Is this a reasonable Audiophile Mac-based Server?


Since I'm a visual person, I've tried to distill what I've learned about music servers and how I might create one. Any suggestions or comments you have would be appreciated.

Here is the link to the website with the picture:
Map of Mac-based Server

My goal is to produce the best sounding Music Server regardless of price.
hdomke
Looks good to me. This is nearly identical to my setup. However I use software on a Mac Mini to control multiple CD players as the source rather than iTunes/hard drive source...of course my setup is 7 years old and, at the design time, ripping a thousand CD's to lossless files was impractical (costly)...ripping to a hard drive still remains a daunting task for me one day when I eventually go to a raid server based source (which I certainly will).

Being able to sit in the listening chair and select and cue music and surf the web for information about the artist and/or musical piece that I am listening too is simply wonderful ( I feel like Austin Powers - yeah Baby!) - certainly better compared to fiddling with CD Jewel cases and feeding a CD tray and punching buttons to select the appropriate track to play all of which just gets in the way of the music)...

FWIW - I think your solution is well thought out.
The connection of using an Airport express to a DAC is not ideal IMO. A USB based DAC such as the Benchmark DAC1USB and Wavelength DACs give much better results.

I prefer having a Mac Mini connected to a LCD display, wireless keyboard, with quiet 2.5'' based HD directly connected in the same room. Simpler and works better than my experiments with the Airport Express.

You won't believe how much more convenient and better the sound is of the Benchmark, fed by the Mac Mini via USB rather than using a standard transport and SPDIF or Toslink interface.

Good luck!
You might also look at the Slim devices transporter.
Restock,
I called Benchmark's technical support and spoke to them at length about your assertion that USB is superior to Toslink coming out of the Airport Express. They assured me repeatedly that Toslink would be "identical" to USB.

That allows me to save several hundred dollars by skipping the USB.

Incidentally the Benchmark staff is great on the phone (as well as online).
We all know how incredibly difficult it is to put a CD in a CD player, sit down on our comfy chair and with this amazing thing called a "remote", hit the play button. And if you don't like the track you're listening to, this devise called a "remote" has a button called "next" or "forward" that takes you to the next track on the CD. It's just insane. Or of course, you can sit on your comfy chair with you laptop on your lap (getting hot) scrolling up and down your list of thousands of track titles trying to decide do I want to listen to this or not, dragging it over to your playlist, over and over and over again. 20 minutes later you've finally completed your selection to play. Yeah, this doesn't get in the way of listening.
Last time I checked, the USB port on the AE is reserved for print server duty and it isn't able to stream audio. Now, that may have changed but I don't think so.

Your set up is very well thought out. And, good grief that's a lot of TB's! Do you have the fmaily movie collection on that thing?

If you're anal about sound quality as I'm assuming you are given your post, I have some suggestions: as Restock pointed out, the weak link in your system is the AE. Even with DAC, it is not going to sound nearly as good as a computer hardwired to the DAC...at least based on my trials. The other issue is that your tunes are making 2 wireless jumps which may cause problems from time to time, although I am so thoroughly impressed by Apple's wireless applications that it may be fine. My suggestion would be to put your laptop on your rack hardwired to the Benchmark via USB, toslink, or whatever. That will exclude the AE in your main rig at least and cut out one of the wireless jumps. The laptop can be controlled using Frontrow, or even better, an Itouch with third party software.

Also, as it seems money is not a significant limiter, ditch the Benchmark and step up to a better DAC.
That looks like a pretty good set up. I tried airport express in my xp network and it failed miserably. It ended up crashing my entire network and it took days just to get my email back. Apple tech support was stumped. But you shouldn't have that problem with Macs.

The thing that concerns me a little is carrying the lossless files wirelessly from your airport base station to the express. If you can go ethernet you'll have a faster and more reliable stream. (Plus, I thought I heard someone say in your other thread that wireless streams get compressed?)

