xDuoo xDuoo TA-66

WaveTheory calls resolution good and the overall presentation clean, with solid spatial holography and texturing for the price. It is not presented as the last word in refinement: the more expensive Bottlehead Crack is said to sound cleaner, more resolving and more refined.

The TA-66 delivers the warm, thick and liquid tube character many listeners seek, but Passion for Sound found it less overly rich or smooth than the TA-26 and more crisp and articulate. WaveTheory also praises natural treble balance, low fatigue and an absence of excessive sibilance.

Passion for Sound describes a clean, punchy and dynamic presentation, with bass impact and control likened to solid-state amplification. Deep bass is said to carry exceptional weight, while the 6XX also gained kick-drum and bass-string impact relative to the Asgard 3 in WaveTheory's listening.

Neither review reports hiss, hum or other background-noise problems in its listening tests. They also do not specifically assess performance with highly sensitive IEMs, so quietness with those demanding loads remains unclear.

Passion for Sound considers it versatile for headphones from roughly 40 ohms upward, apart from the most difficult loads, and strongly recommends high-impedance pairings as the place where it shines. The DT880 and HD6XX-family headphones receive especially positive comments, but the available power and OTL design make it a less universal choice for demanding planars or sensitive in-ears.

Passion for Sound praises the TA-66's attractive embossed fascia, tube plinth, blue lighting and large cherry-red volume knob. The stepped volume control is also reported to provide reliable channel matching even at very low levels, though the reviews say little about internal construction or long-term durability.

This is a focused analogue tube amplifier rather than a DAC/amp packed with connectivity and convenience functions. Its stepped attenuator offers tactile operation and excellent low-level channel matching, although WaveTheory notes that the rear-mounted power switch and volume-control arrangement may not suit every desktop setup.

At approximately $249-$250, both reviewers regard the TA-66 as a very compelling way into tube headphone amplification. Passion for Sound calls it an absolute killer across price, design, features and sound, while WaveTheory describes it as a rock-solid and excellent entry-level option with little to complain about when paired appropriately.