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Author Topic: Valiant as driver  (Read 2967 times)
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Barrie
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« on: April 15, 2009, 08:58:19 PM »

I'm in the process of rebuilding my push-pull 450TL, modulated by 450THs.  I'm also attempting to aquire parts for a driver stage.  The parts are not coming easily.

During the 1990s, when I last had the 450TL/450TH running, I used a 32V3 as a driver for both audio and RF.

I no longer own the 32V3, but I do have a Valiant.  The Valiant would certainly provide sufficient RF drive.  However, I'm worried about the audio.  In my manual, it states that the Valiant will provide 100 watts of audio, which should be plenty.  But it's at 2000 ohms.

How would I match that to the grids of the 450THs?  Or, could I just go straight into the grids with the 2000 ohms?

Thank you & 73,
Barrie
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« Reply #1 on: April 17, 2009, 11:40:09 AM »

Hi Barrie,

    The Valiant audio section is not going to make a very good quality driver for a pair of large triodes in class B. It will not deal well with the modulator grid's plunging impedance near peaks. A tetrode driver like the Valiant's would need an inverse feedback loop around it.

Decent medium power surplus solid state audio amplifiers are a dime a dozen these days. Hammond and Ebay have transformers that can match these to your modulator grids. That's how I'd do it. You might want to stick with the Valiant's innards for some reason. I understand. Just get ready for modification to the circuit to make it work correctly.

Get an old Orr Radio Handbook A.K.A. the west Coast Handbook. The modulator section has a lot of good info which can save headaches.
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