Mac Mini as Music Server

[mb225]

Hi all,

I'm looking to move to a high quality digital music server. I'm thinking of using a Mac Mini with a 2TB drive as my base. I need the 2TB drive since I rip all of my music to wav. I have a Cambridge Audio DacMagic and I was planning on connecting the Mac via digital output (USB, SPDIF, Toslink) to the DacMagic. The rest of my system is:
Rotel preamp and amp (RC-1550 & RB-1582) and B&W 803s.

Today I'm using the DacMagic with an inexpensive CD player and I like the sound.

I'm kind of new the audiophile world so I have a few questions and need some help:

- Will the Mac produce the same digital signal as my CD player? From what I read, a lot of ppl say Macs produce a lot of jitter? I'm using a $100 Sony DVD player as my transport to the DacMagic; I'm wondering if the Mac will somehow sound worse than the CD player; playing through the same DAC?

- What is the best way to connect my Mac and DAC? USB, SPDIF, Toslink? Are there any advantages to one or the other?

- Can I play 24-bit audio with the Mac? It doesn't seem like iTunes supports 24-bit?

- Another option would be to use something like an Olive 4HD music server. Since they are both hard drive based solutions; I think the Mac would be more flexible and I have to think that they would sound the same going through the same DAC. Am I wrong?

- Am I missing anything? I just want to make sure I have all of my bases covered. Example: remote control - I was planning on using an iPod Touch as the iTunes remote. I've seen this before and it looks like a great interface! Is there anything I'm missing?

Many thanks! Any help would be greatly appreciated! :T

[theblue]

it looks like you can play 24 bit audio... google "itunes 24 bit audio"

in theory you can convert your music collection to apple lossless and have no quality loss and free up a lot of space.

optical out from the mac is the obvious way to go.. from there it's a matter of if you have a good DAC in your pre, or if you prefer to use an external DAC. Depending on the DAC you use and how well it works you may also want to get an anti-jitter box in front of it, but my instinct is this may be overkill, can't hurt to audition.

[mb225]

it looks like you can play 24 bit audio... google "itunes 24 bit audio"

Thanks.

Can I send 24-bit audio through a USB, SPDIF, Toslink cable? This has never been very clear to me...

[mjb]

- If you RIP in iTunes to Apple Lossless, the playback will be bit perfect over SPDIF, if the Sound Enhancer and Sound Check playback iTunes options are off.

- The headphone / line output jack accommodates digital optical audio output, analog audio output with a 24-bit, 44.1-192 kHz D/A converter, digital audio output up to 24-bit stereo and 44.1-192 kHz sampling rate and supporting encoded digital audio output (AC3 and DTS). For analog headphone / line output, use a standard audio cable with 3.5mm metal plug. For digital audio, you can use a standard toslink cable with a toslink mini-plug adapter.

- A possible reason for jitter is that it has an optical SPDIF output, and people consider optical more prone to jitter than coax. I have never had a problem, and I can't see how it can be over a short interconnect.

- The best way to connect it, is obviously digitally with a 3.5mm to TosLink cable.

- The MacMini will play 24 bit, you need to visit the Audio MIDI setup to select it as your output format.

- IMO a MacMini makes a great little server, and to remote control iTunes with an iPhone or iPod Touch is excellent.

- Good luck with your choice :T

[Johnloudb]

I think the digital out may allow 24 bit but I'm not sure.

Here's a page on Benchmark's site explaining how to set up iTunes for highest quality output.

http://www.benchmarkmedia.com/wiki/index.php/ITunes-QuickTime_for_Mac_-_Setup_Guide

Edit: Mike posted just before me .... the link is somewhat of a repeat of what Mike just said.

[mjb]

Thanks.

Can I send 24-bit audio through a USB, SPDIF, Toslink cable? This has never been very clear to me...

You need to visit the Audio MIDI setup to select your desired output format.
(the screen shot is not from a mini, but it shows WHERE you can select 24 bit)

[mjb]

http://www.youtube.com/watch?v=AtRy68Z0lv8

[mb225]

This is some great information. Thanks Mike and John!

[mb225]

- If you RIP in iTunes to Apple Lossless, the playback will be bit perfect over SPDIF, if the Sound Enhancer and Sound Check playback iTunes options are off.

Does this mean that if I RIP to WAV, playback will not be perfect?

