Does remote control degrade the sound of tube preamps?

There is nothing that makes remote controlled volume control inferior in sound quality.  If it is implemented with a motorized potentiometer, the quality is entirely dependent on the quality of the potentiometer, not on the motor whose only job is to twist the shaft just as your hand would also do.  Even if your volume control is a rotary step attenuator, it is possible to physically move the dial under motor control (Ayre does this).  Many very good attenuators are ladder step attenuators that are switched by relays, and the relays are always remote controllable.

It is so important to get volume set just right to get optimum sound quality and satisfaction, and that can only be done practically by remote control as you sit in the sweet spot and instantaneously hear the result.  Remote control of volume is pretty much an essential feature, not merely a convenience.  Without it, one tends to just live with something close to the right volume instead of actually determining what is the right volume.

There have been greatsounding preamps that use a remote cj uses relays and switches in individual resistors

Ken Steven’s makes an awesome preamp but his heart is not into convenience 

+1 @larryi 

CJ has been using relay / resistive ladder volume since the CT 6 maybe earlier.  It is proven and in my opinion better than electronic volume controls like the ones CJ used when they built McCormack preamps.   Those were a Burr Brown volume chip,  I hated the volume control on my RLD 1 ,  in fact that was the shortest duration I have owned a preamp.  I replaced it with a CJ Classic 2SE 

My Zesto pre uses a motor that moves an analog volume pot.   The IR circuitry has no effect on performance.   I much prefer analog rotary volume knobs

The remote control of the EAR-Yoshino 868 works just as @larryi describes: a motor manually moves the volume knob, affecting the sound of the pre-amp in no way. The remote's only other control is a mute button. Volume and mute are the only two functions I require from the remote of a pre-amp.