Accuphase E600 voltage conversion

@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. 

I think you have the similar problem.

https://forum.audiogon.com/discussions/usb-input-causes-noise-across-whole-amplifier-musical-fidelity-m5si

@imhififan Thank you very much! The link is very helpful. At least now I know the cause of the issue. 

@imhififan Just wondering if Accuphase E470 voltage conversion from 100v to 120v is same as E600? I'm thinking to give class AB a try as well.