Aux input on tube radio - use iso transformer?

[disorder]

I'd like to install an aux input on my RCA tube radio. I'm going to use a switch and jack installed at the grid of the amplifier stage after the last tuner section and volume pot. I'm wondering if I should use an isolation transformer between the grid and aux jack or could I get away with just running it into a very large value (and large voltage rating) coupling capacitor ? Is one preferable over the other?

[Mick Bailey]

Can you post a schematic?

[Steve Conner]

If your radio is a transformerless "widowmaker" then you'll certainly need the isolation transformer.

[disorder]

No schematic just asking more on a theoretical level... both devices (the cap or iso transformer) would be used to block potential DC from making its way to the AUX device plugged in.. are there any clear advantage over one or the other?

I don't believe its a widowmaker, looks like it has a mains-transformer but I have to double check. IF it is a widowmaker I would need to isolate the line voltage from the rest of the circuit as well correct? So that when I ground the AUX jack and accidently reverse the polarity of the plug I don't get zappered?

[Steve Conner]

Yes, the isolation transformer has a clear advantage because it will work but the capacitor won't. Capacitors only block DC, they let AC straight through, but an isolation transformer can block everything.