Either way, for the short period of time that the airport express worked in my system it constantly cut out to buffer the lossless files.

When the airport express didn't work out I had basically two choices left. SB3 or Sonos. I went Sonos but you probably can't go wrong with the SB3 either. I have it set up similarly to yours but have the NAS connected via ethernet to the router, the router via ethernet to sonos, the sonos via digital coax to the Dac. No desktop computer is needed between the NAS and the Dac. Laptop is wireless like yours for controlling playlists. (I didn't bother with Sonos remote, I live in an apartment. But like having the option for later)

What I like about your setup is that you can stay 100% in itunes.
I think RDC's experience is atypical. I used an XP computer to AE with absolutely no streaming problems. I don't know what happens enroute but the data from the AE is not compressed.

The reason most say that AE route is inferior is that the AE data has a relatively high amount of jitter. If your DAC can handle the jitter then data is data and a jittery toslink data from the AE will be the same as less jittery USB data. I used one with an Altmann DAC which has circuitry to deal with the jitter and it was superb. I would assume other DACs that somehow reclock or deal with the jitter would be fine as well.

The AE cannot output audio data via the USB port, only via the toslink or analog out.
I called Benchmark's technical support and spoke to them at length about your assertion that USB is superior to Toslink coming out of the Airport Express. They assured me repeatedly that Toslink would be "identical" to USB.

I know Benchmark says that it sounds identical. However, I can tell the difference between Airport Express (AE), Slimdevices transporter fed via toslink to the DAC1, or directly to USB. Direct via USB it better with a tighter sound, less glare in the highs, and more low lever resolution.

That allows me to save several hundred dollars by skipping the USB.

I would go with the USB version of the DAC1 in any case:
- More flexibility down the road as you can try USB direct.The excellent USB implementation in the DAC is one of the main reason to go with the DAC1USB in first place.
- Better driver stage in the USB version which is supposed to sound better than the last incarnation of the DAC1.
- You save yourself the $100 for the AE.

As for the interface, it's a matter of personal taste: Frontrow on a larger LCD screen, clicker software with a PDA, Laptop in you lap. Try them out if you can before settling on one.
Henry -

hard to see the walls... but if I were after the ultimate I would take both the wireless and the Toslink out of the design, wireless first.

Wireless is prone to interference which a hardwired solutions are not. You have a choice of Ethernet cable and the Opticis Fiber Optic USB cable for going any conceivable distance it takes to route it. Both are inexpensive, low profile and flexible.

This leaves you with a Squeezebox, Transporter or their new device the Duet at the end of the Ethernet cable which is nice because you can use the remote to access the server (Ethernet is two-way.) Check out the Bolder modified Squeezeboxes and the Modwright Transporter with the modified tube analog section.

The cleanest set-up would be to hang a NAS on the Ethernet network thus taking the computer completely out of the equation except for ripping.

If USB is your preference it is hard to do better then the Wavelength Audio USB DACs since they go from USB to I2S entirely avoiding SPDIF and Toslink. A lot of people seem to be real happy with the Benchmark and Stereophile has a review in the issue that came yesterday.

You can also use any number of devices to go from USB to SPDIF or Toslink. Hagerman and Blue Circle are two of the better known names offering this type of device. Use a very high quality SPDIF or Toslink cable (critical) and go into whatever DAC you own or can get a screaming deal on.

You will need to have a laptop or a Mini to control the server. Check out Front Row (an IF remote) that works with iTunes, that might work for you.

Also browse around for other small remotes - a lot of people have been playing with them and posting recently.
"RDC's experience is atypical"

No doubt. Apple wouldn't sell those AE's like popcorn if they didn't work at all. Henry did open the thread with "best sounding music server, regardless of price"

I doubt AE, SB3 or Sonos is that. Transporter probably isn't either from what I've read.

