ART USB Dual Pre Project Series User Manual

Introduction

The ART USB Dual Pre Project Series is a full-featured, high-quality dual portable preamplifier and computer interface housed in a compact, rugged case. It is engineered for diverse applications, ranging from remote field recording to desktop/studio tracking. Each of its two low-noise input channels offers up to 48 dB of clean gain, equipped with signal present and clip LED indicators. The inputs support either balanced XLR or 1/4-inch TRS connections. The unit's 1/4-inch TRS outputs are buffered and low-impedance balanced.

The USB Dual Pre Project Series can be powered via mains through a wide range of external power adapters (optional), an internal 9-Volt battery, or directly from the USB bus (cable supplied), or any combination thereof. When powered solely by battery, expect over 50 hours of operation with phantom power off. Battery life reduces to approximately 20 hours (depending on the connected microphone) when phantom power is active, which is still sufficient for a typical session.

The integrated low-noise +48 Volt phantom power supply enables powering up to two microphones, as well as the preamplifier itself, regardless of the power source, including the USB bus. For monitoring, a 1/8-inch TRS mini headphone jack, along with level and monitor mix controls located on the rear panel, allows for latency-free local monitoring of inputs during recording and playback monitoring of the USB bus. The monitor mix is also routed to the 1/4-inch TRS balanced outputs, enabling their use as either preamplifier outputs or as a monitor feed to powered monitors.

No special drivers are required for operation. The unit features a compact, black anodized all-aluminum case with rubber sides, ensuring a rugged design. The USB Dual Pre Project Series is built to provide years of trouble-free service. Its high-quality audio channels and versatile powering options make it an ideal choice for a wide array of applications, including Podcasting, Broadcasting, Tracking, and Monitoring. With the USB Dual Pre Project Series, a laptop, and quality microphones, users can achieve professional remote recording results.

Key Features

• USB Connectivity to Desktop and Laptop Computers
• Low Noise Fully Balanced XLR and 1/4-inch TRS "Combo" Inputs
• Up to 48 dB of Clean Gain
• Built-in Low Noise +48 Volt Phantom Power Supply
• Latency Free Monitoring Mix and Level Controls
• Independent Channel Gain Controls
• 1/4-inch TRS Balanced Monitor and 1/8-inch Headphone Monitor Outputs
• Includes Recording & Production Software
• Compact, Stackable all Aluminum Chassis
• Flexible 3-way Power from USB, An Optional External Supply, or 9 Volt Battery

Connections

The front panel features two "Combo" jacks, which accept either balanced XLR or 1/4-inch TRS input connections.

XLR Input

The XLR input connections are primarily used for balanced microphone input. Pin 2 is positive, pin 3 is negative, and pin 1 serves as ground. +48 Volt phantom power, when enabled, is supplied to pins 2 and 3, with pin 1 acting as the ground return. It is crucial not to lift pin 1 when using phantom power. If using the XLR inputs with a balanced low line-level signal or a microphone that does not require phantom power, ensure phantom power is turned off. The maximum gain from the balanced XLR inputs to the balanced 1/4-inch TRS monitor outputs is 48 dB. These inputs can accommodate microphone signals up to +6 dBu before clipping.

1/4-inch Input

The 1/4-inch input connections are designed for instrument or low line-level balanced or unbalanced signals. The high, fixed input impedance is well-suited for guitars and other passive instrument pickups. Both unbalanced and balanced plugs can be used with this connection. Maximum gain from the 1/4-inch input to the balanced 1/4-inch TRS monitor output is 48 dB for a balanced source and 42 dB for an unbalanced source. When the Gain control is set to its minimum, this input can handle signals up to +6 dBu.

Monitor Outputs

The 1/4-inch monitor output jacks are active balanced, with the Tip being positive, Ring negative, and Sleeve ground. Featuring an output impedance of 600 Ohms and a maximum output level of +10 dBu, they provide clean balanced signals suitable for long cable runs. Typically, these outputs connect directly to a power amplifier, powered monitors, recording system, or a mixer's balanced line or insert inputs. While not recommended, if connecting directly to a mixer's balanced microphone input, ensure phantom power is off at the mixer. The mixer's input pad and level controls should be set to minimum gain, and the Monitor Level control on the USB Dual Pre Project Series should be set low enough to prevent overdriving the mixer's input section.

The 1/8-inch headphone monitor output jack is stereo unbalanced TRS with an output impedance of 50 Ohms. It is compatible with a wide variety of headphone models, offering a maximum output level of +4 dBu.

Rear Panel Connections

The rear panel includes a power connector for optional external AC powering. The USB Dual Pre Project Series can operate from any external power source providing 7.5 to 12 Volts AC or DC at 150mA or more. Battery and USB bus powering are also available when AC power is not present.

The USB connector is USB 1.1 compliant and should be connected directly to a USB port on your computer. This connection also powers the USB circuitry within the unit and the entire product if no other power source is active. Your computer recognizes this connection as a "USB Audio CODEC," and the computer controls the sample rate.

