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WooAudio6 Tube Amplifier Full Review - Part I

post #1 of 43
Thread Starter 

This is the first part of a full Woo6 review. Part I is a summary of my impressions upon receipt of this unit (2 hours ago), without burn in. Part II will be after burn in. In addition I will add comparisons to the SP Extreme when I get it as described in this thread.

  • About me
    I have been on these forums for over a year, but active only in about the past month. Before the past month, I have only had headphone amp experience with my PA2V2, which I only used with the HD595 for watching movies. The rest of my listening experience through headphones has been restricted to the ER6i and ER4P with my iPods as sources.

    About a month ago I purchased most of what you see here:
    Sources/Processors: Sony SCD-CE595, Marantz SA8001, PowerMac G5, Presonus Central Station, Philips HD1500
    Amps: Presonus Central Station, Woo 6
    Headphones: Senn HD650, Senn HD497, Senn HD595, Senn PX100, Senn PMX70, Grado SR60, ER4P, ER6i, Audio Technica ATH-ES5SV, Philips HD1500, AKG K701 on the way

    Other than head-fi experience, I have been experimenting with quality amplifiers and speakers for a good 20 years, but I would not call myself an expert in sound engineering or audiophile equipment. I have been playing the piano for 30 years and composing some of my own music for the last 15 years. I mostly make arrangements of music by others.
    Since I came on these forums I have been wondering if amps really make so much difference as people around here say they do. How can I quantify the advantage of tube or SS amps for specific music? How much difference do the sources and the headphones make? What about power and cables? How much difference does break-in make (and if it does, which components need it)? What's the financial point of diminishing returns in amps for me? All hard questions to answer by just reading on these forums, but even harder to spend $5K to find what these answers are for me. I eventually decided to try it out after a year or so.
  • Testing equipment
    For this review I used the HD650 and the Marantz SA8001 for my source. The HD650 have about 150 hours on them and the SA8001 about 80. The K701 are not here yet, but when they get here, I will add to this review. I am also comparing the Woo6 to the Presonus Central Station for reference. I may add a section about the PA2V2 as well, just for reference and to answer the questions of the people wondering how much difference there is between a $50 and a $600 amp. I will try to quantify my experience as much as possible.

    For this review, I used a Dire Straits SACD (Brothers in Arms), Diana Krall SACD (The Girl in the Other Room), Chopin concertos for piano Redbook, Barenboim playing Beethoven sonatas Redbook and Paul Mauriat's Classics in the Air Redbook.

  • Music preferences
    My music tastes are pretty much everything. I mostly listen to classical, different arrangements of classical themes, electronic (Yanni, Vangelis, etc.) and Jazz. I also listen to pop and some rock and I have been through country, world and rap sessions as well. I listen to techno while working out.


Unfortunately I have never heard and I do not have another tube amp to compare the Woo6 to. You will see that I was quite impressed with the way this amp sounds, but maybe other tube amps sound the same and it's not the Woo that's special, but it's the tube amps in general. You be the judge, until I get my hands on the SP Extreme.

For the new people that are wondering (like I was) if an amp is worth it and if the sound changes significantly (especially after reading threads that claim that amps are overrated): Yes, it's worth it and yes it makes a significant difference. Is the difference worth $600? To someone with an annual salary of $75K it is certainly more worth it than to someone with an annual salary of $20K and to someone who cares more about sound than someone else it is also more worth it, so I cannot answer this question. What I can say is that it does make an audible difference. You will be able to tell you are listening to a Woo6 vs. your source's amp vs. the Presonus. This is of course true for the HD650 and my source. With a different setup, there is most probably different sound coming out of the Woo6.

For the rest of the people: This is an awesome amp. The minute I plugged my HD650 on it and started playing some SACD's, I understood what this society is all about and why you people spend all this money on amps, headphones and sources. The sound you get out of this thing has nothing to do with the sound I was used to.

Let's start from the beginning: I waited until the amp reached room temperature, as it was 8 degrees out today. That took about 30 minutes. Then, I plugged it into my Monster HTS 2000 MKII using a Monster power cable. I use PureAV interconnects for the SA8001. I powered it up and watched the tubes go on. I let it warm up for about 15 minutes. I plugged my HD650 in and turned the volume all the way up. Nothing. Pure silence. I was trying to listen for hum, noise, anything. Nothing at all. Just as if I had not plugged in the headphones. I put the Chopin CD in the SA8001 and paused it and listened for noise again. Nothing. Just like before.

