That preamplifer has really impressed me! I think I found the way how to equalise the signal from phone via Bluetooth before the power amplifer, and get the best possible audio from it.. .. this is the way how you can change eq from your youtube music streaming via Bluetooth and the 6J1 tube valves makes the audio signal even stronger and more pleasent.

Aiyima Premplifier links：https://www.aiyima.com/collections/tube-preamplifier

Aiyima TUBE-A3 PRO 6J1：https://www.aiyima.com/products/tube-amplifier-preamp-aiyima-a3-pro