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.
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.
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