Re-thinking Henry's set up, if cost really isn't a factor I'd probably eliminate the desktop in the other room and put a mac mini and the best sounding USB Dac near the hi-fi rig, then use the laptop or some other cool apple device to control it from the listening chair.

And I still think I would hardwire the streaming if at all possible and leave wifi for controlling playlists and other computer tasks...
Henry,
It is a 'reasonable' music server. the 'audiophile' designation is up to you.

It is very similar to
my mac based system (DIAGRAM of LAYOUT) My system is based on equipment I already had as well (except the external DAC) Though I would have to agree with Ckorody about the airport express drop outs. Initially I used an AE connected to my receiver and found it dropped out occasionally ( about once every 3 days). I have since hardwired the connection using Toslink from the office to the living room about a 8 foot cable run. I still use AEs in my garage and bedroom. In either case (wireless or cabled) a DAC is a noticeable improvement.

To put my comments in context--doubt if I can link to my system over on another site-- here is a cut and paste ( a basic audio system )

Digital Source Digital Audio: Apple Power Mac G5 (see below)
Signal Processors Monarchy NM 24 DAC
Receiver Denon AVR 4306
Speakers Tetra 120u
Subwoofer Martin Logan Abyss
Speaker Cables Anti-Cable
Interconnects Ven haus cryo pulsar silver /Audio Art Cable IC-3/ Monoprice digital
Power Conditioning Belkin Pure AV
Other Components Music Server PC: Apple Power Mac G5 Dual 2.3 PPC / LaCie 500GB Big Disk Extreme | Music Server connected to Denon AVR via TOSlink Optical | Apple Airport Extreme/Express network to remote powered speakers in other rooms

the above system also part of an AV system

I found that there is a disadvantage to running iTunes from a laptop as a source to a system: when it goes to sleep(or one closes the lid) the music will stop. I really like the NetTunes application, a sort of VNC into your main server, it provides virtual control of the itunes on the main server. there is a slight graphics lag on the laptop side but acceptable to me. when you close the laptop the music still plays. I also use my ipod for basic FF/RW and pause remote control....that is with Signal Remote.

good luck
ed
Just to add on to Edo who has certainly put together a nice rig -

Running out of a G5 is a nice way to go. Before I moved to USB, I ran the Wireworld SuperNova Toslink from my G5 to my TriVista and it was very very good. Fine solution to 15 feet. No cables longer then that.

There is no "but" except that you really need to pay attention to the quality of the cable. Also be aware that not all Toslink implementations are created equal. So YMMV depending on the DAC.

However you may not need or want a G5 (full size tower) for your listening environment. It works for me because the rig is also my office - I just put up with the low level noise. If you are using a tower, one thing I would recommend is to take advantage of the SATA drive implementation rather then the LaCie USB/FireWire implementation. SATA is much more robust to live with (no FIFO/LIFO nonsense) and doing back-ups between SATA drives (which is essential to plan for) is much faster. Besides again in the office context it makes sense for me,

A lot of guys are doing Mac Mini implementations which seems like a very nice way to go if it works in your room. Both the iPod Touch and the iPhone can control it remotely. Front Row is free etc.
I tried a different approach that probably isn't popular but works in my application. MacPro with Apple Lossless files transfered to 160 GB Apple TV with Toslink connection to Theta Casablanca III with Extreme DACs. Remarkably close to CD's digitally into Theta. Uses Apple TV's interface with I don't mind. Music stored on Apple TV HD rather than streamed actively on wireless. Needs HD monitor.
Apple has just announced some upgrades to the Apple TV along with a price drop. Assuming you have your rig in a room with your HDTV this is an elegant solution.
I'm still a little confused why everyone insists on going wireless instead of getting a Mac Mini, a dac & a huge hard drive that can interface directly to your system. Throw a wireless keyboard/mouse or an Apple Remote under your sofa and you're done.
Synthfreek - good point - I use that setup but no DAC - my mac mini directly controls ALL sources (including CD player preamp and source selection via an USB to serial link to an infra red controller box)
Sammie,
good grief that's a lot of TB's! Do you have the fmaily movie collection on that thing?
No, I'm a visual artist. All my art is stored on there. Here is a
link to my galleries.

the weak link in your system is the AE. Even with DAC, it is not going to sound nearly as good as a computer hardwired to the DAC...at least based on my trials.
Are you 100% sure? You have done careful blind A:B comparisons?

