DA41 Push Pull Interesting design

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Paul Barker
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#1 DA41 Push Pull Interesting design

Post by Paul Barker »

Image

A number of differences to what we do today.

they have bridged the transformer with a cap which raises the HF performance. Scott someone back in the day did a It 6em7 design with a cheap Allied interstage transformer bridged with a cap, but it was SE. first time I have seen it anywhere else.

Notice the 1,000v power supply. Very small cap, Choke input.

Note the AC heating of the DA41.

Added 300ohm in line with the primary IT windings to bias the CF drivers.

AC heating and minimal PS filtering? What were they thinking of?

From the data it is a valve that either has to be used in Class B push pull or permanently in A2 SE. the curves look more like Pentode.

I think this circuit would be great fun to build.

Shame the lack of transformers would prevent it. Can only dream.

A mere 175 watts.
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#2

Post by ed »

this one?


there are quite a few interesting circuits in those old valve data books. I bought one of those CDs of old data books a few years back and I havn't seen a circuit on the net that can't be found in them....Thoroughly recommend buying one(the CD) if you see one advertised....about £5 for just about every data sheet ever published....
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pre65
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#3

Post by pre65 »

Very similar to TZ40 ?
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#4

Post by Cressy Snr »

I have a pair of NOS Tungsram OT100/8005 transmitter triodes.
Their curves look like pentodes. It takes 1500V to get them out of class A2,
so obviously they are meant to be run A2 all the time.

I'll never use them (Gawd knows why I bought them)
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#5

Post by Paul Barker »

Yes near enough.

Edit: meant for Phil.
Last edited by Paul Barker on Mon Apr 01, 2013 9:33 pm, edited 1 time in total.
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#6

Post by Paul Barker »

pre65 wrote:Very similar to TZ40 ?
Yes near enough.
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#7

Post by Paul Barker »

SteveTheShadow wrote:I have a pair of NOS Tungsram OT100/8005 transmitter triodes.
Their curves look like pentodes. It takes 1500V to get them out of class A2,
so obviously they are meant to be run A2 all the time.

I'll never use them (Gawd knows why I bought them)
Look quite interesting.
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#8

Post by Cressy Snr »

Yes, they were used in the Mcintosh MI 200 amp.

I suspect the 200 nomenclature stands for 200W :wink:
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#9 Re: DA41 Push Pull Interesting design

Post by Mike H »

That looks like a very old (e.g. pre WW2) design like the Bavaria-Hunt DHT amp I've got circuits of, that used DA30's.
Paul Barker wrote:AC heating and minimal PS filtering? What were they thinking of?
Given the period, what alternatives were there? Apart from batteries :D
 
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#10

Post by IslandPink »

Many similarities to the 'Amity' really. DA41 must have plenty of gain . Choke-loaded cathode-followers - nice !
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#11

Post by Mike H »

DA41 at National Valve Museum:

http://www.r-type.org/exhib/aaa1213.htm

"Sensibly equivalent to:- CV1076 - TZ40 - VT76"
 
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