The Mark Levinson Nº 33 Reference Monaural Power Amplifier is a high-performance audio component designed to deliver exceptional sound quality. It is characterized by its ability to maintain signal integrity regardless of the demands of the musical signal or the loudspeakers used. The amplifier is capable of generating prodigious power levels into virtually any speaker load, both instantaneously and continuously.
Function Description:
The Nº 33 is a monaural power amplifier, meaning each unit is dedicated to a single audio channel, providing superior channel separation and power delivery. It is designed to amplify low-level signals from a preamplifier to drive loudspeakers. The amplifier incorporates several advanced design features to achieve its outstanding performance, including a massive power supply, AC regeneration, a fully balanced design, and a true voltage source characteristic. It also includes extensive protection circuitry to safeguard itself and connected loudspeakers from various fault conditions.
Important Technical Specifications:
- Rated Power Output:
- 300 w/ch continuous rms power @ 8Ω
- 600 w/ch continuous rms power @ 4Ω
- 1200 w/ch continuous rms power @ 2Ω
- 2400 w/ch continuous rms power @ 1Ω
- All power ratings are continuous (rms) from 20 Hz-20 kHz with no more than 0.3% THD, within 0.1 dB from 20 Hz to 20 kHz.
- Frequency Response: Better than -80 dB (ref. 1 w).
- Signal to Noise Ratio (main outputs): 100kΩ (balanced), 50kΩ (single-ended).
- Input Impedance: 26.8 dB.
- Voltage Gain: 2.3 V for full rated output.
- Input Sensitivity: Typically 840 W (±5%) at idle, typically 210 W (±5%) in standby.
- Power Consumption: Determined by the needs of the country for which the unit was manufactured; cannot be reset by dealer or user.
- Shipping Weight: 435 lbs. (198 kg) each.
- Connector Complement:
- Four custom binding posts per channel.
- One 3-pin XLR balanced input connector per channel.
- Two RCA input connectors per channel.
- Two 1/8" mini-jacks for remote turn-on.
- Two Mark Levinson communications ports (RJ-11).
- One captive high current AC mains cord.
- Output Impedance: Less than 0.05Ω from 20-20,000 Hz.
- Dimensions: 31.0" (78.74 cm) H x 14.0" (35.6 cm) W x 27.06" (68.74 cm) D (excluding spikes).
Usage Features:
- Placement: The Nº 33 is designed to stand on the floor as a freestanding unit, ideally near loudspeakers to minimize speaker wire length. Adequate clearance (at least six inches or 15 cm) behind each amplifier is recommended for cable bending without strain. The power switch on the rear panel should be easily accessible.
- Ventilation: The amplifier dissipates approximately 800 watts of energy as heat when "at idle," so free airflow around the top plate and heatsinks is crucial for adequate heat dissipation. If placed in an enclosure, fans are strongly advised to increase ventilation.
- Spiking: Four machined aluminum spiked "feet" are included to immobilize the amplifier and prevent it from rolling on its casters. Installation requires two people, carefully tipping the amplifier to attach the spikes over the casters.
- Operating Voltage: The Nº 33 can be factory-set for various AC mains operations (100V, 120V, 200V, 210V, 220V, 230V, or 240V at 50 or 60Hz). Users should consult a local electrical contractor for high-current AC hookups, as building regulations vary. The operating voltage cannot be changed by the user; any attempt to do so voids the warranty.
- Power Supply: Features two 2.45 kVA low-noise toroidal transformers in a fully balanced design, with separate power supplies for inverting and non-inverting halves. It uses twelve 39,000 µF low ESR capacitors per amplifier, providing almost ½ a Farad of capacitance and 1200 Joules of energy storage. Heavy oxygen-free copper bus bars enhance power distribution efficiency.
- AC Regeneration: A distortion-free 60 Hz sinewave is regenerated internally to power a separate supply for all voltage gain stages, providing greater line conditioning benefits and avoiding performance bottlenecks common with passive line conditioners.
- Fully Balanced Design: Eliminates the need for an input buffer amplification stage, allowing the differential amplifier to be driven directly by the source. Matched impedances and identical circuit paths ensure superior sonic performance. Balanced output is achieved through two identical amplifiers, maintaining a balanced signal throughout.
- True Voltage Source: The Nº 33 acts as a "voltage source," maintaining the appropriate voltage regardless of current demands from the loudspeaker. It doubles its power output when loudspeaker impedance is halved (e.g., 300W @ 8Ω, 600W @ 4Ω, 1200W @ 2Ω, 2400W @ 1Ω), assuming the electrical circuit can support these levels.