USB Operation and Best Practices

For optimal performance, it is recommended to use a high-quality shielded USB cable, as the USB connection carries high-quality digital audio and bus power. Connecting directly to a computer's USB input is preferred. Using a shared hub can reduce available power and bandwidth, which should be avoided if possible. While the USB Dual Pre Project Series is compatible with USB 1.1 and 2.0 interfaces, USB 2.0 is recommended for better system bandwidth. If a hub is necessary, it should be a powered USB 2.0 compliant hub, especially when using multiple units for increased simultaneous digital audio input channels.

Both analog output jacks and the USB Out can be utilized simultaneously. This is useful for live situations requiring output to a mixer and instrument amp, or when connecting to a computer or recording system for local monitoring via headphones.

For typical recording scenarios where new audio tracks are added via the USB bus to a computer, with external monitoring for low latency, the recommended setup is: Connect instruments/microphones to the USB Dual Pre Project Series inputs, then connect the unit to your computer via USB. Use the 1/4-inch monitor outputs for powered monitors or an analog monitor system, and/or the 1/8-inch jack for local headphone monitoring. Adjust the Monitor Mix control to blend new tracks with the computer playback signal. The new track being recorded will be in real-time with no latency in the monitoring system.

The USB Dual Pre Project Series interface utilizes the standard "USB Audio CODEC" driver, which is integrated into most modern operating systems, including Linux. Setup details may vary across Linux versions. The key is to identify "USB Audio CODEC" as the recording source or playback monitor output when the unit is connected. Your recording software will then manage channel selection for recording and monitoring. For multi-track recording, many software packages are available. If multiple units are used, they will appear as "USB Audio CODEC 1," "USB Audio CODEC 2," etc., in the recording application. Consult your software's documentation for optimal channel assignment and parameter settings.

Latency, the time delay between audio input and USB output to the computer, is minimal (under 2 milliseconds) in the USB Dual Pre Project Series. However, latency from recording software and computer drivers can be more significant. Macs typically have low core audio interface latency. Windows USB audio drivers may introduce noticeable delay during live monitoring. For such issues, low-latency ASIO drivers are available to reduce Windows audio latency. Resources like www.asio4all.com and www.usb-audio.com are recommended for ASIO drivers compatible with the USB Dual Pre Project Series.

Controls and Operation

Gain Controls (Left and Right)

The Left Gain and Right Gain controls directly adjust the input amplifiers, providing control over your source's dynamic range, from 0 to 48 dB. It is advisable to set these controls to minimum gain (counterclockwise) when connecting inputs.

Monitor Mix Control

This control allows direct blending between the internal preamplifier signals and the playback signals from your computer. For recording new tracks exclusively or using the USB Dual Pre Project Series as a microphone/instrument preamplifier, set the Mix control to "Preamp." When using the unit for USB audio output monitoring of your computer's playback, set the Mix control to "Computer." A middle setting provides a blend of the direct preamp signal and computer audio.

Play-Through Function

Some recording programs and computer systems offer a "Play-Through" function, achievable via software or hardware. When enabled (ON), the computer outputs the audio being recorded, introducing a slight delay or latency. This can also create a feedback loop if computer audio inputs and outputs are interconnected, potentially generating loud, disturbing sounds. Therefore, "Play-Through" is typically set to OFF as the default in both software and hardware.

If Software/Hardware Play-Through is ON and the Monitor Mix is set to the middle, you may hear the original preamp signal combined with a slightly delayed computer audio signal, creating an echo effect. This is normal behavior; when using various Monitor Mix settings, it may be preferable to keep Play-Through OFF.

Monitor Level Control

This control adjusts the overall monitor level after the mix circuitry and before the monitor output amplifiers. It affects signal levels for both the 1/8-inch headphone and 1/4-inch balanced monitor output jacks.

Phantom Power Switch

Located on the rear, the Phantom power switch applies +48 Volt phantom power to the XLR input jacks for powering microphones. The switch has a slow turn-on/off characteristic and is current-limited to protect sensitive microphones and minimize audible pops. The LED indicator for phantom power is not illuminated, even when active, to conserve battery life. For microphones requiring phantom power, it is recommended to first turn down the gain, connect the microphone, switch on phantom power, and then gradually increase the gain to the desired level. This process helps minimize pops and stress on the microphone.

Power Switch

Also located on the rear, the Power switch controls power from the battery or an external power supply. Turning this switch OFF disables these two sources. However, if the USB bus is active, the USB Dual Pre Project Series will still be powered by the USB bus, and the red power LED will remain lit, indicating USB power from the computer is active. When the switch is ON and all three power sources are available, the USB interface is powered by the USB bus, while the preamp and phantom power sections draw power from the external AC source or battery if no external source is available. In desktop/studio settings, power modes are usually not an issue. For portable or remote recording, the system (USB Dual Pre Project Series, laptop, microphones, headphones) can be powered entirely from the laptop, or by a 9V battery (if installed and the Power switch is ON), which powers the preamp and phantom sections, leaving the laptop to power only the USB interface, thus maximizing remote recording time.

