Woo Audio WA6: power output and what it will drive

The Woo Audio WA6 is a desktop amplifier at $1099. It delivers 580 mW into 32Ω and 460 mW into 300Ω, which ranks it 45 of 88 for raw power among the sources in this database.

Measured at 100 dB SPL it has comfortable headroom on 310 of the 310 dynamic and planar headphones catalogued here. Single-ended triode with an output transformer, published across five loads — unusually complete documentation for a valve amp.

The manufacturer publishes 580 mW into 32Ω, 550 mW into 60Ω, 590 mW into 120Ω, 460 mW into 300Ω, 400 mW into 600Ω. Everything else in the table above is worked out from those figures, and this table says which is which.

Derivation holds output voltage steady between and beyond the published loads rather than output power, because that is what an amplifier actually does. The full method is written up here.

Source: wooaudio.com, wooaudio.com.

Ordered from easiest to hardest to drive. Headroom is measured at 100 dB SPL, which is louder than almost anyone listens — a small negative number means the source still plays loud, just without reserve for peaks.

These figures come from each manufacturer's own sensitivity rating. A handful of planars — the HiFiMAN Susvara and HE-6se and the Abyss AB-1266 in particular — are widely reported to need far more than their published sensitivity implies, so treat a bare pass on those as optimistic rather than settled.

The manufacturer does not publish an output noise figure for this source, so the hiss estimate that runs on every other page here cannot be run on this one. Rather than substitute a plausible number, this page leaves the question open.

If you know the noise figure from a measurement you trust, the hiss calculator takes it directly and tells you where that noise lands in your own in-ears.

The manufacturer does not publish an output impedance for this source. That is the one number that decides whether it leaves your headphones alone or acts as a tone control, so its absence matters more than it looks: without it, nothing here can tell you how this source will behave with a multi-driver in-ear.

If you find a measured figure you trust, the checker will work out the consequence for any headphone.

Or put any two side by side in the source comparison tool, or run your own headphones through the amplifier matcher.