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NOS DAC - Marketing BS? - Page 23

post #331 of 338

Okey dokey then.... http://www.computeraudiodesign.com/bristol-sound-vision-best-sound-of-show-award-winner/

Distortion is cool if you adjust to for DC correct offset.

post #332 of 338

Well, it might sound good. But it is for sure accompanied by marketing BS.


An example: Computer Audio Design claims to use R2R DAC chips but then when you read more closely, you find out that they use the TD1543. Which is not a R2R DAC but a rather poor multibit chip (it was designed by Philips as an economy part, as explained in its datasheet). By claiming the R2R part, they try to capitalize on the reputation of true high end R2R DAC, such as the PCM1704 or AD1865.


I also wonder how they manage to have, I quote, "less than 1 cm from the USB board to the DAC chips" while using 16 DAC chip in DIP8. Well, sorry, but that seems pretty impossible in terms of size.


The audio optimization guide is also a paradox in itself. This guy design a DAC with asynchronous USB input and galvanic isolation (making it independant of the quality of the USB stream coming from the computer) and then goes on to suggest to disable everything on your computer to improve the quality of the USB bus. Paranoia comes to mind.


I also cannot help but notice that all the reviews are by the same reviewer...


This being said: the TDA1543 has a long history in the diy community. It's very cheap, it's easy to use, it has a strong output (making it easy to use passive I/V), its distortions, while very high by today's standards, are pleasant. Paralleling a boatload will reduce noise and distortions. No doubt it is nice to listen to.

post #333 of 338

lol a bunch of TDA chips for 7K£, I guess the super duper power cable is the real game changer here.

post #334 of 338

Which DAC chip would you suggest that he had used that would have satisfied you in terms of the asking price?

Too many times people focus on the DAC chip used in order to validate the price of the finished product. But you are paying for far more than just a chip. There are also screws, resistors, packaging, support, future R&D, etc. etc.

post #335 of 338

Of course you pay more than the chips... obviously even more so at 11000$. But here the ratio is just ridiculous.


To put things in perspective, it's the same price as the DCS Debussy DAC.

post #336 of 338

I used to own the Metrum Octave, which is a bit different from a typical NOS DAC. No issues with ultra-high frequencies as I measured it to have steep roll-off up to Nyquist. Feeding it high-res files (which effected the same thing as over- or up-sampling) improved the sound a little (and also changed the cut-off filter from what I tested).

post #337 of 338

I believe they keep the model numbers of the DAC chips used in the Metrum Acoustics units secret so it's impossible to read any datasheet and check whether there is actually some oversampling applied internally.......quite frankly not oversampling is not technically possible AFAIK. Even the TDA chips oversample(as per their datasheet proves) as this is mandatory for a D/A conversion, I believe Mr Lavry confirmed it clearly when I raised the subject in the OP. Not oversampling whatsoever is really caveman technology and would throw THD figures up through the roof.

Edited by leeperry - 6/15/13 at 1:09pm
post #338 of 338

With regards to the Nyquist issues has anyone tried interpolating aka upsampling in the PC i.e feeding NOS with 88.2Khz or 176.4Khz, in theory this should push the images and any aliasing to twice (or more) the "normal" frequencies. I have had no problems using the SOX resampler in foobar for this purpose. My dac-ah uses an fairly ancient CS414 receiver so 88.2Khz is as far as I can go..i feel it may well be enough as it will effectively give me 44Khz playback bandwidth before any native NOS artifacts become apparent if indeed they actually are of any significance in the first place, although I am certain the treble is a shade more extended when A-B'ing.


This post could be called "how to double or quadruple the frequency response and of a filterless NOS dac and shift aliasing to 66-68 Khz"

I hope this explains better than I can.






A picture paints a thousand words.

Edited by 405line - 1/25/14 at 10:05am
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