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Emotiva XPR-1 Amplifier Topology




Emotiva XPR-1 Amplifier Schematic

This circuit topology represents one half of the two differential amplifiers (mirror amplifier) with bipolar transistors.  There are a total of 36 (18 per phase) 250 watt ON Semiconductor output devices in XPR-1 amplifier. By bridging two amplifier channels together and making the second channel of the bridged pair 180 degrees phase inverted, the load sees double the voltage compared to a single ended amplifier design. The positive cycle of the input wave is handled by upper amp and the negative cycle is amplified by the lower differential amp with 180 degree phase shift.  The output of each differential amp (in upper & lower stage) is connected to the bases of bipolar transistor in the Darlington scheme shown in the figure. This configuration gives a much higher current gain. The resistors connected to the emitter of each transistor provide intrinsic feedback to control the currents flowing through the transistors. In addition, two differential op-amps are employed. The input signal is connected to the inverting and non-inverting pin of each op-amp. Depending on the polarization of the input signal (+/-) the output of one the op-amps would “turn on” while the other would “turn down” at the same time. The output signals of the op-amps would switch on/off the MOSFETs connected to the “high rail” potentials in order to synchronize the applied voltage to the input signal. This increases the efficiency of the circuit while avoiding any power loss. In other words, when the input signal amplitude goes high, the upper op-amp switches on the upper MOSFET connecting the upper high rail voltage to the circuit and amplifying the input signal. This circuit is an adaptive design.

Microprocessor Control

The Emotiva XPR-1 employs an ARM9 microprocessor to handle all of the front panel LED logic but it does a lot more than that.  It also controls the fault protection for the amplifier, and monitors line voltage, output current and the grounds between inputs and outputs. In addition, the ARM9 monitors distortion levels feedback loops, and controls the Class H drive.


Emotiva XPR-1 Backview

The back view of the XPR20amp outlet1.JPG-1 is a bit pedestrian, but the connector spacing is well laid out and sturdily assembled.  The XPR-1 accommodates unbalanced and balanced inputs which is switchable via the rear panel switch.  Personally I would have liked to see a more robust toggle switch that required more effort to toggle to avoid accidental switching when reaching behind your rack to organize cabling.  The balanced connectors were not the locking type found on other high end amps, but they hold the cable snugly nonetheless.

The speaker terminals are audiophile-grade 5-way binding posts.  Many high power amps won’t accept banana plug terminations but the XPR-1 does.  The connectors are spaced about 3” apart and fully encased in plastic.  These are great countermeasures to ensure no chance of arching between the speaker leads.  There are two 3.5mm triggers (input and output) and a master on/off switch.

The power receptacle will only accept a 20A power cord which Emotiva provides.  Before installing this amp you will have to make sure you have a true dedicated 20A line or have a qualified electrician install one for you.  The XPR-1 employs an auto-commutator which senses the line voltage and auto switches between 120V / 220V depending on what you feed it.  Power mongers wanting to squeeze out every gut wrenching watt the XPR-1 can deliver will opt to install a 220V line for this amplifier.

Like all other Emotiva products, the XPR-1 has full third party CE and FCC / RoHS certification.  Unlike many companies that self-certify, Emotiva makes it a point to have this done independently for complete regulatory compliance and safety.  This is an expensive and lengthy process but demonstrates how far Emotiva is willing to go to tighten up the product design. 


Emotiva XPR-1 frontpanel View

The front panel of the XPR-1 is very posh.  It fact, it’s arguably the nicest looking amplifier Emotiva has built to date in my opinion.  The XPR-1 has a precision-machined, 1” billet aluminum, multi-element faceplate, with laser embossing. There is a giant glass faceplate flanking the center with variable intensity blue metering that can be oriented for left, right or vertical display.  The meter can be set for fast or slow response or defeated entirely.  The LED meter will turn red under fault conditions right before the amp shuts down.  The defeatable blue accent lighting on each side of the front panel really adds a touch of class to the product.  A soft touch power button with inrush limiting located on the front panel along with the buttons to change the function of the LED display. 


Slifloor.JPGnging a pair of XPR-1’s around is no easy feat.  These 100lbs+ beasts require two people to move them into position if you value the health of your spine.  I positioned both amplifiers on the floor next to my Middle Atlantic rack that houses most of the equipment in the 6,000 ft^3 Auralex acoustically treated Audioholics Showcase Home Theater Room.  I connected the XPR-1’s to both my two-channel system and multi channel system.  For two-channel, I ran unbalanced to my Marantz PM-11S2 integrated amp with my Marantz TT-15S1 turntable and balanced to my Oppo BDP-105 Blu-ray player.  For multi-channel, the XPR-1 was connected up to my Denon AVP-A1HDCI processor for a fully balanced connection from source device to the speaker outputs!  In both systems, my Status Acoustics 8T speaker system was used for evaluation.  All interconnect cables were Bluejeans cable and speaker cables were Kimber 8TC with WBT banana compression terminations. 

Switching between two-channel and multi-channel systems was as easy as flipping the XPR-1 backpanel switches from unbalanced (two-channel) to balanced (multi-channel).  I would caution any end-user connecting two preamps to the XPR-1 in this fashion to ALWAYS turn off the unused preamp.  I measured the switch to provide about -60db of isolation, but it’s still a good idea to only have one active preamp powered on when connecting multiple preamps to a common amplifier via its various input connectors. 


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Recent Forum Posts:

Lvnsnfnatk posts on October 17, 2015 13:23
I'm grateful to have found this website! You guys review great gear that is priced resonably. These Emotiva Monoblocks appear to be well made and have good sound. They also make a pure class A amp. Is there a dealer where I can hear this gear A/B'd ?

I'm a power junkie for sure and am so relieved I changed out the 15A crap that was there prior. My room is wired by 3 separate 20A recepticles with my amp getting its own line. I just assumed these lines are 220V as you recommend, but i'm not sure. How can I tell?

Can I somehow wire in a 30A line for the amp? I realize the recepticle and plug is different as on a clothes dryer, but the temptation to get more power has me contemplating it. I wonder if it's possible? Just a thought.
AUTOBOT posts on April 18, 2015 12:10
Please do a youtube video on this amp.
I have a pair of these with dedicated 20 amp circuits for each amp hospital grade isolated ground receptacles.
Love them.
sharkman posts on July 27, 2014 10:47
I stand corrected on McIntosh amps, I didn't realize they made a 2000 watt mono. I think that's way beyond the needs of 99.9% of audio owners as well, and I'd wager they don't sell as well as their 600 watt mono.
gene posts on July 27, 2014 00:30
Macintosh amps are more realistic in the power department. 99.9% of audio owners don't need 1000 watts per channel, and no house is built with 20 amp dedicated lines,

Maybe the meaning of your message was lost in cyberspace but I fail to see how Mcintosh amps are more “realistic” in the power department. Last time I checked McIntosh also builds 2kwatt Monobloc amplifiers.

McIntosh MC2KW Amplifier, 1 Channel 2000 Watts McIntosh MC2KW Amplifier

You're not getting that kind of power from 120Vac/15A circuit.

Need that much power, get a dedicated 20A line or 220V or both. Don't need it? Get a smaller amp.
sharkman posts on July 26, 2014 02:40
Where did I fault Emotiva? I simply said most owners don't need 1000 watts per channel. You characterize something I said wrongly, then attack me for it. Weird.
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