I first tried this out just out of curiosity. The Zana Deux has a pre-amp out, and so I thought about routing the signal out from the pre-amp out to a Beta22 amplifier and hooked the headphones at the Beta22 headphone out.
You see, the Zana has some wonderful qualities as a top-class tube amp, but also the common weaknesses of tube amps such as resolution and control. The Zana has a very magical midrange tone and a superb three dimensional soundstage with very good depth. The Zana’s soundstage imaging is the best I’ve heard so far among all the headphone amplifiers I’ve tried, though the width of the soundstage is much narrower than the Beta22’s. At the other end, the Beta does have its own strengths as a solid state. Resolution, control, impact, soundstage width, are among the strengths of the Beta22 amp. When I hook up the Beta22 as a power amp after the Zana’s pre-out, what I get is the three dimensional soundstage of the Zana, a little bit of its midrange sweetness, added with the superb Beta22 resolution, technicalities, impact, and control. The soundstage is even more three dimensional than if I had used the Zana alone. The depth is increased, and you also get the wide Beta22 soundstage, while instrument separation is far more distinct. With the Sennheiser HD800 headphone, the soundstage pretty heavenly.
I’ve also been wanting to use the Zana to drive the Hifiman Orthodynamics like the HE-6. But that’s not possible because of the Zana’s limitation as an OTL design. But with the Beta22 at the power end, not only do I get an upgrade in sound quality, but now I can also have the Zana flavoring in the Hifiman Orthodynamic headphones. This combination undoubtedly produces the best sound I’ve heard on the HE-6 headphone.
Recently I’ve also tried to pair the Zana with the Nelson Pass-designed Adcom GFA-5802 Power amp. The 300 Watts Adcom also struggles to match the Beta22’s refinement and resolution, something that is very understandable, given the Adcom’s much higher power output. Moreover, I did get some mid and low end coloration that I don’t get with the Beta22. With the HD800, the added noise and grain from the GFA-5802 is very noticeable. However, with the HE-6, it’s less bothersome (though it’s still there), and the Adcom was able to fill the center soundstage void on the HE-6 better than the Beta22 does.
Quite an extravagant and overkill set up for headphones, and it’s not something that you may be interested in, but I just want to share it with you guys.