Amplifier Comparison: Rebel Audio RebelAmp versus Schiit Lyr 3 versus Drop THX AAA 789
This post summarizes my back-to-back comparison between three headphone amplifiers in the $300 to $500 price bracket. These represent mainstream options in their intended styles, and additional spending may go unnoticed or deliver smaller gains. The purpose of this comparison is to communicate what to expect from each amplifiers, and to guide purchasing decisions.
Method
Equipment chain: Schiit Bifrost 2 → Amplifier (3 options) → Focal Clear (original)
Listening and scoring process:
- Listen to a set of standard test tracks with the RebelAmp and generate its ratings
- Listen to the test tracks with the THX AAA 789 and generate its ratings
- Cycle between a 15 minute “ear calibration” on the RebelAmp followed by listening to the test tracks on the Lyr 3. Tube comparisons required step #3 to be repeated nine times for all available tubes (e.g., about 15 hours). Some rating adjustments were made over time. All ratings are relative to the other amps in this comparison, but not indicative of the potential of other hardware.
The tested Lyr 3 6SN7 tubes included one Schiit Tung Sol as recent new production (but used), while the others were vintage tubes. These included: Sylvania “Bad Boy” 3 hole, KenRad Black Glass, Westinghouse Reliatron, Sylvania JAN CHS, and four Foton tubes dated 1952, 1953, 1958, and 1958. The KenRad’s scores are reported because it was the most technical tube and closest to the solid state amps. Individual scores for the others were not reported because of unknown usage histories and because vintage tubes of the same model vary in performance.
Note: All Lyr 3 testing occurred on low gain
Findings
Drop THX AAA 789: This is reported first to get it out of the way, as the comparison revealed the mechanical, artificial, and unnatural character of the amp. The 789 is very clean, but clean in the sense of a eucalyptus cough drop, Listerine mouthwash, or a sandblaster. All intended musical warmth and atmosphere was stripped away, drawing attention to edgy transitions and treble artifacts that were never intended to be heard. Furthermore, the 789’s power delivery seems inadequate – it has detailed bass but limited bass presence. The 789 is a solid choice for production engineers who want to clean up recordings, but unpleasant relative to the other two amps. It can maximize the technical performance of headphones with less potential (e.g., Focal Elex, Sennheiser HD-600 or below), but its resolution was detrimental to the Focal Clear. Metaphors: icy, brittle, sinus clearing, musical vivisection, feeling a cold chill after being awake all night when downing caffeine tablets coupled with black coffee. An unforgiving, undead nightmare.
Rebel Audio RebelAmp: This amp has received strong praise from many. It demonstrates how to build a desirable solid state listening amp that competes directly with tube amps, and sometimes bests tubes. This amp combines the strengths of solid state with the smoothness and rounded corners sometimes attributed to tubes. It has a broad and precise sound stage, is fully extended from low to high range, and has more than enough power to get the maximum punch from the Clear. While single-ended, it’s very clean and I never cared about not having a balanced option. The treble is easy on the ears and relatively subdued versus the 789, but the 789 exaggerates and fetishizes treble artifacts. As solid state, the RebelAmp reproduces the tonal weighting of the source but doesn’t change it. This means that the inherently forward-sounding Clear is indeed forward sounding, with vocals often emphasized in the mix. The RebelAmp routinely makes me want to turn up the volume and keep listening.
Schiit Lyr 3: This tube-hybrid amp has a very powerful solid-state section, and the choice of tube changes some aspects of its tone and character. The commonalities between many tubes revealed the unchangeable character of the amp (ideally it would also be compared to the Schiit Jotunheim 2). The tested tubes fell into three broad categories, with some relatively technical, some exhibiting stereotypical and desirable tube distortion, and some worn out or a poor match with the Lyr 3. I did not report specific scores for tubes except the KenRad Black Glass – it was the most technical tube and it suggests the potential of the amp. In general, all tubes were less defined, less punchy, more mid-focused (less deep bass and high treble), and they randomized some content (e.g., bass rumble, grain, clipping). Sometimes tubes create pleasant harmonics and illusory (aka euphonic) bass that is perceptually loud but not very deep.
Summary of Lyr 3 performance by tube category:
Category 1 – Lyr 3’s Technical Potential: The KenRad Black Glass has a strong reputation as detailed, extended, and producing strong mid-range harmonics. This was true with my example, and it was my favorite Lyr 3 tube before getting the RebelAmp. However, the pricy KenRad can’t compete with the RebelAmp’s clarity, control, broad staging, or punch. In owning both amps, I’d not bother with the KenRad. If only having a Lyr 3, I’d use it as an alternative.
