows the output signal level at all times, and a specially‑designed output stage provides a balanced XLR feed and an unbalanced jack feed which may be used simultaneously. All too often, state‑of‑the‑art components turn in an indifferent performance because of the way they are used maybe the circuit grounds aren't quite right, perhaps the power supplies aren't as clean as they should be, and so on - but Neumann has put a lot of hard work into this design to make sure that the SSM 2017 Analog Devices amplifier chips work to the very best of their capabilities.Įssentially, the MikeMan comprises two independent mic amps, each with a Gain control providing up to 72dB of gain, a Phase Invert switch, a 35dB pad, and switchable phantom power, all on illuminated switches. Most mic preamps now offer reasonable performance, but very few attain the lowest noise and distortion figures made possible by modern component design. Most people know of SPL through their Vitalizer, which is still one of the most coveted enhancement devices on the market today, but in this latest product, technical guru and SPL founder Wolfgang Neumann has focused his creative energies on the more down‑to‑earth subject of mic preamp design. Fortunately, SPL's circuit design is even more impressive than their custom anodised front panels, as Paul White discovers. There's more to building a serious mic front end than putting a standard circuit in a flashy box.
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