My suggestion would be to put your laptop on your rack hardwired to the Benchmark... The laptop can be controlled using Frontrow
I may try some tests with it set up that way. I like the idea of simplicity, and what I have drawn is complex, but if it is all digital, and the data is transferred correctly, where will the loss occur?

Also, as it seems money is not a significant limiter, ditch the Benchmark and step up to a better DAC.
Do you know of any DAC that has better specs?
Ckorody,
... but if I were after the ultimate I would take both the wireless and the Toslink out of the design, wireless first.
I could run an ethernet cable from the Apple Xserve RAID directly to a Mac in my listening room. From the Mac I could use Toslink to connect to the Benchmark DAC1. But it would be a lot less convenient.
And are you SURE I would get better sound?
If so, why?

Wireless is prone to interference
What would that sound like?
My system has the Apple's newest version of an Airport Base Station, the "AirPort Extreme Base Station with Gigabit Ethernet" . Does that help?

This leaves you with a Squeezebox, Transporter or their new device the Duet at the end of the Ethernet cable
I don't understand what part of my system the Squeezbox replaces. Why is it better?

The cleanest set-up would be to hang a NAS on the Ethernet network thus taking the computer completely out of the equation except for ripping.
Forgive my ignorance, I'm not sure what you mean when you say "hang a NAS on the Ethernet network". Please explain.

Thanks!
Synthfreak,
I'm still a little confused why everyone insists on going wireless instead of getting a Mac Mini, a dac & a huge hard drive
That is certainly a simpler solution than the complexity that I have cooked up. But I was basing mine on existing equipment. And it does work, well.

However, I like what you are saying. Instead of using your plan and attaching a "huge hard drive" what if connected the Mac Mini via ethernet to my 5.6 TB RAID in the basement?
That should work. The only thing that I'm thinking now is that you'll want to have an internet connection available(usually via ethernet) to look up cd info and album artwork when ripping newly purchased cds. Do you have a vga jack on the back of your tv to use as a display?
Got to love the Charlie Brown Christmas tree in your picture!
Synthfreak (and others),
There seems to be many of you who feel that a wireless network just won't give the same level of performance that you can get from real wire.

To explore this option, I've assembled a "Plan B" and put it up on the website. You can view it by clicking here

I remain unconvinced that it will outperform the wireless system in plan A, but I am going to try some A:B comparisons once I get my other components (B&W speakers and Classe Monoblock amps) in a 6 or 7 weeks.

One problem with a wired system is : How can I control it from my listening chair?
You should be able to try it both ways to see what works best. I got into this whole thing by trying airport express. It didn't work in my system, but as others have pointed out, that could be the exception rather than the rule.

Try it. If it doesn't work for you, return it to the apple store. Cat5 cable is cheap and easy to test too.

My system ended up being hybrid wireless. Ethernet connections from network drive to router to music server (sonos) then to dac. Wireless laptop controls playback. Simple and reliable.

Just stick a SB3, sonos, transporter or mac mini next to your dac and you'll have great sound that you can control from your listening chair wirelessly with your laptop.

Don't do anything that takes the laptop away from your lap or binds it with wires when it is there. There is a simple way around it.
I use a wireless keyboard with roller ball mouse. I use my HDTV as a screen. (Mac Mini can output 720P with some slight mods to the software that controls the video card)

But feel free to ignore this as I did quite a bit of programming for my setup so that I can control everything (even switch on and off any components using my Mac from my wireless keyboard at the listening position). My setup is for the more technically inclined.
Hdomke -

the wireless system may or may not work to your satisfaction, there is no question that the wired system would. What it would sound like is skips - same as a wireless phone or cell phone losing the connection. Obviously it works well enough to satisfy most people most of the time. But you asked about the ultimate which it is not simply for reasons of absolute reliability - no doubt it is a whole lot more convenient.

