• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Da 42 Triode

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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.
 
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.
 
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.
 
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

GECcv2394~da42.jpg


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

aaj0034a.jpg
 
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!
 
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 redirect

Lovely looking valve the DA42

GECcv2394~da42.jpg


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

aaj0034a.jpg

IF you can find and afford the DA100!
 
I have made two mono-blocks using the DA 42.
Sound great; so long as you use well damped speakers like JBL 2220 or Altec 515's. many modern speakers would be too boomy.{ Hard to get high damping factor}
Max voltage is about 500 volts. I used the Grampian record cutting amplifier. The Grampian uses 811A's with 600 volts but the DA42 only has 40 watts plate dissipation so lower voltage.
Phil
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.