On to the music:
  • Chopin
    Symphonic music is unbelievable through this amp. It doesn't matter how many instruments you have playing at the same time. You can tell every single one apart. You can tell that you have more than one violins on the same passage. It doesn't matter how loud the passage gets. The Woo has absolutely no problem handling it. No clipping, no mud. Nice live sound, all the way to max volume (yes I went that high).

    I recall from a thread I have read here before that someone had a problem with the volume not going up high enough. I can see that. If I am working (I write software for a living), I will listen to about 12 o' clock, but I crank it up all the way to max volume and listen to the music, without it piercing my ears. It's at the limit, though. Any higher and I wouldn't be able to stand it. So, for my listening levels it's perfect. My understanding is that if I were to send it back to Jack to make it more powerful, we would increase the noise floor as well. I am very happy with the way this works now. And yes, I do have the switch in the rear to the 600 Ohm setting. And yes, I did try the other position as well.

    From 3 o'clock all the way to max, no detail is lost. You can hear everything perfectly. I can hear the fingers tapping on the flute and the bow lifting and landing on the violins. I can hear the flute player breathing. And that's in a full orchestra playing forte! The amount of details is amazing.

    I had to pop in a Bach Brandenburg Concerto (Naxos, redbook) just to see if it wasn't that CD alone. By the way, if you have a bad recording, don't even bother with any good audio setup. You'll just hear what's in the recording and you will be very disappointed. A good system will not make your bad sound better. It will just make you hear the good sound (that you were missing before). Back to Bach (pun not intended): Awesome! Amazing sound! I know I use these heavy words now and I promised myself I wouldn't as I do not get excited very easily and I did not want to cause a stir with this review and then make people have high expectations. But I do think the sound is indeed awesome. I did not expect that big of a difference because of an amp. I can even hear someone twitching on their chair, while the orchestra is playing. It's that detailed.

    The sound is also full. I am not very familiar with all the terms that you use here, but I will try to explain: Full, as in you can hear more frequencies out of the same violin. If you compress a violin sound, you lose information and the result is sound that is not as full. That's what I mean by full. It's as if the violin is resonating through and you can hear everything that comes out of it, not just a narrowed down version. That goes for all instruments.

  • Mauriat
    For those not familiar with Mauriat's work, it's modern arrangements of classical music, very similar to Hooked on Classics, that you are probably more familiar with from the 80's. So, we have a lot more percussion and modern drum machines, synthesizers, digital echo and reverb and the classical instruments in the orchestra as well.

    The effects in this recording are far more evident than before, even at low volumes. There are some drum echos that would echo 2-3 times in the past, and it's more like 4-5 now.
  • Krall
    Now for some female vocals. A SACD that you should be more familiar with than the previous ones. Same thing here. Krall's voice is just fuller, as if the microphone gets more frequencies out of her vocal cords. The hi-hat and cymbals are crystal clear without getting in the way and there is more reverb making the sound warmer. The piano sounds very alive. Bass pizzicato never sounded so good in Temptation. You could always hear the fingers pulling on the strings, but not with so much life. you can hear fingers of the left hand sliding up and down the strings, not just the right hand fingers pulling on the strings. I can almost taste Krall's saliva (ok, that's going a little too far).
  • Barenboim
    I've had problems with solo piano in the past. It's solo piano, so you can crank it up and it won't bother you, because there's not a bunch of instruments playing. However, you have notes in all frequencies and with most all of my previous setups (speakers included) I had some clipping at loud volumes. Not so with the Woo 6. I played 6 Sonatas at max volume and not once did it clip. Great, great sound.

    Being a piano player, I have played on Steinways to Yamahs, to Kawais. Recorded music has not been able to reproduce this sound so far, so don't be looking for me to say anything remotely close to that. But of all the recordings I've heard, the current setting is the best sounding so far. You can't tell what piano make you are listening to, but you can easily tell a standup piano from this one.
  • Dire Straits
    Money for nothing is a good track. Starts with vocals and a synth at a low volume. You can hear him breathe in before each phrase. Drum roll after about a minute. Drums are crystal clear and fast. Then, everything jumps in: more drums, louder synths, guitar, base, overdrive as loud as it gets. No sign of clipping. Still perfect separation. Then, there's a break and the lead guitar jumps out in a solo. Sounds so close to me, as if it were right in front of me. Perfect. Really good sound. I don't know what else to say.


