? for any of you amp electronics geniuses (genii?)

[notCardio]

OK, so I've got a little Bugera V5 all-tube amp (don't laugh, I actually like it enough that I bought a second one).

Anyhoo, besides having a variable power output (5w, 1w, .1w), it also has a headphone out that cuts off the speaker output when you plug phones in.

I always thought that you couldn't do that with a tube amp, only ss. So, must there be a preamp circuit in there that's not tube, or what? How is this achieved (in simplistic terms)?

 

[ecc83]

OK, so I've got a little Bugera V5 all-tube amp (don't laugh, I actually like it enough that I bought a second one).

Anyhoo, besides having a variable power output (5w, 1w, .1w), it also has a headphone out that cuts off the speaker output when you plug phones in.

I always thought that you couldn't do that with a tube amp, only ss. So, must there be a preamp circuit in there that's not tube, or what? How is this achieved (in simplistic terms)?

Can't find a map (but must not complain. Peeps and glasshouses etc!) but I suspect the power attenuator circuit is always partially connected and so providing some load to the valve.
Then, for low power amps the "open circuit load" scenario isn't quite so bad, even under heavy drive you are not going to get the terrifying voltage spikes generated by a 50 or 100 watter.

Dave.