Starting to fool with using PC as music source, problem with hum!

[Russellc]

Never used other than CDP for digital, mainly a vinyl user. Have used PC for casual music listening, and used to stream mog through my old Roku box with RCA outputs to my 2 channel rig. Both have the same problem, well not the roku as MOG died, but both as sources always had some hum.

This is in an otherwise dead quiet system of DIY Pass components. Also a tube rig I have experienced the same thing. The hum is buried once music starts, but I dont like it. Using an ultra wide bandwidth Pass F-5 it has tanned the source resistors a couple of times, no harm to other amps...F-5 is really wide...

I decided to tackle the learning curve of PC as source, given various software like J river and others, and the relative inexpensive nature of many DACs out there. Just to get my feet wet, I got an Audioquest DragonFly to play with, and was "reminded" of this hum situation....is this just the way it is? Seems odd I havent had anyone else complain about it, so I figured not.

Any ideas on this hum thing? Sure enough, I had the F-5 in the chain for tryout with some tracks from HDtracks and Spotify, smelled the hot plastic smell, and am changing source resistors, and Power amps!

Thanks in advance.

Russellc

 

[petehall347]

laptop or home pc ? if laptop try on its own battery . if pc its something else .

 

[Russellc]

lap top, but putting in a different power amp cured it. Something about the F-5 does not like its ground or vice-versa.
Thanks. Oddly the F-5 is grave yard quiet otherwise, only PC and Roku gives fits for some reason.

Russellc

 

[Russellc]

The Roku box also gave trouble with a Tube power amp I have as well....

 

[50nstillhifi]

Last time I had this issue... sending signals to my PC via CD player or the like streaming via Pandora.... it turned out to be poorly shielded cables, specifically the leads from the digital device.

For these applications, I have found a "quality"" cable reduces most RF and line interference issues

 

[E.Man]

Not inherent in the concept. Something special for you.

I have PC USB out > DAC > Amp.

which is a no longer sequence and less trouble than my Analog

TT > Phono > Amp.

 

[Russellc]

as noted above, it is something about the way F-5 grounding scheme works...The Pass Burning amp 3 is dead quiet, as was the JBL amp I temporarily stuck in there.

My Analog, using same amps, Pass Pearl 2 Phono pre and Pass BA-3 FE preamp is dead silent...well except for the music.

I've got to rebuild the F-5, stuffed boards and mosfets, but really think I will utilize the same amp chassis, and power supply (dual mono) to install ready to go stuffed Pass Aleph J boards and matched mosfets in. the F-5 is a nice amp, but its a little tweaky and so ultra wide bandwidth it is easy to get sideways with.

Yes, this little experiment worked so well I am going ahead with my plans for a NAS storage system, and either a nicer dac, or more likely a combo dac streamer. This dragonFly is surprising good and will make a dandy headphone player with my laptop when flying on trips...looking at Audioquest Nighthawk or Audeze EL 8 phones.

Russellc