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Woo WA2 and low impedance

Discussion in 'Headphone Amps (full-size)' started by ardilla, Oct 28, 2010.
  1. ardilla
    I am very close to purchasing a WA2 for my high imp phones (HD650 and T1) after many recommendations here on the forum
    However I am a bit puzzled: It seems to be a slight consensus that the WA2 doesn't work with low imp phones?
    Still, I read stuff like this:
    Often, the revered qualities of "fast transients" and "dynamic slam" are not positive qualities to me when it comes to headphone listening, simply because such attributes almost invariably lead to fatigue in monitoring situation in my case. Still, consider the fact that if one preferred low-impedance headphones like Grados and Denons, there weren't many tube amplifiers that offered themselves up for the task. But now, we have a tube amplifier that can be ideally mated with a plethora of dynamic low-impedance headphones, at a very attractive price. Does WA2 offer the ultimate standard in headphone listening? http://www.enjoythemusic.com/magazine/equipment/0709/woo_audio_2.htm
    Also  - the very much respected Skylab seems to think that Hifiman HE6 is a quite good match with the WA2, but recommends the WA6 for low imp phones generally.. 
    Since phones come and go, I'd like to buy an amp that will work with many different phones..
    Anybody have opinions on this?
  2. Skylab Contributor
    The discrepancy from my perspective is something I learned from KWKarth, which I have found in practice to be true.  The issue with using the WA2, which is an output transformerless (OTL), and DYNAMIC DRIVER headphones, is that the mismatch between the high-ish output impedance (typically) of an OTL amp and a low impedance dynamic headphone can result in a poor damping factor, which then can result in some frequency response aberrations - potentially.
    In the case of planar driver headphones like the HE-5, as KWKarth explained to me, there is not an issue relating to damping factor.  The only concern with planar drivers is whether the amp has enough power into the load presented based on the sensitivity of the headphone.  The WA2 is a powerful amp, and it seems to have plenty of muscle for the HE-5 and LCD-2, IMO.
    So essentially, with low impedance dynamic-driver headphones like Grados and Denons, there could, in theory, be some performance issues, but the technical reasons for that don't apply to planar-driver headphones like the HE-5.
  3. ardilla
    Skylab! Tanks for answering :)
    However, the above mentioned review states:  
    ... tube amplifiers are known to have problems driving low-impedance headphones like the Denons (25 ohms) or Grados (32 ohms). AKGs, despite their seemingly benign 62 ohms rating, are known to be notoriously difficult for tube amplifiers to drive as well.
    One thing that will immediately impress any listener upon listening to the WA2 with low-impedance headphones, is how effortlessly the WA2 drives them. (AKG K701, Denon D7000)
    - So this guy at least thinks that K701 and D7000 is great matches with the WA2
    Then - you say that the WA2 is a good match with orthos like Hifiman H5 and LCD-2
    At the other hand - there just was a WA2 for sale (which I missed buy a couple of hours :frowning2: - the owner said he sold it (brend new) because it didn't go well with Hifiman. I asked him about further details have not gotten any answers. 
    So  - is it just a matter of taste? The WA2 drives anything pretty well - but there can be even better matches for some low imp phones? Or does this depend on the sound preferences of the individual listener?
  4. Henerenry
    I have a WA2 and have tested it on a number of different headphones, including grado (allesandro), K701 and LCD2 (on my head now).
    I thought the WA2 did a great job of handling both the grados and the K701. At first, my LCD2 sounded pretty average on the lcd2, I figured it was because the amp was an otl design and they werent playing nice. However after reading skylabs comments in this thread, I decided to roll my tubes from 5998 to 7236's and I have to say, my LCD2's are sounding great, great detail although a bit "drier" than I have been used to with the 5998, I do however think the 7236 are a much better match.
    I am sure there may be other headphone amps which are much better at driving the headphones I have mentioned, but the WA2 is no slouch!
  5. Skylab Contributor


    That's it precisely.  If the damping factor isn't perfect, that doesn't mean that any individual listener won't like what they are hearing!  Some may even prefer it over a good damping factor [​IMG]
  6. ardilla
    What is the short translation of damping factor? High damping factor is thighter control?
  7. oldwine
    I dunno anything about the technical terms, but the WA2 i have, paired with SA5000 and K702, both works great on my WA2, for SA5000, it evens performs better than my DT880/600 as it is initially being the phone that WA2 uses.
  8. Skylab Contributor


    Yes, as I understand it, it means tighter control over the movements of the driver, which is important in the bass, where the movements are largest.
  9. avsBuddy
    My understanding that damping factor is a headroom of the amp, it's the ratio of the  drop in impedance that amp can absorb and compensate. Tube amps in general have very low damping factor so impedance matching is very important. SS amps on the hand usually have high damping factor so they can drive tougher loads. I assume that since WA6 are Transformer coupled- it's able to provide better damping factor that tube only WA2
    Oldwine, I was looking for DT880/600 as closed cup alternative to my Sen HD600 - are you saying there are better choices for WA2?
  10. oldwine
    What i mean is, i originally bought the WA2 for the DT880/600, but after i use it with SA5000, i find the performance of WA2 with SA5000 sound almost, or in some areas, even better than it pairs with DT880.
    However, i need to mention it,
    my SA5000 have been recabled with APS v3 single ended.
    Stock WA2 and the tubes used on WA2 are TS5998, Amperex 6DJ8 "bugle boy"holland white printing, with RCA 6V4
    The WA2 with DT880, gives you a full potential of dynamics, and beautiful vocal (maybe due to the 6DJ8) and plenty of details whereas with SA5000 have extra soundstage and somehow like live performance.
    In simply, i like sitting in the middle of the opera house when i using DT880 while SA5000 lets me come near the stage.

  11. runningman1960
    I find myself looking seriously at both the Woo WA2 and the WA6SE. I've read alot of threads regarding both and they seem to be exellent amps. $1000.00+ is alot of money to me, but I don't want to go the cheap route this time. I have both high and low impedence headphones ( grados sr325is, denons d2000, senn hd650,) and I understand that the wa2 is "better" for high imp phones, and the wa6se is "better" for low imp phones. But can the WA6SE still drive high and low imp headphones very well? Also any other suggestions for all around tube amp would be welcomed. Thanks in advance for any help.
  12. nigeljames
    The Woo6se has no preference for high or low impedance. It drives my 600 ohm T1's as well as the 50 ohm LCD-2's
  13. runningman1960
    thanks, that was a big concern of mine. How would you personally rate the wa6se with some of the other amps you may have heard, if any?
  14. nigeljames


    The Woo6se is a very flexible and powerful amp (disregarding the current 'made for planer' amps). I upgraded from a GS Solo SRG and it was a BIG improvement. I am basically using stock tubes, or similar quality, so it can get even better but I don't feel I need to upgrade it with expensive tubes, at least not yet.
    I currently also have the Roc that is on the same level but I may be selling it to upgrade to the Audio-gd Master-6 :)
    With the variety of phones you have I don't think you would go wrong with the Woo6se however be aware that the Woo6se is not a tubey sounding amp. If thats the sound you are looking for then serious tube rolling or another amp would be in order.
  15. runningman1960
    No, I like more of a dynamic amp with a touch of warmth, (I currently have a Kicas Caliente) and it appears the Woo wa6se might be just what I'm looking for... Thanks for your replies

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