Mark Levinson No. 27.5 Dual Monaural Power Amplifier

The Mark Levinson Nº27.5 is a dual-monaural power amplifier designed and manufactured by Madrigal Audio Laboratories. Developed as a precision high-performance amplifier, the Nº27.5 provides independent left- and right-channel amplification and supports both single-ended and balanced operation, with normal non-inverting and inverting operating modes.

The Nº27.5 delivers a minimum of 100 watts of continuous sine-wave power per channel into 8 ohms and 200 watts per channel into 4 ohms, with both channels driven. The amplifier can also be operated in bridged monophonic configuration, where two Nº27.5 amplifiers can be combined to deliver substantially greater output power. In bridged operation, the manual specifies that a Nº27.5 driving an 8-ohm loudspeaker is capable of delivering 400 watts RMS.

Connectivity includes both RCA-type and XLR-type audio inputs, while the speaker outputs use gold-plated, high-current, five-way binding posts. The amplifier can therefore be integrated into systems using either single-ended or balanced signal connections, with balanced operation particularly recommended by Mark Levinson when long interconnect lengths are required.

Key Features

• Dual-monaural power amplifier architecture
• 100W minimum continuous power per channel into 8Ω
• 200W minimum continuous power per channel into 4Ω
• 400W RMS capability when bridged into an 8Ω loudspeaker
• Single-ended and balanced operation
• Normal non-inverting and inverting operating modes
• RCA and XLR inputs
• Gold-plated, high-current five-way binding posts
• Bridged monophonic operation
• Thermal protection circuitry
• Factory-set AC voltage configurations
• Designed and manufactured in the USA by Madrigal Audio Laboratories

Amplification

Amplifier Type:
Dual Monaural Power Amplifier

Rated Power:
100W minimum continuous sine-wave power per channel into 8Ω, with both channels driven from 20Hz–20kHz at no more than 0.3% THD

4Ω Power:
200W minimum continuous sine-wave power per channel into 4Ω, with both channels driven from 20Hz–20kHz at no more than 0.5% THD

Peak Output Voltage:
48V at rated line voltage into 8Ω

Voltage Gain:
26.9dB

Audio Performance

Frequency Response:
4Hz–122kHz (-3dB)

Input Impedance:
50kΩ shunted by 1.5nF

Power Consumption:
Typically 175W at idle
400W at rated power into 8Ω

Inputs

The Nº27.5 incorporates both RCA-type and XLR-type input connectors, allowing integration with preamplifiers using either single-ended or balanced outputs.

Single-Ended Input:
2 × RCA-type connectors

Balanced Input:
2 × XLR-type connectors

Operating Modes:
Single-ended normal
Single-ended inverting
Balanced normal

The amplifier may be configured for normal non-inverting or inverting operation. For balanced operation, the manual recommends using the balanced inputs, particularly where long cable runs are required.

Speaker Outputs

The Nº27.5 uses gold-plated, high-current, five-way binding posts for loudspeaker connection.

Output Connectors:
4 × five-way binding posts

Connection Options:
Spade lugs
Hook lugs
Pigtail connection

The manual specifies that the output terminals are intended only for connection to loudspeakers and warns against short-circuiting the amplifier outputs or connecting the left and right output terminals together.

Bridged Operation

The Nº27.5 can be configured for bridged monophonic operation when greater power output is required. Two amplifiers are used to drive a single loudspeaker, with the manual specifying compatibility with load impedances of at least 2Ω.

Bridged Configuration:
Monophonic operation

Minimum Load Impedance:
2Ω

Output into 8Ω:
400W RMS

Mark Levinson recommends balanced interconnection for the best bridged performance when the associated preamplifier provides balanced outputs. Dedicated balanced and single-ended bridging connection methods are described in the operating manual.

Protection & Thermal Management

The Nº27.5 incorporates protection circuitry designed to switch the amplifier off if an electrical malfunction or inadequate ventilation causes potentially damaging operating conditions.

Thermal sensors are positioned near each group of output devices. Should heatsink temperature become excessive, the protection circuitry shuts down the amplifier before damage occurs. Following a cooling period, the amplifier can be reactivated.

Normal Heatsink Temperature at Idle:
35°C at 22°C ambient temperature, with unrestricted airflow

Maximum Heatsink Temperature Before Protection:
80°C

Adequate ventilation is required, particularly when the amplifier is installed in a cabinet or enclosed space.

Fuses

The Nº27.5 uses two slow-blow 250V 3AG fuses located on the rear panel.

100V / 120V:
10A

200V / 220V / 240V:
6.25A

The manual specifies that replacement fuses must be of the same type and rating.

Physical Specifications

Overall Dimensions:
19″ W × 6-7/8″ H × 18-7/8″ D

Metric Dimensions:
482.6mm W × 174.8mm H × 479.4mm D

Shipping Weight:
95lbs / 43.1kg

Construction:
Dual-monaural chassis design

Conclusion

The Mark Levinson Nº27.5 represents a substantial example of Madrigal Audio Laboratories’ approach to high-performance amplification. Its dual-monaural architecture, high-current output stage, balanced and single-ended connectivity and ability to operate in either normal or inverting configurations provide considerable flexibility for integration into demanding high-end audio systems.

With a minimum of 100 watts per channel into 8Ω and 200 watts into 4Ω, the Nº27.5 provides substantial continuous power, while its bridged operating capability allows two amplifiers to be configured for monophonic operation with up to 400 watts RMS available into an 8Ω loudspeaker.

Combined with its substantial power supply requirements, high-current speaker connections, thermal protection and carefully specified analogue circuitry, the Nº27.5 remains a technically serious power amplifier from the era in which Mark Levinson established its reputation for uncompromising high-end audio engineering.

*The information provided above has been taken from the manufacturer’s original product manual and is intended as a reference. Specifications, features, dimensions and other details may vary depending on production version, regional configuration or subsequent manufacturer revisions. Please confirm specific details with HFX Systems prior to purchase.

Condition: Good

Colour: Black

Unit does not include original packaging or accessories.