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What happened to call AB Push Pull Outputs

Discussion in 'Amps and Cabs [BG]' started by bweyland, Aug 10, 2012.

  1. bweyland


    Apr 6, 2012
    OK looks like the last thread I tried didn't make it. I see that the preamps are made of 12AX7 tubes in a Class A configuration. The outputs all see to be made from FETS in a class D configuration. What happened to the output being a Class AB push pull tube configuration. Don't they make them anymore??? Can you buy a kit and assemble it your self with matched tubes. What gives. That should be Class not c all in the subject line.
  2. Amplifiers are available in Class A, AB, D, H, T and a bunch of others. If you want a class AB tube amp they are there. Kits can be found but you would need to have some electronic skill to assemble them properly.
  3. jlepre


    Nov 12, 2007
    Parsippany, NJ
    *Eyes glazing over*
  4. bweyland


    Apr 6, 2012
    I have worked in the electronics field for 30 years and have a EE degree. I was Mil Spec certifies at a naval torpedo station I think I can handle it but I am having a real problem finding a kit with at least 500 watts output. I would really like a 1000 watts but 2 500s would work. I think the highest I have seen so far is 100 watts. Guess they don't make them tubes anymore huh? The Class D with 2 FETS is very closs to the AB. I haven't hear of H and T must of come out since I was in school. I will check them out.
  5. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
  6. Hapa


    Apr 21, 2011
    Tustin, CA
    Huh? Tubes for 500 or 1000 watts... it has been done but will never be done for retail for safety reasons and class D close to class AB? You say you are an engineer?

    http://en.wikipedia.org/wiki/Electronic_amplifier for what you must have slept through.

    http://www.chambonino.com/construct/const13.html for what you must have been dreaming about.

    Plenty of class AB amps being made, still the only choice for the touring guys. Retail consumers are class D as its generally cheaper, lighter, and sounds good enough.
  7. Most tube amps will top out at around 300 watts. There are a few that will do in the neighborhood of 400 watts. I have also seen some DIY fellas that rolled their own power sections using transmitter tubes to get 500+ watts.
    With any of these the cost and performance limiting factor is the output transformer. There are not a lot of tube output transformers for amps over 100watts. You are basically looking at a 2nd hand ampeg or mesa transformer or a custom one.
  8. seamonkey


    Aug 6, 2004

    As far as Solid State Power amplifiers go.

    Class-AB and Class-D are sonically the same. The gain, power, bandwidth, ... distortion are all well below human hearing.

    If compare amps in the correct manner, you can not hear a difference.

    But Class-AB and Class-D are different topologies and designs. All the major power amp makers are only doing new designs in Class-D. Lower parts count, less heat, higher efficiency, lower weight, progress.

    You can get a 500w RMS Class-D power amp for two hundred bucks, and it will weight 7 lbs. No need for DIY in the amp part. Spend your time on the pre-amp and signal processing.
  9. Interceptor


    Mar 29, 2005
    Madison, WI

    I haven't seen an audio amplifier of much bigger than the venerable SVT produced ever since AM transmitter manufacturers abandonded high level modulation.

    Start by looking at the transformers that a reputable firm like Hammond or Electra-Print offer. Anything much over 250 Watts is going to need one-off custom transformers which alone will be quite expensive and heavy.
  10. father of fires

    father of fires Commercial User

    Nov 29, 2006
    Chief of Medicine at Damnation Audio
    I'm confused...Are you asking why they don't make the amp class that controls the majority of the MI amp industry???
  11. TomA1234


    Jul 27, 2009
    Fareham, England
  12. bweyland


    Apr 6, 2012
    No I understand why they don't make large class AB tube power amps. Transformers are large and bulky, parts are expensive, and there are numerous other problems with high voltage. I was just wondering what was up when all I could find was a 200 watt kit. But I do understand being and electronics engineer. LOL A FET class D is good enough.

    Thanks for all your input we can get rid of this thread now as far as I am concerned although it could bring up some funnies.

  13. craig.p


    Sep 28, 2008
    New Hampshire
    They still make them. Fender makes a 100W and a 300W. Traynor and Peavey make ones that run somewhere around 200W. Carvin makes a 100W guitar amp that I've seen do competent bass duty, though they recently moved that amp from 6L6 to EL outputs, so it's no longer the same beast. Greenamps -- not sure if they're still around. The web site is unique. Anyway, they're still out there.
  14. this may as well be titled troll bait. I am not saying it is or isn't true, but you can't step in anything more contentious than saying a calss D power amp with tube pre sounds "just the same" as a class AB tube power amp.
  15. Hapa


    Apr 21, 2011
    Tustin, CA
    Fender made a 400 watt amp called the power station.


    it was a piece of poo. Making an tube amp for sale to the public requires safety testing that is very expensive and time consuming. That and being able to pull enough volts out of your wall becomes a serious point of concern over 400 watts with transformers like that. Any accidental mishap with the electronics would be deadly not just a healthy ZAP. Then yea the actual cost of parts, the weight, and heat...that 1000w guy was saying that it doubles as a toaster, looking and the amp I do not think he was kidding. Imagine that amp is a rehearsal room for 4+ hours.
  16. wcriley


    Apr 5, 2010
    Western PA
    He said no such thing.
    Go back and read the first line of the post you quoted:

    "As far as Solid State Power amplifiers go."
  17. WingKL


    May 12, 2007
    There's no such thing as a free lunch. If you compare PA amps designed for low distortion only in it's linear range of operation, then SS class AB may sound the same as class D. All bets are off when you start considering overload characteristics. I'm sure no bass player ever drives their amps into non-linear operation (distortion) even unintentionally.:rollno:
  18. Roscoe East

    Roscoe East

    Aug 22, 2011
  19. 1958Bassman


    Oct 20, 2007
    Class H has been around since the late '70s- IIRC, Hitachi was one of the first to use it in consumer electroncs and it's basically a separate set of outputs in parallel with the normal ones, to be used when the demand requires it, it order to minimize distortion.


    Class AB isn't as efficient and that means bigger iron. People don't seem to want to lug heavy gear around and manufacturers don't want to pay to have heavy items shipped from foreign countries, or over the road in the US.

    For 1000W, I would probably consider a good pro-style amp that's bridgeable.

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