I sold my Woo Audio 6 and bought myself an early Christmas present, a Woo Audio 6 SE (Special Edition).
It features a separate power supply unit which uses 5AR4 or 5U4G rectifier tube and an amplifier unit which uses 6DE7 or 6EW7 dual triodes power/drive tubes. The amplifier unit has two chokes per channel and utilizes direct interstage coupling design, there is no coupling capacitor in the signal path.
My first impression was OMG… this thing screams power, a lot more powerful than my old Woo Audio 6. I’m still trying to get used to the sound of the amp, the amp is surprisingly neutral and smooth. I guess it’s true about solid state being too analytical which is not my taste at all. I have also tried many different kind of musics and I have to say, WA6-SE makes them to sound as good as they possibly can. One thing I really like about the WA6SE is it allows me to enjoy low volume listening with full impact and detail – something I haven’t been able to achieve with other amps I’ve tried.
I have 11 sets of power/drive tubes and 8 sets of rectifier tubes. Fat bottles 6EW7 power/drive tubes seem to have wider soundstage but they also have less impact if compared to 6DE7s which are somewhat more musical. As for the rectifier, I have the excellent Emission Labs 5U4G Mesh, this is one beautiful tube, especially when it’s on. I notice the sonic signature changes to the better side. The changes are minor, bass is a little deeper and controlled, everything seem to be well balanced. I don’t recommend those who own WA6SE or any OPT tube amps to buy more expensive rectifiers unless they want to because of the tubes looks, the changes are minor to warrant the price differences. There are two beautiful rectifier tubes, the Sophia Electric Princess 274B Mesh and the EML 5U4G/274B Mesh. The SP 274B Mesh is just as beautiful as the EML Mesh tube, it’s not a true mesh plate though.
Although the amp has performed flawlessly since day one, I’d like to change a couple of things; the rectification needs to work perfectly, sometimes the rectifier tube emits flash, I’m very concern about it as I don’t want the PSU unit to shorten the life of the rectifier tube. I have a few of very expensive rectifier tubes and I’m very worried if the recent “bad batch” of the Sophia Electric Princess 274B mesh is not really a bad batch but is caused by the design of the PSU unit. I want to use 6FD7 tubes as they are my favorite tubes, I was told I must not use them but Woo Audio does not specify a reason for it. There is a fix posted on head-fi.org for it. The fix is simple, you just have to swap two 470uF/100V capacitors in the amp unit with two 470uF/200V capacitors (I choose Panasonic TS-ED for this application). I will work on it once I have time to play with my soldering iron. I will also swap the bypass caps (220uF/16V) with Black Gate N-series 470uF/16V. Hopefully new caps will improve the SQ. In the future, I may add additional power filter caps to filter out hum that I can hear with my Sennheiser IE8 (IEM – In Ears Monitor). I want the amp to be silent with any phones plugged into it.
So, there you go, a superb headphone tube amplifier that does not cost arms and legs.
Thanks Jack and Wu family, for making this beautiful amp.