[Amps] GDT across a load cap in a tube amp

Geert Jan de Groot pe1hzg at ymbk.nl
Mon Jul 7 19:22:28 EDT 2025


> Could a GDT (gas discharge tube) be wired in parallel with the C2 load cap
> on a GG tube amp....... to protect the C2 load cap? Same deal with the C1
> tune cap.
> On paper, when the GDT fails...they fail shorted. You can get em in any
> break down voltage you want..... up to 8 kv....(which might not be high
> enough for some C1 caps, depending on peak V across the C1 tune cap).
> Right now, I'm using HB adjustable spark gaps. When they arc, they just
> arc, they don't weld shut.

There's a substantial amount of kinetic energy when a HV power supply 
like this "shorts".

Keep in mind a regular glass fuse changes into a plasma when it goes. 
And flashovers have been reported to bend electrodes of tubes.

I'd like to read from others but I worry.

Geert Jan



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