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Woo Audio WA7 Fireflies DAC Headphone Amplifier Review

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Woo Audio WA7 Fireflies Hube DAC Headphone Amplifier

Woo Audio has a reputation of producing very high quality tube amplifiers built in the United States. The company is located in New York and it is a family-run business. The chief engineer, Wei Wu has been designing tube amplifiers for over forty years. Wei’s sons, Zhivong Wu and Jack Wu also help design and build amplifiers. The reputation that Woo has built over the last ten years is stellar. The company is well known in the headphone community for building high quality amplifiers at very competitive prices.

The Woo WA7 Fireflies is a unique design. This modern cube design was inspired by Jack Wu’s wife, who offered input as to what she felt the public would like. The Fireflies is designed as a two-piece unit. The small cube enclosure has a separate power supply which can be placed on the floor. The amplifier takes up little space on a desktop and has a built-in Texas Instruments 32-bit 192kHz digital-to-analogue converter. The amplifier can be hooked into the computer with the USB 2.0 asynchronous connection in the rear of the amplifier.

The WA7 Fireflies also has RCA connections in the rear of the amplifier. The rear switch has three settings in order to control which output you would like to use. The switch can be moved easily to USB to access music files on your computer, watch concert videos, or to listen to online radio stations. The DAC can accept USB input only. It does not accept SPDIF connection such as coaxial, AES or Toslink from transports.

The front of the WA7 has two headphone inputs. One input is for a 1/4-inch headphone jack, the other is a separate, 1/8-inch jack designed for portable headphones and in-ear monitors. The rear, HIGH switch is designed to be used with headphones of 70-600 ohms, and the LOW switch is designed for lower impedance headphones.

The Fireflies is a compact, feature-loaded product that weighs a hefty five pounds, and the power supply brings the total weight to over eight pounds. The glass top is easily removable and the Fireflies houses two Russian Sovtek 6C45 tubes. The 6C45 tube is not seen in many applications. The unique thing about this tube is the gain; it has gobs of gain while being a very musical triode tube. However, according to Jack Woo, the design of the Fireflies was not intended for tube rolling. The only other 6C45 available is the Electro Harmonix gold pins that are available for $100 and sold in matched pairs. The stock tubes cost $55 for a matching pair and is included with the Fireflies. Woo uses a military grade PCB board in the design instead of their traditional point-to-point wiring. The power supply is solid-state regulated. The hand-built output transformer has a nickel alloy core.

The WA7 Fireflies is a very attractive amplifier in either the silver or black color. It has a very elegant modern look and is sure to be a conversation piece for anyone who looks at and marvels at this beautiful amplifier. The amplifier has a very high spouse approval rating and will look very attractive on your desktop. The WA7 was set up on my desktop connected to my 27-inch IMAC computer. Cables used included a Nordost Blue Heaven USB 2.0 cable, a Nordost Blue Heaven RCA for my Oppo BDP95, and a Nordost Power cord.

The Nordost cables are very transparent. The Blue Heaven lets me hear what every component is doing in the system. The headphones I used for my listening session included the Sennheiser HD800, the HD700, the Audeze LCD2.2, the Beyerdynamic T90, the Ultimate Ears Triple Fi 10 in-the-ear monitors and the portable UE6000. The Fireflies was completely burned in prior to my review.

Woo Audio WA7 Fireflies Hube DAC Headphone Amplifier with PSU


The Beyerdynamic T90 had a synergy with the WA7 that was outstanding. The musicality of the Fireflies really excelled in a very dynamic and open sound. The sound stage was very wide and deep and the dynamics were explosive. The Fireflies bass was very deep and controlled, and the treble was never offensive and sounded extended. The focus was razor sharp; I could easily identify different sections in each recording clearly.

The Fireflies had an outstanding midrange. There was no sibilance in either male or female recordings unless the recording was recorded that way.

The Fireflies presentation was both balanced and accurate. The amplifier just got out of the way. In my listening session I stopped analyzing the music; the music gripped my soul. I could feel the passion of the music flowing. While listening to Chris Botti’s Impressions album, I could feel his emotion while he was blowing into his trumpet. I could close my eyes and feel his passion; the music was so alive and passionate. When I switched over to the HD800, l could hear more of the music. The soundstage became very wide and deep. The Wailin Jennys Live at the Mauch Opera House album is a very well-recorded live album and is all acoustical. The female vocals from Nicky Mehta, Ruth Moody and Heather Massey are incredible. I could hear the inner detail of their voices.

