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zenelectro last won the day on March 29 2012

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  1. zenelectro

    AKM new Verita AK4499EQ dac

    This is the first of a portfolio, you can be sure. You can also be sure there will be an 8 ch version which will find it's way to Pro Audio apps. I imagine 140 DR was the target to match Sabre and it took 4 channels to do it.... possibly?
  2. zenelectro

    AKM new Verita AK4499EQ dac

    So they finally ditched the switched capacitor, CMOS opamp output of the 4497 etc and went current OP ..... yaaaaay! There were whisperings over at DIYA quite some time ago that this was their way forward. And it doesn't have that stupid internal ASRC / 100MHz clocking of the Sabre. I hope it's a true high impedance, current OP DAC, as opposed to the usual hundreds of switched unity weighted resistors = very low OP Z in mono mode (Sabre) I'm excited! T
  3. zenelectro

    Singxer SU-1 USB Bridge

    Hi George, If you are referring to I2S direct from PC or a transport, yes USB done right -should- be better. FWIW, USB -is- I2S, that's what generally comes out the back of the bridge. Ideally the I2S is isolated from USB and reclocked. Terry
  4. How would you characterize it subjectively speaking? Measurement wise, it is hard to fault. T
  5. zenelectro

    Crown Beast

    Yes, typical for a pro type amp. I will be increasing cap size but won't go crazy. An other interesting feature is the live, copper bus heatsink. The topology is called grounded bridge, which implies swinging PS rail(s). It's one 150V rail, but it swings 1/2 the signal. These amps actually sound surprisingly good... prolly because even at loud listening levels they are just doing nothing. T
  6. zenelectro

    Crown Beast

    I have three of these in for repair / general service. I measured approx 1000 Watts RMS into 8 ohms. Serious power. T
  7. It's worth noting that the Marantz's 28 resistors could be 14 (2 x 7) per channel in a balanced configuration. FWIW, if you asked me what is the best architecture overall for a DAC - I'd be hard pressed to give an answer - they ALL have strengths and liabilities. T
  8. Just to clarify, it *IS a form of DAC, it's called a box car filter. This is what Bruno used in Mola Mola DAC, HQplayer has a DAC which is same. The pulse stream gets fed into a shift register type arrangement of N equal weighted bits. Each register's OP feeds a resistor. Each clock cycle transfers the registers 'data' (a H or L) to the next bit. All of the resistors which are unity weighted (the same value) are summed into a virtual ground I-V. The virtual ground I-V is not absolutely necessary but it works better (more linear). There are absolute advantages to this type of 'DAC' to a R2R, the biggest one being resistor mismatch doesn't matter. The shift register arrangement has a low pass function but it is very slow roll off and does not have any ringing, ie; perfect transient response. It also has some disadvantages : a/ It still does have a significant amount of HF energy, but far less than the original 1 bit stream b/ There are non linearities associated with finite rise and fall times. So the 'energy content' of the wave is not perfect. The solution to b/ is to use some kind of RTZ (return to zero) or equivalent coding which nulls out the non ideal rise and fall time content of the pulse stream. Terry
  9. Thanks George, Yep, got that one too. It's far too simplistic. I'll get the AES paper on Colinear Architecture by Burr Brown at some stage. T
  10. I checked out some other pics, it is as described earlier, a type of pulse array DAC.
  11. They don't have to, nor would they likely anyway, make their own DAC chip. It's a simple resistor array driven by high speed logic. Or maybe they are using Sabre etc with everything disabled / bypassed. These day there are so many ways to do conversion well - we are lucky. George, on a separate subject, do you have any info on Burr Brown colinear (sign magnitude) DAC arcitecture? I've seen the usual stuff on 1704 but am after more detail on how the CCS's are arranged. I know there is an AES paper, might have to buy it. cheers Terry
  12. George, It appears they are converting everything to 1 bit DSD after which you can directly convert to analog. Looks like a similar concept to the Mola Mola DAC where it is basically a bitstream fed to a multi-element, equally weighted, DAC architecture. I think Chord Dave (pulse array dac) might be same. So if you had say 16 elements (resistors), the DSD signal gets shifted along those 16 resistors, one at a time, with every clock cycle. The end result, at resistor summing point (OP) has some good properties: - The HF noise is attenuated significantly as this acts like a low pass filter. - Even though it is a low pass filter, it is transient perfect WRT the fact that it has zero ringing. - The resistors don't need to be matched. Any mismatch does not affect linearity at all. These DAC's can be made VERY linear so long as you take into account finite rise times, which can be addressed with RTZ type coding. Having said all the above, expect more development of R2R DAC's. They haven't yet fully exploited this technology. The Holo Springs appears to me to be one of the best implementations so far. I do also like the Kassandra DAC using AD1865's in a very smart configuration. T
  13. zenelectro

    PDX DAC project

    7904 / 500 Meg will do it! Are there any modules you haven't got?
  14. zenelectro

    PDX DAC project

    Just a quick addition: The ultimate performance of your DAC will be highly dependent on how you implement the digital side of things. It's all about keeping noise out, distances short, ground impedance low, ground planes where possible etc etc. A 100 MHz Cro is also your friend. T