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Thread: The new Emotiva XPA-1L Mono Block

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    Default The new Emotiva XPA-1L Mono Block

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    Looks like Emotiva has introduced a new mono block to the market.

    Ask any audiophile what kind of amplifier they dream about owning, and they’ll tell you: “a set of Class A mono-blocks!” Audiophiles know that Class A amps sound the best. There is zero crossover distortion, and the output devices are biased up to their most linear operating range. Class A, fully balanced, differential amplifiers, although a rare breed and very hard to find, sound even better!
    Unfortunately, Class A amps are typically very large, very expensive, and tend heat up the whole house when you run them. They also usually aren’t the most powerful amps in the world, either.
    Well, not anymore! We’d like to introduce you to the new Emotiva XPA-1L, with selectable Class A and Class A/B mode switching. Now you can have both: remarkable sound backed by real power.











    In Class A/B Mode, the XPA-1L is a potent, superb sounding, fully balanced mono-block Class A/B amplifier – delivering 250 watts into 8 ohms (or 500 watts into 4 ohms) with incredibly low levels of noise and distortion. Flip the switch into Class A Mode and the XPA-1L transforms into pure Class A, high bias 35 watt sweetheart... with a kick. If you exceed the 35 watt threshold, it seamlessly transitions into Class A/B mode when the signal level goes above 35 watts, allowing it to delivering its full power. You get the awesome purity of Class A for power levels up to 35 watts, with none of the high power limitations. (The XPA-1L does run a bit warmer in Class A Mode, but hey, it worth it.)
    SPECS
    Number of channels: 1
    Topology: Fully balanced, fully discrete, Quad Differential, high current, short signal path, with switchable Class A or Class A/B operation.
    Power output (all channels driven):
    250 watts @ 8 ohm (0.1% THD)
    500 watts @ 4 ohm (0.1% THD)
    35 watts @ 8 ohm; Class A operation
    Note: In Class A mode, under normal conditions, the XPA-1L operates in pure Class A mode at all power levels up to 35 watts, above this level it will automatically transition into Class A/B mode.
    Rated Power Bandwidth (at rated power; 8 Ohm load): 20 Hz to 20 kHz + / - 0.15 dB
    Minimum Recommended Load Impedance: 4 Ohms (which equals one 4 Ohm load or two paralleled 8 Ohm loads).
    Frequency Response: 10 Hz to 80 kHz (+ 0 / - 2 dB).
    THD + noise: < 0.005%
    Signal to Noise Ratio (8 Ohm load): > 90 dB at 1 watt (A-weighted).
    > 116 dB at rated power (A-weighted).
    Damping Factor (8 Ohm load): >500
    Speaker Output Connections: Audiophile grade five-way binding posts, gold plated with clear insulator, 1 pair.
    Power Supply: 90,000 uF of storage capacitance.
    450 VA heavy duty toroidal transformer
    Input Sensitivity (for rated power; 8 Ohm load): 1800 mV.
    Gain: 29 dB.
    Input Connections: Unbalanced (RCA); balanced (XLR); switchable.
    Input Impedance: 50k ohms.
    Trigger: Trigger Input: 5 - 20 V (AC or DC); <10 mA input current required.
    Trigger Output: 12 VDC; can drive any load up to 100 mA.
    Power Requirements: 115 VAC or 230 VAC +/- 10% @ 50 / 60 Hz (automatically detected and switched).
    Front Panel Controls and Indicators: Standby; push button (halo ring changes color to indicate Standby or On).
    Status LED; illuminates blue for normal operation, flashes red during power-up or when a fault occurs; (may be disabled by rear panel Status LED switch).
    Rear Panel Controls: AC Power switch; rocker controls AC mains power.
    Status LED switch; rear switch disbles front panel Status LED.
    nput selector; toggle switch selects between balanced and unbalanced inputs.
    Protection: The XPA-1L is protected against excessive operating temperature, shorted speaker connections, ground faults, and other common fault conditions.
    Dimensions:
    unboxed: 17” wide x 3.875” high x 19” deep (includes feet and binding posts).
    boxed: 23" wide x 8.75" high x 24 1/2" deep
    Weight: 35 lbs (45 lbs boxed)
    Emotiva's Website
    Magnepan, B&K, Emotiva, HSU

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    Default Re: The new Emotiva XPA-1L Mono Block

    Sweet! They are kicking butt lately.