[theblue]

no, uncompressed .wav will be exactly the same quality as apple lossless, but with something like 50% larger file size.

Also, you'll want the free logitech touchmouse application which will allow you use your your ipod touch or iphone as a touchpad mouse for your mac mini (which you want to display through your TV).

You won't just have a good music server, you'll have a great DVD player etc...

[mjb]

WAV isn't very Mac/iTunes friendly, and I think you'll have to manually edit the tags which will get tedious. I've always just stuck with Apple Lossless.

[mb225]

WAV isn't very Mac/iTunes friendly, and I think you'll have to manually edit the tags which will get tedious. I've always just stuck with Apple Lossless.

iTunes creates an XML file to track all of the tags. You would never know the difference between a tagged/un-tagged file type from within iTunes. :T

[mb225]

A possible reason for jitter is that it has an optical SPDIF output, and people consider optical more prone to jitter than coax. I have never had a problem, and I can't see how it can be over a short interconnect.

- The best way to connect it, is obviously digitally with a 3.5mm to TosLink cable.

So should I use TosLink or coax? Is there an option for coax?

Thanks again! This is some really helpful stuff!

[mjb]

So should I use TosLink or coax? Is there an option for coax?

The choice is analog or optical, so go with optical!

[mb225]

The choice is analog or optical, so go with optical!

My DAC supports USB. Is there an advantage to optical over USB?

[theblue]

good question... I guess is it would be the same over a short run of cable?

it shouldn't cost you anything to test out.

[littlesaint]

Unless your DAC has drivers for the Mac, I believe USB is limited to 48KHz. That may have changed since the last time I tried it with my Macbook. I use optical. No problems.

[mb225]

Unless your DAC has drivers for the Mac, I believe USB is limited to 48KHz. That may have changed since the last time I tried it with my Macbook. I use optical. No problems.

Good to know.. Thanks!

[mb225]

Does anyone have any experience with sound quality? I guess the direct question is, will it sound as good (going through the DAC) as my CD player?

[wettou]

Does anyone have any experience with sound quality? I guess the direct question is, will it sound as good (going through the DAC) as my CD player?

Apple TV will have better sound quality straight HDMi :T

[theblue]

sound quality should be identical from your CD player out assume you go digital to your DAC in both cases. It might even be better from the mac since a hard drive source will make less read errors than a CD.

[mb225]

Thanks for your help!

Does anyone know if the Mac Mini (running as a music server) consumes a lot of memory? I'm a PC guy and I've never owned a Mac before. I'm trying to decide if I need the 2GB or 4GB model? I have to think 2GB would be more than enough to run a music server.

[theblue]

I would probably not pay for more memory up front. you can probably max it out with memory after you buy it for $40.

[Hdale85]

2GB's would be plenty if you're just doing music.

[JonMarsh]

Some more comments regarding the Mini- I use one.

Maybe I should work backwards through the thread.

A number of Mac users report that they have better sound quality with 4GB versus 2GB of RAM. Whether this is a placebo effect or is dependent on what other software they run or have installed, I don't know.... I have been using a early 2009 model for sometime with 2GB, but have a 4GB upgrade I'm installing with a new hard drive soon. Soon as I find the time.

Something to keep in mind with digital audio from a computer or disk player is that there is a rather large continuum of sound quality, and some solutions with fairly good sound quality can be easy to implement, but improvements may involved addressing specific bottlenecks. One of those, as I think you surmise, is the basic digital transmission element from your Mac Mini to the DAC.

Another basic decision to make is whether you plan to only work with CD quality music or will look into high resolution sources in the future. HDTracks, Linn, and others sell some high resolution music online- for example, I have a 24/96 version of Robert Plant's/Allison Krause's "Raising Sand" (the Grammy winner). I have a lot of 24/176.4 material. Moving to any of these kinds of sources in the future will place additional requirements on your system.

TOSLINK SPDIF is built in to the Mac Mini, supporting up to 24/96, but optical has rather poor digital jitter characteristics, not because of the light principle involved, but because of the performance of the commercially available receiving chips uses in these systems. GOOD coaxial SPDIF will generally be able to run at higher frequencies and bit rates with lower jitter, IF the implementation is well done.

Repeat after me: Implementation is everything, no generalization is worth a damn. In God we trust; all others, we verify.

