My WA11 Impressions
Gear - Sony NW-WM1z (K Mod Ultimate) for analog input, iPhone XS Max for digital input, Focal Utopia and Sennheiser HD820
Background
My primary reason to get the WA11 was for the HD820. My WM1z can drive the HD820 fine volume wise, but it just can't give the full experience like a desktop power amp can do. I wanted a portable solution so I can sit anywhere in the house and also take with me abroad. I was also curious to figure out why my Utopias sounded a little warmer from my WM1z versus my desktop setup.
Fit and Finish
I've been a fan of Woo Audio since I first owned the WA7 + TP. The quality of the materials, design, and finish have always been at the top. The WA8 was no exception and I thought it was one of the best pairings for my Utopias. The WA11 carries on Woo Audio's reputation. While one can see the paper specs for weight and dimensions, you really need to hold this in hand to feel the quality. I found it a lot smaller than what I was expecting and was pleasantly surprised at how light it was compared to WA8, making for a good portable package.
Note on IEMs
Both of my IEMs in my sig are not particular sensitive, but I found the background to be silent and with the right amount of input level, a pretty usable volume range at low gain. I don't intend to use the WA11 with IEMs because I am perfectly satisfied with my WM1z. I will just briefly say that both my IEMs sound fine. This is also the first Woo Audio amp that pairs well with my JH Laylas which I've found to be a very picky IEM for amping.
Note on Output Volume
If you want to hear what the full output capability is for the WA11, use it in DAC mode at 100% volume (if your source allows for volume, otherwise it will default to 100%). I was amazed at how much power the WA11 puts out. My HD820 was telling me "no mas!" at around a quarter turn in high gain. The Senns are not particularly difficult to drive given their efficiency so here is an important note. I would highly recommend whatever source you plan to use - you must have a variable output whether it be analog or digital. I found the volume control to proportionally adjust to input levels so if you want to fine tune the volume control to give you a good balance of travel to volume level, you got to have a variable input.
Here is a good example of what I am talking about. Using the WA11 DAC and 100% input volume, I can't even use my HD820 in high gain much past a quarter turn. But when I set to lo gain, I just get ok volume even at full turn. When I use my iPhone as the digital source it does allow me to adjust input volume so at around 80%, I can listen to my HD820 at high gain with my preferred volume right around half volume turn which is ideal.
If you are using analog input, I would also recommend a balanced level north of 2V. I'm not sure what the WM1z voltage levels are but I found high balanced output at 100-110 out of 120 volume level to be ideal for my gear. On normal gain, the volume level was too low on WA11. With all my head gear, 100 on my WM1z was optimal since I could listen to IEMs on low gain with decent amount of volume travel and both Utopias and HD820 played nicely at high output.
Note on WM1z
I found the analog out via balance on high gain to be a great source. While there is a long running dogma against "double amping", the Sony line of DAPs that use the S-Master digital amp do not have a separate analog headphone amp circuit. This is similar to Chord's FPGA architecture. Basically the S-Master digital amp is a variable line out. Having said that, I don't really see a problem using headphone outputs from the latest DAPs either because all of them measure very low in terms of distortion and the high impedance input of the WA11 basically creates a no load condition which is the optimal point of measurements. In fact if your DAP has audible noise, WA11 will probably clean that up.
Sound (Using WM1z analog input)
Overall, I would say the WA11 is a balanced sound that does not emphasize or diminish any particular frequency range. I would not call it "just a wire with gain" either. The sound is organic, full, with great extensions both low and high. It's not going to change the characteristics of your source except for an exceptionally low noise floor. You will also benefit by giving all the power and speed your headphones want so you get the full experience. In brief, if you want a portable amp for full size headphones, WA11 should be one of your top choices to audition with or without using the built in DAC (more on this later).
Bass - As I noted at the beginning I observed a warmer lower mid on the Utopias playing straight from my WM1z. At first, I thought this was good as Utopias are not known to be warm. However, over time, I thought that created an ever-so-slight veil between high bass and lower mids. With the WA11, that warmth disappeared and the bass became noticeably faster and cleaner with no bleed into the lower mids. I also find the lowest sub bass frequencies to be stronger as the physical sensation of the lowest notes can be felt in my chest. It seems even the Utopia benefits from the extra power. As for the HD820, really no contest against the WM1z. I would say WA11 is really close to my desktop amp for the HD820.
Mids - I find mids to be a good balance of weight, but not too forward. The transition from upper mids to lower treble is nice and clean. Using my Utopias, I'm hearing slightly better separation in instruments thru the WA11 instead of direct from my WM1z. It's more noticeable on more complex recordings.
Highs - A great combination of extension without sharpness or glare. Good air and separation, but not Chord level air which I find a little too sterile. Not a whole lot of difference compared to straight out of WM1z.
WA11 DAC versus WM1z Analog Input
Using my Utopias straight from WM1z, then analog out into WA11, then WA11 stand along DAC here are my impressions. Overall tonality and timbre are pretty close across the board. What I do find different is in the lower mids to upper bass. For anyone who want's to really hear what "low end speed" sounds like, I find Basia's "Cruising for a Bruising" track to really highlight this quality. If the bass is more liquid instead of punchy and/or the transition from upper bass to lower mids is not clean, the tempo of the track will sound noticeably slower.
Slowest (Purely for baseline) - WM1z stand alone, Faster - WM1z analog out to WA11, Fastest (by a nose) - WA11 stand alone. The "correct" speed comes down to personal preference and also the rest of your chain but my preference is the middle but I would be fine with just the WA11 too. As for the rest of the spectrum, I think the WA11 DAC gives a slight more edge to the highs, but it's not noticeable to my ears with every track so can't really be sure plus I think it's more related to transients than tone. If I had to guess, I think Woo Audio has opted for a minimum phase filter for the DAC - more accurate, but a touch leaner in the lower frequencies. But I also can't discount the mediocre to poor quality of the USB digital feed coming out of the iPhone.
At the end of the day, I will likely keep using the WM1z as the analog source because that allows me to use all of the features and DSP options built into the WM1z. However, I plan to try a cheap smartphone or DAP as a digital transport because WM1z + WA11 essentially becomes a desktop by weight LOL.
Last Words
At the moment, the only headphones I have that require the WA11 for portable use are the HD820. Utopias do sound better as noted above, but no so much better that I am willing to go through the hassle of lugging around the WA11 in tow. However, I plan on keeping the WA11 for a long time since I don't know what future headphones I will acquire. I'm 99% sure whatever my future headphones will be, WA11 will drive them just fine.