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    Default Re: The new Emotiva XPA-1L Mono Block

    Looks like a damn decent amp IMO! At 500w @ 4ohm I figure I could use about 2 or 3 of them!
    Magnepan, B&K, Emotiva, HSU

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    Default Re: The new Emotiva XPA-1L Mono Block

    At $3495 for 5 of them you would be hard pressed to get more amp for the money all things considered.

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    Default Re: The new Emotiva XPA-1L Mono Block

    It is a really interesting amp that could answer the question does high-bias class-A sound different.
    Even if it doesn't it is a nice sized mono that doubles-down on power for hard to drive speakers.

    There are problems with them in the initial release. They click and lock into A/B mode.
    t has been reported A mode (for the fist 35 watts) you are looking at about 200 watts idle.
    That is something to think about.

    High-bias class A like the Parasound A51 idle at 108 watts (according to an email from Parasound).
    The XPA-1 is reported to have 10 watts of Class-A operation.
    Those probably cover most casual listening levels.

    I wonder if you can infer the class-A bais by the idle power usage and number of transistors used?
    For example, the Outlaw 75 idles at 80 watts and has 60 transistors, so 1 watt at best per transistor at best

    But then again, if it amplifying the waveform properly with very little distortion, why would they sound any different?

    - Rich

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    Default Re: The new Emotiva XPA-1L Mono Block

    Traditional Class-A biasing is great if you think your electric bill is too low and you'd like your amplifiers to double as space heaters. It won't make the amplifiers sound different from good, and much more efficient, Class-AB (or sliding-bias Class-A) amps, however. There have been innumerable careful, level-matched, double-blind comparisons of amplifiers over the years, and as long as the amps being compared have flat response within about 0.1 dB over the audible band, have adequately low noise and distortion, and are not overdriven, nobody can tell them apart by ear. Which is as it should be.

    Class B amplifiers can cause audible distortion because they produce relatively large amounts of distortion at low signal levels. When distortion is high in proportion to the signal level, it may not be fully masked by the signal, thus becoming audible. The culprit is crossover-notch, or switching, distortion, which arises because transistors are very nonlinear when they switch on or off, as happens when a waveform crosses over from negative to positive or positive to negative and is passed between the two transistors of an output pair. Class A takes a sledgehammer approach to the problem by running a steady bias current through the transistors large enough to keep them from every completely switching off, so no crossover distortion. This is tremendously inefficient, however, and, fortunately, overkill. The traditional approach is to bias the transistors high enough that they never switch off on very small signals but do switch when the signal gets large enough to fully mask the crossover distortion. This Class AB approach does not require a lot of bias current to do the job effectively, so it's possible to get all the audible benefits of Class A with very little sacrifice in efficiency relative to Class B. An alternative, invented by Nelson Pass when he was at Threshold and later adopted by a number of Japanese manufacturers (Technics, for example), is sliding-bias Class A, in which the amplifier varies the bias automatically according to the signal level so that the transistors never go out of conduction, just as in traditional Class A. But since amplifiers typically operate at outputs of less than 1 watt so much of the time -- well over 90% in most cases -- the electrical efficiency is similar to that of Class AB.

    The difference in distortion between Class B and AB can be seen in a plot of THD (total harmonic distortion) versus output. A Class B amp will show a sharp rise in the distortion percentage as the output drops very low, whereas a Class AB amp will show relatively little increase at the bottom. You have to do a true THD measurement, though. The easier and far more common THD+noise (THD+N) will show a rise at the bottom either way just because of noise.

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    Default Re: The new Emotiva XPA-1L Mono Block

    How does slew rate fit into this?
    Often it is described as the speed, but as I understand it, it is more of an indication of the bandwidth or how well an amp can produce square waves at 1 kHz.

