Ultimate Equipment Test!
We have seen tests where users have been asked to judge the quality of equipment by comparing a recording of it's output to a direct copy of a digital source file. The recent Squeezebox test on PFM was interesting due to the low cost of the equipment.
I think tests like the above mentioned are very stringent because not only are you comparing it to a pure digital source file, but you also include any distortions generated by the equipment used to record the item under inspection.
It seems to me that such user interactive listening methods have started to get some credibility for the notion that affordable digital gear can be very good.
However lets see how far we can take this...
I have uploaded three files below. File A is a direct bit accurate copy from the CD. File B is played through my DAC, and then recorded by my ADC..... [B]ten times[/B]! So that means the file was played and recorded, that file was then played again and recorded again, and again and again... Each time the distortions of the equipment will build up, just like taking a copy of a tape from a copy. File X is a mystery, it is either the same as A or B.
I'd appreciate if you would download each of the three files and listen to them on a quality system. Burn them to a CD if you can't play from the computer. Take your time to listen and don't feel any pressure to be right or wrong. This is a test of the equipment, not of you! Please then vote on which file you think X is the same as. Is it the pure digital rip or is it the the 10x recording? You may also vote if you are not sure.
I'd like to add that I have no preconception about this test. I believe doing it once through the chain is inaudible... but ten times? I'm not so confident as it is a damn tough test!
Please Note: This test is running on multiple forums. Please only vote on one forum as I will compile the results later.
Also, the recording is 'We Added It Up' by 'My Brightest Diamond'. I hope no one will object to its use in this test but if you do, please let me know and I'll remove it.
Comments
I've never made the time to participate in these tests before, though I agree they can be very interesting.
Surely there are additional variables at work here also, not least the replay system the listener will use (making the fairly safe - I hope - assumption that the upload, download and the mediafire server/processes are completely benign).
I'll try to do the test within the week, though getting it onto the big system is a faff compared to the office system.
Thanks.
The more times i listened, the less sure i became, but i couldn't make myself change my mind after a few listens.
There's my head on the block...
:-/
Yes mun - We've been tricked...!
BTW, I object mildly. It's a bit...meh.
Drum roll...
:-?
8->
As you are dealing with Ultimate Test Equipment, perhaps I can interest you in this.
My partner and I have been employing here in Italy a new test - Nul Test Difference - which was perfected by him. We employ it, for example, to test the fidelity of signal coming out of DAC compared to original track.
Please see this independent review for an example:
http://translate.google.com/translate?u=http%3A%2F%2Fwww.nexthardware.com%2Frecensioni%2Famplificatori-dac%2F582%2Fweiss-dac202_5.htm&sl=it&tl=en&hl=&ie=UTF-8
Firstly, I'll try to give you some brief indication on NTD:
The capture card cannot generate errors...it sounds obvious...it has to be very stable. precise and constant.
The same card doing a "self" NTD in loop, therefore placing a complex signal in antiphase, must generate a null signal. If one changes a component, such as a power cable, differences can be noticed (if variations with a power cable are possible) by doing a double acquisition of a piece of music with one cable first, and then with the other cable taking into account the very same capture level (dB).
The two signals are placed in a sort of sequencer, then time alignment on the first samples is needed within 30ns and, finally, one of the two signals is going to be reversed (absolute phase).
Simultaneous playback through the sequencer will make the two acquisitions face each other. Like into a mirror, the two are compared in terms of both amplitude and time domain.
The produced signal (or not produced), which is the result of the two signals put in antiphase, is going to be sampled (with the same capture card). Then moving it onto an analyzer, further assessments/considerations on the level of error produced can be performed.
All this explanation is for testing a single component, that is trying to catch a difference between the two.
However, when you test the degree of fidelity between two devices, after having acquired the signal, it will be necessary to compare directly with the original track. It is possible to assess the deviations in amplitude and time domain. Obviously, an extremely precise, micrometric procedure of calibration is required, as the system is quite sensitive. At least you should maintain a range of difference not exceeding 0.01 dB.
A detailed explanation is at http://www.nexthardware.com/forum/computer-audio-hi-fi/74675-null-test-difference-di-tom-gefrusti.html but unfortunately is in Italian.