"...The USB interface is bidirectional, and has built-in error correction and buffering at both ends; it is an asynchronous interface. Clocking synch problems associated with SPDIF are not present with USB. The result is that the data on the disk is identical to what is leaving the DAC all the time...At start-up, the DAC tells the computer it can handle 16 bit audio at 32K, 44.1K and 48K. Since the USB receiver only has to handle these 3 frequencies, the clocking to the DAC has almost no jitter. SPDIF actually has to be synched to the exact frequency of the transport (i.e. if the transport is working at say 44.0896K instead of 44.1K the DAC has to sync to that frequency). Therefore the jitter problems of SPDIF are all but eliminated. The result is a zero error protocol to link between computer and DAC, with ultra low jitter... I wrote that there is no filtering : However, this unit uses a tube in it's output stage ("...Once converted, the analog signal is sent directly to a 6GM8/ECC86 dual triode output tube, which in turn drives a pair of output transformers..."); the tube probably has some sort of filter-like effect..."

Those considering a USB DAC may want to read my impressions in the above-linked post.

jd*

jessie.dazzle wrote:

Those considering a USB DAC may want ....

People make DACs for 30 years very complex and very expensive, some of them a very good. The last few years there is an army of little USB that sold for very little money has a few chips and a few op-amps. Many people who make them have even no own recourses to write own USB drivers. I do not make assumption that those DACs are not good, they might be very good but I juts a bit skeptical then they are not as good as the USB topology might allow them to be.

So, for sake of preventing a self-delusion, in a competition USB DACing vs. dual-clock DACing I would like to hear the USB DAC driven by S/PDIF and get a feeling that is a good DAC itself. I do not see people talk a lot about it… That is what I see a “problem” with idea of USB DACing.

tuga wrote:

Hello, I have owned a TDA1543 based Kusonoki style (passive I/V, digital filterless, non oversampling) DAC for almost two years. You can have a look at the measurements here. I find that this kind of implementation (Kusonoki) has a very distinct signature that is not very compatible with the reproduction of symphonic music: it's dynamically challenged, coloured, veiled and lacking at the frequency extremes. One could almost call it the digital version of single driver speakers.

tuga wrote:

...of manufacturers claims. They have to make a living out of selling their gear. From what I gather, the "select top 5%" are just that: no physical diferences, just tighter quality control.

tuga wrote:

About your comparison, it would help to know what speakers you are using and the material you played. The ADCOM uses the PCM1702 20bit chip which is technically superior but I had a Denon with the same chip that sounded like crap (in part due to a "tiny" transformer).

alexd wrote:

Hi all. We are small company, dedicated to creation of highest quality audio products. Analog and Digital. We have auditioned many music servers on the market. However most of them do not sound as good as good quality 16Bits cd transport. The approach of connecting MAC or PC to high quality External DAC is not an audiophile solution. The switching noise from MAC or PC power supply will find its way into your digital signal, which will cause jitter, noise, reduced soundstage, and harshness on your analog output. The best approach is to use a completely dedicated music server. Designed for Audiophile applications to start with. We have designed and built high quality external DAC (now selling direct from our web site), which deals with jitter. Our DAC improved computer generated output (SPDIF or USB-AUDIO) significantly, still the sound is better from High quality CD-Transport . Alexd 3 Dimension Audio www.3d-audio.com

alexd wrote:

Hi all. We are small company, dedicated to creation of highest quality audio products. Analog and Digital. We have auditioned many music servers on the market.

alexd wrote:

However most of them do not sound as good as good quality 16Bits cd transport. The approach of connecting MAC or PC to high quality External DAC is not an audiophile solution.

alexd wrote:

The switching noise from MAC or PC power supply will find its way into your digital signal, which will cause jitter, noise, reduced soundstage, and harshness on your analog output. The best approach is to use a completely dedicated music server. Designed for Audiophile applications to start with.

alexd wrote:

