I think the amp section adds some colour as well, imho it adds some controlled presence hard to achieve with eq alone or drive.The Type 85 has a very high input impedance, so it doesn't present any load to an amp if you use it on the speaker output. But that won't sound any different than using the amp's line out -- both would have the 'color' of the preamp, and the amp portion doesn't really add anything to the sound, particularly at low levels.