ModWright KWA 150 Stereo Power Amplifier (TAS 199)

It was not going to be a walk in the park for the KWA 150. I was determined to test it in the context of two challenging loads. First in line was the Final Sound 1000i electrostatic. This is a capacitive load with an impedance swing of about a factor of 30 from bass to treble. Many amplifiers struggle with such a load. An etched and bright treble range is often the first sign of trouble. Not so with the KWA 150. It evinced supreme transient control with absolutely no high-frequency ringing. This resulted is a slightly softer sound relative to other solid-state amps. Midrange textures came through as smooth, suave, and richly layered in the lower mids. The upper mids were also portrayed convincingly without a trace of the textural hardness and dryness endemic to most 1970s solid-state amps (e.g., Dyna 400). In particular, female vocals sang sweetly and were tightly fleshed out within the confines of a wide soundstage. The tonal balance was not quite neutral, being slightly weighted toward the lower mids. Sterility in audio terms has been defined by some as lack of distortion and coloration. That rather sounds flattering and is not at all aligned with my interpretation of the term. Think whiteness, bleached out harmonic colors, and suppressed microdynamics. Sterility in my book equals boring, uninvolving sound. The polar opposite applies to the KWA 150. It was clearly facile in humanizing the music, in reproducing its rhythmic drive and verve, and never interjecting any electronic haze into the mix. So far so good, so it was on to the next speaker load.

The Analysis Audio Omega is a planar-magnetic/ribbon speaker with a nominal impedance rating of 5 ohms, though it dips to around 3 ohms or so in the lower midrange. It requires an amp with substantial current drive in order to scale the dynamic spectrum. The KWA 150 did exceedingly well in this context, faithfully delivering an orchestral crescendo without power compression. Only rarely was I able to clip the KWA 150, and that was at fairly loud playback levels. Bass reach and pitch definition were excellent. The low output impedance guarantees minimal load interaction and an excellent damping factor. Jazz bass lines were negotiated without any confusion and exhibited a satisfying tonal weight. I was able to confirm the sonic superiority of the high-bias setting. Switching over to low bias caused harmonic colors to wilt. Textures were not nearly as rich and the sense of immediacy, of being there, was reduced as well.

The ModWright seemed to bring out the best in the Omega, including a remarkable sense of timing, plenty of spatial conviction, and admirable midrange suaveness. There was plenty of low-level detail in evidence, and while I didn’t feel that I was missing anything essential, I nonetheless suspected that it was not a resolution champ. To test that theory, I enlisted the help of the LAMM Industries M1.2 Reference Monoblocks. Yes, the LAMM is about four times more expensive, but that’s not why this is a bit of an unfair comparison. A monoblock version of any given design would most likely exhibit enhanced channel separation and reduced intermodulation distortion, so I should add the caveat that in bridged mono it’s quite possible that the KWA 150 would have performed as well as the LAMM in this area. However, with only one stereo amplifier on hand bridged mono was not an option. It became obvious, on something as simple as vocal overdubs, that the LAMM monoblocks were more resolving, and in general more revealing of a recording’s origins. The LAMM evinced a greater sense of speed and superior treble precision. By contrast the ModWright sounded warmer in the midrange, a bit more euphonic if you will, and more adept at erecting a believable soundstage. It struck me that the sonic differences between these two amps define the on-going debate between solid-state and tube amplification, with the KWA 150 sounding distinctly more tube-like.

My stance to date can be summarized as follows: No rain, no rainbow; no tubes, no tube magic. In view of the KWA 150, I’m willing to modify my position somewhat. It doesn’t quite fool me into mistaking it for a tube amp. But I can’t believe that I’m listening to a bipolar solid-state amp with suave mids and imaging magic. It’s hard for me to curb my enthusiasm in the presence of a sonic miracle. To my ears, the KWA 150 represents a smashing success, combining the musicality of tubes with the punch, power delivery, and bass reach of transistors. Factor in the performance and looks of this amp relative to its asking price and the result is a fantastic value. Kudos to ModWright for delivering the sonic goodies, while avoiding sticker shock. Buyer beware: Once auditioned, this amp is hard to walk away from.