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"Shiny Stockings" from Big Band Basie [Reference Recordings RR-63CD] is a treasure trove of dynamic information, soundstage, detail and with a magnificent performance courtesy of Keith O. Johnson and the musical mastery of Clark Terry, Frank Wess and Bob Lark performing with the DePaul University Jazz Ensemble.

"I Wandered by a Brookside" from Eva Cassidy Time after Time [Blix Street Records G2-10073] is simple purity of recording and vocal talent with delicacy, detail and emotional nuance.

"A Call to Arms" from Glory Original Motion Picture Soundtrack: James Horner [Virgin Records CDV3087] is one of Horner’s stellar efforts. Wide dynamics and frequency range contrast with the intimacy of the Harlem Boy’s Choir and the haunting refrain of the trumpet’s call.

"Unto the Prophet Jonas I Read" from Watkins Ale: Baltimore Consort [Sorian DOR-90142] offers the virtues of Dorian’s minimal microphone technique and wide dynamic range. Hall acoustic, clean female vocals defined in space and warm period instruments combine attack, decay and body.

"The Mystics Dream" from Nights from the Alhambra: Loreena McKennitt [Quinland Road QRCDDVD2-110-N] is a lovely recording on both CD and DVD of a live performance captured at the Alhambra in Spain. It’s a remarkable fusion of Middle Eastern and Celtic styles that honors both and becomes something unique unto itself.

"Carioca" from Michael Nesmith The Newer Stuff [Rhino R2 70168] is an interesting compilation of what is now not so ‘newer stuff’. Nesmith steps away from monkey business and proves himself a capable solo artist and engineer here, with some cuts in earnest, most wonderfully tongue in cheek, creating a unique new musical form and taking time out to introduce the concept of the modern music video to the world. Well recorded, with ample definition of space and instrumental detail.

"Concerto for Oboe in D Minor: Allesandro Marcello" from Baroque Delights: Tafelmusik [Analekta AN 2 8760] is a rare chance for the oboe to take top billing in this delightful compilation CD. The Tafelmusik orchestra is in good form and recorded with generous air and warm acoustic.

Noise: Operationally quiet.

Resolution and Dynamics: Should it surprise that the 6550 did not perform to the standards of cost-no-object designs? Resolution was good but not up to the level of higher-priced units like TrueHarmonix’s own Sound Master Reference Series, the Audio Space Reference 2S/Bel Canto combination or the Wyred4Sound STI 1000 integrated. Overall detail was a little homogenized especially in the lower octaves where it became slightly thick. Transient information was slightly blunted in comparison to those higher-priced pieces and as a result the amplifier exhibited a noticeable degree of veiling. The two more expensive tube-based combinations managed a combination of hard edge and edge detail that eluded the 6550 especially in UL mode. In triode there were gains in overall resolution although some of this was caused by dynamic compression and a shift in tonal balance favoring the upper midrange. To put these observations in proper perspective, while the performance of the 6550 may have fallen short of designs benefiting from infinite resources, it was still quite respectable and well ahead of the typical mass-market fare that people will be used to. In that context, for most listeners the performance of the 6550 should prove revelatory.

Dynamics were the major surprise. In ultralinear mode and despite the 60-watt rating, the amplifier did not sound underpowered. It managed to produce increasing volume levels on dynamic source material that kept forcing me to back off the volume not due to apparent distortion but sheer intensity. This was most unexpected and spoke well for the capabilities of the amplifier stages. While not capable of unlimited output levels, it did demonstrate subjectively satisfying ones well beyond the hard numbers. The amplifier exhibited a dynamic liveliness that was quite engaging, managing a good gradation of swing from micro to macro. In this respect it bore a striking resemblance to the Sound Master No 88.6 Reference amplifiers, which had also performed admirably with the Apogees. I should state that my preference is for realistic rather than PA system sound pressure levels so individuals demanding the latter may be less impressed.

In triode mode compression was more evident even though the amplifier proved remarkably capable of decent levels regardless of the 30-watt power rating and inefficiency of my Apogees. There were obvious dynamic limits but the amplifier always seemed game to try and overcome them. The compression manifested itself not as a deficiency in loudness but rather as progressive soundstage collapse as well as a loss of dynamic palette when pushed past comfortable limits. Driven to even higher volumes the amplifier showed signs of distress but at more reasonable levels, the TrueHarmonix regained some of the liveliness that was a strong suit in UL with relatively few shortcomings.

In both triode and UL modes the 6550 was able to maintain  good dynamic gradation over a wide range without significant changes in tonal balance, this being especially noticeable at lower volumes. For sheer dynamic chutzpah, the 6550 in this evaluation proved a worthy challenger to the loftier competition.

Frequency Characteristics:
Ultralinear and triode exhibited different frequency characteristics which were divergent from those I had encountered with the Sound Master Reference components or the Audio Space Reference 2S combinations. Where the Reference components showed flatter response and harder edge in UL, the 6550 was softer especially in the frequency extremes to produce a quite warm sound. The TrueHarmonix had good authority descending from the upper through mid bass with a hefty kick that extended almost into the lowest regions, albeit with progressively less definition and control in the lowest octaves. This loss was slight and its progressive nature made the change in character less noticeable. The midrange was as expected and a traditional tube strong suit. Although mildly veiled, it had remarkable solidity. The upper end was sweet, grainless and slightly rolled off, giving a more romantic hue to the music.

Triode showed considerably more midrange and upper midrange prominence and purity with subjectively less veiling. This provided greater life to vocal material and revealing considerable tonal and dynamic information in that region. The punch and dynamic life exhibited in UL was largely retained when not pushed to higher volume levels and highlighted the midrange and upper midrange. Instruments such as violin and trumpet were well served and quite convincing. Vocals were also well delineated with good presence. In the lowest regions, bass levels were diminished and lacked some impact. In overall comparison to the Sound Master Reference combination, the tonal balance of the TrueHarmonix 6550 in triode mode was closer to that of the Sound Master in UL mode, albeit with significantly less refinement and a loss of bass amplitude.