As much as I love listening to the HD600 with a really clean, neutral DAC & amp (i.e. the ODAC & O2).. the sheer musicality & euphonic sound of running it through a nice tube is where it's at.
For those looking for an impressive (and quite affordable) tube that pairs exceedingly well with the HD600, check out the
Zaerix 6DJ8/7DJ8 (I purchased my tube from this vendor.. safe, fast shipping & genuine quality). I've had it in my TubeDAC-11 for the past month (so the tube's been burned in plenty.. well over 100 hours now) and it continually impresses.
Bass is tight, extended, & effortless. The punch has a soft, round, deep quality that's smooth & airy. The midbass presence is just right, IMO.. and stays completely free of the (gorgeous) midrange. It's perfectly suited to the HD600's (native) lower frequency tuning. Listening to soulful house, it's like a gentle massage for your ears & brain
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This tube's midrange is the showstealer, folks. It possesses the perfect balance of coloration & neutrality for my tastes. Get ready for more superlatives.. it's wonderfully liquid, dynamic, smooth, airy, and detailed. It accentuates all the things the HD600's wonderful midrange is renowned for.. while providing more body to notes, and just the right amount of lushness. This is what listening to the HD600 is all about, IMO.
Treble is smooth, crisp, airy, & utterly effortless. It's able to sound quite detailed yet non-fatiguing. You'll get more treble presence with this tube than you would from the HD600 through a typical neutral, solid state amp... but it won't sound harsh, sharp, or unnaturally boosted. It's very clean and smooth.. and has the right balance with the rest of the tuning. Excellent depth, sparkle, and dimensionality with this tube, too.
The soundstage and imaging is quite impressive, as well. The HD600 doesn't have the widest soundstage despite being an open phone.. but this tube definitely gives it a more spacious, open feel. Again, there's great synergy with the HD600's native soundstage presentation. It's well proportioned between depth & width & enjoys a very silent, black background, so imaging & clarity is excellent.
The 7DJ8 has such an inviting sound quality to it.. and it is very diverse in terms of compatibility with various genres. Rock music will sound great as the hint of warmth and 'wet' lushness accentuates distortion guitars, drums, and vocals perfectly. It sounds just as good with soul, jazz, vocal/singer/songwriter stuff, electronica, acoustic, and hip hop.. this goes back to the tube's complex, delicate coloration that sounds oh so natural.. but doesn't impose itself too strongly on the music.
As I said before, I've had this tube for well over a month & look forward to using it with the HD600 at every given chance. When I'm at my desk, the TubeDAC-11's solid state ouptut has gotten little use as I remain completely enamored with how immersive the HD600 sounds with the 7DJ8. For $20, I'm amazed at the resolution & overall quality of sound it delivers. Highly recommended!