PRICE REDUCED! Rogue Audio's RH-5 is a headphone amplifier and line-level preamplifier whose hybrid circuitry includes MOSFET transistors and two 12AU7 tubes (ECC82s can also be used). It has an output impedance of <0.1 ohm at 1kHz, and outputs 3.5Wpc into 32 ohms.

It has two studio-grade headphone jacks, each combining a ¼" phone jack and a three-pin XLR jack. To their right is a four-pin, balanced XLR jack. The RH-5 permits the simultaneous use of two pairs of headphones.

This amp has such a clean and transparent sound, but never sounds dry or boring. It pairs beautifully with just about any headphone you can throw at it, including the notoriously hard-to-drive HifiMan Susvara.

Here are some reviews:

https://www.stereophile.com/content/rogue-audio-rh-5-preamplifier-headphone-amplifier

http://www.enjoythemusic.com/magazine/equipment/0917/Rogue_Audio_RH5_Headphone_Amplifier_Preamplifier_Review.htm

http://everythingaudionetwork.blogspot.com/search?q=RH-5