• 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.

Smoothing choke physical size

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#22
The varnish used for motors and transformers etc. hardens by applying heat.
Where to get hold of such varnish I have no idea.
Another method could be to use a different kind of varnish and brush it on for every layer as you wind.
 
#24
For chokes, I find that the core mechanical sturdiness is more important than the windings. For EI lams, you could varnish them during assembly, but you'll also have to clamp/glue the airgap region.
For C-cores, my more quietest performance comes after epoxy gluing the cores together.
 
#25
Hello,
I am using several Lundahl chokes in choke input. Some up to 2A current. I never had a noisy one.
I have had several made to measure chokes which i bought locally in the the Netherlands a few decades ago which were also quiet.
Of course if you are going to use them in a tube power amp there will be a considerable voltage across them and i expect some low grade chokes wont like that because they are made as cheap as possible.
If it is made with the right skills they should not vibrate!
Better buy the right choke once you know the current you need.
Greetings, Eduard
 
#26
Buy a choke that exceeds you required current rating by 25% or more to avoid mechanical vibration and heat. Chokes get noisier the closer to their rating most of the time. I’ve purchased some well made chokes from Aliexpress that were actually well made and priced right. The shipping was the killer!
 
#31
Air gapping is done to reduce overall permeability and that depends on the application. You don't necessarily air gap something, because it's called a power filter choke. An ungapped choke can exist too, if you are satisfied with its performance within the chosen circuit.
 
#32
eduard said:
Hello,
Just like output transformers otherwise they cannot handle dc.
Greetings Eduard
Click to expand...
Well, they can handle DC up until the core is saturated, which probably will leave very little room for signal current.
Introducing an air gap enables the transformer or choke to handle more DC without saturating, at the expense of reduced overall inductance.
 
#35
That's more like a conformal coating for PCBs.

The links I posted were for high temperature varnishes for electric motors and transformers, as used by motor re-winders in industrial applications.

Sometimes it's good to know how the "Professionals" do it.
 
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