It seems this happens every time I try to go without my preamp/buffer. Maybe it is my SMc monos, which have input impedance of only 10K ohms
Can't tar everything with the same brush, with this 10k input.
10k is a very low input impedance, there's no need for it these days, as things have problems diving it.
47k or higher is the industry standard, some tube amps like Rogue M120 mono were up to 1000k!!! (1mohm)
But if your source output stage is weak and maybe cap coupled (which could be too small with 10k) it's the problem, not because your going direct.
Cheers George