Since the performance is location specific the only thing to do is try it - after all you know you have a back up plan.

In describing your Apple (which sounds way cool)I think you are mixing your technologies. Airport Extreme is the same as WiFi - technically it is called the 802.11 standard. The newest version of the standard is "n" - as in 802.11n. You can read a nice description on Wikipedia - basically its the next evolutionary step - faster - but also able to handle more clients at once which you really don't benefit from in a home like you would in an office.

Gigabit ethernet has nothing to do with WiFi. Ethernet is a different communications protocol based on wires. The confusion comes in that some devices such as the Squeezebox can handle both Ethernet and 802.11.

Ethernet comes in several flavors (speeds). Most installations use what is called 10/100 which refers to how many bits the ethernet router can handle. Gigabit is a much newer standard and because of its greatly increased bandwidth (data carrying capacity) is preferred in SOTA installations that require high bandwidth - just for the record, audio does not need high bandwidth.

The Squeezebox or any of the other products from SLIM Devices, would basically replace the link from the Mac to the DAC. Because they are on Ethernet (or WiFi) the software enables you to use a remote control to control the SLIM box from your easy chair, just as you could use a remote to control the Mac mini.

A NAS is a network attached storage device which is a node on an Ethernet network. Thus my slang about "hanging it on" meaning it would have a unique TCP/IP address. A NAS is cool (and arguably the ultimate) because you can install the SLIM software in it and run the music system without needing your computer to be on at all. Check out the SLIM site.

Props to you for doing your homework and laying it out on paper - I am sure you will come up with a great system.
Henry, looking at your plan B I still don't think that Toslink will give you the same performance as a USB connection. I had several people over today and we performed some more comparisons in my system:

1) Slimdevices Transporter direct using the internal DAC in the Transporter
2) Transporter feeding Benchmark DAC1 via toslink
3) Mac Mini feeding Benchmark DAC1 via USB

Out of the above 1) and 2) were very similar, despite the different DACs.
Switching to USB made the biggest difference, i.e. 3) was clearly better, less hf noise, tighter more extended bass.

As for remote contrallability: The Macbook as well as the Mac Mini come with a Infrared remote to control iTunes or Frontrow. Alternatively take a look at Salling Clicker, which allows you to use a PDA or cellphone as remote (works great too).

Again, just my own experience, but have been playing with several of the combinations you suggested in my own system.
Restock's experiment is inconclusive. When you have multiple variables in an experiment it is impossible to determine which causes the effect. The conclusion that USB is better than toslink ignores the fact the transporter may be introducing large amounts of jitter. This may be the cause of the inferior sound and may have nothing to do with toslink. A better comparison would be

1. Mac Mini feeding Benchmark DAC1 via USB
2. Mac Mini feeding Benchmark DAC1 via toslink

even though this isn't conclusive either since despite what Benchmark says the DAC may indeed work better with USB. This isn't saying USB beats toslink every time, only that the Benchmark may be better with USB.

All I can say is that in my system ....XP computer - wireless - Airport Express - toslink - Altmann DAC the sound is fabulous, jaw dropping, stunning, ..(insert your own adjective here)
Amazing all the conjecture against Wireless 802 system and in preference for USB.....IMHO both should sound indistinguishable provided you buy modestly good gear...after all none of this is rocket science...do we really suspect manufacurers are all inept and incapable of building something that works.

What happens at the clock in the DAC itself is anyone's guess in a specific setup with your house mains power and whatever other applicances you have connected - but rest assured that most manufacturers are building perfectly good gear. There is no reason to be assuming the worst from teh outset until you find a problem. There is no cause for such fears from the outset.

