SUCA-AUDIO Tube-T1 Preamplifier, Vacuum Tube Amplifier Buffer Mini Hi-Fi Stereo Preamp with Treble & Bass Tone Control for Home Audio Player (6K4 Tubes) : Amazon.com.au: Electronics
Schiit Audio Freya+ Balanced Stereo Pre-Amplifier – Addicted To Audio
6 Tube Stereo Pre
This Tube Preamp Has A Nixie Volume Display | Hackaday