Cary Audio HH-1 Hybrid Tube/Solid State Headphone Amplifier
Cary Audio HH-1 Hybrid Tube/Solid State Headphone Amplifier ($1,599)
I have had a somewhat mixed experience with Cary Audio products when it comes to headphones. I own their SLP-05 tube preamp, which, as a preamp, is such a phenomenal product that I think it's a very easy recommendation, even at its (gulp) $8K price. I bought mine used, and it took my main two-channel system to a much higher level than it was prior to the Cary's arrival. I hold the SLP-05 in VERY high regard.
That said, I was also excited that the SLP-05 had a separate tube headphone stage. Unfortunately, that headphone section was flawed in two ways. One, the headphone jack was milled into the faceplate in such a way that NONE of my high-end headphones could be plugged into it without using an extension cable with a smallish 1/4" jack. But much worse, the headphone out very clearly had a 12 dB/octave bass rolloff. It's hard for me to understand what was going on there, but it was VERY plainly audible. The headphone out wasn't just a little soft in the bass, it was so bass-light as to be unusable. The SLP-05 is such a good preamp that I kept it anyway, but I was disappointed in the headphone out.
So as one might imagine, I approached the review sample of Cary's new $1,599 HH-1 headphone amp with some trepidation. Cary had some proving to do. And while it's not "perfect" (and what product is), the HH-1 is nonetheless a very fine sounding product.
I am NOT a fan of the "much deeper than wide" form factor that the HH-1 has, but readily admit I may be in the minority. It's shelf-friendly, but not all that desktop friendly. The HH-1 is quite solidly built, if fairly basic stylistically. It is also pretty simple around back - line in, and line out (presumably allowing the HH-1 to also serve as a one-input preamp) on pcb-mounted RCA jacks. The front contains the power button, 1/4" single ended headphone jack, and the volume control. Simplicity defined.
The HH-1 uses two 6DJ8/6922 vacuum tubes in the gain stage (which allows for almost endless tube rolling possibilities), and then MOSFET (Metal Oxide Semiconductor Field Effect Transistor) solid state devices in the output stage. This "hybrid" configuration is often used to give a tube sound to the device while driving more power at the output than could easily be done with tubes without a massive power supply and creating lots of heat. And further, according to Cary, these MOSFETs are operating in "Class A" mode at all output levels. I know some Class A freaks who will be drooling at that. However, the HH-1 is not a particularly powerful headphone amplifier by today's standards, offering 300 mW at 30 ohms and 200 mW at 300 ohms. As such, using the HH-1 with the HiFiMan HE-6, for example, was out of the question, and I was worried that there wouldn't be enough power for the Audeze LCD-3. More on that later. The HH-1 will be better paired with reasonably efficient headphones.
Also, I think that the MOSFETs have a significant impact on the HH-1's sound. The stock Electro-Harmonix tubes sounded only slightly different than some other 6922's I had, several of which actually took the Cary in the wrong direction (think "over the top"). So while I am usually a massive tube roller, I'm not sure how mandatory it is in this case. And I do think tube amps where you have to open the case to roll the tubes are less inviting for tube-rolling, overall.
I used both the Audio Technica W3000ANV and the Ultrasone Edition 8 for the review, and the HH-1 was outstanding with both. My primary source for the review was the Red Wine Audio Isabellina Pro DAC.