Author: Karsten Hein
Category: Gear & Review
Tag: Power Amplifiers
The XL-280 stereo power amplifier is arguably one of the best devices the Hafler has ever made. Offering 145 watts RMS into 8 ohms, it runs stable down to just 1 ohm and is thereby capable of driving even the most challenging speaker loads without having to fear instability, overheating, or the amplifier going into circuit protect mode and shutting itself down. The XL-280 was therefore predestined as a work horse to power the magneplanar and electrostatic speakers of the 90s, but also served more demanding conventional designs, such as some Infinity models. 145 RMS may not seem like a lot of power at first glance, however, this perception might change, if we consider that the watts nearly double as the ohms are cut in half, if the architecture and power supply permit. Thus, at 2 Ohms the XL-280 delivers 360 watts per channel, whereas many more conventional amps will simply throw in the towel.
The XL stands for Excelinear, which—according to Hafler—means that it excels in linearity. The aim was to build an amplifier that would have the linear properties of a single straight wire. The benefit of such an amplifier would be that it neither adds or takes away from the signal it receives from the audio source. Hafler writes that “In phase, amplitude, transfer characteristic and other distortions, the XL-280 sets new standards for accuracy. It is so close to perfection that for the first time you can make a meaningful comparison of this amplifier with the classic zero distortion: a straight wire. (...) An Exclinear amplifier enables the ‘golden ear’ who demands the absolute in system linearity to move one step closer to perfection.” The operating manual goes on to describe that with the addition of the XL-10 switch box, A/B comparisons in distortion differences to a straight wire are possible, and that the XL-280 offers built in controls for load adjustment to accommodate specific speaker loads. To allow for this adjustment while the amp is closed, the top panel has two small holes that are sealed by rubber plugs through which a screwdriver can be inserted.
Halfer, like Harman Kardon, believed that musical bandwidth should not be restricted for the sake of music integrity. The XL-280’s exceptionally wide bandwidth is demonstrated by the specified 1 watt output performance of ± 3dB from 0.1Hz to 500kHz. Impressively, phase shift within the conventional audio band (20Hz to 20kHz) is specified at less than 0.5°. In terms of build quality, the XL-280 is very similar to its predecessor, the DH-220, although it is actually 25mm wider. The black case consists of four construction units: 2 pressed steel sections which form the chassis and lid and 2 large anodized heat sinks—one on each side—to which the amplifier modules are attached and the 6 output transistors are screwed for passive cooling.
In their review of the Hafler XL-280, stereo-amplifier.net writes: “Set up for Quad ESL-63 loudspeakers the Hafler XL-280 gave a truly exemplary performance. The bass was absolutely firm and seemingly more extended than I am used to hearing, despite the fact that my preamplifier has a built-in LF roll-off. The treble was crystal clear and wide open sounding, with no trace of sibilant 'splash' and the overall stereo sound stage rock-solid regardless of the dynamic activity of the music used. Some of the more subtle subjective differences one hears in top-end hi-fi equipment are terribly difficult to quantify, sometimes even to express, but my overriding impression of the Haller XL-280 is that it neither adds to nor subtracts from the source material fed to it. The word that kept coming to mind as I listened over a period of weeks was 'authority' and I can't think of a power amplifier that I've used, or for that matter heard, which demonstrates that quality more convincingly.”
In my own listening so far, I can well relate to the relative authority which the amp attributes to the music. There is no halo, no trace of uncertainty in the representation of voices or piano notes. The amp rather seems to have an ultra-tight grip on the music that is truly fascinating. I cannot yet confirm the bass extension that we have come to know and enjoy from the DH-220, however, a fact that could mean that the capacitors in our unit have dried up over the years. While this would not be surprising for a unit that has been playing music since the 80s, it does mean that there is still some work ahead of us to reveal the XL-280’s full potential. Considering its fresh-from-the-shop condition, I would assume that this particular Hafler has been stowed away in the basement or attic for a long period of time, which is generally bad news for capacitors. Since we have already fallen in love with this amp, restoring it to mint condition will be well worth it.