The VT40 has an output jack for an extension speaker, which when plugged-in, automatically switches the ohm setting on the output X-former,, whereas the VT22 has a three position switch so that you select the setting that you want. It's no big deal,, the VT22/V4 was set-up that way because they were designed to be able to use multiple cabs, usually for bass. The VT22/V4 uses four 7027s, and was rated ~100 watts, while the VT40 uses two of the same tubes, and was rated at ~60 watts,, IIRC, they cranked the B+ on the VT40s up ~25>30 volts above the VT22s,, they push the tubes a bit harder to get the max 30 watt rating from a 7027. Be a bit careful with tubes, a lot of tubes don't like the voltage that VT40s run at, and have shorter lifespans,, the JJ 7027s are a favorite for new tubes, they're tough and easily handle the B+ in a VT40. You'll love the amp, you'll find the controls nothing like most "typical" amps,, the B/M/T are active,, they both boost and cut,, the midrange rocker switch sets the broad range, and the knob controls a real tube driven inductor circuit,, it's pure magic. Have fun.