There are three basic types of USB audio implementation. Adaptive mode, Asyncrhonous mode, and custom. The first two are supported by both Windows and OSX, and is the "mainstream" way that USB audio works.

Adaptive sends in blocks typically around a msec in length and can require the receiver to "adapt" to transmission rate changes; the clock is generated at the computer end. This is the most commonly used mode, and is what most equipment still uses, especially units under $1K It can sound fairly decent, for example, adaptive mode on a PS Audio DLIII is not bad at all, and compares well with a lot of CD players in the sub $1K range. (if that sounds like damning by faint praise, well, it is...)

Asynchronous requires much more complex firmware on the receiving end, and is more difficult to implement- it is used by Wavelength Audio, Ayre Acoutics, and a few others. The clock generation is at the receiver, so you're not sending the clock signal over USB, and the jitter can be far lower. Compare the performance in published reviews at Stereophile for Wavelength and Ayre QB-9 compared with conventional USB products, especially for jitter. Unfortunately, the least expensive Asynchronous products I know of are around $1K and up. The Ayre QB-9 is ~ $2500. It probably represents the pinnacle today for USB interfaces unless you go to a dCS Puccinni, which also includes USB, or to the new Esoteric.

That leaves "custom", where a company creates their own hardware approach and writes their own drivers from scratch to implement a USB audio interface. Examples of this are the M2tech Hiface ($150) which is a standalone USB to SPDIF coaxial (RCA or BNC) interface, or the Antelope Zodiac DACs, coming out in March, I've heard, which use a proprietary USB interface. The M2Tech Hiface support standard sample rates at multiples of 44.1 kHz and 48 kHz up to 192 kHz, using two internal crystal oscillators. It's probably the best available budget computer interface for driving standard DACs with SPDIF coaxial inputs.

The Antelope Zodiac units are complete DACs, but also include SPDIF outputs, and incorporate Antelope Audio's clock technology for very low jitter. Antelope Audio's main business is ultra high quality clocks and clock distribution amplifiers for the studio environment; they've probably forgotten more about clock design and distribution than most companies have ever learned. I have one of their Antelope Isochrone DA clock distribution amplifiers/reclockers; it works very well, and is reasonably priced considering competitive products with less features and performance may be up to 3x the cost.

Firewire is another alternative- and long used in the pro area with Macs. Firewire audio interfaces cover quite a range in price, Weiss holding a solid spot in the top end of that range. But Weiss licenses chips and technology from TC Electronics, and they have a budget prosumer interface, the Impact Twin, available for $399 street price, with mic preamps, line inputs, and DAC output up to 192 kHz sampling rates, and SPDIF input and output. I have some of their older products, which are very solid performers, but I don't have this one. May pick one up later this year to try for a bedroom system.

True pro products in Firewire interfaces, like the RME Fireface series, go a step further and support word clock inputs and outputs so that the clocking system in a record/playback setup can be locked to a high precision ultra low jitter external clock. They have a very good PLL style clock built in (though not as good as Antelope's), and work flexibility with pretty much any kind of source signal, and include SPDIF input and output up to 192 kHz. They also carry pro price tags, and very solid driver and software support; I have an RME Fireface 800 and am very satisfied with it. Of course, this unit has multiple channels of AD/DA, and four balanced inputs with phantom power- not something you'd usually be needing.

The Mac mini supports Firewire and I use that for acoustics and some work, but right now I'm primarily testing the Hiface interface, and comparing it against the RME on my Mac Pro. Either one are fed into an Antelope DA for buffering/clocking, and to my main DAC, a Berkeley Audio Alpha DAC. This combination goes far beyond the transient impact, fidelity of timber, and imaging that something like USB into the PS Audio DL-III can deliver. But the DL-III over USB is still quite listenable, especially for background music or a secondary system. OTOH, there are many CD players in the sub $1,000 range I don't consider to be listenable. In that range, I'd usually recommend vinyl for a serious music lover/audio nut.

I do have two disk transports I use with this setup, one a modified Pioneer DV79AVi, which outputs converted SACD in LPCM at 24/176.4, and a standard Tascam CDU01 used as a CD disk transport.

