Different PC + Identical system = Different sound!?!

earplay · « **on:** 20 May 2009, 08:27 pm »

I plugged my mega-buck HP Pavilion into my audio system. It replaced a low-buck eMachine.

I was surprised to hear the sound of the Pavilion was very noticeably different than the eMachine. Every other aspect of the system was the same, including the software and it's settings. The audio files were aiff off an external drive.

The cheap eMachine was much smoother and more revealing of low-level details than the Pavilion. The Pavilion made the system sound like a boom box.

I think it's been a given that the PC should not make a difference, all other things being equal. Is there any emerging thought on why different PC's would sound different?

Here's my reference system: PC> iTunes> HotAudio usb DAC Straight> MAC AgQ IC> Glow Amp 1 (JAN GE Triple plate 5670's/NOS Mullard EL84's/Herbie's)(MAC power cord)> WLM DIY Cables (braided) captive on Hornshoppe Horns.

JoshK · « **Reply #1 on:** 20 May 2009, 08:34 pm »

That is a head scratcher for sure.

Is this a USB output? USB isn't galvanically isolated, so it is possible that the Pavillion is noisier, especially if its got a lot more *stuff* inside it.

earplay · « **Reply #2 on:** 20 May 2009, 08:53 pm »

JoshK,

I just added "usb" to my reference system description. Thanks.

Yes, it is usb output. The Pavilion is an entertainment version and has waaaay more stuff inside. Retubing was not enough to correct its harshness. It was quite pronounced.

The dac is external. If it was the effect of the extra circuitry in the Pavilion, then we have yet another factor to consider.

earplay

rahimlee54 · « **Reply #3 on:** 20 May 2009, 09:04 pm »

Different drivers that are controlling the usb? Same OS?

JoshK · « **Reply #4 on:** 20 May 2009, 09:06 pm »

Well, the point I was trying to raise is all that extra stuff inside the pavillion raises the probability that the grounds inside the computer are being contaminated by EMI/RFI. The insides of computers are known to be a source of noise. Being that USB is not galvanically (ground) isolated, that means the noise from the PC can enter your external DAC via the ground (through the USB).

earplay · « **Reply #5 on:** 21 May 2009, 01:12 am »

rahimlee,

The OS's are the same. The dac is plug and play. No proprietary drivers needed.

toddbagwell · « **Reply #6 on:** 21 May 2009, 01:23 am »

Is your PC a laptop or a desktop? the June 2009 stereophile has a bit of info about digital jitter and USB audio outputs of laptops with and without the battery / PSU supplying the juice. It looks as if different DACS do varying jobs of rejecting said jitter. Worth a look if you believe in jitter and its audibility. YMMV.

todd

planet10 · « **Reply #7 on:** 21 May 2009, 01:50 am »

I just saw a very interesting set of jitter measurements Cambridge did with their DacMagic. It was a comparison of USB attached to a laptop running off the power supply/recharger vrs off the battery. Difference in jitter was huge. The conclusion from that is that the PC power supply can make a VERY big difference in sound quality.

I'll see if i can scan the 2 charts & post them.

dave

edit: looks like todd beat me to the submit button

earplay · « **Reply #8 on:** 21 May 2009, 02:20 am »

More info: the smooth sounding eMachine desktop was plugged into the wall. The ragged sounding HP laptop was plugged into the wall.

Oh oh, I forgot another variable. The smooth sounding eMachine is not plugged directly into the wall, but into an old Power Wedge II. That might account for some of the difference, but I don't think it accounts for the HUGE difference I heard. I'll try the laptop on battery power and plugged into the Power Wedge tomorrow and report back.

Keep in mind, the difference was HUGE, so we may be onto something.

earplay · « **Reply #9 on:** 21 May 2009, 04:06 pm »

The Power Wedge made no appreciable difference. It's all back to the PC's.

I hate to think there is yet another variable in a system, but I'm starting to believe that the machine itself makes a difference.

It may be in the hardware of the machine. Some dacs are immune to the grounding effect of the usb, I think, but I don't know about the design of mine.

