Music Server Computer transport - Hop On!

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Hi Danny,

Which resistor values are needed to get the spdif signal as it should be?

Let me answer this, as Brian is jammed out already.

There is no simple answer. If you have an SPDIF output on a chip supplied with 3.3V and your Output is standard CMOS you need around 200 Ohm series resistor and 110 Ohm Shunt resistors. Many Transformers however may not well driven by this kind of signal, so such an output is best transformerless.

If the output is extra buffered as in the Musiland by five parallel inverters, increase the series resistor to 220 Ohm.

If your SPDIF output is from 5V Logic use 300 Ohm series and 100 Ohm shunt. If extra buffered use 330 Ohm series. Again transformerless.

However, these are only ballpark values, you may be better off tuning everything on a good high frequency 'scope and with a precise 75 Ohm resistive load. you want an exact doubling of level with the load off vs off. And you want 0.5...1V peak-peak with the load attached.

Finally, if you use transformers you want square wave output with minimal slowing of the edges and as little ringing and other problems as possible. This may need more than transformer and resistive divider.

I hope this helps.

Kind regards Thorsten
 

ra7

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Has anyone looked at the wadia itransport? For 400 bucks its a wonderful solution. It takes the digital signal from the ipod and outputs its to whatever dac you might want to connect to it. I think it will save a lot of hassle and space. And everyone probably already has an ipod.

it comes with a remote too.
 
Hi,

Has anyone looked at the wadia itransport?

Gordon Rankin did. He concluded it used a Burr Brown PCM270X USB to SPDIF chip, which is a much worse solution in terms of jitter (about ten times worse) than the (modified) Musiland.

And it is limited to using I-Pods as source, with all the problems about file formats (no FLAC) and the need to use Apple's Spyware (oops, iTunes) and all that.

Oh yes, it is limited to 16Bit / 48KHz as well.

And everyone probably already has an ipod.

Well, alas I doubt it is "everyone".

I find current iPods sound much worse via the headphone out than my Windows Smartphone and they would be just another box to carry, plus, what would the GF use to listen to music if I took that iPod away with me?

I have a 1st Generation iPod that was given to me for free, I never touch it. Too much hassle converting my music to something it understands, much less storage space than my current smart phone (which is three years old!) and too much hassle in general. Sounds okay on the 'can's, but not much better than my smartphone and with that I can do crossfeed for 'can's in software.

I am sure it is a solution that suits the dedicated iPod crowd/generation very well, especially where every family member has their own iPod.

For many others it comes with too many strings attached and too many limitations, mainly due to Apple's "style over function" and "cripple functionality severely for a super simple interface" and "cripple compatibility with anything mainstream so customers have to keep giving Apple Money" policies applied to their products.

Ciao T
 
Hi all,
i´m just new to the topic and try to hop on the pc-audio-train step by step.
I really like iTunes ´cause you can see the cover of albums etc. and the
most important...it´s easy to use.
As i see brian uses a different player and T doesn't like apple anyway ;-)
What alternative is there to use as software on windows with all the comfort?

Greetings ulf
 
Hi,

I really like iTunes ´cause you can see the cover of albums etc. and the most important...it´s easy to use.

My problem with iTunes is that apart from not recognising the most predominant lossless Audio Format (FLAC - neither does Windows Media Player/Centre - but this is easier to fix) it really is of the "Computer Software" Type of interface.

I like my media PC to be more like a Standalone System and I guess I have been permanently spoiled by using systems like Windows Media Centre, Media Portal, XBMC and the like for many years.

They work with the MCE remote control and allow use very much like a normal CD-Player with an added huge library that is navigated using the cursor keys browsing through the covers and mobile phone style T9 text entry for quick jumping and searching.

This is just so much easier and slicker than navigating folders and files with a mouse, I refuse to use anything that is less capable. So iTunes feels kind of prehistoric and outdated to me.

BTW, you can see some notes about my own most recent Media PC that is still in daily use here:

Computer Audio Asylum - My OLD Mini ITX Fanless Music Server - Thorsten - May 29, 2010 at 05:36:02

An externally hosted image should be here but it was not working when we last tested it.