For your situation, I'd recommend the M2tech Hiface as an interface to start with, or trying the TC Impact Twin on firewire and using the built in converters (which go to 192 kHz).

iTunes is easy to use in this setup, as Core audio supports downconversion to 44.1 if you're playing high resolution files- sometimes, their big advantage is that they're mastered more carefully. iTunes will work with a lot of standard files for playback, but I'd suggest Apple Lossless for retaining CD quality and reducing file size, or AIFF if you want an "uncompressed" file that requires less playback computation, (like WAV) but which supports meta data tagging and is more transportable retaining data.

Last, if you want to move beyond the limitations of having to do manual rate switching and restarting iTunes, consider getting a copy of Pure Vinyl, the 3.0 beta includes a good upsampling playback engine with licensed high quality SRC routines, and is a memory player, that is, it reads the tracks into memory and is doing no disk access while playing. Many feel it compares well with Amara, which is far, far more expensive. It would upsample your CD based materials with better algorithms that often used on chip DACs (similar to what I do pre-converting with Wave Editor for some material in a different system). You probably don't need the vinyl capture capability of Pure Vinyl, but the playback system alone is good value for the price.

[mb225]

Thanks Jon! What a great post. I feel like I need to digest all this information. I had to read it 3 times! It seems like you might have a bit of knowledge on this topic. :lol:

So this might be a very amateur question but... my DacMagic claims to have a "32 bit Texas Instruments Digital Signal Processor (DSP)" to "significantly eradicate jitter".

I know my DAC isn't really at the level of many other ppl on this site, but I need to start somewhere. :T

My guess is that the DacMagic isn't really doing a good job of reducing jitter? Hence all the suggestions for better "bit cadence".

[JonMarsh]

Your DAC magic probably is doing what a number of other recent commercial DACs in the $400 to 1K range do, including the Benchmark DAC and the PS Audio DL-III- they use an SRC (sample rate converter) up front after the receiver chip and do up conversion to a fixed or selectable frequency. In this way, while converting to a higher sample rate, they also filter the jitter to a degree. Unfortunately, this does also change the sound in some cases, and of course, the converter isn't getting the original bits, not necessarily even a direct integer upsample of the original bits (such as 44.1 X 4x = 176.4 kHz).

There is a group of people who don't like this upsampled sound, and have pursued non-upsampling older DAC chips and gone for fairly expensive clock modifications or upgrades, as well as power supply upgrades, to fix things at the source. Inside a CD player, this approach can work fairly well, as the local clock is in the player, but with a computer/DAC combo, it's more problematic. This is why more attention has to be paid to the type of interface.

In the Benchmark, it's a 110 kHz fixed frequency, as this is the highest frequency that the BurrBrown/TI DAC chip set used in that DAC that can support more exacting anti-aliasing calculations; above 110 kHz, it runs out of computation power and has to use a simpler anti-aliasing digital filter. Doing it with a separate DSP chip gives more flexibility than if a premade SRC converter like Cirrus logic's or TI's is used- but this may also account for the small errors JA noted when he benched the DAC Magic at Stereophile and was testing with 24 bit data. The DAC Magic does offer a choice of digital filters, both linear phase and minimum phase (apodizing, which only ring following the transient, don't pre-ring like linear phase digital filters in most DACs).

The DAC Magic USB input is a pretty typical Adaptive mode input, and the noise/distortion floor rises significantly compared with coaxial SPIDF input, according to JA's measurements. JA said the jitter rejection via the SPDIF input was very good- USB not so good.

Now, a good think about Mac OSX is that it is normally very easy to get "bit perfect output" as their is no Windows K mixer that want's to transcode CD 44.1 kHz to 48 kHz (hardly an integer like conversion). On the Windows side, you have to have ASIO or WSAPI drivers for your sound system to avoid this in most cases. With your setup, I'd consider trying an M2tech Hiface for SPDIF input to your DAC Magic- for $150 it can offer a more stable clocked signal at all the sample rates you're likely to ever need, even should you upgrade from the DAC magic someday.

US distributor for Hiface



It's available with a BNC output, too, which is the version I have. Made in Italy, so it probably goes well with a good dry Chianti. :W

[theblue]

^
that's some great information, I really appreciate you taking the time to explain this in detail.

[mb225]

Made in Italy, so it probably goes well with a good dry Chianti. :W

That's funny! :rofl:

[mb225]

Jon, I can't thank you enough for all your input. I think I'm going to go with the M2tech (for now).

