Accuphase E600 voltage conversion

@imhififan I just came home from work and test. When I disconnect all sources from E600, only the speakers are connected to the E600, 3-pong power cord is used, I don't hear any noise even when I turn up the volume to 12 o'clock position. 

When I disconnect all sources from E600, only the speakers are connected to the E600, 3-pong power cord is used, I don't hear any noise even when I turn up the volume to 12 o'clock position.

I believe the noise problem is not the E600, please connect the sources one at a time to test and see which one causing problem.

@imhififan I disconnected all sources and connected each one at a time, I found that the DAC produced noise the most. Other sources did have some noise but much less. 

What concerns me is with another amp, the noise level from the DAC is just about 50% compared to with E600. 

Currently, I am using the Accuphase APL-1 power cord, which doesn't use the ground prong. The E600 is dead quiet. The AP-1 power cord is a great power cord, it's a big jump from generic power cable.

However, it would be great if I could use other 3-prong hi-end power cords with E600.

@quanghuy147 

It seems like some grounding problem between components. Would you provide detail information what components are in your system and how they connected together, maybe we can figure out what is the culprit.

@imhififan I have borrowed 1 DAC and 1 pair of speakers from dad to test this Accuphase amp. 

Here is what I found: 

-the pair of speakers that I borrowed has lower sensitivity so the noise is lower

-the DAC that I borrowed has lower noise than my DAC 

-if I use 2-prong power cable (the one with no ground cable) for the DAC, there is absolutely no noise from the speakers. 

My system are like this: 

-Computer (small form factor, no monitor connected) -->USB--> DAC --> Amp --> Speakers

-Computer, DAC are connected to their own power conditioner

-Amp is connected to its own power conditioner.