Next, I'll try my Pavilion laptop with running off the battery to test the power supply issue.

ebag4 · « **Reply #10 on:** 21 May 2009, 04:18 pm »

Steve of Empirical Audio has a thread titled "All USB ports anre not the same", here is a link:

http://www.audiocircle.com/index.php?topic=54881.0

Aparently some machines have a mix of 1.1, 1.0 and 2.0 USB ports. You might try other USB ports on the laptop.

Best,
Ed

rahimlee54 · « **Reply #11 on:** 21 May 2009, 07:25 pm »

Quote from: earplay on 21 May 2009, 01:12 am

rahimlee,

The OS's are the same. The dac is plug and play. No proprietary drivers needed.

I was getting at what was mentioned about USB ports that ebag4 posted, plus the drivers controling the usb ports varies from company to company based on the motherboard inside the machine, which may cause problems. I am just throwing out suggestions though.

earplay · « **Reply #12 on:** 21 May 2009, 09:17 pm »

Here's something I forgot.

With the HP laptop in the system, the music would occasionally be interrupted by a high volume white sound, like a tv channel on snow. I would stop iTunes and restart it to get the music back.

Switching to battery power did not overcome the harshness of the HP.

With the eMachine, the system sounds gorgeous. With the HP, the system sounds harsh.

I want to thank everyone for their thoughts. I think we have come across yet another variable in the system mix, roughly speaking, the PC. More precisely, interactions of hardware and, maybe, software. It seems like there is an emerging notion that the PC hardware is a variable in the system. Exactly how the hardware interactions affect the signal is yet to be determined.

Does that fit with what y'all think?

planet10 · « **Reply #13 on:** 21 May 2009, 10:09 pm »

Here is that set of Cambridge charts from the latest Stereophile

I don't do Windows, but i understand that iTunes uses the official windows calls for audio and that they are not as good as the ones that bypass the windows toolbox. Perhaps someone can elucidate on that.

dave

earplay · « **Reply #14 on:** 21 May 2009, 11:51 pm »

Dave,

Thanks for the charts. I find almost everything sounds better off batteries. I've got a couple of SLAB's for running my T-amp.

Those charts sure tell a story.

You need to bypass the Window's kernel in the pre-Vista systems for improved sound. I think that is what you are referring to. I should have mentioned that Vista is on both my PC's.

I have a Mac, also, but I don't use that for music, though I might bring it out for a trial in my system. That would be interesting.

Thanks again for the charts. I appreciate the effort. The more I am online with this hobby, the more I appreciate the help I've received from so many.

Niteshade · « **Reply #15 on:** 22 May 2009, 12:58 am »

Very interesting- but there is not a graph for a desktop Windows PC.

earplay · « **Reply #16 on:** 22 May 2009, 03:31 pm »

It occurred to me that my $350 eMachine with its minimal internals may be better suited for audio reproduction because of its minimal internals.

Brown · « **Reply #17 on:** 22 May 2009, 03:44 pm »

would be curious to now if you use the computers media center or say J. River or other for playback eliminating everything to do with Windows. Are you using ASIO4all as the drive ?
An isolation transformer and monster power conditioner worked out well eliminating any noise whatsoever. Adding a shielded powercord also made an improvement.
The DAC we are using is a Musicstreamer + which has no power supply maybe that in itself is a reason for the ultra quite presentation. I'm guessing here not an engineer. Any thoughts ?

earplay · « **Reply #18 on:** 22 May 2009, 08:10 pm »

As I said in earlier posts, I'm using iTunes in Vista on both machines. Vista does not need ASIO4All because Vista, unlike earlier versions of Windows, provides bit-perfect transfer.

I don't know where you are using your power conditioner, but there are few I would use with my dedicated audio components because they tend to compress dynamics. I unplugged my amp from mine and it came to life. Shielded power cords, too, are reported to have a detrimental effect on dynamics. Mine is braided.

I am unfamiliar with the Mainstreamer, but all dacs have a power supply of some sort.

Mr Content · « **Reply #19 on:** 22 May 2009, 08:22 pm »

Synergy!.............

when all things should be equal, but aren't

Mr C aa