I'm somewhat new to the audiophile world so I'm having a very hard time knowing where to spend my budget. I thought the DacMagic would be okay since it's in the same price range as my other components (rotel); but it sounds like it wasn't the best choice? In the future, what would be my best upgrade, clock or DAC?
1) Mac Mini -> M2Tech -> Antelope Isochrone DA -> DacMagic
2) Mac Mini -> M2Tech -> New DAC

Or would I need to get a clock and a new DAC?

What kind of price point should I be looking at for a new DAC? Would I see an improvement moving to something like the PS Audio DL-III? Or is the next jump at the $1,000-$2,000 price point?

Thanks!!

[mjb]

There is *NO* difference between the S/PDIF output of the MacMini and the S/PDIF output of an external USB converter. Any difference you hear is imagined, so save your money. S/PDIF does not have an audible signature, it is a data stream. Optical or Coaxial transport is also irrelevant, the data stream is the same regardless. Does a SATA hard drive sound better than an IDE one, or better than a data CD?

The DAC is doing all the work, the gubbery before it is just converting the medium.

[Hdale85]

That's not true at all! You can actually measure differences in different SPDIF outputs. There can be more jitter from one then another and so on. Weather or not everyone can hear these differences maybe not, but there are certainly differences and they can be measured a good digital output vs's a cheaply designed one can make a big difference.

[mb225]

That's not true at all! You can actually measure differences in different SPDIF outputs. There can be more jitter from one then another and so on. Weather or not everyone can hear these differences maybe not, but there are certainly differences and they can be measured a good digital output vs's a cheaply designed one can make a big difference.

Do you have any published data on this? I'm a nerd and find this stuff fascinating! :T

[Hdale85]

If you look on diyaudio.com for people that have modded the digital section of the squeeze boxes or what not you will see a lot of info.

[chrispy35]

There's an AES paper on the audibility of jitter somewhere and how SPDIF is not really well suited to being a low-jitter scheme. One conclusion of the paper is that jitter of a certain level is audible...I can't remember right now how much is req'd.

Bits are bits in determining amplitude but timing is relevant in determining frequency.

Chris P.

[Hdale85]

There are other issues than jitter that a poor spdif design can have I just can't think of them off the top of my head.

[littlesaint]

Digital transmissions rely on clocks to encode the signal on the wire. Unless you're using cesium clocks in your SPDIF (doubtful), no clock is perfect and will affect the signal. This is measured a jitter. Generally, the quality of the digital transmission components (and their cost) is directly proportional to the quality of their clock.

I don't get to caught up in audio jitter, as usually it can't really be heard, but it's certainly there. As you get into faster transmissions over distance like 10Gbps Metro Ethernet, the quality of your clocks becomes very apparent, very quickly. We use cesium clocks for those.

[JonMarsh]

There is *NO* difference between the S/PDIF output of the MacMini and the S/PDIF output of an external USB converter. Any difference you hear is imagined, so save your money. S/PDIF does not have an audible signature, it is a data stream. Optical or Coaxial transport is also irrelevant, the data stream is the same regardless. Does a SATA hard drive sound better than an IDE one, or better than a data CD?

The DAC is doing all the work, the gubbery before it is just converting the medium.

In principle, for a converter with a standard receiver chip, and not using an SRC chip like the popular TI and Cirrus (Crystal) models, the clock recovered from the SPDIF IS the system clock for the DAC, and the jitter of the source signal is quite important. If it weren't important, and weren't audible, there would be no market for products like the Antelope Audio Isochrone OCX or Isochrone 10M in recording studios, much less their Isochrone Trinity.

Unfortunately, many things can happen in the generation and distribution of clocks, due to power supplies, common mode and differential mode system noise, etc. The ideal situation is an all in one system with a local high precision clock controlling a transport or clocking the data signal. But when you use standard consumer approaches such as a separate small computer with either optical or electrical SPDIF, then things are compromised to one degree or another. It simply becomes a case of how much compromise you are willing to accept, and how much sound quality you expect. The best performance I have heard with a computer system using AES/EBU or SPDIF has been using a computer interface that supports using a high performance external clock. Period.

