The little card says it all, so I don’t have to. (Thank goodness.) It’s the beautifully designed Bottlehead Smack WOT (with output transformers) headphone amplifier kit.

Adjustable output impedance: 16, 32, 64, or 128 ohms
Works with headphones from 16 to 600 ohms
Switchable single-ended TRS or balanced XLR outputs
200mW outputs—6-10dB headroom over IHF standards
Uses 5687/7119 tubes with Bottlehead’s premium active-loaded, hybrid shunt-regulated, single gain stage circuit topology
Custom output transformers designed by Bottlehead’s Paul Joppa
Retail price: $549

I listened to it, too. I neglected to take notes because I was too busy following Piper Payne around, but I remember thinking that the music had natural highs and a clean, clear midrange.

Visit Tyll Hertsens' InnerFidelity for more on this and other headphone products.