Real quick: There's no comparison to the PA2V2. This is just for reference and those new guys (like me) who may be thinking (like me) that all amps do the same thing: take one signal and boost the volume without altering the signal in any other way, so they all sound the same. The PA2V2 clips my piano, has a more narrow soundstage, no instrument separation, no dynamics, no fullness to the sound.

Now for the Presonus Central Station. Well, the Presonus is an SS amp, this may not be a Woo6 vs. the Presonus but rather a tube vs. SS amp. I have not heard any other tube amps to be able to determine what the case is. Either way, The Woo6 with the HD650 and the SA8001 for source sounds more mellow, more full an meaty. Volume range is about the same. The CS sounds metallic and dry. Less reverberation on the CS. This does not mean that the Woo6 is muddy or the bass is over-represented. It is where it needs to be. Not too much, not too little. Warm yes, full yes, undefined no.


I think this concludes my first review (the first part of it anyway). I think the Woo 6 is a great amp that with a good source can make good headphones shine. Very well balanced, very audible difference from my previous setups, clear difference from the Presonus, no noise. This is without any break in at all on my part and stock tubes (except 12 hours that Jack said he did).

What would I change if I could? Well, I already got a custom loop out. Maybe another input? Maybe some more volume while maintaining quality? I really have no problem with the volume, though. I've been listening very pleasently at 5 'o clock for the past 2 hours. And I use the Presonus main out as input, if I need switchable sources. Maybe I'll get more ideas about upgrades once I listen to other tube amps and/or tube combinations.

All in all I am extremely happy with this amp. I am looking forward to comparing it to the SP Extreme, listening to changes in sound after 150 hours and rolling some tubes.

Well, great job there Jack. I am definitely not selling this amp.

Added a little later:
  • After playing from a different source (my G5 computer through the Presonus line out) I realized that the line out of the SA8001 is a little low voltage in comparison. This is why I could play the Woo6 at full volume. I can't go past 12 o' clock with different sources. I noticed that the same thing happens with the Presonus amp if I source from the SA8001: I can go all the way on the volume knob. Most certainly your source will have a lot more drive available for the Woo6, but even with the SA8001 I am more than satisfied.
post #2 of 43
Wow - fantastic review. This is the kind of thing that makes Head-fi great!
post #3 of 43
What a wonderful addition to Head Fi you are sir. Nicely done and we all look forward to more.

Great setup btw.
post #4 of 43
Wow! Very excellent review. I am in hunt for an amp and this review really makes me want a tube amp, specifically the Woo.

One question for you...I listen to mostly classic rock and a bit of jazz, how is the Woo on speed and attack with the 650's (I have 650's also)? Is it quick enough for the 650's?

Thanks again for the great review!
post #5 of 43
Awesome review! Can't wait to hear your thoughts on how it sounds compared to the SP Extreme.
post #6 of 43
Awesome review. Very Professional. Like I was reading 6moons. Love the pictures as well. Plus, that setup you have is sweet!

Great job.
post #7 of 43
This is why I joined Head-fi. Enough of all the useless threads this is what it's all about! Great review!
post #8 of 43
Originally Posted by trose49 View Post
This is why I joined Head-fi. Enough of all the useless threads this is what it's all about! Great review!



Very good initial summary George. I have a few of the same components that you own...Woo Audio 3 (well, close anyway)...Central Station, PA2v2, HD 650 , ER4P.

You mention using max. volume with the 650, with my WA3, max. is quite loud, I often hit the wall at around 2 o'clock. My source is a Pioneer Elite DV-45A (universal player). For Redbook CD I use a digital connection into the CS using its DAC. I do have 2 other components in between the CS & WA3 so that might be an issue with my resuts. I do agree that as the volume goes up, up ,up there is no loss in quality...it's very involving, a very addictive thing!

The WA3 & WA6 are beautiful amps. I had many of the same emotions when listening to my WA3 for the first time. Easily worth the money. At the time my best can was the DT-880 which also sounds wonderful with tubes.

I actually like the CS amp for its razor sharp detail, it is my favorite amp for my DT-770 (Darth Beyers). For most music I do prefer tubes with my 880 or 650.

------------I look forward to more impressions-----------------

yeah baby!
post #9 of 43
GREAT review.... I hear the same out of my Woo3.... Mine is going nowhere!