- Extensive Protection: Shuts down if it senses fault conditions such as DC at the output, over/under-voltage on AC mains, unsafe operating temperatures, or sustained output current exceeding 80 amperes. It will not turn on until the fault is corrected. AC input to each transformer is fused, and in-rush limiting prevents premature aging of power supply components. A controlled clipping circuit prevents output devices from saturating, avoiding harsh high-frequency harmonics.
- Front Panel:
- Standby Button (1): Toggles the amplifier between completely off, standby, and fully on. When first connected to AC mains (and the rear panel switch is ON), the amplifier is off. Pressing the button once brings it to standby (after a 10-second stabilization delay). Subsequent presses toggle between standby and fully on. To turn completely off, press and hold for approximately one second.
- Indicator Light (2): Shows operational status:
- Full brightness: On and ready.
- Blinking slowly: In standby.
- Dimly lit: Main power supply off, supervisory supply operational.
- Completely off: Rear panel AC mains switch off, supervisory supply disengaged.
- Rear Panel:
- Single-Ended Inputs (1): RCA connectors for single-ended inputs (inverting and non-inverting). Single-ended signals are converted to balanced signals immediately. If using single-ended, connect to the non-inverting RCA input and short the inverting input of the XLR connector with the provided U-shaped strap (pins #1 and #3) to reduce noise pickup. Consistent use of either inverting or non-inverting input is crucial to avoid phase issues.
- Balanced Audio Input (2): XLR connector for balanced inputs. If using a balanced interconnecting cable, remove the shorting plug from between pins #1 and #3 of the XLR input. Pin assignments are: Pin 1: Signal ground, Pin 2: Signal + (non-inverting), Pin 3: Signal - (inverting), Connector ground lug: chassis ground.
- Communications Link and Remote Turn-On Inputs (3):
- Communications Ports (RJ-11): Allows control by a "linked" Mark Levinson 30-series preamplifier. Connect the preamplifier's master port to the Nº 33's slave in port. Subsequent Nº 33 amplifiers can be "daisy-chained" from the first amplifier's slave out to their slave in port (up to six amplifiers total). This enables toggling between standby and fully on, and reporting fault conditions (e.g., HOT!, DCO!, ZAP!).
- Remote Turn-On Jacks (1/8" mini-jacks): Provides compatibility with other products for remote turn-on/off. Operated by a 3–12 volts DC positive-polarity pulse (at least 100 milliseconds duration). Two jacks allow "daisy-chaining" multiple amplifiers; the last jack in the chain must be terminated with a dummy 1/8" plug.
- Speaker Binding Posts (4): Custom-made, gold-plated, high-current binding posts for output termination to loudspeakers. High-quality speaker cable with spade or hook lugs is recommended. WARNINGS: NEVER connect output terminals to anything other than a loudspeaker, short-circuit output terminals, or connect output terminals of one amplifier to another.
- AC Mains Cord and AC Mains Switch (5): Features a captive high-current AC cord and a specially-designed AC mains module. Conventional IEC power cords are not suitable. The AC mains switch on the rear panel disconnects the supervisory power supply from AC, effectively turning the amplifier completely off. This switch must be ON for the amplifier to respond to power-up sequences or remote turn-on commands. WARNINGS: Consult a qualified local electrical contractor for AC wiring. Do not defeat the "third pin" or earth ground of the AC power cord. Potentially dangerous voltages exist inside, even when disconnected from AC mains. No user-serviceable parts inside; refer service to a qualified Mark Levinson dealer.
Maintenance Features:
- Cleaning: Use a feather duster to remove dust. For dirt and fingerprints, use isopropyl alcohol and a soft cloth, applying the alcohol to the cloth first, then lightly cleaning the surface. WARNING: Do not apply liquid cleaners directly to the Nº 33, as this may damage electronic components.
- Warranty:
- 90-Day Limited Warranty: Covers defects in material and workmanship under normal use. Extendable to five years by returning the warranty registration card and original receipt.
- Five Year Extended Warranty: Covers defects in materials and/or workmanship for five years from purchase. Repairs or replacements (at Madrigal's option) are free of charge for parts and labor. Does not cover misuse, abuse, or alteration.
- Obtaining Service: Contact your Mark Levinson dealer for service. Return authorization from Madrigal's Technical Services Department is required before shipping. Provide a specific, comprehensive description of the problem. Include a copy of the original bill of sale for warranty verification.
- Packaging: All returned units must be properly packaged, preferably in original packing material, with return authorization numbers marked on the outer carton. Improper packaging may result in shipping damage, for which Madrigal or the dealer will not be responsible. New shipping materials can be ordered from the dealer for a charge.
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