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Woo Audio WA7TP (tube power supply) Impressions Thread

Discussion in 'Headphone Amps (full-size)' started by warrenpchi, Apr 20, 2014.
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  1. Shini44
    i am Ultra Carious how would these sound compared to  RCA clear top :p 
     
  2. groovyd
    are the spec differences something to be concerned about damaging the supply or amp?
     
  3. Dogmatrix

    Similar to clear top in terms of clarity but bigger gain and more open stage a much stronger presentation
     
    I did some research yesterday on tube rectifiers and it turns out most of the parameters I listed don't have much to do with a rectifier circuit
    Key parameters for a rectifier are all in the power capacity specs like plate voltage and dissipation
    For plate voltage the 6350 and 12au7 are almost identical being rated at 300v nominal and 1000v peak DC
    For plate dissipation the 6350 can output 3.85 watts per plate the 12au7 2.75 watts per plate but as I understand it these are maximum figures and the tubes will only output what the amp requires
    Another key figure with rectifiers is cathode saturation but I can't find any figures on that
    I was concerned about the heater current as the 6350 draws 0.6 amps to the 12au7 0.3 but there are no signs of transformer overload so far
    Noise floor is something I am looking for , there is nothing obvious but there may be a slight hum it is very distant and close to my own personal background noise so I am not 100% it is real . Tube rectifiers have very specific filter circuits tailored to a particular tube these smooth out the bumps in the DC left from removing the negative AC wave . Only a theory but it is possible the DC coming off the 6350 is a bit more lumpy than the filter is designed for
    Damage is always a risk with this kind of extreme rolling but the rewards are high
    Since I don't know the capacity of the transformer or the nature of the rectifier and filter circuits it is a suck it and see sort of scenario
    All good so far
     
  4. Dogmatrix
    Re possible noise with 6350 mentioned in previous post
    All is well it was just my laptop fan . Last night I hooked up my ASG 2 iems and everything was absolutely as it should be .
    With everything hooked up and running but music paused I could run the pot to its stop in perfect silence
    Nothing detectable under the music or between tracks either just the usual Wa7 deep black
     
  5. groovyd
    here to hoping mr. woo will divine us with whether or not this may damage the unit or the amp indirectly.  little nervous to roll them in once they arrive.
     
  6. Dogmatrix

    That would be nice , I would like to be certain the transformer can handle the 0.6 amp heaters long term . I think 5814a also have 0.6 amp heaters but that may be two in series the data I have is not clear
    There doesn't appear to be any sign of anything being over loaded , temperature of amp and ps is normal and the lights and heaters on the 6c45 tubes are also no brighter than normal
    Sound wise there is no distortion at high volume , no background noise and the increase in gain is only a few percent
    Where my comfortable level was around 12 with the HE500 it is now 11:30
    I think you would be safe to try them out for an hour or two , you may not like the change
     
  7. groovyd
    but then again i may :wink:
     
  8. hawke000
    Hey Everyone,
     
    I am back and found that the tubes did need to be toasted to get a cleaner sound but it just "thickened" a little bit but never really opened up. I'm going to try some better tubes at some point. Strange thing is I went to this website to test frequency and everything seems to be playing back fine, low end is there everything is great. Perhaps it's just the media I'm listening to that's doing this? Is this a different test than what I should be doing?
     
    http://www.audiocheck.net/soundtests_headphones.php
     
    Best,
    hawke
     
    EDIT: Ran the sweeps through the headphones on that website and started to listen again and the bottom end came up? How is this possible? Am I going to have a stroke? It's day and night at the moment... Here's where it opened up.
     
    https://soundcloud.com/khamari-barnes/hotline-bling-drake
     
  9. Dogmatrix

    I have used that audio check a few times I think it is quite good
    What material are you listening to ? I think the soundcloud stuff is quite compressed
    You have a quality set up and it will be revealing of any shortcomings in what you feed it
     
  10. groovyd
    my adapters and tubes arrived today... any last minute issues regarding these tubes to be aware of before giving them a try?  still cool? nothing burned out?
     
  11. Dogmatrix

    No problems here in fact I don't think I will ever go back to 12au7 I think the 6350 makes a much better rectifier
    Can't wait to hear what you think of them
     
  12. JoeDoe
    Gentlemen! I've got a complete WA7 + tp set up en route and I've got a question just out of curiosity:

    Could someone water down an explanation of how rolling tubes in the power supply so drastically affects the sound coming from the amp itself? The fact that I can change sonic characteristics in this way is boggling my mind a bit...

    Btw, my rig is coming with EH tubes for the WA7 and I pulled the trigger on NOS Sylanias and GE mil spec 12au7s this weekend...
     
  13. Jeb Listens

    It's a damned good question.  I've always just assumed some kind of dark-arts / magic , but there might be some science involved too. 
     
    Hopefully some more knowledgeable Head-Fi'ers will arrive momentarily.  
     
    Anyhow congratulations on your new equipment.  When you're set-up, some pictures are always welcome... when you have a chance, of course :)
     
     
    What headphones will you be using ? 
     
  14. JoeDoe

    I'll definitely post once I'm rocking and rolling!

    I run three full size cans: RS1s, HE500s, and a pair of heavily-modified T50rps.
     
  15. Dogmatrix

    First up I am not an engineer so this is just what I could put together from scanning some heavy technical journals I didn't fully understand.
    The tube rectifier is a switch , it is on when the positive part of the ac is flowing but then because it will only allow electrons to flow from cathode to plate it is off when the ac goes negative .
    An ideal rectifier would switch off and on with a sharp almost square wave so when a number of these wave forms are combined at slightly different timing a flat dc current would result
    However tubes react differently to the switching task some switch on fast but off slow some visa versa so some tubes would make sharp bumps some soft bumps
    Rectifier circuits use things like chokes and capacitors to smooth out the bumps and produce a clean flat dc supply but it is never perfectly flat as a battery might produce
    Some part of the individual character of the tube comes through to the amp in the form of imperfections in the "shape" of the dc stream
    How this translates into stronger bass or wider sound stage etc , I have no idea but it most certainly does
     
    Jeb Listens likes this.
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