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nhuwar 12th January 2007 04:43 PM

more output transformer questions
Is there a problem that anuyone knows of about using a push pull ot on a single ended amp.

The only reason im asking is the tube im using has a high plate resistance and only the pp trans go high enough.
Also is hammond a good output transformer & what other brands are out there.

Thanks Nick

cerrem 12th January 2007 05:33 PM

I would not go that route, using a P-P OPT for SE application is opening a can of worms.....
What tube are you using ???
WHat operating conditions are you operating this tube at???
What performance are you expecting????
Once this info is known, then some of the members of this forum can chime in on suitable transformer options...


nhuwar 12th January 2007 06:26 PM

The tube is a 3-500zg runnig in ab1

SY 12th January 2007 06:40 PM

How are you going to run AB1 in single-ended???

In any event, p-p transformers are generally not suitable for SE service except at VERY low powers. The absence of a gap means that the DC will saturate the core.

nhuwar 12th January 2007 06:47 PM

kinda didnt give enough info sorry. the tube is a zero bias triode.

I want to run it at 3000vdc that gives me a max signal plate current of around 350ma requires 12.5 watts rms drive z= 4300 ohms.
Hope to get a useful 200 to 250 clean watts rms more would be better.
If I have to though I can lower the B+ to 2kvdc to lower the z


nhuwar 12th January 2007 06:48 PM

ab2 I typed the wrong thing earlier

SY 12th January 2007 07:01 PM

OK, then, how are you going to run AB2 single-ended???

nhuwar 12th January 2007 07:06 PM

ok so I'm assuming you cant run ab1 or to unless it's pp with 2 tube.
Forgive my ignorence I'm use to rf and class c .
The spec sheet on the tube refernce to class ab2 for af thats what i'm going by.
Would this be class a

SY 12th January 2007 07:23 PM

Well, you'd have to run class A because this isn't a tuned circuit. That means your efficiency is going to be pretty terrible (25% on a good day, wind at your back, going downhill). And a SE transformer for that current and voltage will cost a fortune, not to mention being too heavy to lift unassisted.

As you've noted, tubes in this class tend to need very high anode loads, which means that the transformers are even more difficult to make without severe bandwidth restrictions.

All of this is a long way of saying:

1. Don't use SE for high powers.
2. Don't use power tubes that require high impedances.

nhuwar 12th January 2007 08:23 PM

so pp is the way to go I could run it at 1500vdc in push pull and an output transformer isnt a problem or is this a bad idea?

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