31 Responses to Woo Audio WA7 Fireflies DAC Headphone Amplifier Review

  1. MacedonianHero says:

    Brilliant review Frank! Looks like one killer amp/dac solution in a small footprint.

  2. Frank Iacone says:

    Thanks Peter. Jack did a fantastic job with the amplifier

  3. Clayton SF says:

    Great review, Frank. I am always at a loss of descriptive words when I am trying to describe sound to someone and you did a very good job in capturing in words the essence of the Fireflies sound stage. It is also great that Woo Audio choose to use an external power supply for the Fireflies.

    • Frank Iacone says:

      Thanks Clayton. The design choices Jack made with the WA7 were well thought out. The separate power supply was a very good choice and the amplifier also sounded much more powerful than it stated 1W power.

  4. Dubstep Girl says:

    great review! it looks like you really enjoyed the WA7 and that Jack really did a good job with this amp!!!

  5. Lee Shelly says:

    Well written and considered review, Frank! My brief time with the WA7 left me with a similarly positive impression. Great photos too!

  6. Frank Iacone says:

    Thanks Lee and your pictures for Woo Audio are terrific,

  7. Wow, now I wanna go find some of the tracks and albums you mentioned. I think I have most of them… The fun will be finding them and playing them! Good read, Frank.

    • Frank Iacone says:

      Hi John,
      Thanks for the comments. The Reference Reordings Doug Mcleod album is a very special recording and the music is stellar.

  8. rosgr63 says:

    Great review Frank. Thanks for sharing. The WA7 looks very nice and your review confirms it sounds very good too.

  9. pegamush says:

    i don’t get what’s the third position of the source switch for (d/a), or did i miss something in the review?

    • Frank Iacone says:

      The switch covers switching between USB,RCA and the third switch allows for the WA7 to be used as a dac.

  10. moodyrn says:

    Great review Frank! Seems that this amp/dac sounds as good as it looks. Great job at conveying the emotional connection it was able to achieve.

  11. Frank Iacone says:

    Thank You. I am glad you enjoyed the review.

  12. Great job Frank! Killer read – you’re really finding your stride

  13. rattesp says:

    Excellent review Frank ! I had the chance to hear the WA7 at the SSI in Montreal and it’s really a terrific amp. And you are absolutly right about the incredible synergy between the T90 and the WA7.

  14. Frank Iacone says:

    Thanks Simon. The T90 is a special headphone with the WA7. I am glad you liked the review.

  15. Warren Chi says:

    I’ve been lusting after this ever since I first laid eyes on it. I think that just about the only flaw is that it’s not in my budget atm. Pity, I would have shown it the lovin’ it deserves.

  16. Frank Iacone says:

    I enjoyed my time with the WA7. Nice product.

  17. Paul says:

    I hope your on commission as you just sold one. Very nice review and I will be looking for some of those recording to try it out too. Thanks for taking the time to do the review

  18. Frank iacone says:

    Hi Paul,

    Glad you liked the review. It was a great amp and one I highly recommend it. It was one of my favorite reviews this year. Congratulation on your purchase,

  19. Warren Chi says:

    Frank, so I’ve finally got my paws on a WA7 (as you no doubt know from the headphone meet at CAS4). Got a quick question for you as my impressions differ ever-so-slightly from yours… do you happen to remember which tubes you used for the review? Thanks! 🙂

  20. Francesco says:

    Hi Frank, can you give me some other detail on sinergy of WA7 with Senn HD 700?

    • Frank Iacone says:

      The HD700 played well on the WA7. The WA7 played every headphone i tried with well. it is a good match for most any headphone except the AKG 1000 or HE6

  21. Dudley says:

    I’m thinking of pairing this amp with my Oppo PM1’s – any reason why that wouldn’t be a good idea?

  22. Rick says:

    Great review! I’m in the market and I have been looking at the WA7d with the WA7tp, together they run $1600 or the WA6-se with a Schiit Bifrost DAC which together cost $1600. Which of these two combos would you recommend?

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