I use the same software and skins on Brian's Touchscreen Nettop that is in daily use at the office and has delgated all CD-Players and Transports in the place (quite a few!) to a new duty as dust catchers.

As i see brian uses a different player and T doesn't like apple anyway ;-) What alternative is there to use as software on windows with all the comfort?

I recently covered this topic in the Diyhifisupply Forum over at audioasylum (DIY HiFi Forum - RE: info about setting up ASIO player for Cleo - Thorsten - June 21, 2010 at 08:35:33). This also covers some of the needed setup, so I guess it is valid to essentially just repost this here...

Cleo and Morello have two audio interfaces on the PC side.

Standard windows audio (WDM) and audio streaming input output (ASIO).

On Vista and Windows 7 the windows audio system includes WASPI which is a viable alternative to ASIO but is currently not widely supported by playback software.

As far as Cleo and Morello is concerned you only install the driver, that is it.

Each software has different settings, the Cleo Manual shows the ASIO setup for the free J-River Music Juke box software.

An externally hosted image should be here but it was not working when we last tested it.


This is very much a "Computer Software" type player (similar to iTunes), for use with mouse etc.. It is free to download and unlike Windows Media Player and iTunes handles any music file format known to mankind out of the box.

We also recommend Album player which has very similar and simple settings for ASIO.

An externally hosted image should be here but it was not working when we last tested it.


Album player is very at home with touchscreens and as remote controlled stand alone media device.

One of the best thing for a CD-Player like playback of a music library is to use Album Player and the MCE Remote.

An externally hosted image should be here but it was not working when we last tested it.


This allows very easy use of the whole system. It is supported by Album Player.

Both programs need no add-ins or the like to work with ASIO.

When I last used Foobar (quite a few years ago) it needed a suitable plug-in to work with other audio systems than windows audio. The same applied also to Winamp the last time I looked and neither software was easy to set up or to use. To be honest I feel that Winamp and Foobar are now depreciated and would not recommend them any longer for use, they are so Y2K.

Compared to a few years ago we now have Computer Music Players with the highest quality quality very easy. The issues of software induced jitter that several prominent audio player softwares where designed at least in part to minimise have been resolved. There is no longer any need to jump through major hoops to optimise the hardware and software.

Using an asynchronous USB or Firewire DAC like the Cleo or SPDIF converter like the Morello reduces differences between playback software that operates bitperfect (that is no oversampling, upsampling or other digital signal manipulation) to very small at the very least.

It is worth noting that XXHE and CMP^2 are routinely used with upsampling, different upsampling processes of course sound still different.

Even though things are much easier now I would still recommend using a dedicated PC/Laptop and starting with a completely clean windows installation.

I would recommend strongly against using a wireless Network connection, most Wifi Card Drivers seem very badly written and can cause "stutter" even with async USB DAC's and large buffers for ASIO. Remove as much of the unneccesary software as possible (including Windows Messenger, Office Enablers, Adobe Reader Quick Start and all those tchotskies. You can find a fair few guides how to do this on the net. Then install your Music Player and consider to run the machine without internet access and without antivirus.

An easy tool to check if the PC can play music well is called "DPC Latency Checker". There is no need to chase super low latency, just make sure the machine stays in the "Green". I found several machines that where "red" (cannot stream audio well) turned green once the WIFI connection was disabled. Some supposed Anti-Virus software (which I found is worse at killing your PC than any of the viruses it failed to stop anyway) also caused huge latency.

My own dedicated Music PC was set up to not have any Internet Browser installed at all (so no-one can get on-line) and the windows firewall is set up to paranoid mode, letting only the Media Software talk to the Internet, to get coverart, CDDB to get proper track info for CD's being ripped etc., but no antivirus at all.

I use Devolo power line networking to interconnect all the stationary PC's in my place, including my Media PC.

BTW, these days I use dBPoweramp reference for ripping. Mainly because it decodes HDCD's into a 20Bit FLAC file, which is an excellent reason to get a Cleo, as HDCD's offer one of the largest libraries of High Resolution material that people actually want to listen to and often already have ton's off on their shelfs...

