The B173 is one of the most “bang for your buck” preamps in existence, and is now available in the 500 series format. The B173 500 not only delivers the beefy lows, buttery mids, and polished highs of a classic 1073 preamp, but does so at a fraction of the price!
The preamp and line amp circuitry found in the B173 500 is identical to the original B173. Not a single component or design feature was compromised while converting it to a smaller package. As a result, the circuit boards are jam packed with all sorts of delicious components, including a brawny Cinemag input transformer!
The power supply is the backbone of any preamp design, and can make a huge impact on the overall sound and performance of the preamp. The +24V rail needed to power the B173 500 is painstakingly converted from the +/- 16V rails of a 500 series rack using a custom DC-DC converter circuit specially designed to keep any unwanted noise or modulations out of the signal path. Complete isolation is then achieved through the use of inductors, ferrite beads, decoupling capacitors, power regulation, and a custom enclosure surrounding the entire circuit.
GAIN (stepped, 12-position switch): clockwise rotation yields an increase in input signal amplitude, counterclockwise rotation yields a decrease in input signal amplitude
48V: engage to turn phantom power on, disengage to turn phantom power off
PHASE (Ø): engage to adjust input signal polarity by 180°, disengage to leave input signal polarity unchanged
OUT LEVEL: clockwise rotation yields less attenuation, counterclockwise rotation yields more attenuation (for beginners, it’s best to leave the output level fully clockwise and increase Gain as needed so as not to saturate the input transformer)
Hi-Z: engage to select faceplate TS jack as input source, disengage to select XLR input jack on 500 series rack as input source (GAIN does not adjust signal level, however, OUT LEVEL does attenuate the signal)