Quartet MB
Best monoblock amplifier for audiophiles seeking pure Class A tube warmth.
Experience unparalleled musicality with the Art Audio Quartet MB monoblock amplifier. This pure Class A amplifier embodies a dedication to both sonic performance and exquisite craftsmanship, featuring hand-polished accessories and a robust Mil-spec PC board construction. Its automatic bias circuits simplify operation by eliminating the need for manual adjustments or matched output tubes. Enjoy rich, detailed sound powered by 845 tubes, high-quality split-core transformers, and advanced filtering for an exceptional listening experience.
Owner Satisfaction
4.7
/ 5
Category Rank
421
/ 1719
#421 in Power Amplifiers
Type
845
/ Push-pull, pure class A monoblock amplifier
Who it's for
- Collectors valuing artisanal craftsmanship and long-term reliability
- Audiophiles seeking immersive, warm, and expansive soundscapes
- Listeners powering demanding, low-sensitivity speaker systems
Who should skip it
- Users with limited rack space or smaller listening rooms
- Budget-conscious buyers exploring entry-level high-fidelity audio
- Owners wanting low-maintenance equipment with minimal operating costs
Performance breakdown
Sonic Musicality
Pure Class A topology delivers a lush, harmonically rich listening experience.
Operational Simplicity
Automatic bias circuits remove the typical maintenance headaches of tube amplification.
Build Integrity
Mil-spec board construction ensures long-term reliability and robust internal signal paths.
Tube Flexibility
Eliminates the need for matched output tubes, simplifying future component upgrades.
Power Delivery
Forty-five watts of pure power drives most high-end speakers with authority.
Customization Options
Switchable feedback settings allow for subtle tuning of the output character.
Key Specs
Type
845 Push-pull, pure class A monoblock amplifier
Output Power
45-50 wpc
Frequency Response
5Hz-60kHz ± 0.5 dB @ 1W
Input Impedance
180 K ohms
Output Impedance
4 and 8 ohms
Tube Complement
2 x 845, 1 x 12AU7, 2 x 12BH7A
Dimensions
18.25 x 13.75 x 10 inches (W x D x H)
Warranty
3 years parts/labor; 90 days on tubes
Features
- Pure Class A monoblock design
- Automatic bias circuits for easy setup
- No need for matched output tubes
- High-quality split-core transformers
- Solid-state rectifier with choke filters
- Switchable feedback from 0 to 6dB
- Standard 845 tubes with upgrade options
- Built on Mil-spec PC board
What customers say
Customers consistently praise the Art Audio Quartet MB monoblocks for delivering an intoxicatingly musical sound characterized by detail and an expansive soundstage unmatched by many solid state rivals. The core theme centers on unparalleled sonic performance, offering natural warmth and emotional depth even with demanding speakers. Build quality reflects its premium status, showcasing artisanal construction. Users value the authority and dynamic headroom these units provide for driving various speaker systems. While performance is stellar, the ultra premium pricing and required tube maintenance present practical considerations. Ultimately, the overwhelming consensus positions the Quartet MB as an endgame component for dedicated audiophiles seeking the ultimate expression of classic tube amplification.
Know before you buy
The automatic bias circuit removes the need for manual maintenance or specialized tools. It continuously monitors and adjusts the tubes for you, ensuring optimal performance without the hassle of periodic calibration.
No, you do not need matched output tubes. The design of the Quartet MB is engineered to handle variations between tubes, giving you more flexibility and lower costs when it comes time to replace them.
The switchable feedback allows you to toggle between 0 and 6dB. Lower feedback generally provides a more open, natural sound, while higher feedback can offer tighter control and a slightly more precise presentation, letting you tune the amp to your specific speakers.
The Quartet MB features both 4 and 8-ohm output taps, making it compatible with a wide range of speaker impedances. With 45-50 watts of pure Class A power, it is well-suited for most high-quality bookshelf or floor-standing speakers.
Tube life varies based on usage habits and environment, but the 845 tubes are known for their durability. The amplifier comes with a 90-day warranty on all tubes, while the internal components are covered for three years.
Each monoblock measures 18.25 inches wide, 13.75 inches deep, and 10 inches high. Because they are monoblocks, ensure you have enough shelf or floor space to place them near your speakers to keep cable runs short.
Still have a question?
Ask Hayley anything about this product before you decide.