If the machine must do occasional duty as work (or just occasional internet browsing) machine, set it up with a clean copy of Windows XP (if using ASIO) or Windows 7 (if using WASPI) for dual booting. Again, ton's of how-to's can be found on-line. That way you can run the clean copy of windows without all the usual resource hogs like Skype or Windows Messenger and so on. In this case you can drop back in to "productivity" mode within a few minutes.

Ciao T
 
Must Read From Thorsten: State of the Union - Asynchronous USB DAC - Caveat Emptor

Folks,

Some questions that came way in recent times and some more observations of my own make me think that someone needs to give a short rundown that is easy to understand.

I hope I'll be able to keep this straight forward.

First, the combination of "Asynchronous", "USB" and "192KHz" seems to be the latest "must have", something we may not entirely innocent in, having announced probably the first shipping high end units.

At the same time there seems to be considerable confusion what "192KHz capable asynchronous USB DAC" really means.

For example quite recently a high profile audio journalist* compared the Upsampler Chip in one DAC** to a true Asynchronous USB DAC***, implying their operation was similar or identical (which it emphatically is NOT).

In another case a Vendor**** advertised (most likely out of simple ignorance, rather than an ill will to decieve potential customers) a DAC as 192KHz Asynchonous USB DAC.

True, this DAC was "Asynchronous" by using an Asynchronous Sample Rate Converter (ASRC) which untill very recently used to be called "Upsampler" and it was "192KHz" by virtue of using a 192KHz DAC Chip. So where is the problem you ask?

This DAC used a Burr Brown USB chip limited to 48KHz and 16Bit, so M$ Window$ or Mac O$X will downgrade your 192KHz/24Bit File that you pay'd good money download, to 48KHz/16Bit (of course without telling you) and in both cases the downsampling is certainly not "studio" quality, so you would have been better off paying less for the CD-Grade copy.

The End Result is a little like ripping a CD to low grade 128K MP3 and then turning the result back to CDFiles and selling the result as the original CD.

I'm sure the vendor meant no ill.

He likely saw someone using "192KHz Asynchronous USB DAC" in advertising (Us?) and looked at his products feature sheet (the product was designed in china for him, maybe he does not even "get" digital?), noticed it said "USB" somewhere, read it said "Asynchronous something" somewhere else and found "192KHz/24Bit" written somewhere else and cheerfully concluded:

"Hey, I have one of these too, high time to tell the whole world that I do!"

(*/**/***/**** The identies of the individuals and products are generally known, but so as not seem to target anyone specifically for a mistake many may have made the identies are omitted)

To clear the confusion and to give anyone thinking about buying a High End USB Audio Product I'll try to clarify some of the terms...

19KHz/24Bit - It ain't necessarily so



("It ain't neccesarily so" is a Song from Gershwin's Jazz Opera Porgy & Bess - sung by the character "Sporting life")

First, 192KHz/24Bit is easy to explain, as are the issues.

If taken strictly it implies a device that capable to accept a digital audio data stream at a sample rate of 192KHz and with 24 Bit wordlength and it should be able to decode the 24 Bit while offering a dynamic range significantly greater than CD. In theory 24 Bits allow 144dB dynamic range, so strictly speaking there is no such thing as a 24 Bit DAC as a 144dB dynamic range eludes so far even the most determined designers.

In reality many "24 Bit DAC's" mange nowhere near this dynamic range, nor do most domestic situations allow anything like 144dB Peak levels, so this shortfall from the theory is mostly academic. Still, there are also "24 Bit" Dac Chips out there that do worse in terms of available dynamic than CD, obviously these are better avoided.

If in doubt it pays to find out the actual DAC Chip used and check the manufacturers Datasheet.

In order not to take pot shots at others, let's examine the DAC in the Cleo. It is a Burr Brown Device with 113dB Dynamic Range. This means when you play music with a 113dB peak level at your listening position the noise from the DAC will just cross the hearing threshold of the most keen eared listeners.

As the background noise in most listening rooms is higher than 20dB you would have to play music with 133dB peak levels to hear the limitations of the DAC. So in practical terms one may say that this DAC performs well enough, even though it falls far short of 24-Bit performance.

