Woot, woot! I was thrilled when I saw the announcement for this amplifier. I was tempted to order one sight unseen and sound unheard. Why? First off, it employs the newest (as of March 2025) class-D amplification technology. Second, it can accommodate all sorts of audio systems, from an eight-channel surround setup to a megalomaniacal two-channel stereo system. Third, the specs, even in the context of its technology, are impressive. And fourth, I can lift it by myself—easily! How can I pass this amplifier up?
Peter Lyngdorf has played a major role in the development of modern class-D amplification, starting at NAD (pulse-code modulation to pulse-width modulation, in 1998), continuing with TacT (whose technology became Equibit, the patented PCM-to-PWM conversion algorithm from Texas Instruments) and, most recently, with Purifi and its Eigentakt technology. Considering that history, it is a bit surprising that the MXA-8400 is Lyngdorf Audio's first Purifi-based product. What is not surprising is that Lyngdorf's implementation is not just hooking up OEM-sourced modules and a power supply in a box. The MXA-8400 includes some innovative, logical features.
It is not uncommon for amplifier manufacturers to license the technology and produce the modules themselves for reasons of efficiency and cost. Lyngdorf (meaning, from now on, the company, not the man) goes a step farther with the MXA-8400, producing a single large circuit board for all eight channels. The individual amplifiers on the board do resemble familiar Eigentakt modules, but there is "more space around the components, a four-layer PCB with thick copper traces and good grounding, ideal voltage and current supply under all conditions, and select components where it has an advantage." The quote is from an email exchange with Lyngdorf Director of Product Marketing Roland Hoffmann.
Optimizing the power supply is important because the performance of all amplifiers is crucially related to the quality of the power. This applies to Eigentakt amps as well; their output is almost directly voltage-dependent, and the eight channels in the MXA-8400 increase power demands. Lyngdorf employs a single PowerPerfect power supply for all the channels, although channels 1–4 and 5–8 are supplied with opposite polarities for optimal efficiency (footnote 1). The rated capacity of the power supply is 3.2kW, but more significant is that it supports a maximum output current of 25A for every one of those eight channels and a maximum peak-to-peak output voltage of 58V per channel. The bridged voltage output peaks at 116V!
This, then, is a high-powered (200Wpc into 8 ohms, 400Wpc into 4 ohms) eight-channel amplifier. In addition, the MXA-8400 allows pairs of outputs to be bridged to provide four channels of even higher output (800Wpc into 8 ohms). Most multichannel power amplifiers come with channel counts of five or seven in recognition of traditional 5.1 or 7.1 setups with powered subwoofers. For such applications, adding another channel makes no sense.
On the other hand, adding that extra channel might grab the interest of audiophiles who use electronic crossovers and active amplification. They would appreciate having six channels to biamp three speakers or triamp a stereo pair. The extra channel provides yet another option for multichannel: How about bridging three pairs of outputs for a really powerful Left–Center–Right speaker trio? That was my first thought when I heard about the MXA-8400: I could do that and still have amplification for two height channels, all in one box!
Delivery and unpacking
I knew the weight and dimensions of the MXA-8400 in advance, so I was surprised when the box arrived: It was huge and weighed 42lb! The discrepancy between the amplifier's weight and the shipping weight was due partly to generous and secure packaging. A substantial rack-mount adapter, which was also included, contributed to the gross weight. A second, inner box contained an AC power cord, eight Neutrik speakON NL4 connectors, and an Owner's Manual. The MXA's chassis, in Matte Black, is sturdy, clean, and modest. It was however stylish—a sweet spot between the many module-based class-D amps that come in formed sheet metal containers and the unnecessarily lavish amps of all classes. A deep horizontal groove in the front panel relieves the amp's aesthetic blankness. At the bottom left is a small Lyngdorf logo and an LED. The LED illuminates when the amp is turned on, blinks slowly in Standby, and blinks rapidly when a fault is detected. A small "MXA-8400" label is at bottom right. The back panel makes it obvious that this is not just another power amplifier: There are no speaker binding posts! In their place, the MXA-8400 employs Neutrik speakON connectors, which offer several advantages over traditional loudspeaker connections and are being used with ever-greater frequency for critical pro-audio applications. SpeakON electrical connections have extremely low resistance, lock in place securely, and are not susceptible to accidental shorting or disconnection. They are quite easy to attach and detach without the use of tools: To attach, just insert and twist, and it's locked. To detach, press the tab (just like the one on an XLR cable), twist, and pull. I have been using speakON connectors in my system for some years; they're used with the Benchmark Media AHB2, my reference amplifier. I'm annoyed whenever a review forces me to revert to banana plugs (lockable or not), spades (even with my AudioQuest wrench) or, Heaven forbid, bare wires.
