I am just swapping my pre-main-amp combo for a vintage almost-TOTL Onkyo A-8650 integrated amplifier. The former NAD preamplifier has a headphone out impedance of 120 ohms, driving not only my Sennheiser HD580 (300 ohms), but even my portable close-back Sennheiser PX360 (32 ohms) and a Grado SR225 (32 ohms) very satisfactory.
Looking on the schematics of the new Onkyo integrated, not being connected yet, I see a pair of 390 ohms resistors stepping down power from the speakers amp output. According to the 10x rule 390 ohms is too high even for the HD580. I know it will sound anyway but will it sound good? I prefer to avoid such an impedance mismatching.
My question for you is, would it be helpful swapping the Onkyo's 390 ohms resistors for lower ones like 120 ohms?
Thank you in advance!
OK, thank you! I already use a HP amp for my electrostatics and would like to avoid one more device in the rack. Let's see! If at least the high-Z Sennheiser HD380 sounds good through the Onkyo intergrated, I'll be satisfied.