I would also like to know whether an AM radio that uses vacuum tubes instead of transistors, can have a better reception quality?
Depends on what you mean by "reception quality", and what the solid state design is. A vacuum tube oscillator will produce less noise than a phase locked loop (PLL) design. The PLL has the advantage of being able to produce a wide choice of frequencies, useful for fixed channel services such as CB or aviation communications. The drawback is that the PLL is a servo mechanism, and like all servos, it goes out of control once the error signal disappears. The PLL will therefore generate small frequency variations around a center frequency. This incidental FM generates sidebands (phase noise) that can mix noise into the receiver.
(PLL phase noise is
your problem in a receiver. If the PLL is the master oscillator of a transmitter, it becomes
everyone's problem. A max legal ham rig can elevate the noise floor across an entire band for miles around. The phase noise may amount to 1.0uW, and that doesn't seem like much, yet a run-of-the-mill comm reciever can detect signals down to 10^-15W.)
A vacuum tube oscillator operates in a self regulating, gain saturated mode that pretty much eliminates incidental AM that plagues BJT oscillators that have to operate in Class A. If your VT oscillator has a substantial, preferably with brass plates, tuning capacitor that readily radiates heat, and an air coil, you can drive it hard enough to eliminate phase noise as well. You'll have a quieter receiver. Of course, there are work arounds for solid state that overcome these limitations.
AM reception also depends on the linearity of the IF stage(s). THD introduced at IF frequencies becomes audio THD after demodulation. Here, VTs beat transistors in linearity, and produce less THD.
If you're referring to audio quality, again, that depends. For comm receivers audio quality isn't a consideration since modes such as SSB produce horrid audio quality, but that's OK so long as the received signal is intelligible. High fidelity AM on the ham bands isn't needed nor is it legal. Thus, most comm receivers, whether hollow state or solid state, have rudimentary audio subsystems that won't give superior sonic performance. Receivers that are designed with sonic performance as a design criterion are usually "tuners" that are intended to be connected to an external amp.