Most of the rear surface of the MXA-8400 is occupied by two rows of eight round jacks. The upper ones, labeled 1–8, are Neutrik speakON NL4 connectors; the lower ones, also labeled 1–8, are female XLR connectors. These are arranged into four groups, each containing two input XLRs and two output NL4s; the odd-numbered pairs are more brightly outlined. Small print says that the odd channels are different from the even ones. So what's up with that?
Fastidious readers will notice that this amplifier is advertised as offering bridged-channel output, an option that's uncommon in class-D amps (footnote 2). Those amplifiers that do offer it require the use of a switch (as with the MXA-8400); they also demand care to connect the speaker cables in a unique way to achieve the desired output, in order to avoid damage to the amps. This is not a concern since the MXA-8400 utilizes separate and dedicated speakON cables for normal and bridged operation.
To use the MXA-8400 unbridged for up to eight channels, just connect your speakers to any output using a cable terminated with an NL2 speakON (or with an NL4 speakON wired only to its +1/–1 terminals). For bridged output, up to four channels, connect your speakers to any odd-numbered MXA-8400 output with a cable terminated with an NL4 speakON wired only to its +2/–2 terminals. If you wish, you can bridge some channel pairs and leave others unbridged, though you will need to compensate for the difference in gain, as the single High/Low sensitivity switch applies to all channels.
On the left and right sides of the central I/O panel, you'll see some familiar features. To the left is an RJ45 network jack designated for service only. Below it is the Sensitivity switch (High, Low) and Power State switch (ON/Trigger In, Low Power). Between the switches are 3.5mm Trigger In and Out jacks. If the Power State switch is on Low Power, the amp will turn on when an audio signal is detected and switch to standby when it has not detected a signal for 15 minutes. If the Power State switch is set to ON/Trigger, the amp will remain permanently on unless the Trigger In jack is in use; in that case, the state of the trigger signal will switch the amp between ON and Standby. Over on the right is an IEC power receptacle, an ON/OFF switch, and a blank panel for some future option. The MXA-8400 does not need more channels, but a Dante/AES67/Ravenna network input would be nice.
Setup
Setup was easy—I just transferred the three XLR input cables from my Benchmark amplifiers to three inputs on the MXA-8400, then moved the three speakON-terminated speaker cables to the corresponding outputs on the MXA-8400. This was, by far, the most efficient installation I have experienced, but that might not be true for most. Users with unbalanced (RCA) sources and with traditional two-wire connectors (bare, banana, spade, or phone-plug) will need adapters or new cables, or even new sources. Lyngdorf includes eight speakON connectors in the box; these can be attached to most speaker cables without soldering by using the included hex wrench. The choice between Lyngdorf 's high and low input sensitivity will depend on your system. I chose high for the bridged channels and low for the unbridged channels to most closely approximate the Benchmark amps' 23dB of gain. I then trimmed the output gain in JRiver to get it spot-on so that the front L/C/R channels remained balanced with my surrounds and subwoofers. I originally set the Power State switch to Low Power, but that meant the amp went to standby after 15 minutes without signal, and I was bothered by the amp being off too often during the day. With my listening habits, I would have preferred a longer interval before the shift to Standby. Because the interval is not adjustable, I switched the Power State to ON. I switched it on in the morning and off at night (when I remembered). The MXA-8400 required no further attention, and it remained barely warm to the touch regardless of how hard I drove it.
Footnote 1: The polarity difference is of course corrected internally. Footnote 2: Standard bridging strategies are verboten with many Purifi amp modules since neither output terminal is at ground potential and should not be connected to an external ground. Also, both output terminals are internally connected to feedback circuits in their own channel and should not be directly linked to those of the other channel.
Optimizing the power supply is important because the performance of all amplifiers is crucially related to the quality of the power. This applies to Eigentakt amps as well; their output is almost directly voltage-dependent, and the eight channels in the MXA-8400 increase power demands. Lyngdorf employs a single PowerPerfect power supply for all the channels, although channels 1–4 and 5–8 are supplied with opposite polarities for optimal efficiency (footnote 1). The rated capacity of the power supply is 3.2kW, but more significant is that it supports a maximum output current of 25A for every one of those eight channels and a maximum peak-to-peak output voltage of 58V per channel. The bridged voltage output peaks at 116V!
This, then, is a high-powered (200Wpc into 8 ohms, 400Wpc into 4 ohms) eight-channel amplifier. In addition, the MXA-8400 allows pairs of outputs to be bridged to provide four channels of even higher output (800Wpc into 8 ohms). Most multichannel power amplifiers come with channel counts of five or seven in recognition of traditional 5.1 or 7.1 setups with powered subwoofers. For such applications, adding another channel makes no sense.
