Woo Audio has one of the finest selections of tube amps around. They’ve been an acquired taste for tube amp enthusiasts and general audiophiles that have the the money to spend on this kind of gear. What we have here today might fit a different kind of crowd. The new Tube Mini from Woo Audio is a portable USB DAC/Amp to costs $499. This still might be a steep price for some, but if the Tube Mini can contain Woo Audio’s quality sound reproduction it could be a force to be reckoned with. Let’s see if it succeeded. 

What You Get

• Tube Mini USB DAC/Amp
• Zipper case
• USB-A female to USB type C male cable
• Lightning adapter

Build

I would compare the overall design of the Tube Mini to Audioquest’s Dragonfly series of USB DAC/amps. The Tube Mini is much bigger than those, but still small enough to carry around as easy as any other DAC dongle. You also get a balanced 4.4mm headphone output, which is already a major advantage over the Dragonfly amps. With the Tube Mini you’ll need to select between balanced and single-ended though, as both cannout run at once. Woo Audio gives the Tube Mini a small switch on the side for this, as well as a play/pause button. 

Of course, the main draw of the Tube Mini is the tube itself, which you can physically see in all of its glory through a window on the face of the device. This comes with minor disturbances though, which Woo Audio is fully aware of. Those familiar with tube amps are more than likely aware of microphonics. The Tube Mini is just as prone to noise as any other tube amp. It results in a ringing sound that can be heard when no music is playing. This is caused by general handling of the device while it’s active.

So, this ringing can be avoided by leaving the Tube Mini stationary while in use, which kind of devalues its portability a bit. Cellular data also also interferes with the vacuum tubes due to high EMI. It makes the Tube Mini harder to use when connected to you phone, unless you’re planning on downloading all of your music to use when out and about. Even then you would still need to avoid handling, so maybe the Tube Mini isn’t best to use in public spaces. The full potential of the Tube Mini is best experienced with over-ear headphones anyway, so the best way to use it might be when plugged into a laptop or tablet at home. 

Sound Impressions

If you follow the instructions on the proper way to handle the Tube Mini without disturbances, the sound you get from it is unlike anything a portable DAC/Amp is capable of. For the price, that’s kind of what you’d ask for, but it’s still a spectacular presentation nonetheless. With the Tube Mini, Woo Audio provides one of the most potent portable adapters. Easy-to-drive headphones and IEMs are almost explosive, and you should take extra precaution about where you’re volume is before you hit play on your first track.

Grado headphones like the Hemp felt massive, with expanded imaging and extra body. The Sundara, also had more of a kick to it, and added more shape to the instruments as well. I tried the Tube Mini with the Ananda and Arya as well, and they both benefited by offering increased tallness and scope. Because of their lower impedance, you’ll have more headroom then you’ll ever need form these specific selections. You’ll never have any trouble getting your headphones or IEMs to a comfortable gain. However, you should start at zero volume and work your way up no matter what you’re listening to just to be safe.

Higher impedance headphones like the Fiio FT3 and Sennheiser HD 660S2, work almost the same with just a bit more juice. There’s plenty of room for adjustmjent, even moreso than most desktop amps around the same price. I’ve never heard the 660S2 sound so wide and tall than when using the Tube Mini. Some treble elements pushed through more aggressively than with any other amp, but otherwise the highs gave me more height and crisper detail. It still has its mid-bass groove, but the response feels roomier in general. The same goes for the FT3, which gave me even larger imaging and separation between the sound elements while using the Tube Mini.

Timbral elements just felt cleaner throughout, no matter what pair of headphones I was using. Sometimes these super powerful DAC/amps find issue with presenting your music as too pushed out and inflated. Thankfully, the Tube Mini doesn’t fall into this type of response. Your tracks are always presented articulately. You never get any unwanted bloat from the tube either. All of the warmth that the Tube Mini can add to your headphones is always well controlled and wonderfully textured. 

Summary

With an incredibly large output that is able to reveal a pristine sound, the Tube Mini is easily one of the best sounding portable DAC/amps I’ve heard. It takes a lot more care and precaution than most products like this. The actually portable aspect of this portable USB amp is lessened due to all of the noise that can be caused by handling. This is the trade-off to having a real vacuum tube in your pocket. Using the Tube Mini for your tablet or laptop is the best way to use it. You’ll also get the most out of its output when listening to high-impedance over-ear headphones. It really makes the Tube Mini more of an entry point for tube amps, rather than an amp dongle. 

Check out more from Woo Audio here.