Introduction
To begin I have to apologize for adding to the Woo Audio fire. Lately threads and posts concerning Woo Audio amps seem to be popping up on a daily basis, which I certainly don't view as a bad thing, but I know that some of you might be getting a little tired of the hysteria.
I took delivery of the original Woo Audio 4 about 10 months ago, in October 2006. I wrote my initial impressions, and posted a few pictures which you can check out here:
http://www.head-fi.org/forums/showthread.php?t=207234
A little while ago - I'm not sure exactly when - after the Woo Audio 6 craze hit Head-Fi, some members started to experiment with capacitor upgrades, and many of them experience very favorable results. It progressed to the point where Jack Wu began to officially offer upgrades for that particular amplifier, which could be built in during its construction. While I was intrigued by the upgrades, I was quite satisfied with my own amp and never pursued the upgrade bath beyond tube-rolling.
It wasn't until this August that I contacted Jack and asked him about upgrade possibilities for the Woo Audio 4. Among a number of Blackgate and V-Cap capacitor upgrades, Jack said the amps topology could also be significantly modified to make it headphone-only, which he said would also noticeably improve performance. While the amp was always designed
primarily for headphone use (it's speaker section can only drive highly efficient speakers), Jack said the headphone-only conversion would completely optimize it for that purpose.
I asked Jack what he thought about a maxed out headphone-only version, with V-Caps and Blackgates. He had actually built one such amp, and had this to say about it:
"In brief, the newer version offer the fastest speed among all other models we build. This version has better dynamic, separation, and bigger soundstage than the previous builds." -Jack Wu
So I sent my amp off to Woo Audio!
Preamble/Disclaimer
I obviously do not have a stock WA4 to compare my upgraded version to, so these impressions will be inherently subjective. I try to be as reasonably as I can, but alas this is not a scientific examination. Also, there are people here who are much better audiophiles than I am, so my descriptions and lexicon might not be the very best. There are adjectives people use here to describe how music sounds to them, and I really have no idea what they mean, so I try to stay away from anything ambiguous. I might be using words in the wrong or untraditional context, so I have to apologize up front. Hopefully what I mean to convey will be self evident.
I have absolute pitch and studied classical piano for a large part of my life, but I freely admit I do not hear certain things. Differences between power cords, interconnects, component burn-in (except in a few examples), all illude me. With that in mind, I can't offer any opinion on those things, and some of you might find my descriptions lacking in detail.
Finally, I love this amp. I loved it before the upgrade, and I love it even more after. I generally don't keep gear I don't like, and I usually don't take the time to review it either. I make an effort to avoid sounding overly preachy, but know that this review will be highly positive.
Impressions
If I were to chose a few words to describe how the upgraded WA4 sounds they would be: powerful/authoritative, smooth, clear, deep, heavy, fast, separation.
I'll start with the last one: separation. I generally consider something to be legitimately improved, or at least
changed, if you listen to a very familiar track and hear something previously unknown, or it catches your attention because it sounds different. I start to question myself if I'm straining to hear differences, and can't reliably discern them. There was certainly no straining with the WA4; as soon as I plugged it in and started listening to a few old and familiar tracks, I was immediately experiencing "what the hell was that, I need to rewind" moments.
I would have said that my old V2-SE had a slight edge over the stock WA4 in terms of separation, but the upgraded Woo far outdoes the Gilmore. There are notes on tracks that I've heard thousands of times, coming out like I have never heard them before. I really can't emphasize enough how taken back I was by the separation and clarity of each sound. Complex and layered music is breezed through.
The 1981 version of Gould's Goldberg Variations taken from the analog masters (the original release was done on inferior digital equipment), is a great recording. To illustrate what I was describing in terms of separation using this album, the key strikes are so sharply defined and clearly cut out, it feels like a key was hit in front of your head.
The WA4 is an absolute powerhouse of an amplifier, which I think is necessary when driving the HD-650's. The Woo dominates the Sennheisers into total submission, it drives them almost laughably. I hardly venture beyond 13 O'clock on
low gain. That being said, the amp was delicate enough to drive my Shure E500's in a way that my portable can only dream of.
Notes are heavy, impactful, and authoritative. This ties in with the separation in that not only are things clear and distinct, but they're bold and full of body.
Speaking of impactful, the bass on the upgraded WA4 is nothing short of epic. And to be sure, I don't mean that in the sense that it's bottom heavy, or that it's warm, because it's none of these things. What I mean is that it delivers serious bass on par with the power that it delivers the entire frequency range. The bass is like a marble statue: heavy, carved out to the finest detail, and impenetrable.
A few bass gems like the opening of Strauss'
Also sprach Zarathustra, The Alan Parsons Project's
The Raven, or Radiohead's
Everything In Its Right Place, were sending low frequency chills down my spine. It was mesmerizing.
There's also an airiness, or sparkle to the highs. They're very smooth, yet very crisp. I'm not trying to contradict myself here, but I just want to say that the highs oozing sharpness and definition, but there's not fatigue or harshness associated with them. In fact yesterday while doing a project and listening to Paganini's 24 Capricci I found myself in a daze for nearly 15 minutes before I looked at the clock and realized I had just been sitting there mesmerized doing absolutely nothing.
Final Thoughts
In my mind the biggest improvements are in separation, speed, dynamic impact and punchyness, bass, and detail. This is by no means an all inclusive list, and I would probably go so far as to say the amp is totally improved (and it does measure better), but I won't reach for a million words to say essentially the same thing: the upgrades are significantly noticeable.
I'm extremely pleased. I mentioned earlier that I was pleased before I even decided to upgrade, and really never felt the need to, but asked out of curiosity. Now I'm glad that I did.
One interesting thing about the upgrades is that when I turn the amp off now, it will continue playing music of almost a minute before it dies out.
A few negatives:
1. The amp runs
very hot. And because it's so big, it puts off a lot of heat. This thing could double as a space heater.
2. It's huge. Not really a problem for me, and I actually enjoy its massive presence, but some people might not want a 35 pound amp.
3. Woo Audio builds a ton of great amps, and now many of them have upgrade options. Jack is more and more willing to customize amps, which is a great thing, but it can almost make choosing an amp more and more difficult. Singlepower, for example, offers really not "standard" setup, virtually every amp they make is built to order, and I sense that Woo Audio is moving in a similar (maybe less extreme) direction. These new options and models are exciting, but can be overwhelming, and make it difficult to discern differences.
Overall, however, Jack and Woo Audio are a class act and make incredible products with incredible build quality, performance, and value.
Woo Audio 4: A Brief Re-review (upgraded)
Linear Mode
