U-X, U-T, U-AS, U-8A. U-A is same as U-T, except with silver pin.
U System Amplifier Specification
The U system is a fully interchangeable and interoperable capsule and amplifier system. The U amplifiers are the microphone "bodies" for the U capsules; the U amplifiers convert +12V to +48V phantom power to +9V plug-in microphone power, and generate a buffered, low-impedance output. U capsules may be used with phantom-powered U amplifiers, or can also directly connect to low-voltage (+3V to +12V) plug-in powered microphone inputs.
The U-A and U-T amplifiers may be visually distinguished by pin color (XLR and miniplug): the U-A uses silver-plated connectors; the U-T uses gold-plated connectors. The U-AS amplifier has a longer body with a barrel switch to select gain, together with the U-A's silver connectors.
The U-T andU-8A amplifiers support a single U capsule. The U-A,U-AS, andU-X amplifiers have two independent channels (tip to pin 3, ring to pin 2), which support one U capsule with balanced output or two U capsules with stereo unbalanced output.
The U-8A amplifier offers variable polar pattern (continuous, from bidirectional to omnidirectional) when used with the U-8S capsule and variable gain control (from 0dB to +11dB). The U-8A amplifier may also be used with all other U system capsules; the polar pattern should be set on bidirectional ("figure-8") with other capsules, which will yield the best noise rejection.
The U-8A's pattern control is labeled with blind holes to indicate polar pattern: two overlapping holes represent the figure "8" of a bidirectional pattern, and a single hole represents the "O" of an omnidirectional pattern. The cardioid pattern is selected with the knob straight up (12:00 position), with the intermediate patterns between (in order; bidirectional, hypercardioid, cardioid, subcardioid, omnidirectional).
The U-8A has a female XLR input, and includes the U-R miniplug to male XLR adaptor. The U-R may be directly connected to the U-8A, or extended via a standard XLR microphone cable up to 30' (10m) from the U-8A. U capsules may also be extended via miniplug/minijack extension cables, but the total run of extension cable from U capsule to amplifier should not exceed 30' (10m).
U amplifiers are inverting input, such that the tip input will appear as an inverted signal on pin 3, and ring input will appear as an inverted signal on pin 2. When connected to U capsules, this will generate a positive polarity signal (positive pressure will result in positive voltage on pin 2 with respect to pin 3).
In addition to direct support of U capsules, U amplifiers can act as a phantom power adaptor for other brand plug-in power microphones in mono or stereo configurations, with appropriate adaptor cables.