M700 issue

Hi, We just purchased a new pair of M700 mono’s and we are having issues with ground loops and a high frequency sound coming from my PSB Synchrony One speakers. I fixed the ground loop by plugging everything into the same Furman PST8 power strip. But I have a very faint high frequency sound coming from both speakers when I use my high end desk top computer that I use as a music server. I custom built it with a high end, low noise power supply as well as a high end motherboard. My DAC is a Luxman DA-06. My preamp is a Pass Labs B1 that I built.

I tried different RCA interconnects but there was no change.
I tried a cheater plug on my computer, no change
I tried shielded power cords and power cords with ferrites but the sound remained.
I moved the computer about 4 ’ away higher up but no change.
I tried an AQ Jitter Bug and an Uptone Regen with a second Jitter Bug plugged into another usb port. but no change. My usb cable is a Wireworld Starlight Red.

I had issues with my Pass Labs X250 amp and a Parasound A21 amp. If I can’t figure it out I will have to return the amps which is too bad because they sound great.




You are going to have to start with just the amps and speakers and nothing else to verify that the noise is not there at that point then add back one piece at a time until you find the offender. B1, then Luxmen, then server. If this is the third amp combo with the same noise then it is coming from somewhere else. For now keep the accessory parts and pieces out of the equation.

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It does not happen with the other 2 amps, only the M700’s. We also tried different DAC’s and preamp. And it only occurs when the music is playing from my music players- Bug Head, JRiver and Audirvana. So it is definitely the computer. I have tried 2 desktops and each creates the noise. I just tried a laptop and there is no noise. So it must be due to AC power. It can’t be due to a graphic’s card because I am using integrated graphics as these are all dedicated music computers. My custom built computer uses all SSD’s and high end parts and fans. I use it in my referency system with my Pass amp, BAT preamp and Luxman DAC- no issues there.

I would bet cheater plugs on the amps would fix the problem but I am not going to try them with the amps as PSA does not recommend that.

I am borrowing an IFI purifier 3 and an iGalvanic3.0 tomorrow, so I will see it helps.