ART Solo MPA Multivoice Tube Preamplifier

Important Safety Instructions

WARNING: To reduce the risk of electric shock, do not remove the cover. No user-serviceable parts inside. Refer servicing to qualified personnel. [Electric Shock Warning Symbol]

WARNING: To prevent fire or shock hazard, do not expose this appliance to rain or moisture.

• Read and keep these instructions.
• Heed all warnings and follow all instructions.
• Do not use near water or block ventilation. Install per manufacturer instructions.
• Avoid heat sources and protect the power cord from being pinched.
• Use only manufacturer-specified attachments/accessories.
• Use only with specified carts/stands; exercise caution when moving.
• Unplug during lightning storms or prolonged disuse.
• Refer servicing to qualified personnel for any damage.
• Caution with earphones/headphones due to potential hearing loss from excessive volume.
• Do not expose to drips or splashes; do not place liquid-filled objects on the unit.
• Ensure adequate ventilation (1U space above, 10cm/4in at rear).
• Battery safety: do not recharge non-rechargeables, observe polarity, avoid heat/fire, do not disassemble, handle leaks carefully.
• Proper disposal of batteries and electronic equipment (WEEE symbol [WEEE-disposal-symbol]).
• Wireless equipment precautions: use only in country of purchase, respect local restrictions.
• Laser Information: Class 1 Laser Product. Do not open enclosure.
• [Important Information Symbol]

Introduction

The ART Solo MPA Multivoice Tube Preamplifier offers a blend of pristine low-noise/low-distortion solid-state circuitry and a warmer Class-A tube mic preamp. It allows users to tailor their sound with flexible EQ controls, 48V phantom power, and variable input impedance, making it suitable for dynamic, condenser, or ribbon microphones. Its compact 1U rack-mountable design ensures reliable operation in studios or venues.

Key Features

• Adjustable input impedance (600 to 80K ohms) for flexible microphone voicing.
• Flexible Tilt EQ for emphasizing presence or low-end warmth.
• Tunable Lowcut Filter (10 Hz to 200 Hz).
• Variable Voice Tube/Solid State control for blending stages.
• Analog VU meter with front-accessible meter trim.
• Backlit function switches.
• Discrete Class A FET input microphone preamplifier.
• Low noise at low gains and low THD.
• Wide frequency response.
• Front-mounted Instrument/DI Input with very high impedance.
• +4dBu/-10dBV output level selection.
• Automatic switching to instrument input when plugged in.
• 1U Rack mount aluminum front plate.
• Removable IEC cord and internal power supply.
• 3-year parts and labor warranty.

Installation

Rack Mounting

Mount the unit in a standard 19-inch rack using the supplied kit. Remove the unit's feet before mounting. Ensure 1U space above and at least 10 cm (4 inches) at the rear for ventilation.

AC Power Hookup

The Solo MPA operates on 100-240V~, 50/60Hz, 25W via an internal power supply. Use a grounded outlet. Do not alter the power cable. If damaged, replace immediately.

Audio Connections

Connections are available via XLR and 1/4-inch TRS connectors. The XLR pinout is standard: Pin 1=Ground, Pin 2=(+) HOT, Pin 3=(-) COLD. The 1/4-inch TRS pinout is: TIP=(+) HOT, RING=(-) COLD, SLEEVE=GROUND. Unbalanced 1/4-inch cables are supported, but high-quality cables are recommended.