Category 2 – Stereotypical Tube Character: Most of my tubes had the characteristics of why people buy tubes (e.g., 3 of 4 Fotons, with the other sounding dead). In sum, they exaggerate harmonics and resonate. Female voices often ring and sustain. My notes mention songs sounding smooth, creamy, bloomy, and simply “fun.” This is why one buys a Lyr 3 – not to reproduce the source but to change it to a personally desirable and in fact retro-sounding fashion. These tubes effectively remix the source recordings, even as some songs and albums are produced with similar methods for the same tone. Tubes always involve a loss of detail, and can slip into being cloudy or hazy too. When the losses were excessive (per each tube or source track), they shifted to Category 3.
Category 3 – Worn or Incompatible Tubes: Some of my tubes either didn’t get along with the Lyr 3 or were seriously worn with odd personalities. One of these was the highly regarded Sylvania “Bad Boy.” My Bad Boy was simply bad, with thick or fuzzy notes, severe mid-range bloat (rolled off bass and treble), and flat dynamics. Other tubes were merely flat, dead, and uninteresting.
Comments on the Bifrost 2 → Balanced Interconnect → Loxjie P20 → Balanced Cable → Sennheiser HD-600 setup
While not scored, this setup resembled the RebelAmp more than the Lyr 3. The Lyr 3 is not a technical amp, nor does it have a large or clean stage. The Loxjie P20 is technical for a tube hybrid, and extremely communicative of the DAC’s character. Following comparisons, I’ve concluded that bad DACs likely led to some criticism of the P20. The Bifrost 2 had a strongly positive impact. When used with triple mica 6N3P tubes, I’ve described the P20 as a “THX AAA 789 with the edges smoothed.” It has clean staging, clean definition, and serves as a junior edition of the (fully superior) RebelAmp. With 47 ohm output impedance the P20 works best with the HD-600 and similar headphones.
Data Table
| Scored on a 1 to 5 scale with low = 1, high = 5 | Rebel Audio RebelAmp | DropTHX AAA 789 | Schiit Lyr 3: Avg 9 tubes | Schiit Lyr 3: KenRad Black Glass |
|---|---|---|---|---|
| Bass Extension: Lowest pitch of audible notes, even if soft and not impactful | 5 | 5 | 4.0 | 4 |
| Treble Extension: Highest pitch of audible notes, even if soft and not impactful | 5 | 5 | 4.6 | 5 |
| Bass Presence: Relative loudness of the lower range, even if not “deep” per se | 5 | 3 | 3.9 | 4 |
| Mid Presence: Relative loudness of the middle range | 5 | 4 | 4.9 | 5 |
| Treble Presence: Relative loudness of the high range, even if not “bright” per se | 4 | 5 | 4.1 | 4 |
| Bass Texture: Detailed, controlled bass per known source recordings | 5 | 3 | 3.1 | 4 |
| Bass Rumble: Random, uncontrolled bass per known source recordings | 1 | 1 | 2.7 | 1 |
| Note Thickness: Normal = 3, “analytical” amps = 1 or 2, audible distortion = 4 or 5 | 3 | 1 | 3.2 | 3 |
| Stage Size: Perceived area of music - within head to extended outward (relative) | 5 | 3 | 3.0 | 3 |
| Localization: Individual sounds heard in a fixed, specific location in sound stage | 5 | 5 | 3.3 | 4 |
| Dynamics (Punch): Loudness and intensity of sudden or increasing notes | 5 | 3 | 3.8 | 4 |
| Definition (Controlled / Black): Relative difference between notes and silence | 5 | 5 | 3.6 | 4 |
| Air: Presence of very high frequency “wind” or “sparkle” above specific notes | 5 | 5 | 4.0 | 5 |
| Detail: Each sound is hearable and distinct versus other simultaneous sounds | 5 | 5 | 3.9 | 5 |
| Grain (vs. Smooth): Subtle roughness in mid range notes versus other setups | 1 | 3 | 2.0 | 2 |
| Clipping: Amplifier adds characteristic distortion to all content. This is usually desirable with tubes, but mostly harsh with solid state amps. Compare impact to the vocals in Peggy Lee’s “Fever” or Elle King “Love Stuff” – added sizzle. | 1 | 1 | 2.6 | 1 |
| Comfort (Low Fatigue or Tolerable): Personal perception after 1.5 hour playlist | 5 | 3 | 4.6 | 5 |
| Rating: Personal desire and intent to use amp ever again | 5 | 3 | 4.4 | 4.5 |