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I'll write a detailed guide up soon and post all the suggestions I have found and post them in my forum and on my website.

For now, I'll throw five really simple and quick suggestions out there to get you started on a Mac, that is dedicated to music server duties, ie., you don't use it for anything else:

First off--use Amarra
Second--Use a good USB to S/SPDIF converter
Third--turn off "Spotlight":

How to disable Spotlight in Snow Leopard? - Super User

Fourth--disable your Airport card while listening.
Fifth--for critical listening, do all listening on battery power, not with the AC connected. For background/non critical listening, I just leave mine plugged in.

Start with those, if you hear a difference, great, if not, great.

Peace,

Lee

Thanks Lee, your website has some great tips for Mac users. I was able to change my optical output via the Audio Midi Setup to 24bit/96Hz and my DAC confirmed the new input. I was using 24bit/44.1kHz.

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There are a lot of jitter studies out there, as well as white-papers. Here is mine:
jitter

Malcolm Hawksford also wrote extensively on jitter, and was interviewed in the November AudioXpress. He provides jitter demonstration files here:

http://www.audioxpress.com/magsdirx/...ttertracks.zip

The tracks are:

1) unchanged track
2) sinewaves at 44050Hz, 44150Hz
3) sinewaves at 50Hz, 100Hz, 150Hz, amplitudes 1:0.5:0.25
4) sinewave at .2Hz
5) sinewave at 10Hz
6) sinewaves at 1Hz, 50Hz, and 11025Hz
7) all of #2-6

Steve N.
Empirical Audio

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Thanks for the information, Lee. I tried running my laptop from battery instead of AC wallwart (fifth point), and it really makes a difference.

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There is something very wrong here. I did not read those papers, but 250nsec? Are you really talking about 250nsec? or is it 250psec?

250nsec is 1000 times bigger then 250psec.

The SPDIF data rate for a 44.1KHz sample rate is 5.6448Mhz which is 177nsec. If the jitter is 250nsec, you will be missing a lot of data (or repeating data) to the point of such breakdown of the sound, that jitter is no longer the issue. Something is screwed up here.


When you transmit digital audio, the transmitter has a clock and you send one data state at each clock.


Inside the receiver, there is also clock circuit. The clock is locked to the AVERAGE rate of the data, so in fact it is at the same rate as the transmitter clock. The receiver clock happens once for each data bit. If the reciever happens every 177nsec, but you allow a jitter to be greater then 177nsec you may will miss the data, or have a "double clock" causing the data to be repeated. All the other bits will be out of sequence. And such a violation is not subtle. A single violation is going to make a 6dB sudden step, a terrible distortion.


In fact, jitter figure is in r.m.s. and random jitter has a bell shape curve - normal distribution. Put it together and you find that the peak to peak of the jitter (peak to peak deviation) for a 250nsec is 1.5usec!!! That is for 3 sigma so that only covers some 99.9% of the times. In reality you want to have than 25nsec to just make for reliable data transfer, before any consideration for sonics.


So even data transfer of 44.1KHz spdif requires much less then 177nsec timing error (less than 25nsec or so). And at 25 nsec it the jitter is huge. For good audio one needs to clean it way down. The issue is than about how much jitter was removed before it gets to the critical circuit where it matters.


I wrote about the differences between data transfer jitter and conversion jitter. Maybe my posts are too complicated. I tray to keep it simple, but it seems to me that what I say is not sticking too well. In this case, 250nsec (that is 1/4usec) does not make sense to me at all. I assume we are talking about digital audio and spdif...


Regards
Dan Lavry

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My pleasure, I will write up a detailed list soon, as soon as I can devote some significant time to list and explain everything

Peace,

Lee

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Thanks, just one of many tips. I'll compile a complete list soon.

OT--How does one "multi-quote" so I can answer multiple post in the same post?

Peace,

Lee

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Interesting, downloading them now. How do the magnitudes translate to time variations or are these the sidebands created by the jitter ?

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Yes, 250ns - it is in the Ashihara paper !


http://www.jstage.jst.go.jp/article/ast/26/1/50/_pdf

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These are just the modulation frequencies and amplitudes.

Steve N.

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Hi Lee,

For multiquoting you select the messages you want to quote by clicking on multiquote (the icon just right of quote) on all the messages. Once you have selected all messages, you can click "quote" and they will appear in the order you have selected them. I hope it was helpful.

Regards,

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Lee, I could justify $1300 for a good USB to SPDIF converter, one like yours for example, but I cannot justify $999 for a media player like Amorra.
I know I am probably wrong but that's how I see it.
BTW I use your USB CryoParts Cable and I have heard the difference!
It's great!

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That's why i got Amarra mini for around $400. Same SQ just no bells and whistles, they both work with itune, solved my fatigue issue with computer audio that i had since day one....and i have spent an arm and a leg dealing with that issue. Smoothes out all of the rough edges for me but keeps or helps the dynamics.

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Nice, very helpful. Thank you! Crazy interwebs.

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Thanks for the kind words.

FYI-Amarra has a mini version for $395. I don't offer Amarra, but you can contact one of their dealers for a demo version.

Peace,

Lee

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Hi dallan, could you please explain what was your fatigue issue and how it was resolved using Amarra?
Thanks