drdigital

I have to say that once again Mr Nugent is actively selling his products claiming scientific fact without reference to measurements or calculations! Steve, I think we are all well aware of where you are coming from, gives us some figures or shut up! Your posts are words circling a drain! Power supply rejection ratios, regulator noise are all basics understood by 11 grade DT students. Quite why the moderators let you get away with such obvious promotion of your products in this way is beyond me. Once again, here is the challenge; prove it or shut up.

The writer of any Media player software would be able to show why his product produced an 'improved' output compared to rival players and yet not one offers any validation for their claims, mind you why should they when there are plenty of subjectivists ready to lap it up. As someone said; Personally, I would rather fly in an aeroplane designed using mathematics and measurement than one designed by someones 'opinions'!!!

Interesting comments, very informative, thanks. They do have a good catalogue. Have a look at http://www.gimell.com/ if you are keen on The Tallis Scholars they offer recordings up to 24bit/96k.

Quote:Here are some interesting opinions from other industry experts: http://www.positive-feedback.com/Issue41/ca_intro.htm You will notice that jitter is #1 or high on the list of almost all of them. Steve N. Empirical Audio End Quote Steve; It is hardly suprising that hi-enders spout on about jitter, it became an industry obsession years ago so any hi-end manufacturer would be foolish not to jump onto the 'Jitter-wagon' !!! In one of your posts you completely trashed the pro-audio industry as DAC makers but you completely miss the point that it is the self same pro-audio industry that supplies most of the ADCs used to make the recording in the first place. As any digital audio engineer knows; Jitter at the ADC causes the same problems as at the DAC!!!

Has anyone used these? They appear to be DRM free.

Did you manage to resolve this? Does the DAC need bespoke drivers or can it use the default drivers (restricted to 16bit 44k I think)

Tom, if you really want to produce a minimal install then use a program like nLite to make a new XP installation disc with the minimum of components. I used it to make a tiny XP installation for my Asus EEE. If you search the Asus EEE support forums there is a list of XP components that can be removed safely. It is a good way to waste an evening though!!!!

So Steve, you were design lead on Pentium2, shame your hyperlinks to your many patents don't work! I will have to take a close look at my old P2 PC, I didn't think there was any valves in it but I might be mistaken!

Tim, Amen and Hallelujah!!!!!!!

Steve, Quote: The problem with 99% of consumer (and most pro gear), is transient response, not frequency response. This is the response to an impulse function. Most gear compresses the impulse function. This is never in the measurements.End Quote. I presume you have measured this and therefore have the figures to back this up? If so could we see them for ourselves please. Also a transient response of your USB DAC with valve in it would be intertesting, come to think of it distortion figures would be useful as well. I hope you can oblige

Jitter on a DAC sample clock produces noise sidebands either side of the wanted signal, the level of these sidebands can be calculated and unless the DAC system is really bad the noise sidebands are well down at or below the noise floor. Hifi gurus often spout theories and scientific fact without any quantitative data to demonstrate the magnitude of the effect especially if they have a magic product to sell. There are thousands of words by such people on this forum but without solid supporting data they are just words circling a drain! Ignore them and get on with enjoying your music, leave them to their obsessions about Jitter, the quality of the 0s and 1s, the crystal structure of their cables and any other 'problem' they can invent a magic cure for!

Jitter is present on all digital transmission systems, in a digital audio system it is only of importance in 2 places, the sample clock on an ADC or a DAC. However digital audio data is transmitted it doesn't matter how much jitter is present on the data stream provided it doesn't cause a data error. The downstream device would be expected to generate a sample clock of adequate stability whatever the incoming data jitter. Jitter on the DAC sample clock is measurable by measuring noise sidebands on the audio output. Interestingly, purveyors of so called jitter busters never seem to publish such measurements, you can draw your own conclusions from that!!!