We have designed and built high quality external DAC (now selling direct from our web site), which deals with jitter. Our DAC improved computer generated output (SPDIF or USB-AUDIO) significantly, still the sound is better from High quality CD-Transport .

alexd wrote:

Alexd 3 Dimension Audio www.3d-audio.com

alexd wrote:

We are small company, dedicated to creation of highest quality audio products. Analog and Digital. We have auditioned many music servers on the market. However most of them do not sound as good as good quality 16Bits cd transport. The approach of connecting MAC or PC to high quality External DAC is not an audiophile solution. The switching noise from MAC or PC power supply will find its way into your digital signal, which will cause jitter, noise, reduced soundstage, and harshness on your analog output. The best approach is to use a completely dedicated music server. Designed for Audiophile applications to start with. We have designed and built high quality external DAC (now selling direct from our web site), which deals with jitter. Our DAC improved computer generated output (SPDIF or USB-AUDIO) significantly, still the sound is better from High quality CD-Transport .

Alex, I would like to point a contradiction in what you say. Your “high quality external DAC” is not usable with “many music servers” as it look like your DAC is 16/44. I can’t imagine anybody build a music server to play juts 16Bit files. Particularly considering that you agree that “sound is better from High quality CD-Transport”.

The point about switching noise from MAC or PC power supply is well taken and well know. It very much makes sense to build a conventional PS, non-impulse PS fro music servers, though I did not credible comments that it does make any sonic improvement. Intellectually the switching suppers are bad, I would agree with it, even thought I have no idea how switching supply might cause jitter. Noise, yes. The residual switching pulses, yes? But jitter? I do not think so, explain if I am wrong.

Also, I would like to hear your opinion what methodologically appropriate was you might suggest to identify that my current music server does suffers from switching PS problems?  I hear very same sound with no identifiable difference between direct feed of my preamp driven from tuner vs. the preamp driven via AD-DAW-DA path. If so, then how shell I learn about the tangible switching PS problems? BTW, sine I use “external”  PS for my DAW I might ease to try it…

alexd wrote:

Why are you so aggressive? Te specs on web site are most generic on purpose. We do not want the competition to copy our design before we applied for patents and protected our IP. If you'd like to know more details, call us and we will try to explain to you what we are doing, not how. Our company is in Carson City, Nevada. and by the way we are using Analog Devices dac IC in 16 bits version (DAC18), we will be using Texas Instruments in our 24 bits version (coming soon). The DAC18 got its name, because it took 18 month to create this product. It is not intended for music server application, but for highest quality Red Book  CD reproduction. For people, who want to use for a music server, we do have a USB input option. As far as Music Server goes, the single board computer with linear power supply or battery supply is correct approach, I was talking about MAC or PC.

alexd wrote:

To answer your question about DAW output vs tuner. Well Tuner is not highest quality source to start with. I do not think you will hear much difference between DAW analog output and tuner analog output.

It is unquestionable that an FM tuner technically speaking is not a highest quality source to start with but my demands for DAW is very practical and utilitarian – I record FM and my objectives for music server to be able handle FM, nothing more or less. I do not upload up CD, tapes or LP to music server. Still with all my familiarity with FM limitations I might assure you that good FM incredibly complex source for DAW recording and reproduction. A good FM station, a good tuner and a good quality LIVE Broadcast is so sophisticated material that any if not the best A/D, DAW, D/A will round it, even at the limited technically quality of FM. You see, LIVE is live and it has (in some cases) such a complexity of imaging and space that bad digital kills. I have a few cheap USB-based A/D and D/A in here that I was conceding to use for second recording system – they just do not handle FM quality, whatever the quality FM is. So, I would be cautious with your discard of FM quality. I believe that I do have an access to the very good alternative to FM sources (CD, LP, Tape) and frankly speaking I do not feel that FM is some kind of “black ship” among audio sources.