    What about bass performance, is that just a matter of an amps ability to deliver current into low impedance load?

    - Rich

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    Default Re: The new Emotiva XPA-1L Mono Block

    Quote Originally Posted by RichB View Post
    How does slew rate fit into this?
    Often it is described as the speed, but as I understand it, it is more of an indication of the bandwidth or how well an amp can produce square waves at 1 kHz.
    Slew rate is how fast the amplifier can change the voltage of its output. So a signal's slew rate goes up in proportion to both frequency and amplitude. Practically speaking, what this means is that the toughest challenge an amplifier ever faces in terms of slew rate is full-power 20-kHz output on a test bench, which has never been an issue for any amplifier I can remember. (Music or soundtrack signals that might require full output are always down below 1 kHz, while very high frequencies tend to be very low in level.) Inadequate slew rate will result in distortion, but you'd have to go out of your way to design a modern amplifier that didn't have a much higher slew rate than it ever will actually need. Slew rate is not related to an amplifier's class of operation.

    What about bass performance, is that just a matter of an amps ability to deliver current into low impedance load?
    Same as for its performance in any other frequency range. You want low noise and distortion, flat frequency response, and enough current capability to handle whatever the impedance happens to be at the signal frequency. The only thing special about bass is that you might actually need a reasonable amount of power down there sometimes, whereas the probability of even a pretty low-power amp being taxed in that regard at high frequencies is essentially zilch.

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    Default Re: The new Emotiva XPA-1L Mono Block

    Quote Originally Posted by MDRiggs View Post
    Same as for its performance in any other frequency range. You want low noise and distortion, flat frequency response, and enough current capability to handle whatever the impedance happens to be at the signal frequency. The only thing special about bass is that you might actually need a reasonable amount of power down there sometimes, whereas the probability of even a pretty low-power amp being taxed in that regard at high frequencies is essentially zilch.
    Is there such a thing as speed at delivering current for bass reproduction?
    I ask this because the Sunfire amp did not seem to have the same impact as the Outlaw when I did some tests swapping them in and out. I suppose the difference could really have been in the upper frequency range.

    - Rich

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    Default Re: The new Emotiva XPA-1L Mono Block

    Quote Originally Posted by RichB View Post
    Is there such a thing as speed at delivering current for bass reproduction?
    I ask this because the Sunfire amp did not seem to have the same impact as the Outlaw when I did some tests swapping them in and out. I suppose the difference could really have been in the upper frequency range.
    Current just follows voltage, according to Ohm's law. Current is only an issue if the speaker is trying to draw more than the amp can supply, which is pretty rare -- unless the speaker's impedance is very difficult, the amp will almost always run out of voltage first. Trying to compare the sounds of two amps by swapping them in and out is a waste of time unless one of them is really off in some way. Any difference you think you hear is likely to just be something you thought you heard. Auditory memory for small differences fades in a matter of seconds. You really need instantaneous, level-matched (to within 0.1 dB) comparison, preferably blind. Even with speakers, which often really do have obvious sonic differences, this type of comparison is better -- more revealing and more accurate.

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    Default Re: The new Emotiva XPA-1L Mono Block


    One further thought: You mentioned a Sunfire amp. There was a period when Bob was selling some amps that had what he called his T-Mod, for "transfer function modified". They were designed to mimic the output characteristics of one of his tube amps. Mainly this involved raising the output impedance (i.e., lowering the damping factor). If the output impedance is high enough relative to the speaker's impedance, the amplifier's frequency response will tug toward the shape of the speaker's impedance vs. frequency curve. The most notable effect of this is likely to be a bump in the bass response, because dynamic speakers normally have a big impedance rise at their low-frequency resonance. Tube amps, with their transformer-coupled outputs, typically have much higher output impedances than transistor amps, enough so that this impedance interaction can actually generate an audible frequency-response error (hence the warmth of the so-called tube sound). This is almost never an issue with conventional transistor amps, but if you have a T-Mod'd Sunfire amp, it might actually sound different from other transistor amps on some speakers.

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