Steve, the effects of mismatching are easily calculated and measured. Quoting a scientific fact is of little value unless the magnitude of the effect is calculated or measured. Like many in the Scientific and Engineering community I despair when people use quotes of scientific fact in this way especially when it is done for commercial or political gain. "A lot of USB terminations are so bad that they will not work with the specified 5m cable length. I have to mod them to make them work." Do you mean specialist audio devices, I don't imagine you mean the 100s of millions of Printers, Digital Cameras, Back-up Drives, Mobile Phones etc etc in daily use!!!! In fact the subject of downstream device termination is covered in great detail in all the USB specs. At the end of the day a compliant system will handle considerably higher bit rates than those used for audio streaming without error, and if you read my previous post you can see how this can be proven. The USB spec also fully specifies data jitter, the designer of any USB device would be aware of the data jitter limits his product is expected to work with (since he would want his device to be compliant) and take the appropriate steps. If data jitter within USB spec limits have a measurable effect on a USB DAC it is reasonable to conclude that the DAC designer has either ignored it or made a mistake. I mean no offence but it is vital to give calculated or measured results when using scientific facts so the magnitude of the effect can be seen, with apologies to fans of Hitch Hikers Guide to the Galaxy I will sign off with a misquote: Due to an error of scaling the entire alien invasion fleet was swallowed by a small dog.

Steve, USB spec requires 90 ohm characteristic impedance line terminated in 90 ohms, therefore the SWR is unity and there are no reflections in a compliant system. Losses and dielectric absorption are not relevant since the USB cables are short, the attenuation allowed in the USB spec indicates this. It is 650 pages long but I really recommend reading it. I agree with your last comment!!

Dear Tim, good questions!! EMC is ElectroMagnetic Compatibility, basically these are set of rules and regulations intended to make sure that any electrical/electronic item that you buy neither interferes with another product nor is interferred with by another product. The USB specification covers this issue in great depth since it is critical to achieving high data rates without errors, suffice it to say that at the relatively low bit rate of streaming audio there should not be any corrupt bits at all even in the most hostile domestic environment. It is conceivable that an extreme external event might produce an error but the system is really robust provided all the USB elements comply to the standard. Isochronous data transfer, such as live streaming, involves sending data packets in sequence at regular intervals, the system cannot repeat a data packet if it is received with an error, this is different from the way data would be sent to say a hard drive where the received data packets are checked for error by the reciver and if a corrupt packet is detected the receiver requests the host resends it, (this is handled by the USB hardware). Taking the industry standard TI part, PCM2902, if our hypothetical error occurs there is a no way the DAC chip can know, so it simply converts the audio samples as received, so the audio output would have very noticable distortions in it. e.g., with a 16 bit PCM audio word:- MSB 0111111111111111 is maximum positive 0000000000000000 is zero signal 1000000000000000 is maximum negative Say we have a sample at maximum negative, 1000000000000000, if the most significant bit was changed due to an error then the code becomes 0000000000000000 and the DAC will output zero not maximum negative. Infact for any data value, negative or positive, if the most significant (sometimes called sign bit) changes then there will be a jump equal to half the peak-peak signal level. If a received bit is in error then any of the bits from the most significant to the least significant have an equal probability of being affected so you can see that by the law of averages once in every 16 errors the audio distortion will be huge (50%). Since we do not hear these gross distortions it is reasonable to conclude that there are no errors in the received data. (As Spock said: If I let go of a heavier than air object on a planet with positive gravity I do not need to see it fall to know that it has fallen to the ground, approximate quote!) The same argument applies to the S/PDIF data, if an audio bit is received incorrectly over a S/PDIF link by the law of averages sometimes it would produce gross distortion in the audio output. If you don't get obvious clicks, periods of mute or occaisional gross distortion then your system is bit perfect, nothing less. Where several AC mains powered devices (especially ones using Switch Mode Power Supplies like a PC) are electrically coupled through interconnects there will be a possibility of some low level high frequency currents flowing on the interconnects, in practice these should be very small (EMC standards again) and should certainly be nothing like large enough to cause data errors. The bottom line Tim is that you would be very aware of any data errors if they were occurring so rest easy!!!