The Quantum driver utilizes the bus master Direct Memory Access (DMA) to transfer audio data directly to and from the main memory without using CPU processing and the overhead that would come with it. DMA supports 64-bit addressing on systems with 4 GB or more of RAM. A companion DMA engine was also implemented in the Quantum hardware to read digital audio data directly between the ADC/DAC and the computer memory, one sample at a time.

For maximum efficiency, samples are transferred from the Quantum DMA engine directly into driver memory as a 32-bit word to match the way the Quantum driver handles the audio. Where possible, audio samples are also transferred into driver memory in the exact order that the driver expects. This helps to avoid alignment problems and the like, allowing you to run your Quantum drivers at extremely low buffer settings without overtaxing your CPU.

At PreSonus, we know that the microphone preamplifier is a key component in the sonic quality of a recording. The Quantum audio interface includes eight custom-design, high-voltage, Class A XMAX preamps with discrete components for accuracy and transparency.

XMAX preamplifiers are built with three key elements:

• Class A. Class A circuits have no crossover distortion and deliver purer, clearer, and more musical results than the Class AB designs that are found in many preamps.
• High Voltage. The XMAX preamplifier runs on power rails of 30V. Most off-the-shelf, op-amp-based designs run on power rails of 10V to 18V. Higher-voltage power rails deliver more headroom, deeper lows, smoother highs, and a richer overall sound.
• Discrete components—not op-amps. We only use genuine transistors, resistors, and capacitors. Op-amps add noise, coloration, and harshness to a signal. Our discrete design delivers ultra-low noise and transparency.

The net result of the XMAX preamp design is high headroom, low noise, wide dynamic range, extended frequency response, and—most important—musicality and transparency.

The Quantum’s XMAX preamps offer another advantage: They are recallable. In 1995, PreSonus patented digital control over analog circuits with our first studio product. Building on this legacy, we created a separate digital volume-control circuit ahead of our analog XMAX preamp design, providing the convenience of digital recall without sacrificing fidelity. The preamps can be controlled from the unit’s front panel, from UC Surface control software, from Studio One’s mixer, from Studio One Remote, and via MIDI in Pro Tools, Logic, or Live so you can save the settings with your recordings.

The Quantum’s eight analog inputs, ten line-level analog outputs, two stereo headphone outputs, and stereo S/PDIF digital I/O might be all you need today. But your studio is likely to grow in time, and so can your Quantum recording system. Its dual ADAT Optical I/O provides up to 16 more channels of digital I/O at up to 48 kHz (up to 8 channels at 96 kHz).

The Quantum’s ADAT I/O lets you add any ADAT-compatible A/D/A converter but we highly recommend the PreSonus DigiMax DP88 preamp/converter, which seamlessly extends the analog I/O on the Quantum with eight digitally-controlled XMAX preamps, and word clock I/O. The DP88’s mic preamps are fully remote-controllable from UC Surface, Studio One^®, and Studio One Remote when connected via ADAT Lightpipe to the Quantum so that they naturally extend your analog inputs both sonically and functionally.