EQ box or no, the ratio of 135 ohms nominal output impedance to 75K ohms nominal input impedance is plenty high enough of a differential ratio to negate the possibility of matching problems. In fact, 135 ohms output impedance is on the low side for an all-tube preamplifier, though it's a safe bet that the quoted figure actually rises at the frequency extremes, and 75K ohms input impedance is on the high side for a SS amp. Still, even if the pre output figure were to hit a couple of thousand ohms in the bass region, you would probably not hear any ill effects as long as the amplifier input impedance were about 20X greater, which yours apparently surpasses.
