Review on AIYIMA Tube T6 PRO Bluetooth 5.0 Tube Preamplifier - Hi-Fi Headphone Amp, Vacuum Tube Preamp for Home Audio Amplifier, Wireless Receiver, Audio Decoder, Preamp PC-USB DAC with APTX by Janet Rivera

My headphones are ATH-M40x. Great sound until I changed the ear pads. To get the sound quality back I bought this amp. Great help but not exactly what I wanted. I swapped out the standard tubes for a US made set and .WOW! Detailed bass, better clarity, improved soundstage. I also liked the controls in this device. No noise, no hum, no hum. I liked the amp out of the box, I'm VERY happy with the different tubes. It's like hearing all my music like I've never heard it before.