Front Panel Controls

1. Power Switch: Turns the unit on/off. Power on the unit with all monitor levels down, and power off after lowering levels. VU meters light when powered on. Allow 1-3 minutes for tube warm-up. Check fuse if unit fails to power on.
2. Instrument Input: 1/4-inch jack for instrument or DI use. Input impedance is >1M ohm. Gain is adjustable. Plugging into this jack disables the rear balanced input.
3. Gain Control: Adjusts input signal level from 0dB to 40dB. Affects both mic and instrument inputs. Use in conjunction with the +20dB Gain switch and Output control for desired gain and "tube" character.
4. Impedance Control: Adjusts the mic/line input impedance (600-80K ohms) for variable microphone voicing. Does not affect the instrument input.
5. Low Cut Control: Tunable High Pass Filter (10 Hz - 200 Hz) to remove low-frequency noise or "pops".
6. Tilt EQ Control: Adjusts high presence or low-end warmth.
7. Voice Control: Blends between the Solid-State and Tube stages.
8. Gain Switch: Engages +20dB gain, increasing tube drive.
9. Phantom Switch: Engages +48V phantom power for condenser microphones. Turn off for dynamic mics or line-level inputs. Mute outputs when engaging/disengaging.
10. Phase Switch: Inverts the audio signal phase. Useful for correcting phase issues or microphone placement.
11. VU Meter: Analog meter for monitoring signal levels.
12. Meter Trim: Adjusts the meter's "0" point.
13. Output Control: Adjusts the rear output signal level (+15dB to mute).

Rear Panel Connections

1. I/O Level Switch (+4dBu/-10dBV): Sets the output level to match system requirements. 0 VU can correspond to +4dBu or -10dBV.
2. Balanced Inputs: XLR connectors (AES standard). Input impedance is variable (150-3K ohms). Max input level: +19dBu (balanced), +17dBu (unbalanced).
3. Balanced Outputs: Available on 1/4-inch TRS and XLR connectors. Low impedance for long cable runs. Max output level: +27dBu (balanced), +20dBu (unbalanced).
4. IEC Power Connector: Standard fused IEC input for power.

Operating Instructions

Obtaining the Best Noise Performance

1. Turn Input Gain and Analog Output knobs down. Set +20dB switch out.

2. Increase Input Level until meter reads above -10dB.

3. If level is still low, center Input Gain, engage +20dB switch, and increase Input Gain until sufficient level is achieved.

4. This optimizes gain for widest dynamic range.

Adjusting the Input Impedance

The Input Impedance control (on XLR inputs only) allows fine-tuning microphone voicing. Lower impedance can reject noise and dampen resonance, while higher impedance offers a more "open" sound.

1. Start with the Input Impedance knob centered (20K ohm load).

2. Experiment with settings to find the desired sound.

Specifications

• Frequency Response: 15 Hz to 50 kHz (+0, -1dB)
• Dynamic Range: >110dB ("A" weighted)
• CMRR: >90dB
• THD: <0.005% (typical)
• Equivalent Input Noise: -129dBu (XLR, "A" weighted)
• Maximum Input Level: +19dBu (XLR), +17dBu (Instrument)
• Input Impedance: 600-80K ohms (XLR), >800k ohms (Instrument)
• Maximum Output Level: +27dBu (XLR)
• Output Impedance: < 47 ohms (XLR)
• Maximum Gain: 75dB
• Meter Calibration: 0VU = +4dBu (mode +4dBu), 0VU = -10dBV (mode -10dBV)
• Low Cut Filter: Single pole, 10-200Hz adjustable.
• Tilt EQ: +/- 12dB adjustable.
• Power Requirements: 100-240V 50Hz/60Hz, Fused IEC connector.
• Dimensions (HxWxD): 1.75" x 19" x 6.0" (4.45 cm x 48.3 cm x 15.2 cm)
• Weight: 5.6 lb / 2.5 kg

Block Diagram

The signal path begins with either the XLR or 1/4-inch instrument input. The signal passes through an input impedance control and gain stage, followed by a Low Cut filter and Tilt EQ. The Voice control allows blending between the Solid State and Tube stages. A Phase switch inverts the signal phase. The signal then goes through a final gain stage, potentially boosted by the +20dB switch, before reaching the output level control and the analog VU meter. Outputs are available via balanced XLR and 1/4-inch TRS connectors.

Warranty and Service

Applied Research and Technology (ART) provides a 3-year limited warranty covering defects in workmanship and materials from the date of purchase. This warranty excludes misuse, abuse, or unauthorized alterations. For service, contact ART via www.artproaudio.com to obtain a Return Authorization (RA) number. Pack the unit securely, clearly marking the RA number on the exterior, and include proof of purchase and a description of the problem.