• 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.

Air gapping transformers

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#21
db! said:
The enamel wire I am using is rated for 3500V; I don't think I'll be going that high just yet. As for the tubes, I am experimenting with a large variety of tubes. Some of the tubes I plan on using are GK-71, 211/854, 833A, Eimac 4-xxxA series and various other russian transmitter tubes. I am planning to "create" various primary impedances by using different impedance speakers on the secondary.

The B+ will be pretty high, I plan to have it in the 1.5 - 2.5kV range. Now, before someone starts harping on how dangerous this is and why I should abandon this project; I'll have you know that I've been in the HV scene for a long time. I've managed to build and operate tesla coils, jacob's ladders, marx generators, etc without getting zapped/killed. I'm pretty confident that I can handle 1.5 - 2.5 Kv
Click to expand...

Something to remember is that these are all high impedance tubes and will present some challenges to getting full audio bandwidth with a simple transformer geometry. It may require some trial and error. I concur that blowing the primary open is a relatively unlikely event and not worth trading off performance for.

It might end up that you can wire multiple secondaries for different impedances.

There is also parallel feed...

Another thing to remember is unless you're talking about some fairly large scale equipment, the HV generators you listed may not have the kind of energy capacity that a transmitter anode supply has. Calculate the storage capacity in Joules of the transmitter B+ filter caps plus the energy capacity of the AC line and compare it to e.g. the Marx generator. Not that these things can't kill you also, but I think there is likely an order of magnitude more energy in the typical 4-250A power supply than the typical HV experimenter's marx generator.

Not that you won't be safe, just that sometimes those of us giving advice feel responsible.

Cheers,

Michael
 
#22
Hi Michael, thanks for the suggestions. I didn't even know about parallel feed, I will look into this.

As for the transformer, I am not too worried about the sound quality, frequency response. I am only using it for "Proof of concept" of the amp before I dish out some big money for a properly made transformer.

As for power, I have a large plate transformer (1800V@1A) I picked up at a hamfest; I will probably be using with a variac to dial the voltage up.
 
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