Review: Z-infinity 20/40 WPC Class A amplifier Tube amp

Category: Amplifiers

My somewhat unusual goal was to find an amplifier that could drive my insensitive Hifiman he-6 headphones. Even my usual 2a3 amps were not enough for this, but I wanted to stay with a pure class A single-ended approach. High powered single-ended amps are rare so the Z-infinity offering caught my eye, plus they are local (Redmond/Seattle).

Results of demoing the amp for ~20-30 minutes:
The Z-infinity probably had the most realistic and engaging guitar reproduction I've heard (Toad the wet sprocket etc) - my favorite aspect of this amp. Moving up in the spectrum, the initial transient of snare drums was very crisp and cymbals had good decay.

Ultralow bass (on Neuroticfish tracks) was not wooley, which is unusual for a tube amp.

The inevitable Vienna Teng test showed great vocal presence. - fits with the guitar reproduction.

These results are all via my headphones, but the average speaker will actually be more efficient, so they should hold up. My current amp is an F5, so that's my strongest point for judging these characteristics. The Z-infinity had more detail than I generally expect from a tube amp so when I say it's warm, it's NOT muddy, but rather has a midrange presence that makes it clear you're not listening to SS.

Recommended to try if you're looking for a relatively high-powered NFB Class A design.

Associated gear
Hifiman HE-6
ESS Sabre 9018 Dac
Panamax power supply

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