As for me, I would build it and then cross check it against a CD player direct into the amp (using exactly the same test tracks as on iTunes) - that is what I have always done in the past (switching back and forth with the remote endlessly until I am satisfied I have no idea which one is which). If you can't hear any difference after this kind of extensive auditioning then it is good enough to stop worrying (just make sure to precisely level match volumes as even a very slight increase in loudness sounds better)
Herman, the experiment you describe was the first one I did when I got the DAC1 a while ago (I started out with a Airport Express and a Macbook with optical out)...


A better comparison would be

1. Mac Mini feeding Benchmark DAC1 via USB
2. Mac Mini feeding Benchmark DAC1 via toslink

even though this isn't conclusive either since despite what Benchmark says the DAC may indeed work better with USB. This isn't saying USB beats toslink every time, only that the Benchmark may be better with USB.

The differences between 1) and 2) were similar to the more recent experiment but even more pronounced. Similarly for the Airport Express which I also have. In fact, I was expecting the transport to do much better since it is isolated from the PC, but I guess that is not necessarily the case.

Certainly the observations are true for the Benchmark, which is the DAC Henry was considering. In fact, your experiments with the Altman are more of a singular experience, since Altman put great care in the toslink interface ;)
Also just to ad some information to the above experiments: I used a Glass toslink with a mini to regular toslink adaptor which works better than the Monster plastic optical fiber cable (as determined in previous trials.
Restock, maybe I missed it but I don't see where you used anything but a jittery optical out compared to the USB.
Restock, maybe I missed it but I don't see where you used anything but a jittery optical out compared to the USB.

I agree it looks like there is an excess amount of jitter in the toslink output of the Airport Express, Mac Mini and Transporter (at least compared to USB). But that is why I recommend to Henry not to got the Airport Express or Macbook to toslink route. By the way, I don't see why your source (Airport Express) has any less Jitter, just that you have a very good anti-jitter circuit in the Altman Jisco.

In any case, I would recommend (to Henry) to get the USB version of Benchmark due its upgraded circuitry and added USB output compared to the Standard DAC1, try the wireless setup with AE and compare it to the USB version. Best to make up your own mind about this and trust your own ears. The differences are subtle to say the least., but since the goal is to assemble the"best sounding Music Server regardless of price" it would be best to keep options open.

As far as the wireless 802 network vs. ethernet work debate goes, dropouts are going to be unlikely with an all Mac setup. you only might run in trouble down the road for playing back high rez 24/96 files. There I really don't see that much of a difference soundwise for 16/44.1 file playback.
Regardless of what sounds better, wireless is not as reliable as wired connections. I have two wireless systems, one a Squeezebox and the other an Airport Express, they usually works flawlessly, but sometimes they just won't.
Onhwy61 makes the point elegantly and succinctly - the issue here is not capability but reliability...
Onhwy61 makes the point elegantly and succinctly - the issue here is not capability but reliability...

a reliable connection that sounds like crap is as worthless as a unreliable one that sounds great.

Unfortunately there are no definites here. I have been using a wireless connection in many scenarios with absolutely no reliability problems. Evidently some have had problems. At this point you have many opinions but the only way to know for sure is to try it. An Airport Express is only $100 and you can get most of that back on eBay if you find it doesn't meet your needs. That is the cheapest first stab at the problem.
I did a listening comparison with several of the methods listed here (see link below for conclusions)

http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1196311011&openmine&zzBruce_1&4&5#Bruce_1

I have ordered 9m of Canare coaxial cable which give me the following setup: Computer->USB->Hagerman->9m of cable->Tri-Vista as DAC. The Hagerman cost $119, the cable cost $102, and for $221 I think I'll get the best sound I can short of investing $1000+. I'll let you know what it sounds like once I get the cable to see if I'm right.
Hdomke,

Thanks for the link to your gallery...very beautiful work! OK, on to your questions...I used the benchmark dac with and without the AE. I felt that the direct route from computer to DAC sounded better. But, I didn't like the benchmark all that much so I moved up to a Wavelength Audio DAC, which I suggest to you if you tire of the Benchmark at some point. Or, possibly an Empirical Audio coverter to a more traditional DAC or a CDP with a digital input.

