scd-1 hiss/noise

this scd-1 come with clock, opa and capacitor mod. before i can appreciate any benefit of this mod. i noticed a hiss by the following: play a cd, stop and crank up the volume. now, a hiss can be heard very easily. in order to prove my setup was not fuzzy, i use another cdp and it is dead quiet.

i do not feel this is right but have no idea what would be the cause.

i changed opa627 back like 5532 but it is the same.

one thing i observed is the noise floor is very high, evn on my 20Mhz oscilloscope. i bought a spectrum analyzer, which is on its way to see what is the source of this noise.