Our excuse for using it is simple. It sounds surprisingly good, better than quite a few better specified similar Chips from AD and BB. Just like ancient TDA1541 still sounds better with CD than most better specified later DAC's.

Hence if you are buying a "24-Bit" DAC I'd suggest to expect better than 110dB Dynamic range for the actual DAC Chip, less would ring my alarm bells.

USB - Have you got your funky bus fare?



("Double Dutch" by Frankie Smith opens with the line: "Give me a HO if you've got your funky bus fare...")

Give me a "HO".

Okay, I'm good now.

USB is short for "Universal Serial Bus". It is simply a way of connecting a computer to a wide range of external devices, Flash memory Sticks, iPods, external hard-drives, printers and yes - USB DAC's and other USB Audio Devices.

It was meant to replace a lot of different computer peripheral connections systems, the names of which only curmudgen's that grew up in Mainframe "Dino-Pit's" still remember and has largely succeeded.

An alternative to it is called Firewire by the marketing guys and IEE1394 by engineers. It works largely similar to USB but is used much less frequently. It may be a little better in some ways than USB but the reasons are obscure and keep geeks debating all night over rounds of beer, to heavy for here.

In many ways we can lump USB and IEE1394 into one basket where high end audio is concerened. In my experience IEE1394 is a bit of PITA with a lot of chipset incompatibilities and can be a nightmare. If it works, it works fine but dislikes "hot-plugging". While a bit flaky and "plug & pray" in the early days I find the current USB systems mature enough that they work reliably pretty much all the time.

So, USB as such, absolutely no issue, no inferiority complex to firewire (no matter what man behind the curtain says). So, all clear.

USB Audio - The Guns of Brixton - Class Warfare writ large?



("The Guns of Brixton" is a song from the 1979 Album "London Calling" by London reggae punk rockers "The Clash", foreshadowing the race riots in Brixton and on the Broadwater Farm Estate in Tottenham in the mid 80's)

The first digital audio chips with an USB in/out appeared around the year 2K or so. The early 2K's saw a number of USB Audio devices, some of which where very bad (but are still used), while especially the Burr Brown PCM2704/2705/2706/2707 series allowed digital outputs that where at least as good if not better than really well implemented SPDIF at it's best (and "like it's not even funny" better than badly implemented SPDIF).

It is at this point that some High End audio companies with some vision and foresight started to integrate and optimise these Chips into their DAC's (or in my case into CD-Players) and the two new product categories of "USB DAC" and "USB connected CD-Player" were born.

I think it is just to credit Wavelength's Gordon Ranking as the father of USB DAC's, while yours truly had a bit to do with the second category.

Now the first generation USB Audio Chips as well as the second generation Burr Brown PCM270X Chips and some quite recent chips (such as the chip in the two 96KHz USB to SPDIF converters reviewed in last month stereophile) all use the Drivers that M$ build into Window$ and that Apple put into O$X.

These are known as "USB audio device class" with a 1.0 implied.

USB audio devices that work according to this specification (short called USB Audio Class 1.0 which is still not very short) can be connected directly to a PC or MAC and work almost immediately, no special drivers are needed, it is just plug and play.

There is a catch of course. You knew there would be one, right?

The vast majority of USB Audio Class 1.0 Devices are limited to 48KHz/16Bit though a very select few can handle 24 Bits and up to 96KHz sample rates in Class 1.0.

The Solution, you guessed it, is called "USB Audio Class 2.0". It can do 192KHz, even more if I read it right. It can do pretty much anything anyone would have wanted USB Audio to do ten years ago. I have been hearing about this for years now, everytime it would be out really soon now. And I have evaluated a number of USB Audio 2.0 Chipsets and solutions. They generally all work okay.

Why have you not yet got the chance to buy a High End USB Class 2.0 Audio DAC (actually, there may be one or two, but even I have not heard about them)?

Because M$ broke the USB Audio Class 2.0 Driver build in Window$ XP Service Pack 2 (IIRC) and Apple did reputedly a job only slightly better implementing it in O$X (means it works. sometimes. kinda.).

