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  1. #151
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    And I agree, however; when we look at how each [valve and solid state designs] deals with the constant impedance fluctuations, over frequency response; a valve amp will at least try to maintan the correct power at its output.
    Quote Originally Posted by RothwellAudio View Post
    "Flat response" loudspeakers will only give you a flat response if driven from a constant voltage source.
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
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  2. #152
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    Quote Originally Posted by anthonyTD View Post
    I should also take this opertunety [while its fresh in my mind] to stress why when it comes to wide power bandwidth [where valve amps are concerned] a good quality output transformer, with a decent amount of iron is necessary!
    Unless you use and OTL amp which means you don't have any of the problems associated with big lumps of iron

  3. #153
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    Ahh, but then first of all; you are limited to the type of valve you can use in the output stage, due to the low impedance needed to drive a real world loudspeaker direct, unless multiple valves in parrale are used, and then you have all the negatives of matching said valves, and the type of circuit, and finally, the risk of directly connecting these high voltage devices [which often fail being run in this manner] to your precious loudspeakers! That's not to say though that OTL's cant be made to work, and perform exceptionaly well, they can, but for me, and in my honest opinion, the negatives out weigh the positives.
    Quote Originally Posted by Jimbo View Post
    Unless you use and OTL amp which means you don't have any of the problems associated with big lumps of iron
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    We Send our kids to school to be Educated, not Medicated!

  4. #154
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    Quote Originally Posted by anthonyTD View Post
    Ahh, but then first of all; you are limited to the type of valve you can use in the output stage, due to the low impedance needed to drive a real world loudspeaker direct, unless multiple valves in parrale are used, and then you have all the negatives of matching said valves, and the type of circuit, and finally, the risk of directly connecting these high voltage devices [which often fail being run in this manner] to your precious loudspeakers! That's not to say though that OTL's cant be made to work, and perform exceptionaly well, they can, but for me, and in my honest opinion, the negatives out weigh the positives.
    Unless you use MOSFETs in the output stage.?

  5. #155
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    Are we talking Hibrid designs James ? if so, that's a diffrent story.
    Quote Originally Posted by Jimbo View Post
    Unless you use MOSFETs in the output stage.?
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
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  6. #156
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    Quote Originally Posted by anthonyTD View Post
    Are we talking Hibrid designs James ? if so, that's a diffrent story.
    Yes Anthony, I am talking of the Croft Series 7 power amplifier.

  7. #157
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    Ok,
    Hibrid designs can work very well, and combining both topologies, you can overcome some of the short comings in each,[you just have to choose what those are, and what you want to achieve] in my hibrid design I chose to go solid state front end, valve output, where as Glenn, and others decided on the reverse, either way; both can be very rewarding.
    Quote Originally Posted by Jimbo View Post
    Yes Anthony, I am talking of the Croft Series 7 power amplifier.
    "Today scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
    Nikola Tesla



    We Send our kids to school to be Educated, not Medicated!

  8. #158
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    All this of course ably shows that there's no such thing as the 'perfect amplifier', so as with anything else in audio, all you can do is choose your compromises!

    On the subject of valves, however, I will say (as experience has shown it) that hybrid and/or OTL designs, certainly those I've heard, no matter how well designed, don't sound like the best valve amps should, which is why, as much as I acknowledge what they're capable of doing well, I haven't gone down that road.

    It's an old saying in audio, but quite simply, there's no 'free lunch', when attempting to build an amplifier that on paper is seemingly devoid of any of the vices of either valve or solid-state technology, or is touted as being the 'best of both worlds' (as often hybrids designs are), because in reality that just doesn't exist. You're likelier to end up with a 'master of none'...

    That's because as soon as you address what's worst about valves or transistors, by attempting to 'fix' it, and in turn trying to make it do what the opposite is better at, you automatically compromise (in some way) on what the technology itself [valve or transistor] is inherently BEST at! Hence, no 'free lunch'

    Marco.
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  9. #159
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    Ah I see Anthony beat me to it!

    Marco.
    http://www.thestainedglasscompany.com

    "A man is a success if he gets up in the morning and gets to bed at night, and in between he does what he wants to do" -- Milan Kundera.

    BE HAPPY EVERYDAY!

  10. #160
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    Quote Originally Posted by anthonyTD View Post
    And I agree, however; when we look at how each [valve and solid state designs] deals with the constant impedance fluctuations, over frequency response; a valve amp will at least try to maintan the correct power at its output.
    Yes, that's the point I've tried to make several times - loudspeakers require a constant voltage drive, not constant power. Trying to maintain a constant power dissipation over the frequency spectrum results in an uneven frequency response which follows the impedance curve.

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