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Thread: Modulator or AF PA output transformers...bigguns...

  1. 03-20-2013, 06:50 PM #1
    N8YX
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    Modulator or AF PA output transformers...bigguns...

    I'm thinking about revisiting a design I played around with years ago: 2x 4X150A or 4CX250B in push-pull, running either Class A or AB as an audio amplifier.

    So I'm going to need an output transformer which is rated for 3KV+ breakdown on its primary winding, and I'm probably going to run 1800-2100v on the anodes of the tubes. Screen grid voltage and balance will be done dynamically by a separate circuit so I won't need a tap for those.

    Secondary impedances of 4/8/16 ohms.

    Total power output of the envisioned contraption will be on the order of 2KW (1KW each pair/channel); by going with fewer tubes and higher plate impedance I ought to be able to keep the THD figures pretty low.

    Where can I source such a beast? Hammond makes them rated to 300w and 1KV, but this setup requires a stouter configuration.
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  2. 03-20-2013, 06:58 PM #2
    NQ6U
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    Man, no clue. It's hard enough finding a modulation transformer of any sort these days, let alone one with those sorts of specs.
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  3. 03-21-2013, 05:50 AM #3
    mw0uzo
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    Get it custom wound. It will be worth the extra and, I have found, that the extra charge for a custom job isn't massive.
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  4. 03-21-2013, 06:22 AM #4
    N2CHX
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    What the heck are you going to do with all that audio power?
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  5. 03-21-2013, 07:44 AM #5
    KC2UGV
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    Quote Originally Posted by KKM View Post
    What the heck are you going to do with all that audio power?
    That's what has me confused...

    Generally, in the audio world, if you are looking for a component that doesn't exist/very hard to find; your design needs to be re-worked. And, that's the assumption I'm having here. Seems like an awful lot of power for audio.
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  6. 03-21-2013, 02:56 PM #6
    N8YX
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    Max Headroom:

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  7. 03-21-2013, 03:49 PM #7
    WØTKX
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    Jeebus, are your speakers inefficient? You gonna blow up your MagnaPlanars?

    When I was a kid in the prehistoric tube days, I hooked up two identical transformers to get about 450 VAC. Somebody gave me some EL34's to play with...
    Last edited by WØTKX; 03-21-2013 at 04:19 PM.
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  8. 03-21-2013, 04:11 PM #8
    K7SGJ
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    Quote Originally Posted by N8YX View Post
    I'm thinking about revisiting a design I played around with years ago: 2x 4X150A or 4CX250B in push-pull, running either Class A or AB as an audio amplifier.

    So I'm going to need an output transformer which is rated for 3KV+ breakdown on its primary winding, and I'm probably going to run 1800-2100v on the anodes of the tubes. Screen grid voltage and balance will be done dynamically by a separate circuit so I won't need a tap for those.

    Secondary impedances of 4/8/16 ohms.

    Total power output of the envisioned contraption will be on the order of 2KW (1KW each pair/channel); by going with fewer tubes and higher plate impedance I ought to be able to keep the THD figures pretty low.

    Where can I source such a beast? Hammond makes them rated to 300w and 1KV, but this setup requires a stouter configuration.
    Maybe Marv can help......


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  9. 03-21-2013, 04:20 PM #9
    WØTKX
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    LOL!

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