And either company has yet to properly fix their operating systems, quite a disgrace given how much time they had to do so. So USB Audio Class 2.0 is right now going up about as well as the proverbial led zeppelin.

Given that a few chip makers have sunk small fortunes into developing USB Audio Class 2.0 silicone - maybe they can put enough pressure on Apple and M$ to get their fingers out some time this century.

Until then, if you want 192KHz/24Bit to work properly across USB you have to write your own driver for Window$ and O$X. I have a great deal of respect for Gordon Rankin's effort in writing his own software for the BB USB Chip, the technology he now markets as "Streamlength Asynchronous USB", but writing a really working USB Audio Class 2.0 Driver for Windows is a lot harder, come on, even M$ can't do it right ;-). No idea what it is like for people with Mac's, no picnic either suspect.

Big Companies like Creative/Emu pioneered writing your own drivers that avoid the USB Audio system entirely. Such drivers and the related devices use what is called "bulk mode", normally reserved for external hard drives to shift a lot of audio data quickly to the USB Audio DAC. There a local clock determines how the data is send to the DAC or SPDIF connector.

One further good thing for Windows users is, you normally get an ASIO interface which, with the right playback software neatly sidesteps all the hoops you normally have to jump through to get windows to produce a "bitperfect" (not re-/up-/down-sampled) datastream.

So, if your USB DAC claims to be 192KHz/24Bit but does not come with it's own Driver CD, I would have major alarm bells going off. Of course, the state on this subject is quite fluent and it may change tomorrow, when both Apple & M$ release service packs to fix their audio systems (yeah, right - and pigs fly).

This brings us to Asynchronous USB DAC's (finally I am sure you think, will he NEVER shut up?).

Asyncronous USB - Holding out for a hero??



("Holding out for a hero" is a Song by Bonnie Tylers from the "Footloose" Movie Soundtrack. It was written by Jim Steinman who also wrote most of the songs for Meatloaf - I guess you'd call the genre dramatic bomblast rock, just like the kind played by the fictional Band Disaster Area, you know, terrible songs with lyrics like girl being meets boy being under a full moon, which then for no apparent reason explodes. High Kitsch, so bad it's good. Boy the 80's where WEIRD!)

A crucial topic in digital audio is Jitter, well not in the 80's (toldcha, they where wierd), but nowadays.

Systems that work "Synchronous" imply that two clocks are being kept in good oldfashioned german goosestep, with one part of the system giving the marching beat to the other.

With both SPDIF and early USB Audio a system called a Phase Locked Loop (PLL) is employed and the source determined the actual clock for the conversion, with the DAC, SPDIF, USB or indeed Firewire playing slave to the CD-Transport or PC. Now the issue is that in order to be able to synchronise to the source, the slave must be able to change it's speed.

Worse, it must do so quite quickly, in case the source changes it's speed. So now first of all the DAC, in our case the clock slave will follow all the changes of the source clock and top of this it will add some of it's own and then there is the quite inadequate SPDIF connection system in CD Transport/DAC combo's.

Just to keep things interesting, copmuters have something called "Software Induced Jitter". It is largely similar to the problem with CD-Transports where a scrached disk is read 100% without errors but still sounds worse than a clean unscratched disk. In the CD-Player the servos work harder to read scratched disks and thus modulate the clock that usually runs of the supply.

In a computer running CPU intensive tasks while playing music causes power supply modulations in a very similar way to scratched disks in CD-Transports. And our DAC's being slaved to this faithfully follow all these "jitters".

Is there a way to untie this gordion knot? Sure. In a Transport/DAC combo we simply put the clock into the DAC and send it to the Transport, so the roles of slave and master are reversed.

Can we do the same for USB Audio?

Sure. We put a clock into the USB Audio Device together with a big memory buffer (it used to be called a "Digital Lense" in the old days).

Now our local clock in the USB audio device controls the audio stream and our software just needs to make sure to send enough data to the USB Audio Device to keep the buffer topped up.

