Yes, the audio is different from a tube. That was one reason Ham Radios kept tubes longer than they should have. Another reason of course was the transistors couldn’t hold up under the power needed to transmit 100 watts or better. Last I heard you could get tubes from China, you might tell your friend that.I don’t know how good they are.
thanks!
Here is a cheesy little video I made a few years back when I was selling some tube testers on ebay. You can see one of my first ham rigs if you look close, it’s an old 6v6 oscillator on a piece of varnished board...all of 3-4 watts CW on 80-40mtrs. Put the tiny plate and filament supply right onto the board, neon bulbs for tuneup indicators....silly thing still works fine....best contact was 2600 miles.
http://www.youtube.com/watch?v=BX9Y8LLB2Ns