I found new old stock Mullards to sound the best, both in the power supply and DAC.. I have a late 50's Mullard GZ34 fat base in the power supply, late 60's 6922 in the 205.. I tried 4 other expensive pairs , the most expensive Amperex pinch waist that cost as much as $600 if you can find them, and still the Mullards sounded better to me.. Amperex super detailed but the Mullards was more musical to me and more analog sounding.. I've tried the Phillips ( Holland ) 5R4GY, Mullard better..