On the other hand, adding that extra channel might grab the interest of audiophiles who use electronic crossovers and active amplification. They would appreciate having six channels to biamp three speakers or triamp a stereo pair. The extra channel provides yet another option for multichannel: How about bridging three pairs of outputs for a really powerful Left–Center–Right speaker trio? That was my first thought when I heard about the MXA-8400: I could do that and still have amplification for two height channels, all in one box!
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Delivery and unpackingI knew the weight and dimensions of the MXA-8400 in advance, so I was surprised when the box arrived: It was huge and weighed 42lb! The discrepancy between the amplifier's weight and the shipping weight was due partly to generous and secure packaging. A substantial rack-mount adapter, which was also included, contributed to the gross weight. A second, inner box contained an AC power cord, eight Neutrik speakON NL4 connectors, and an Owner's Manual. The MXA's chassis, in Matte Black, is sturdy, clean, and modest. It was however stylish—a sweet spot between the many module-based class-D amps that come in formed sheet metal containers and the unnecessarily lavish amps of all classes. A deep horizontal groove in the front panel relieves the amp's aesthetic blankness. At the bottom left is a small Lyngdorf logo and an LED. The LED illuminates when the amp is turned on, blinks slowly in Standby, and blinks rapidly when a fault is detected. A small "MXA-8400" label is at bottom right. The back panel makes it obvious that this is not just another power amplifier: There are no speaker binding posts! In their place, the MXA-8400 employs Neutrik speakON connectors, which offer several advantages over traditional loudspeaker connections and are being used with ever-greater frequency for critical pro-audio applications. SpeakON electrical connections have extremely low resistance, lock in place securely, and are not susceptible to accidental shorting or disconnection. They are quite easy to attach and detach without the use of tools: To attach, just insert and twist, and it's locked. To detach, press the tab (just like the one on an XLR cable), twist, and pull. I have been using speakON connectors in my system for some years; they're used with the Benchmark Media AHB2, my reference amplifier. I'm annoyed whenever a review forces me to revert to banana plugs (lockable or not), spades (even with my AudioQuest wrench) or, Heaven forbid, bare wires.
Most of the rear surface of the MXA-8400 is occupied by two rows of eight round jacks. The upper ones, labeled 1–8, are Neutrik speakON NL4 connectors; the lower ones, also labeled 1–8, are female XLR connectors. These are arranged into four groups, each containing two input XLRs and two output NL4s; the odd-numbered pairs are more brightly outlined. Small print says that the odd channels are different from the even ones. So what's up with that?
Fastidious readers will notice that this amplifier is advertised as offering bridged-channel output, an option that's uncommon in class-D amps (footnote 2). Those amplifiers that do offer it require the use of a switch (as with the MXA-8400); they also demand care to connect the speaker cables in a unique way to achieve the desired output, in order to avoid damage to the amps. This is not a concern since the MXA-8400 utilizes separate and dedicated speakON cables for normal and bridged operation.
To use the MXA-8400 unbridged for up to eight channels, just connect your speakers to any output using a cable terminated with an NL2 speakON (or with an NL4 speakON wired only to its +1/–1 terminals). For bridged output, up to four channels, connect your speakers to any odd-numbered MXA-8400 output with a cable terminated with an NL4 speakON wired only to its +2/–2 terminals. If you wish, you can bridge some channel pairs and leave others unbridged, though you will need to compensate for the difference in gain, as the single High/Low sensitivity switch applies to all channels.
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SetupSetup was easy—I just transferred the three XLR input cables from my Benchmark amplifiers to three inputs on the MXA-8400, then moved the three speakON-terminated speaker cables to the corresponding outputs on the MXA-8400. This was, by far, the most efficient installation I have experienced, but that might not be true for most. Users with unbalanced (RCA) sources and with traditional two-wire connectors (bare, banana, spade, or phone-plug) will need adapters or new cables, or even new sources. Lyngdorf includes eight speakON connectors in the box; these can be attached to most speaker cables without soldering by using the included hex wrench. The choice between Lyngdorf 's high and low input sensitivity will depend on your system. I chose high for the bridged channels and low for the unbridged channels to most closely approximate the Benchmark amps' 23dB of gain. I then trimmed the output gain in JRiver to get it spot-on so that the front L/C/R channels remained balanced with my surrounds and subwoofers. I originally set the Power State switch to Low Power, but that meant the amp went to standby after 15 minutes without signal, and I was bothered by the amp being off too often during the day. With my listening habits, I would have preferred a longer interval before the shift to Standby. Because the interval is not adjustable, I switched the Power State to ON. I switched it on in the morning and off at night (when I remembered). The MXA-8400 required no further attention, and it remained barely warm to the touch regardless of how hard I drove it.
Footnote 1: The polarity difference is of course corrected internally. Footnote 2: Standard bridging strategies are verboten with many Purifi amp modules since neither output terminal is at ground potential and should not be connected to an external ground. Also, both output terminals are internally connected to feedback circuits in their own channel and should not be directly linked to those of the other channel.