Anyway, I would suggest you run some listening tests trying different ideas and then let us know what works best for you.

Also, tweaking the computer can improve sound quality....I use Stillpoints under my laptop that sits on my rack, which has added a nice improvement.
I've recently set up my system similar to that being discussed.

I purchased a Mac Mini and ripped my CD's using Apple lossless. The Mini connects to a Bel Canto DAC3 via usb.

Other than the occasional drop in signal somewhere, somehow, it sounds fantastic.

After auditioning multiple pre amps and CDP's, this set up sounds better than everything I listened to in it's relative price range.

I just hope I can determine what's causing these drop outs.
Anyone been experiencing similar symptoms?
S789F,

It's wierd you're experiencing drops. I have same set up as you with different DAC and no drops ever. A couple ideas: are you streaming music to an airport express in some other part of the house? Cordless phone? If so, they may be interfering with each other, which will cause drops in the main system.

The only other possiblity I can think of: did you rip your music using error correction? Also, did you stay off of the computer while it was ripping? BTW, for future rips....MAX is a superior ripper to Itunes. You may want to give that a try...

Also, check out this site for proper Itunes/Mac set up:

usbdacs.com

Good luck.
I'm considering a Mac based server w/ outboard DAC, and just read in the current issue of Stereophile; Manufacturer's Comment from Benchmark Media Systems concerning "iTunes 7.5 bug" that sounds suspiciously like S789f's dropout problem....can anybody help with experience on the iTunes 7.5 (Mac updates automatically) so a heads up is worthwhile.

S789f, no dropouts ever with my Mac Mini. What length USB cable are you using? USB may have problems if longer than 3m or 10ft.
I'm considering a Mac based server w/ outboard DAC, and just read in the current issue of Stereophile; Manufacturer's Comment from Benchmark Media Systems concerning "iTunes 7.5 bug" that sounds suspiciously like S789f's dropout problem....can anybody help with experience on the iTunes 7.5 (Mac updates automatically) so a heads up is worthwhile.

If you follow Benchmark's suggestions for setting the Audio Midi sampling frequency before opening itunes (check Benchmark website), then there should not be a problem. Also, Gordon Rankin of Wavelenth has been checking this by doing detailed measurements and could not verify a serious problem with itunes.
i just went to the benchmark and read that article. it seems mac has already done an update. i'm running itunes 7.6 with leopard which is current.

just ran 2 dedicated circuits from my panel. circuit 1 to the stereo the other to the mac.

STILL THE OCCASIONAL DROP OUT! WTF!
7" usb. i tried a couple cables. no luck
S789f: i believe you're experiencing a 'clocking' issue. i had this same problem when i 1st hooked up my Mac mini to my Emm Labs DCC2. problem was gone once i activated Emm Lab's master clock function. unfortunately, i'm not familiar with the Bel Canto DAC3 & therefore not able to offer you more advice.
S789f, have you checked if iTunes - which I suppose you use - is set up to download album pictures automatically? I had occasionally drop outs, but when I unchecked this option in the preferences, they disappeared.
i have had that unchecked and just unchecked everything automatic.

still happening!
S789f, I guess there might be a problem with the Bel Canto then - do you know anyone in the area with other USB DACs that you could try out. Would a Benchmark have similar problems?
I would test your DAC with another software and PC than iTunes and your mac mini. There are many programs that play music....surely you can find something and just test to see if you get drop outs...in which case it would lead one to suspect the DAC.

Is there anything else that might be hogging the USB bus...do you have a dongle and wireless mouse or something plugged into USB (printer/scanner)that might cause latency in the USB port?