little big amp: the little big amp

It all started with this huge triode!
The 100TH made by Eimac for radio transmitters in the 1940ties
Could run at 3KV @ 225mA!!
Found it in a military dump shop in Holland.
Yes.
It could be used for a Single Ended Triode amplifier.
With lots of power....
For a SE that is...
Well over 25Watts!!!!
With one tube!!

Had to build a serious power supply.

1200V with 250mA
Drove it first with a high voltage FET

That worked.
But of course you can't drive this huge glass and metal construction, which weighs almost a kilo, with a bit of plastic....

This thing needs some smaller tube to drive it.
A 6EM7 would do.

Tubes for TV's....
Dissimilar triode.
Strange, 2 different triodes in 1 bulb.
1 makes a lot of voltage, the other a lot of current.

Wim drew the diagram.

Tried it all out.
Still alive.
There is a thousand volt on the anode!!
And that with 100mA.
So it needs 100Watts just to exist.
No sound yet.
Nothing.

And the heating...........
5V at almost 10 amps... that's 50Watts too.
That's why it's red.
Red hot.

Still no sound.
150W per channel.
Just to run it.
I only will use it in the winters

Had to find some serious transformers...
And found them.
Ebay is great.
Hooked up some loud speakers to one side and Norah Jones to the other.

Amazing!!!!
SE, now I knew.
Everything they write about it is just right,

Then I thought:
If that little tube is so great at driving the huge one....
Could it also drive an output transformer?
Yes.

Wim?

In stereo....
13 components per channel.
And nothing in the signal path.

Build it all on a plank to see what would happen with Norah Jones.

More output transformers.
A lot smaller this time...
These ones are for 300b's (later)

And a semiconductor rectifier.
That could not be right.

More transformers and a nice tube rectifier.
Now we're talking!
Norah liked it too.
1 Watt per channel.
I calculated and measured and modified.
Nothing doing.
1 Watt.
That's it.

Build some speakers....

2x 16ohm Electro Voice in parallel with a Fostex on top.
Open baffle

With a simple 6dB filter

So that's close to a square metre.
Need some surface to have bass with 1 Watt.

The speakers liked the amplifier
So did Norah.

A box.
Daniel.
Is a wizard with wood.
I drew it up and Daniel....