Can't wait to read Part II....
post #10 of 43
Thread Starter 


Thank you very much for the warm comments. Very encouraging. Truth is that I am very busy and this review took me a while to compose, but it's the least I can do for the community here. I have taken so much in the past year. About time I give a little. It's very encouraging to write Part II when the time comes.

I don't have any CD's with classic rock, but I'm playing from my computer now. Unfortunately, everything I have is compressed in rock (128 - 192 kbps). Therefore, I can't give a very educated opinion on how rock would sound with a good source. What I can do, however, is give you a comparisson to the Presonus, which is a SS amp.

I played Cheap Trick, Def Leppard, Pat Benatar and Poison. I have to share the same impression as GreatDane here. The Presonus does indeed have more attack and more speed. You can hear it in the drums. Still not as warm and full as the Woo 6, but definitely more attack. Definitely a lot of power with the Woo. I can't turn the knob past 12 o' clock (unlike with my SA8001 source). Presonus is a little brighter. I want to say maybe more accurate or clear, but it's probably because of the speed. If you have a particular song or artist you would like me to audition the Woo 6 with, let me know and we'll see if I can find it in my library.

Here's a song most people should be familiar with: You shook me all night long, AC/DC. Electric guitar gallore and lots of drums. A bunch of stuff all put together (sorry, I don't mean any disrespect here). I am not sure if I like this more on the Woo or the CS. It's definitely different. Warmer on the Woo, but without loss of detail. The sound is not as crisp as in the CS and the CS is certainly faster. Snare cuts off very abruptly. The guitars are brighter, crisper. The highs are definitely more present. I hope this helps. Let me know if you would like me to listen to a particular song at a particular spot.

You're right on about the volume pot. I switched a source and I can't go past 12 o' clock, and even there it's very uncomfortable. I added something about that at the end of my review above, after the last picture.

About the detail of the CS: It's faster and crispier with rock. I guess this would be more detail. On my usual jazz and classical music I do hear things a bit better with the Woo. I can now hear them in the CS, but if I don't listen for them, I would not have noticed. With the Woo, they're just there. "Things" would be the climbing of fingers up and down the bass strings and the taps on the flute keys. I guess these are more bassy sounds, so they come out better on the Woo.
post #11 of 43
Just a fantastic review ! Pro quality THANK YOU. It is nice to see a musicians viewpoint on sound. I play guitar myself and this site is wonderfull and full of great people who really do appreciate great sound.
post #12 of 43
Great review style and read. I love the quality feel and look of the Woo products, but I have stated this a few times before. One thing that can really change a tube rectified amp is the rectifier. It is part of the circuit, and a major part when Mullards or like tubes are used. They can change the speed because of internal resistances of the tube and attack will also improve. There can also be a noticable change in stage and transparency due to a better source of the electric, which translates into a better DC for the AC musical signal to ride on. When the DC is stripped from signal by the output transformers the AC musical signal is cleaner when you have a higher quality DC signal that a good Mullard or like tube can provide. Of course any DC from a recitifier is worked by the resistors and caps as the DC gets to the driver and power tube but just like anything the better the foundation the better the end result.
post #13 of 43
Excellent review. I sent the amp back to adjust for the AKG 701's and now at 12 o'clock the amp is perfectly loud for normal listening levels. The Woo 6 is equally good with Grado's and Senns. Solid state detail with tube smoothness and texture. A true giant killer.
post #14 of 43
George nice review! I see you went all out and bought lots of equipment! I hope you are enjoying the HD650 and Marantz I recommended.
post #15 of 43
Originally Posted by jamato8 View Post
Great review style and read. I love the quality feel and look of the Woo products, but I have stated this a few times before. One thing that can really change a tube rectified amp is the rectifier. It is part of the circuit, and a major part when Mullards or like tubes are used. They can change the speed because of internal resistances of the tube and attack will also improve. There can also be a noticable change in stage and transparency due to a better source of the electric, which translates into a better DC for the AC musical signal to ride on. When the DC is stripped from signal by the output transformers the AC musical signal is cleaner when you have a higher quality DC signal that a good Mullard or like tube can provide. Of course any DC from a recitifier is worked by the resistors and caps as the DC gets to the driver and power tube but just like anything the better the foundation the better the end result.
Just put in a amperex bugle boy rectifier and very noticable difference.More sound detail comes out like sound extension from the engeneering.Put in two rca's but couldn't tell a difference.Cryoset will do the rca's for $3.00 each.
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