LED Metering

Each channel features LED metering circuitry designed to aid in setting gain and indicate clipping with a fast attack. The metering is positioned in the signal chain just after the preamp circuitry to assist in setting signal levels sent to the computer. Monitor controls follow the metering, allowing users to set overall input gain for optimal dynamic range and then adjust Monitor Mix and Level for the connected monitor system. The red "Clip" LED illuminates just before clipping (2dB before digital clipping, 6dB before analog clipping) and should only light on musical peaks. The green "Signal" LED illuminates around 10dB below the "Clip" LED, indicating signal level relative to clipping. This "Signal" LED has a longer release time and should typically remain on during performance; if it is off, it may indicate that the signal or input gain is too low.

Customer Service Note on Noise

Customers sometimes report their ART preamp is "noisy." If experiencing unwanted noise, consider the signal source and destination. Sending a preamp's signal to a mixer's mic input (instead of a line input) can increase overall noise, as ART preamps are designed to output a line-level signal. Feeding a line-level signal into a mic input often results in the circuit adding extra gain, leading to noise. Treat the output signal as line-level for a clean, warm sound. This also applies to guitar and bass players using ART preamps; connect to a low-gain input or a "loop return" jack on an amplifier to bypass the amp's solid-state preamp.

Applications

Microphone Pre Amplifier

The USB Dual Pre Project Series functions as a high-quality microphone preamplifier suitable for dynamic, condenser, and ribbon microphones. It offers an upgrade over budget-minded mixer preamps, providing greater flexibility and a more robust tone. Simply connect a microphone to the XLR input, apply phantom power if using a condenser, and adjust the gain using the front panel LEDs for visual feedback. Route the output to a mixer, workstation, or computer via the 1/4-inch or USB output. The overall analog output level is adjustable at the unit.

Its battery-powered or USB bus-powered operation makes it ideal as a portable microphone preamp for remote performances or laptop recording.

Phantom Power Supply

Many mixers and computer interfaces do not provide +48 Volt phantom power on all microphone inputs. The USB Dual Pre Project Series is an ideal solution for condenser microphones requiring this power, allowing connection to existing mixers or computers. Portable laptop recording with high-quality condenser microphones needing phantom power is readily achievable.

Instrument DI

The USB Dual Pre Project Series also serves as a functional Direct Input (DI) for bass, acoustic guitar, and virtually any other instrument with a 1/4-inch or XLR output. Many users prefer the responsiveness of ART preamps over standard DI boxes and preamps, enjoying enhanced flexibility and control. Operation involves inserting the instrument's output into the unit's input. Ensure the instrument's volume is set high and that any effects do not significantly increase the overall output. Adjust the input gain knob while referencing the front panel LEDs for visual gain indication. Route the output to a mixer, workstation, or computer via the 1/4-inch or USB output. Both analog outputs and the USB port can be used concurrently, allowing the 1/4-inch output to feed an amplifier or monitor system, and the USB to connect to a computer. The built-in monitor mixer provides maximum flexibility during recording.

Warranty Information

Limited Warranty

Applied Research and Technology (ART) warrants this product and its components to the original purchaser against defects in workmanship and materials for a period of three years from the date of purchase. ART will, at its discretion, repair or replace defective products or component parts free of charge upon prepaid delivery to the factory service department or an authorized service center, accompanied by a valid sales receipt as proof of purchase date.

Online Registration

To ensure prompt warranty repair servicing, ART recommends registering the product online at www.artproaudio.com. Navigate to "Support," then "Product Registration," and submit your information.

Exclusions

This warranty does not cover misuse, abuse, unauthorized alterations, or repairs. The warranty is void if the serial number is altered, defaced, or removed. ART reserves the right to make design changes or improvements without obligation to apply them to previously manufactured products. ART is not liable for consequential damages, including loss of use. Some states may not permit limitations on incidental or consequential damages, so these limitations may not apply. This warranty grants specific rights, and users may have additional rights that vary by state.

For units purchased outside the United States, an authorized distributor of Applied Research and Technology will provide service.

For your reference:
Date of purchase: ___________________
Purchased from: ___________________

Service

In the unlikely event your unit requires service, please follow these guidelines:

1. Verify the unit is the cause of the problem. Ensure it has power, all cables are correctly connected and functional. Consult your dealer for troubleshooting assistance.
2. If you suspect the ART unit is at fault, visit www.artproaudio.com.
3. Select "Support," then "Return Authorization Request" to obtain a return authorization number.
4. When returning the unit for service, pack it in its original carton or a suitable substitute. The original packaging may not be adequate for shipping; consider using an additional box. Clearly print the RA number and your return shipping address on the outside of the shipping box.
5. Include a note with the RA number, your contact information (including return shipping address – P.O. boxes are not accepted – and a daytime phone number), and a description of the problem (preferably attached to the unit). Also, include a copy of your purchase receipt.

Specifications

Note: 0 dBu = 0.775Vrms

ART maintains a policy of constant product improvement. Therefore, specifications are subject to change without notice.

For the latest information and support on the USB Dual Pre Project Series, visit www.artproaudio.com.