Got a 4.5 preamp off of Reverb recently to pair with a Mitsubishi DA-A30 that I also just bought. This is in an effort to upgrade from a Sony STR-DH190. There is a ground hum on the phono setting that goes away if I (1) touch the preamp, or (2) hover my hand over the preamp near the phono section. The ground connection between the 4.5 and my turntable is solid. Looking inside, the unit has never been serviced. The original cartridge loading resistors are still installed. Nothing looks amiss visually.
I think there’s also a general lack of clarity and resolution in this system, whether I’m using phono or the CD input. Also whether on straightline or high level mode. It still sounds good, and I can tell the phono preamp performs beautifully, but it just doesn’t seem very “precise.” I thought this upgrade from my entry level unit would completely blow me away but that’s not the case. I’m listening through Monitor silver 300’s, so I think I should be able to confidently hear a difference. It could always been the amp, which also appears to never have been serviced.
Is any type of service to the components in the 4.5 likely to solve any of these problems?