The result? Computer clock and audio clock are completely divorced. Software induced jitter is cancelled. Best of all for a small high end audio company, the whole issues of clocks, clock jitter and all that are now well understood and we can do something about them.

That is why TRUE asynchronous USB Audio (be it using Class 1.0 Drivers, Class 2.0 Drivers or custom drivers) is so crucial.

If you want to know just what it takes to minimise jitter in synchronous PC Audio Systems head over to the Computer Audio asylum and have read of the CMP^2 meta thread.

Asynchronous USB Audio simply puts the problem back into the hands of the device designer. It does not as such mean that the implementation is competent or good, but it means at least that it can be.

It used to take me days to optimise a PC for Audio Replay via USB, now it is much, much simpler.

Now there is no way to easily check if a device is truely asynchronous. Many of the budget USB Audio units units draw their power from the PC, so even if they are Async, they bring the whole problems from inside the PC with them. Others have bad clock implementations, still others have both.

I wish there was as simple a way to determine if a given USB Audio DAC is "well implemented Asynchronous", but there ain't. Here you rely on the vendor to be open and to tell you what they use and how.

For now, confirmed asynchronous USB Audio Devices I personally know are the following (alphabetical vendor order):

Ayre QB-9 DAC - based on the Wavelength Audio Streamlength System, limited to 96KHz

diyhifisupply Cleo & Morello based on heavily modified Musiland Digital Cores with new powersupplies, clocks, tubes output stages etc., 192KHz/24Bit, ASIO, WASPI, WDM...

M2Tech Hiface and related devices - the original HiFace draws power from the computer, has not so great clock implementation and lacks ASIO but does 192KHz with it's own driver

Musiland Monitor Series - very good software and digital hardware implementation, shame about the rest, 192KHz, ASIO, WASPI, WDM

Wavelength Audio Streamlength based DAC's, limited to 96KHz

Some others claim Async, but I have been unable to verify their claims at this time (other may be able to do so) so just because I do not know about it does not mean it is not Asynchronous. In fact I would encourage those who know for sure (and understand the facts) to add to the list of "verified asynchronous" devices.

Some "commodity" USB Pro Audio devices are likely asynchronous (confirmed for EMU 0404 USB for example) however their power supply and clock implementations usually make Musiland look good and hence cannot be recommended as playback devices.

Currently I am unaware of any asynchronous firewire DAC (Pro Audio or High End), Weiss uses the TC Audio DICE chip, which has an extremely clever way of reducing jitter (also works for the SPDIF inputs), but it is not asynchronous. Any device using Bridgeco Chipsets is at last count also not asynchronous.

All of the major chipmakers USB Class 2.0 Solution Chips I tested where not asynchronous when tested and indeed, several where not even bitperfect.

Conclusion - Jessie paint your picture?



(The Joshua Kadison Song "Jessie" is supposedly about his breakup with "S*x in the City" Actress Jessica Sarah Parker. It is a song about promises not made good.)

For now, when you hear about the latest 192kHz Asyncronous USB DAC and you get "Fever" to buy one, take a cold shower first, then check the facts. That way you make sure you get what you think you will be getting.

I hope the above can help a little.

Ciao T
Sometimes I'd like to be the water
sometimes shallow, sometimes wild.
Born high in the mountains,
even the seas would be mine.

(Translated from the song "Aus der ferne" by City)
 
Hi J,

Very good write-up/summary Bcerry/Thorsten.
One correction perhaps - I would consider the clock implementation in the stock Hiface superior to the clock implementation in the stock Musiland.

Well, my comment on how musiland implemented everything that is not software and the raw chips was summed up with "shame about everything else".

Both HiFace and Musiland benefit from using external powersupplies, better powersupplies for the clock and in the case of the Musiland removing the clock from being directly generated by the USB Chip in a pierce oscillator.

And yes, the stock Hi-Face sounds often better than the stock Musiland. However, given both are USB 2 SPDIF converters it muct be noted that both have implementations of the SPDIF interface that are what I would call "defective by design", so there will DAC's where one or the other performs better.

So either M2Tech HiFace or Musiland Monitor need a lot of reworking to work correctly.

Ciao T
 
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