Sonic Compass · Mojo Review · Amplifier (headphone) · Session Review
Erzetich Bacillus II+
A compact class-AB, dual-mono, fully balanced headphone amp that drove everything I own, from 300 ohm dynamics to the HE6se V2, with tight bass, smooth detailed treble and a wide, holographic stage.
A compact balanced class-AB amp that drives nearly anything I own with tight, controlled bass, smooth detailed treble and a wide holographic stage. The hardest headphone, the Genesis One, needs full volume.
- Drives nearly everything, planars included
- Tight, controlled, muscular bass
- Smooth treble with excellent resolution
- Wide, holographic stage
- Fully balanced dual-mono class-AB
Where it sits
Sonic Compass does not score gear out of ten. Gear and listeners are plotted on the same seven axes, so a review tells you where a product sits — and you can see how far that is from where you sit. A position is a description, not a grade.
- Tone ColourBalanced · 58%
- Texture DetailVery detailed · 86%
- Dynamics JumpVery punchy · 82%
- Space & ImagingVery spacious · 82%
- Timing & FlowRhythmic · 68%
- Comfort & FatigueBalanced · 55%
- Emotional EngagementVery immersive · 80%
Vivid and lifelike with an effortless naturalness. Slightly warm; the warmth he names belongs to the ZMF Verite (high = warm on this scale).
Smooth but highly detailed treble with excellent resolution. Every detail and nuance can be heard.
Punchy, snappy, exciting and fast, with tight, muscular bass.
Wider than you would think from a small box, holographic 3D, with the stage going out behind the head and instruments well separated.
Placed modestly: the only evidence is that quick metal passages are not tripped up or muddy.
Near neutral and inferred: smooth, non-sibilant treble, but no fatigue remark in the video.
Gobsmacked on the HE6se V2 and 'magic' on Erzetich's own headphone. Exciting dynamics and personality.
Sonic Compass does not grade gear. We plot gear and listeners on the same seven axes, so a review tells you where a product sits and you can see how far that is from where you sit.
The Erzetich Bacillus II+ is a compact, fully balanced, dual-mono class-AB headphone amplifier from Slovenia. I have reviewed Erzetich headphones before and I thank Blas at Erzetich for the opportunity. I have had the unit for quite a while.
I ran it from a Gustard R30 DAC, streaming Tidal from my PC over USB, into a stack of hard-to-drive headphones.
Listening journey
Metallica, One (metal) — The stage goes way out left and right, behind my head, and does not diminish early. Some headphones seem to start in one place, end in another and fade off. That did not happen on any headphone I tried here. Instruments sit nicely in the staging and are separated very well. Quick metal passages are not tripped up or muddy.
ZMF Verite Open (300 ohm dynamic) — A wonderfully warm headphone, and the Bacillus II+ opens it up. It brings more detail, though the Verite was not lacking, punchier dynamics and a great helping of quality bass.
Beyerdynamic DT880 600 ohm — Converted to balanced, it sucks them back like a plump oyster.
HiFiMAN HE6se V2 (planar) — Rated at 83 dB. I am about two or three clicks off the end of the volume knob, listening as loud as I need to. Zero distortion, a black background, and a ton of bass, treble and stage. I was gobsmacked.
An AMT-driver headphone — Loud, detailed and punchy, with a ton of headroom left. (The name is unclear in the captions, so it is not listed here.)
Lily Audio Genesis One — I would say the most difficult headphone to drive on the planet, needing massive voltage swings. The Bacillus II+ gets them to about 80 percent of my preferred listening level, with the volume maxed and nowhere left to go.
Erzetich's own flagship headphone — The headphone the amp was made for. Magic. Resolution is magnificent and every detail and nuance in the recording can be heard.
| Track | Position | Note |
|---|---|---|
| One | 85% | Stage goes far left and right behind the head, instruments well separated, fast passages stay clean |
Critical observations
Where the Bacillus II+ sits — Clean, confident and detailed, with a wide stage and fast, punchy dynamics. The strongest axes are Texture and Detail, Dynamics, and Space.
Bass — Tight, controlled and surprisingly muscular. Not bloated or boomy, but not shy either.
Tone and vocals — Vocals and instruments are vivid and lifelike, with an effortless naturalness to the tonal balance.
Treble — Smooth but highly detailed. No ice-pick moments, no sibilance, just refined sparkle with excellent resolution.
Stage — Wider than you would expect from a small box, with a nice holographic, 3D presentation.
Dynamics — Punchy, snappy, exciting and fast.
Power — The maker lists 157mW single-ended (6.3mm) and 314mW balanced (XLR) into 32 ohms. It is not a nuclear reactor like some desktop amps, but it easily drove 99 percent of my headphones, planars included. I assumed a good voltage swing but did not ask Blas.
Build — Solid, with a minimalist front panel and a very smooth volume knob. The industrial design feels fantastic. It was made for Erzetich's flagship headphones.
Read this against your own profile — I like a warm, detailed sound with tight bass, and I listen to a lot of metal and other dynamic music. If that is you, and you want one compact amp for a wide range of hard-to-drive headphones, this fits. If you need a lot of headroom on the very hardest headphones, note the Genesis One needed full volume.
Honest limits — The unit was supplied by the maker and I have had it a long time. By ear only, with no measurements, from one source chain. I made no direct comparison with another amp. Timing is judged only from how quick metal passages stayed clean, and Comfort is inferred from the smooth, non-sibilant treble, so I have placed both modestly. Specs are the maker's.
- OneMetallica
- Driver Configuration
- Headphone amplifier, fully balanced, dual-mono, class-AB
- Driver Details
- 157mW single-ended and 314mW balanced into 32 ohms; 8 to 600 ohm headphones (Erzetich)
- Weight
- 2,990g (Erzetich)
- Build Materials
- Steel chassis with wooden sides (Erzetich)
- Cable Connectors
- Inputs: 3-pin XLR balanced and RCA. Outputs: 4-pin XLR balanced and 6.3mm single-ended
- Isolation Leakage
- Not applicable
- Power Requirements
- Mains powered, 9W consumption (Erzetich)
- Accessories
- Not stated
- Build Quality Notes
- Maker price 1,999 euro. 260 x 105 x 240mm. Photos: Erzetich.
A compact balanced class-AB amp that drives nearly anything I own with tight, controlled bass, smooth detailed treble and a wide holographic stage. The hardest headphone, the Genesis One, needs full volume.
<p><strong>Buy it if</strong>… you want one compact amp that handles dynamic and planar headphones, including hard-to-drive ones; you like tight, controlled bass with smooth, detailed treble; or you want a wide, holographic stage from a small box.</p><p><strong>Skip it if</strong>… you need huge headroom for the very hardest headphones; or the maker's price of 1,999 euro is more than you want to spend on an amp.</p><p>As always, stay Slovenian metal.</p>