A very good approach is to keep the clock local, but use asynchronous USB, such as Wavelength, Ayre, and dCS employ. Then the external effects are minimized. This does not mean that such a DAC will sound better than one using SPDIF- implementation is everything, and a good $5K design running SPDIF or AES/EBU may beat out a $2500 product using asynchronous transfer. And by beat out, I'm talking about how much the reproduced signal approaches the mike feeds and the master; what kind of imaging is reproduced, and even issues around timber and micro as well as macro dynamics. Obviously, we don't normally have access to those master recordings ourselves at home. My own experience is that very low jitter CD reproduction with a high grade DAC can approach or exceed the playback quality of a high resolution signal on a middle grade DAC- but it's not easy or common. We're not talking about TOSLINK feeding a $400 DAC in that case.

SPDIF coaxial is often preferred in consumer because it's easier to get good cable termination for characteristic impedance- but with professional length cable runs, the much higher operating voltage of AES/EBU may bring benefits in measured and audible performance with good cables.

And last, if you think SPDIF quality doesn't make that much difference, try connecting an Antelope Isochrone DA between a typical CD player or computer coaxial SPIDF and a high end DAC, and see what even just high end re-buffering and noise isolation sounds like. You might be surprised...

[mb225]

Jon, I can't thank you enough for all your input. I think I'm going to go with the M2tech (for now).

I'm somewhat new to the audiophile world so I'm having a very hard time knowing where to spend my budget. I thought the DacMagic would be okay since it's in the same price range as my other components (rotel); but it sounds like it wasn't the best choice? In the future, what would be my best upgrade, clock or DAC?
1) Mac Mini -> M2Tech -> Antelope Isochrone DA -> DacMagic
2) Mac Mini -> M2Tech -> New DAC

Or would I need to get a clock and a new DAC?

What kind of price point should I be looking at for a new DAC? Would I see an improvement moving to something like the PS Audio DL-III? Or is the next jump at the $1,000-$2,000 price point?

Thanks!!

Anyone have an option about this post?

[theblue]

I think you should do it in stages.. start with the optical out to your current DAC, then later on get / demo the M2Tech to your current DAC, then later on try a better DAC. don't buy anything unless you can hear a difference... make a friend give you a blind test so you're not being biased towards the expensive solution.

[mjb]

I think you should do it in stages.. start with the optical out to your current DAC, then later on get / demo the M2Tech to your current DAC, then later on try a better DAC. don't buy anything unless you can hear a difference... make a friend give you a blind test so you're not being biased towards the expensive solution.

I agree. This is good advise in view of some of the comments.

The Mac Mini's built-in Optical Out sounds excellent, and there are lots of posts on various forums which say it sounds better than some very expensive CD players do. I'd start out with a MacMini connected either by USB or optically to your DAC, rip some tracks in Apple-Lossless, and see how you like it.

I've read posts (on other forums) where people discuss at great length which USB port sounds better, or which DRAM manufacturer sounds better, or whatever. I personally don't buy it, but perhaps you do. So experiment, and choose the equipment and setup which YOU prefer.

[mb225]

theblue, mjb,
That's some great advice! I was planning to buy everything in that order, for that exact reason. :T If I can hear an improvement with the M2Tech, it stays.

I guess my question was more about my DAC? Is the DacMagic the weakest link in my current setup?

I really like this site! I really appreciate everyone's help here! And it's fun to talk/learn about this stuff.

[theblue]

I don't think you can really call the DacMagic a weak link. At this point you're getting more into what's the best flavor of ice-cream?

I would guess your real weakest link is your listening environment / room, unless it was purpose built.

[mb225]

I'm going to switch from my current (WAV) setup to AIFF or Apple lossless.

Another rookie question... Should I use iTunes to import my CDs? Does iTunes ignore disc read errors or something else bad? Should I use different software to make sure the data integrity is retained during import?

Thanks!

[littlesaint]

I'm going to switch from my current (WAV) setup to AIFF or Apple lossless.

Another rookie question... Should I use iTunes to import my CDs? Does iTunes ignore disc read errors or something else bad? Should I use different software to make sure the data integrity is retained during import?

Thanks!

Rip from sbooth.org is good. His Play app is good for playback as well if you want to get try something other than iTunes. Also try XLD for ripping. Both a better than iTunes IMO.

http://sbooth.org/Rip/

http://tmkk.hp.infoseek.co.jp/xld/index_e.html