So......... TOTALLY worth the wait!
A few years ago I sold all the headphone gear I owned, because I discovered that the headphone jack on my tube loudspeaker amp made my Grado 325's sound about as great as I'd ever heard them. I even sold the 325's! And I bought myself a pair of Grado GH1's to pair up with it, and life has been grand. Except I really wanted a desktop rig......
I knew from past experience that Senn 650's would be perfect, so when the Massdrop 6XX drop came along I dove right in. Shortly after that they did a drop for Cardas cables for the 600-line. Boom. Got me a cable. Then I grabbed the SMSL M8A mini-dac. Perfect! But I had to wait for the amp.....
A few years back, I had the rare pleasure of owning an Eddie Current Balancing Act, with the upgraded Alps pot and upgraded tubes. I had it paired with Audeze LCD-3's. Folks.... Steve Guttenberg listened to that rig at a NYC head-fi meet and was boasting about it in his write-up. It was bliss. But for various reasons I decided to reallocate my audio capital to loudspeaker gear, so I sold that stuff.
So when I saw that Massdrop was doing an Eddie Current drop for an amp that was perfectly sized for a desktop, I knew I was in. It may not be an actual Eddie Current model, "ZDT Jr" is a made-up name after all. But the Eddie Current logo does at least mean that Craig Uthos said "Lemme see that thing" and started playing around with upgrading parts before deciding it was something worthy of slapping his brand name on. That alone tells me this amp was the worth waiting for.
Well, we all know that the wait turned out to be a lot longer than expected. I was originally supposed to receive mine in June, it ended up showing up on August 30. I had read that some people saw some issues with hum, so that was the first thing I was looking for when I powered it up. But as hoped, this thing is quintessential Craig - incredibly low noise floor. There is absolutely no sound whatsoever when music is not playing. Zero. And also quintessential Craig, the volume pot is superb. The zero noise includes when turning the pot to full blast, there's not a hint of hum or buzz, even near my computer and the associated WiFi signal.
Musically, I thought it was really good out of the box. I'm not sure if the second batch got extra attention in quality control before they were sent out, perhaps they had some hours already played. But mine sounded really good right away. The only thing I took note of was that the bass wasn't overly impressive. It was there, but I knew the 650/6XX packed more punch than I was getting.
Enter the GE 5654W JAN matched pair that I got on eBay for $18. I had seen a few people recommend them, and I can definitely add my recommendation. I'm hearing a lot more detail and a fuller low-end than with the stock 6Z1P.
With the new tubes I have to say that I am thoroughly impressed now. I'm not putting it up against a Balancing Act. Nor am I putting 650's against LCD-3's. But this little desk setup cost me under $1000 for the dac, the amp, the headphones, and the Cardas cable. Retail for LCD-3's alone was $2000. The Balancing Act without the upgraded pot or the tubes was $4000. You get the point.
What I'm hearing from this amp is the incredibly balanced and neutral presentation that I'd expect from an amp that Craig put his name on. Nothing stands out. Everything is just as it should be. Firm presence at the very low end, and a nice crisp high-end without being overly bright or sibilant. Great extension from cymbals, etc. The amp gets out of the way and let's the music do the talking. Nice wide head-stage, without any artificial airiness. Very clean sounding and "tubey" without sounding overly bloated. Low-end presence at low volume.
Fantastic amp. It's a keeper.