First impressions of the HDVA 600 amp fresh out of the box with the HD650s.
I first listened to the setup I'm used to: My Darkvoice 336se tube amp with an unbalanced input from my Matrix Mini-i DAC. HD650s unbalanced (single-ended) with stock cable.
Next, I listened to the HDVA the same way - unbalanced in and unbalanced HD650 with stock cable.
Then I fed to the XLR balanced signal from the Mini-i to the HDVA. HD650 with stock unbalanced cable.
Lastly, I changed headphone cables to a ZYCable balanced cable and tried the balanced output of the HDVA.
As I went through each stage I didn't really notice much appreciable difference until I got to the balanced setup. Before I listened to the balanced setup, the difference in the amps was what you'd expect from solid state versus tube. The tube amp was a little less dynamic and slightly thicker. The HDVA has really great dynamics. They're controlled but fast and exciting. With the tube amp there were parts in songs where I noticed the dynamics swelling for no reason. This didn't happen with the HDVA. The soundstage is wider and more impressive with the HDVA too.
With the stock unbalanced cable I switched around between the HDVA, the Darkvoice, and my Presonus Central Station, which is more of a studio piece but has always impressed me for the price. You get a TON of I/O for 500 bucks and the headphone outs are very, very useable.
The balanced setup on the HDVA is where the comparisons finally have some separation. There's no way for me to know how much influence the cable is having, but I would imagine it's more about the balanced output than the cable. At least I can say the cable is comfortable, seems well built, and certainly isn't detracting from the sound.
To try to describe the sound of the balanced setup: As you may know, it's real hard to explain when something has that sound. It's high-end, hi-fi, whatever you want to call it. It's a little intangible but it's just a cut above. It has smooth dynamics but fast, exciting transients. Definitely a solid-state sound that I think really complements the thick-ish 650s. Upper-midrange harshness in some songs isn't as annoying with the HDVA.
Is it worth 4-5x the cost of my Darkvoice? Probably not. OK, definitely not, but I'm learning that 10% improvements at this stage cost a grand. If you want to hear these differences, you have to pay accordingly.
So, to apply some arbitrary percentages here, if the difference between an HD600 and an HD650 is 30%, then the difference between these amps is probably 10%. Along the same lines, this amp reduces the differences between these two headphone to 10-20%. I usually like the 600s sound signature more than the 650. The 600s are nice and clear while think the 650 gets too thick and yes, I hear the infamous veil. But through the HDVA, the 650s sound bigger, smoother, sweeter, and more "impressive" than the 600s, which sound too peaky in the upper-mids. There were a few songs tonight where I still like the 600s better, but I'm glad I just re-bought the 650s.
I've learned a few things:
1.) This is a nice amp, especially with the HD650s.
2.) Balanced operation is an improvement, at least with this setup.
3.) The difference between different headphones is WAY larger than the difference between amps, which is (slightly) larger than the difference in DACs.
4.) The price to performance ratio is not linear. I knew that already, but this is just another affirmation.
So, considering the huge difference in price vs. the relatively minor difference in sonic improvement, am I keeping the HDVA 600? Yeah! It's got the sound I've been after, and makes these 650s shine.