- Written by Chris Groppi
- Published on 05 January 2009
I listened to the XPA-1s both with my normal Gallo Reference 3.1s, and the fantastic THIEL CS3.7s I just reviewed. They were driven via the balanced inputs from an Emotiva RSP-1 preamplifier. As these were prototype amps, they were already well broken-in, so I could get to listening right away. To be sure I got around any warm-up problems, I left the amps on all the time. Given they do consume 90W each at idle, I would probably use the 12V trigger from the preamp normally, and just turn them on a while before any serious listening. I had no problem running the pair of them, along with all my other audio gear, on a single 15A 115V circuit. My Gallo Reference 3.1s are 87 dB/W/m sensitivity, and the THIEL CS3.7s were 90, so I never approached sustained power delivery anywhere near what the XPA-1 could deliver.
The point of high power amplifiers is not just to drive low sensitivity, low impedance speakers that require the power. Pretty much any dynamic loudspeaker without super high sensitivity can benefit from a powerhouse like the XPA-1. It all comes down to dynamic contrasts and transients. With any sort of transient musical event, like a drum hit or movie explosion, your speakers will demand a tremendous amount of power for a very short period of time. If your amplifier can't deliver, that transient will get smeared in the time domain. This smearing will homogenize the sound and decrease the impact of dynamic contrasts.
The dynamics delivered by the XPA-1 were the first stunning aspect of these amplifiers. After listening to the super high sensitivity Zu Audio Druids, and several systems at the Rocky Mountain Audio Festival that sounded so alive and energetic, I was painfully aware of the main drawback of my system: lack of dynamics. While the Emotiva RPA-1 offered exceptionally smooth and liquid sound, the dynamics were always somewhat limited compared to the most alive sounding systems. The dynamic contrasts present in these great sounding systems lend a presence and reality to the sound that is impossible to fake. One way to deliver these contrasts is with very high sensitivity loudspeakers, like the Zu Druid. Another is with an amplifier with exceptional power and current delivery. With the XPA-1 in control, my Gallos genuinely came alive. What was dynamically flat before was able to compete with the memory of the Zu Druids, but without some of their drawbacks. Dynamic contrast, both macro and micro, were improved across all frequencies. The most dramatic result was in the bass. This might normally be expected, but the Gallos have a separate amp driving the second voice coil of the woofer. Still, the added impact and control of the XPA-1 not only improved the agility and precision of the bass, but also improved the perceived bass smoothness. Maybe it was speaker positioning, but even the measured frequency response in the bass was smoother with the XPA-1s. Driving the THIEL CS3.7s, with their relatively high sensitivity but very low impedance, the XPA-1s were the key to releasing their true greatness. With the RPA-1, the THIELs were a bit flat, both dynamically and spatially. The XPA-1 allowed the full dynamic contrast available to be released, and simultaneously added soundstage width and depth.
A second great improvement with the XPA-1 was the retrieval of detail from recordings. Certainly helped by the dynamic contrasts available, the true magic might be from the fully differential design. The noise floor was stunningly low. Tape hiss became clear on virtually every analog recording. Not obtrusive, but clearly audible and identifiable. The blackness of the background clearly revealed loads of detail that was barely audible or inaudible before. Examples included the piano pedal noise and breathing on Tori Amos' Icicle from the album Little Earthquakes. While aware these sounds were there with the RPA-1, I was only able to clearly hear their detail and texture with very good headphones with lots of isolation. With the XPA-1s, they were all there as clear as day. Bass agility and clarity were on display with Slide Hampton's album "Dedicated to Diz." On the track "Blue and Boogie", George Mraz's acoustic bass solo, the detail revealed in every note was fantastic. This solo was not close miked, and has realistic dynamics, meaning it is way less loud than the rest of the band. An amp needs to be able to pull out lots of subtle detail in the face of much louder competing sounds to get this solo right. With the XPA-1, the result was the best I've heard in my room.
The detail presented by the XPA-1 also improved every aspect of soundstaging and imaging. Spatial cues were all much clearer, improving soundstage width, but especially depth and room ambiance information. Images remained razor sharp as with the RPA-1, but the added detail made those images sound more real, since subtle changes in spatial location and image size were more clearly conveyed.
Compared to the RPA-1, the XPA-1 did have a brighter presentation. The XPA-1 is very detailed and has lots of high frequency extension. This extension could be unkind to poor recordings, or components that sounded hard on top. The Oppo 983, which is brighter sounding than my Bel Canto DAC-1.1, was not the best choice for bright, hard recordings. They sounded a bit better with the Bel Canto. The RPA-1's sweet and smooth treble did not pull out as much detail, but was kinder to bad recordings. Overall the RPA-1 was a bit more "tube like," while the XPA-1 reminded me of high dollar solid-state amps from the likes of Krell, Mark Levinson and Jeff Rowland.
The high gain of the XPA-1, when combined with the relatively high sensitivity THIEL CS3.7s, made the volume knob of the preamp very sensitive, and useful over only the first ¼ of its travel. The high sensitivity also revealed some high frequency hiss when the amps were on but the preamp off. This was inaudible with the Gallos, but loud enough with the THIELs that I left the preamp on all the time too. If any components in your system are noisy, the high gain of the XPA-1s might reveal a little more of that than you want if combined with high sensitivity loudspeakers.
For me, those small caveats were irrelevant. The XPA-1 brought the dynamics to my system that I was craving after hearing several great systems at the RMAF. Now, I have that sound, and without sacrificing any other area of performance. The bass power and extension of my system, and most importantly the smoothness of the frequency response, were greatly improved. On top of all that, retrieval of detail also saw a significant improvement. And that's over an amp, the RPA-1, which I absolutely love. The RPA-1 will be going up for sale, to be replaced by this pair of XPA-1s.