Emotiva XPR-1 Introduction



Ever dream of owning an exotic sports car with more performance and style on hand than you’d probably know what to do with? What about owning a power amplifier of that caliber but without the unapproachable price tag? Emotiva has such a solution with their new 1 kilowatt XPR-1 Mono-block power amplifier. For those wondering what the term “mono-block” means, it’s quite simply just a way of saying that the product contains only one amplifier channel per chassis. The advantage of a mono-block over a stereo amplifier is twofold:

1. The ability to utilize a larger power supply for just the single channel and

2. Theoretically improved (reduced) crosstalk, since each amplifier channel resides in its own chassis, running off its own power supply and supplementary circuitry.

You’re probably wondering, “Who would need that much power?” Well, quite frankly most people don’t. But when you’re assembling the very best two-channel or multi-channel home theater system with large power-hungry speakers, having too much power on hand is NEVER an issue. Since I’ve been testing the new Status Acoustics 8T Audioholics reference speakers, I’ve been on a quest to find an amplifier with virtually unlimited power (or as Darth Sidious would say it “Powah!”) to drive them. Could it be possible that I’ve found such an amplifier in the $1499 Emotiva XPR-1? You’re going to have to review the review, or at least skip to the measurements section, to find out.

Design Overview

The Emotiva XPR-1 amplifier is chock-full of very cool tech, most worthy of dedicating some real estate in this review to explain how it works.

Emotiva XPR-1 Top View with cover removed

You can see the layout is very clean and symmetrical. It basically takes two amplifier channels and bridges them together to form a fully differential amplifier stage from input to output. In fact, if you use the balanced input on the XPR-1, the signal remains differential all the way to its output driving the speaker. Thus the loudspeaker has no ground reference. All things being equal, differential topologies are superior to single ended designs, because they offer better noise immunity (up to a 6dB improvement) and lower distortion.

The XPR-1 features a massive centralized power supply to feed this baby all of the power your wall outlet can deliver. There is a preamp stage consisting of high quality op-amp amps that gets bypassed when using the amplifier’s differential (balanced) input.



The Power Supply

The Emotiva XPR-1 is quite an innovative amplifier design. It is a class A/B amplifier topology with a Class H modulating power supply. Unlike many of the high-efficiency Class H pro amps that utilize SMPS power supplies, Emotiva spared no expense and instead employed a much cleaner traditional linear power supply with a 30lb 2.5kVA transformer and 24 10,000 uF capacitor bank. Unlike their original MPS-1 amplifier that employed a Class H topology where only one high voltage rail was used while the output modulated above the input signal, the XPR-1 employs two rails. The low rail is set for +-36V allowing the amp to operate as pure Class A/B up until about 200 watts or so. Once the power levels go higher, the output rail modulates above the incoming input signal to achieve over 1 kilowatt of power into an 8 ohm load off of +-72V rails. I’m sure some forum sharpie will note that +-72V isn’t a high enough supply rail to reach the 1000 watt power level but they would be mistaken once they considered the fact that the output stage of the XPR-1 amplifier is differential, essentially bridging two channels together. Thus the output stage feeding the loudspeaker sees no ground reference allowing the amp to swing virtually the fully difference between the +- rails (144V – minus losses). This effectively doubles the total voltage swing which has the potential of increasing the power output fourfold in the process. You never really achieve a 4x increase in power for bridged amplifiers, else it would either burn out the output devices or be current-limited by the power supply or wall voltage. In reality, the bridged configuration doubles the power in this case. As you can see, there is plenty of rail voltage to do well over 1 kilowatt of power in this configuration.

Emotiva XPR-1 Power Supply

Another trick feature of the XPR-1 is how the capacitors are distributed on the power supply. First let me point out that the capacitors are actually manufactured by Emotiva for the XPR series of amplifiers. They are designed to be extremely low ESR and low ripple. The 24 10,000uF caps are only rated at only 50V but there is method to their madness here. The low rail actually sees a bank of 6 of these caps in parallel for a total power supply capacitance of 60,000uF or 120,000uf between the +- 36V rails. The high rails see a series-parallel combo for an effective capacitance of 30,000uF per rail or 60,0000uF between the +- 72V rails. Using multiple smaller caps lowers the profile of this already beastly amplifier and also reduces ESR, especially for the low rail to minimize ripple for the lower power levels where the most control is needed to keep things sounding crystal clean. The resistors on the output of the power supply are used for discharging the caps once the power supply is shut down.

Jump to: Introduction Emotiva XPR-1 Amplifier Topology Emotiva XPR-1 Mono Amplifier Sound Quality Tests Emotiva XPR-1 Mono Amplifier Power and Distortion Measurements Emotiva XPR-1 Mono Amplifier Review Conclusion