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HiFiTubes
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« on: January 01, 2010, 06:27:16 am » |
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I thought some of you might find this interesting. I don't have a map of my system so I will explain as best I can.
I'm using a Peachtree Nova which has these sources connected: Tascam 112mkII, Oppo BDP83, Pro-Ject mini FM tuner, and 1616M via BNC.
The preamp out feeds an 8-10 watt 6BM8 power amp to which are connected 94db/w sensitive Omega bookshelf speaks and sub. the line out feeds back into the 1616M.
I rolled some new 6BM8s in the other day and finally got my 1616M back from getting BNC swapped in; my system was offline for 3 months, a long story.
Anyway, my 80w picopsu driven mini-ITX board has one PCI slot which is how the 1616M connects. I bought a Cat7 cable to connect the external 1616M unit because I had read about the construction being more durable and robust than cat6 (and it is).
So I get the system back online over the last few days, and start hearing what sounds like "tube rush". You know, a little light crackling here and there; NOT sharp digital artifacts from sync drop. I remember thinking, man those Matsush*ta tubes were new in box, doh, I never tested them on the AT1000, oh well, I roll some Amperex in there later.
So by today I had the system all back in, room cleaned up, off work early, and I start listening to the speakers up close, and I can here the whine of transistors switching. I move my mouse, and I here fuzz mimicking my every move. Granted, this was quiet, or so I thought, eventually it got under my skin as I have never really had this in 10 years of playing with PC audio. It painfully became evident this was unacceptable as I realize, this is loud wonky cr*p I'm observing. I'm hearing it on my couch, and starting to freak out. 3 months of rebuilding this setup.
Then I start disconnecting, powering down, unplugging the web of gear. Moving things around in the power conditioner. Ideas rise and fade; the PC is connect to a UPS via USB, that's got to be it, ground loop?! Nope. turns out I had never even connected my PC to my new UPS either, duh, it was still in the power conditioner.
I end up with 1616M disconnected from the Nova (cat7 unplugged), unplugged Nova, everything unplugged really.....and just the PC on (on a new outlet off the conditioner) with the power amp. I can STILL hear this noise.......... getting on the powerline?! I had some shorting plugs and the result was silence with just the amp on with speakers. BUT, I hadn't unplugged the analog RCAs going into the Nova, so with it still unplugged, I pull all 3 sources out, and connected it back to the power amp.
And plug the Nova back in to DEAD silence. TINY hum, expected from a tube amp, but what a peaceful sound that was. I suddenly realized how loud all the nastiness was. I vaguely remember similar hash when I used one of these cables before on my Oppo. I think the shield is only connected on one end. I still don't fully understand this, I'm not an EE. How was this noise getting from the PC into the amp? EMI I imagine picked up like the cable acting as an antenna is my guess.
Finally, I almost gave up because I was burnt out on rebuilding and just couldn't tell if I was being really anal, but when it didn't feel right, I am glad I pursued it with such a great result; perfect to start off the new year.
I'll have to play around with XXHighend sometime and see how it sounds, but for now I'm enjoying my custom Last.FM 1920x1080 track info screen in JRiver MC14, something I can't live without.
Just thought I'd share this crazy tale because I feel pretty confident I am getting great sound from a PC, something many don't think is possible. So even if I'm not using XXHighend, we share the love of PC audio in common.
Happy New Year.
HiFi
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