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Thread: 300B Class A gorgeousness

  1. #1
    Join Date: Oct 2012

    Location: The Black Country

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    I'm Alan.

    Default 300B Class A gorgeousness

    I have a 300B amp in atm and to be frank it wasn't anything to write home about.
    Very well proportioned output transformers but lack lustre bass and a thickening of the sound as the wick was turned up.



    Investigation revealed it to be a zero feedback design, now IMHO that exposes all the weaknesses of the active devices, not an approach I am keen on.
    However with a small modification it transforms into a stellar performer. Gorgeous Class A clarity and with a really solid taut bass that you would hope for from generous output transformers.

    I've not heard a 300B amp before but this one now is world class, sensational sound.

    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  2. #2
    Join Date: Feb 2013

    Location: W Lothian

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    I'm Grant.

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    Quote Originally Posted by Firebottle View Post
    I have a 300B amp in atm and to be frank it wasn't anything to write home about.
    Very well proportioned output transformers but lack lustre bass and a thickening of the sound as the wick was turned up.



    Investigation revealed it to be a zero feedback design, now IMHO that exposes all the weaknesses of the active devices, not an approach I am keen on.
    However with a small modification it transforms into a stellar performer. Gorgeous Class A clarity and with a really solid taut bass that you would hope for from generous output transformers.

    I've not heard a 300B amp before but this one now is world class, sensational sound.

    one of these for sale somewhere...i saw it recently....???
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  3. #3
    Join Date: Mar 2017

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    I'm Edward.

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    Interesting

    I assume you implemented some feedback? By how much and can you do it such that it is switchable between none and whatever value you chose?



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  4. #4
    Join Date: Oct 2012

    Location: The Black Country

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    I'm Alan.

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    Yes Edward, only about 4dB and it could easily be made switchable.

  5. #5
    Join Date: Jan 2009

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    It’s an Audion - Silver Night perhaps? These are somewhat renowned for having reliability issues as I recall.
    Account Deleted

  6. #6
    Bigman80 Guest

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    Well done Al, glad the mods have worked out.

  7. #7
    Join Date: Oct 2012

    Location: The Black Country

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    I'm Alan.

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    Quote Originally Posted by YNWaN View Post
    It’s an Audion - Silver Night perhaps? These are somewhat renowned for having reliability issues as I recall.
    Thanks for that heads up Mark.
    I have noticed that two of the 3W rated anode loads are dissipating 2W.

  8. #8
    Join Date: Mar 2017

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    I'm ROGER.

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    Quote Originally Posted by YNWaN View Post
    It’s an Audion - Silver Night perhaps? These are somewhat renowned for having reliability issues as I recall.
    The early Audions did have a few issues but the model here and later models were fine, and I think something of a bargain secondhand.

  9. #9
    Join Date: Feb 2008

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    I'm NotTakingLifeTooSeriouslyTheseDays.

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    Tend to agree with you on the feedback Alan,
    All this purist stuff about zero feedback is as you say; often deteremental to the over-all performance that could be gained by using just what's needed, nothing more and certainly nothing less!
    Feed back, when used correctly ie; not as a sticking plaster, but as a tool to make a good circuit great, is IMHO a no brainer, some of my earliar amps were/are fitted with adjustable feedback controls.
    Quote Originally Posted by Firebottle View Post
    I have a 300B amp in atm and to be frank it wasn't anything to write home about.
    Very well proportioned output transformers but lack lustre bass and a thickening of the sound as the wick was turned up.



    Investigation revealed it to be a zero feedback design, now IMHO that exposes all the weaknesses of the active devices, not an approach I am keen on.
    However with a small modification it transforms into a stellar performer. Gorgeous Class A clarity and with a really solid taut bass that you would hope for from generous output transformers.

    I've not heard a 300B amp before but this one now is world class, sensational sound.

    "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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  10. #10
    Join Date: Oct 2016

    Location: London

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    I'm David.

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    For me, you've missed the most vital piece of information which is: what speakers are you using to test this amp? To my ears, and many of my clients, 300b, 845, and 805 amps sound best with no feedback, in the right circuit and driving sensitive, easy load speakers. Of course, difficult loads or insensitive speakers can cause the whole sound to collapse, which is where feedback comes to the rescue.

    I've built amps with variable and switchable feedback but, again, with the right speakers and amp circuit the sound always closes up when feedback is switched or dialled in.

    Don't get me wrong: I'm not anti feedback and happily run Radfords, Lebens and others to drive my Tannoy Canterburys. It's just that the valves above in the right circuits sound best driving the right type of speakers with no feedback

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