Cheers from Ukraine, guys! Just my 2 cents about 1990s. At first I'd been using them with Yulong Daart Canary for about 3 months and I was quite happy, tbh, and then I added DIY tube amplifier... It changed everything! These headphones appeared to have such hidden potential it blew me away! The bass improved even more, became full bodied, deep, tight. Sub-bass, Mid-bass, the slam - omg! Instruments separation improved greatly. The music started to flow. Sibilants calmed a little bit. New details appeared in the music I thought I knew well! This is the famous tube sound it seems. I'm very happy I've been able to find the man who makes these absolutely amazing amps. I'm not technically skilled to tell you much about the amp. It doesn't matter, every skilled DIYer has it secret sauce anyway, lol. it uses 2x6SL7 and 1x6BG6-GA (If I'm not mistaken) tubes and looks like this: It absolutely destroys the AMP that's build-in within the Canary. So I use the Canary as a DAC and they sound so good together! I'm not advising anything, I'm but a noob myself. But 1990s paired with a tube amp may surprise and shock you in a good way! Oh, and I'm using "B" pads, and cheap Audioquest Tower RCA. I'm yet to try US tubes, surely they'll improve sound even further compared to soviet tubes!