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Old 14th October 2008, 04:54 AM   #1
exurbia is offline exurbia  Australia
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Question Da 42 Triode

The burning question,

Has anyone tried or succeeded in using this Triode for Audio.
The horribly low 3.0 mav suggests class B with a powerful driver and interstage tranny.
The dissipation is 40 W and max anode voltage is a rather hot 1000 V.

Any takers ?

If you would like to build with them, i have quite a few of them sitting in my cupboard.
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Old 14th October 2008, 12:35 PM   #2
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If my memory is correct this book should have some designs using the Da42.

http://www.audioxpress.com/bksprods/products/bkaa31.htm
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Old 14th October 2008, 05:12 PM   #3
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You can find this GEC design for a 175 watt Class B push-pull design in the spec sheet for the DA42 on Frank's Electron Tube Pages, but it involves EL84s driving KT66s driving a transformer which drives the DA42s, with a 1000V power supply (which involved a valve-based bridge rectifier in those days), so the best of luck! DA42s were designed for Class B use for this sort of PA duty. I wonder if they used one to call the employees back to work t the Brook Green M-O.V factory.
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Old 15th October 2008, 07:04 PM   #4
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IIRC the book/article referred to by astouffer is available at Pete Millets site.

/Olof
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Old 15th October 2008, 09:35 PM   #5
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But it's quicker to go to www.tubedata.org and read the "amplifier supplement" in the second, longer entry for the DA42. It's essentially the same article as in the book (which I have).
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Old 16th October 2008, 12:25 AM   #6
exurbia is offline exurbia  Australia
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I built the DA42 design from GEC/MOV, it was an absolute monster, and it sounded very good. The trafos from it are sitting in the shelves waiting for something. I also built a PSE version that wasn't too brilliant. I got out twice the driving power

it is not an easy one to use, zero bias class b does suit it.
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Old 16th October 2008, 10:10 PM   #7
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WOW!
This must have been quite something!
Two designs using the DA42 are detailed in the GEC book "An Approach to Audio frequency Amplifier Design"

The 175W amp of which Barreter talks is just a baby, there is also a 200W amp utilising an HT rail of 1250v for the DA42s!!

As previousl;y pointed out, these designs are available here www.pmillett.com/technical_books_online.htm

Lovely looking valve the DA42

Click the image to open in full size.

But the DA42 is for wimps; real men use the DA100!

Click the image to open in full size.
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Old 16th October 2008, 10:44 PM   #8
exurbia is offline exurbia  Australia
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There are 2 DA 100's sitting in my cupboard, they look nice, that's about it, as both have got open filaments.
oh well.
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Old 16th October 2008, 10:57 PM   #9
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Realistic men would use the DA42 as you can still buy them at reasonable prices (a quartet of them went for 32 on eBay today) whereas the cheapest DA100 I could find on the net was 467 for a used one (Billington), and 588 for new ones from Colomor.
But if you want to thump your chest and be a "real" man you use the 833A - 3000 volts, 10 amp heaters, bright red anodes, etc. You will find examples in the backfiles here.
Personally I have a penchant for the 845, much nicer curves all round!
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