In a contrary to what you said when I try to observe a difference between DAW analog outputs (I used externals DAC) and tuner analog output, in case if I screw up something with my DAW, then I do hear a very clear difference. Over the time I have developed my own methodological ways to tell is the A/D-DAW-D/A chains performs well and equal to what my FM stream does. Change 1dB of gain on DAW – and the A/D-DAW-D/A chain immediately underperforms... There are some other check points… That is why I asked you if you have any check points for subjective testing the noise from impulse PS.

alexd wrote:

by the way we are using Analog Devices dac IC in 16 bits version (DAC18), we will be using<br>Texas Instruments in our 24 bits version (coming soon). The DAC18 got its name, because it took 18 month to create this product. It is not intended for music server application,<br>but for highest quality Red Book&nbsp; CD reproduction.

jessie.dazzle wrote:

In my case, the CD transport (which is no slouch) is soundly beaten. Apart from using it to make the occasional comparison, I have not touched the CD transport since unpacking the DAC.

Jessie, I see an inconsistency in what you say. You are pleased with your USB DAC driver from you DAW but you still load files to you music server from CDs, that mean that you still read then via some kind of transport, would it be DAW transport of external dedicated audio transport. Where I see the contradiction is in my view is that what we look at the performance of the transports we need to abstract ourselves from our takes on DACs. Feed the DAW’s transport and dedicated audio transport into the same DAC. Do you still feel that it is “soundly beaten”? 

Let me give you a test to discover for yours where the sound is been lost. Find a raw stream from any good A/D converter. You must not use DVD-A, SACD of any other souses – they are already ruined by media. You need a raw 16/44stream from A/D. Save it in 16/44 format and listen it from you music server. Then use any available fore you mean to put this file to CD and read it from any transport you have. No matter what you do you will have severely worsened sound, make a conclusion.

The point is that CD format itself, not even the 16/44 is a bitch. The same is with any other format. You might have a good 24/96 file but as soon you load it to DVD-A it turns to shit. A raw 1-bit at 2.8224 MHz DSD is very fine but ported to SACD disks is it loses a lot, not to mention that the whole DSD conversion saga is a fraudulent in a way. The transports of DAC is not a problem the media is the problem. So, the fact that you do not touch the CD transport since you did whatever says very little as you still are touching a CD transport each time you are uploading you CD to you DAW.

scooter,

I think you are not clearly understand at what kind “forum” you are participating. There is no “board awareness” and there are no needs for any “board demo trail”. One of the accomplishments of this site that people do not give a damn about other and everyone on their own. I insist that it is the way how it shell be and if you propose other alternatives the you are in a wrong place. There are absolutely no needs for “group consciousness”. If you like Alex’s DAC then contact him directly and do not convert this site inot AA of DIYAudo type of crap. There is no need for you to discuss or to argue the subject of the “horde evaluations” any further in this thread.

alexd wrote:

The issue of properly handling FM signal is related to the capabilities of your A/D converters. Your A/D converters have analog and digital anti-aliasing filters and delta-sigma modulated A/D chips.

Actually if I am not mistaken my A/D do not use any delta-sigma modulated A/D chips as it is a pure multibit A/D. It is not important however. What is important is that for sake of A/D conversion the FM recording is surprisingly nasty thing. FM cares its stereo information in subcarrier up to 53kHz and if the subcarrier and the 19kHz pilot are not properly killed then they interferes with A/D inputs. Anyhow, this is not the subject of FM and it’s recording so I would call myself for a discipline. However, the message I would like to send that there is no need to demean FM as some kind of inferior sources. In my home FM beats hands down any other source and if you have a good local station then it would do in your home as well. Saying it, I do aknowledge and understand all limitation of FM.

alexd wrote:

Even then, every recording is highly depended on recording engineer's taste and skills. In your home set-up, you have very limited control, almost everything,  except gain is preset.

And here is where the live FM broadcast acting as a liberation force, taking the “taste and skills recording engineers” (which are mostly insultingly-barbaric) out of the consideration. It is my favorite subject but it s not the subject of this thread, I have a separate forum dedicated to off-air audio.