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Thread: Class A power amplifiers

  1. #21
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    I wish I understood even 10% of what you've just written, Mark - reminds me of a post I made long, long ago...





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    Yeah, I remember it well Alex
    Bests, Mark



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  3. #23
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    Yes fully agree but in my case its about 5%
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  4. #24
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    It should actually be written into the Ethos that a) you're not allowed to leave - ever - and b) that you will be immortal - refer to point a) ! Seriously, I do love reading your authoritative posts - even when I don't fully understand them!
    Alex

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  5. #25
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    Alex, I got into electronics simply because I wanted to make certain parts of my system that I could never afford to buy That landed me a good few jobs by the way as well...

    This is kind of a dream, but one that can be brought to fruition. No sensible person would ever run 3 x Krell KSA 250s or FPB 200s in an active system as they'd need serious air conditioning & a seriously deep wallet to pay for it & the electricity bills

    Having done similar previously (the twin amp low dissipation class A thing) I know it's possible, now I'm just going to push it to it's (present technology) limits & given time I'll get there

    A 400W RMS class A amp would probably dissipate 1000W of heat allowing for component losses. I aim to get that down to less than 150W at full power & about 115W idling. Still going to warm the room up in summer given six amps but not like 6KW would


    As a brief explaination the errors that the class D amp generate should be taken care of by the low voltage class A output stage. The class A output stage is driven by a totally different voltage amplifier which would be similar to a standard class A amp of decent design. If the class D amp makes a mess of things, there is enough voltage & more than enough current in the A stage to correct for the mess.

    I'm no good at explaining this in simple terms in all honesty It's more complicated than a standard amp by quite a bit so how do I expect otherwise

    Watch the first one come together, it's all in my head
    Bests, Mark



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  6. #26
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    Quote Originally Posted by Reid Malenfant View Post
    Alex, I got into electronics simply because I wanted to make certain parts of my system that I could never afford to buy That landed me a good few jobs by the way as well...

    This is kind of a dream, but one that can be brought to fruition. No sensible person would ever run 3 x Krell KSA 250s or FPB 200s in an active system as they'd need serious air conditioning & a seriously deep wallet to pay for it & the electricity bills

    Having done similar previously (the twin amp low dissipation class A thing) I know it's possible, now I'm just going to push it to it's (present technology) limits & given time I'll get there

    A 400W RMS class A amp would probably dissipate 1000W of heat allowing for component losses. I aim to get that down to less than 150W at full power & about 115W idling. Still going to warm the room up in summer given six amps but not like 6KW would


    As a brief explaination the errors that the class D amp generate should be taken care of by the low voltage class A output stage. The class A output stage is driven by a totally different voltage amplifier which would be similar to a standard class A amp of decent design. If the class D amp makes a mess of things, there is enough voltage & more than enough current in the A stage to correct for the mess.

    I'm no good at explaining this in simple terms in all honesty It's more complicated than a standard amp by quite a bit so how do I expect otherwise

    Watch the first one come together, it's all in my head



    Theory then mark?




    jon

  7. #27
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    Anyone know how the XTZ AP100 power amp sounds running in class 'A' mode? Is this a good amp for relatively little money (£560)?


    Love to hear any views/thoughts/experience please, thanks.
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  8. #28
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    Talk to Frank Seriously Frank (Effem) has an XTZ, apparently it sounds very nice indeed even if it is sliding bias class A

    E2A:- Frank might have the integrated, not a lot of difference though...
    Bests, Mark



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  9. #29
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    I imagine nice some nice reviews and heard a lot of their other stuff to suspect it be a good one
    Loves anything from Pain of Salvation to Jeff Buckley to Django to Sarasate to Surinder Sandhu to Shawn Lane to Nick Drake to Rush to Beth Hart to Kate Bush to Rodrigo Y Gabriela to The Hellecasters to Dark Sanctury to Ben Harper to Karicus to Dream Theater to Zero Hour to Al DiMeola to Larry Carlton to Derek Trucks to Govt Mule to?

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  10. #30
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    Quote Originally Posted by jon1 View Post
    Theory then mark?

    jon


    Just boring number crunching...

    For a 400W RMS class A amp into 4 ohms...

    4 ohm x 400W = 1600. Square root of 1600 = 40. That is the RMS voltage you need to swing. Now you need to calculate the current needed on a push pull output stage. 40 x 1.414 = 56.56, that incidentally is the peak voltage you need to swing into the speaker, pk - pk would be double that

    56.56/4 = 14.14 Amps, that is the peak current into a 4 ohm load when 56.56V is accross it. Now as you have a push pull output stage you can divide the current by 2 = 7.07 Amps.

    7.07 Amps x 56.56 Volts x 2 as there are two rails = 800W. As I say, allowing for component losses somewhere near on 1000W will be dissipated for a 400W class A power amp (per channel)..
    Bests, Mark



    "We must believe in free will. We have no choice" Isaac Bashevis Singer

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