Looking at the old schematics like the 100S, the Vibrato is situated in the circuit before the Reverb. This means that the modulated guitar signal is being fed to the reverb. This is unlike a Fender amp where the reverb gets a relatively clean signal and the tremolo is applied afterword. In the 190L and 350L, the Vibrato is moved so the Reverb gets a clean signal but the Reverb is returned after the Vibrato so you can't get a simulated echo effect. Has anybody ever noticed?