New Audio-gd R2R 7 & R8 Flagship Resistor Ladder DACs

Discussion in 'High-end Audio Forum' started by Currawong, Jun 30, 2017.
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  1. astrostar59
    That is correct, my AMR has an NOS board and has a filter still, as did the early Audio Note DACs which are NOS R-2R. Later they removed the filter and they sounded better. And R-2R does not always signify NOS, as in many of the MSB DACs, that upsample to then apply there filtering.
  2. Currawong Contributor
    According to their tech specs, the "NOS" refers to a new-old-stock tube used on the S/PDIF circuit. The rest of the description suggests some kind of filter in use, at least for the DAC chip used for high-res music. The "bit perfect" filters for the 16-bit chip could be of a closed-form type, which would match those criteria. The rather confusing explanation on the page suggests as much, so there is almost certainly a filter of some kind and the DAC is NOT NOS.
  3. FredA
    It is common knowledge however that nos dacs have rolled off highs. You most definitely need a compensation filter to avoid a loss of high frequencies that is caused by outputting a stepped wave and let it be passively filtered by your gears downstram. That is basic digital signal processing knowledge. I took this course in my younger days. Audio-gd does this digitally.
    Last edited: Jan 1, 2018
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  4. astrostar59
    Quote from the manual:

    CD1. Bit-Perfect I – this mode directly takes the data extracted from the inputs and re-clocked to generate themusic signal. Due to the complete lack of digital or analogue filtering, the treble frequencies are slightly rolled off,making the sound somewhat soft and laid-back. For the same reason, the mid-range and below is very natural andrealistic. The reproduction of impulses is completely undistorted. This mode often helps to tame overly-bright recordings.

    As to wether the 16 bit perfect part of the board is NOS, I believe it is, as have read that statement in magazine reviews and quotes from AMR back in 2015 when the DP-777 was quite popular. The DAC has 2 digital engines (celebrate PCBs) and using the 16 bit one and in 'Bit prefect mode 44.1' it won't accept anything above Redbook, not even 88.2 or 96k. I believe it is NOS, it was marketed as such, and the whole point of the other board (Gemini engine) was the option or more traditional DS conversion.

    It actually sound really good using the Bit Perfect board TBH. I will probably keep it as a spare DAC after my Aries Cerat Kassandra Ref II lands.
    Currawong likes this.
  5. FredA
    Read my explanation above. Technically, compensating rolled off highs is not oversampling. So you can legitimately apply this kind of processing/filtering and still call the dac Non Oversampling
  6. Currawong Contributor
    Thanks for those explanations.
  7. astrostar59
    I would say (again) the 16 bit perfect board in the AMR is non oversampling, it is not DS technology, it has no filter in mode 1, and because of the non oversampling or up sampling has a 'negative' aspect to loosing -3dB at 20khz. The TotalDACs say the same thing. What is muddying the waters a bit is the chip quoted by AMR has no data sheet in the public domain according to the 2015 AMR threads on various forums that flagged that up. Oddly, AMR seems to have fallen asleep somewhat. The website has not been updated for 2+ years, and the Signature version of the DP-777 was badly handled which lost a few customers IMO. But I would say, the standard DP-777 is a great sounding DAC at it's price point, and used can be had used for <1.5K. It has a very natural timbre and flow to the music, possibly as the line stage is also tubed, and the power supply and parts quality seems good. It can be upgraded with Duelund caps, though I haven't done that myself. Interestingly is has a tube at the S/PDIF input which is quite an oddball. Seems to work well though.

    The rolled off highs, quite possibly, but in my system I don't seem to miss that effect TBH. The Stax 009s are already very transparent already even when fed by my Carbon DIY amp, and my big Zingalis also don't seem to miss it much either. Many DS DACs that purport to a perfect response, huge dynamic range, vanishly low distortion and noise figures fall flat in real life listening IMO. The CH Precision C1 for example, it sounded way to synthetic for my taste, just too 'hi-fi' and untimately not a long term listing experience. Same with the Esoteric K-01 and D2, MSB Platinum IV, so many others.

    I am hoping my life long search for digital sounding as good as analogue is coming to a close...
    Last edited: Jan 1, 2018
  8. FredA
    No problem. I dug this question a few months ago. It was puzzling me as well.

    From a certain sample rate up, you don't need to compensate. It's most important with 44/16 material. The compensation function needed depends on the sampling rate. Personnally, i prefer when os is done. It gives a more dynamic sound, but this addition of dynamics can make a dac sound artificial. There are an infinite number of interprations to the samples and i assume designers make design hypothesis and choose whatever they think sound best in the end. With hires formats, you don't need to play that guessing game so much. In any case, i find that today's dacs really do a fine job of emulating hires. As a proof, i don't care so much about hires, although i can hear the difference with true hires stuff, meaning not those pseudo hires files some seller i will not name has available online.
    Last edited: Jan 1, 2018
  9. FredA
    Still with the accurate fw.

    One jumper only, att1, whatever this secret setting does. I have a cold so take my impressions with a grain of salt.

    I have a semi-forgiving interconnect combined to an unforgiving one in the chain. I hear a very good balance, the sound is not bright, or so little. Compared with att0 and att1 on, i have a cleaner more resolved sound, with more texture, but brighter without the cable swap. Old jazz starts to sound as i like. The soundstage does not have as much depth as with the 6moon config but with recordings that actually have depth, like Dizzy Gillespie Concert of the Century, the soundstage is impressive. I have some software os done also (2x), which smooth things out a bit.

    For whatever reason (jumper only?), the accurate fw does not sound as bright as in my souvenirs. Overall, besides inferior soundstage and the highs that can a little bit over the top without tuning, i consider it better on everything else. I think it's could be more fatiguing but i will try this config for a few days to validate my thoughts.
    Last edited: Jan 3, 2018
  10. DACLadder
    Hi @FredA, what other DSP jumpers do you have set besides adjusting ATTx modes with Accurate FW? Are you operating in NOS mode? thanks...

    My headphone setup has finally run in a bit and time has come to try again the latest FW in the Singularity 7.
  11. FredA

    I only have the att1 jumper on (so in OS mode) now with the accurate fw. I might try the 6 moon config doing sw upsampling next, i'll see. I am not sure if the accurate fw changes the sound of the s7 cause it's not the same load you drive with the dsp (the only difference with the accurate fw is it configures the dsp outputs to the dac modules to have more driving capacity). It makes a big difference in how the r2r 7 sounds however. Like they say, the devil is in the details.
  12. DACLadder
    Oh, I see.. interesting and thank you.
  13. FredA
    It's been almost a week of playing with settings with the accurate fw.

    Back with the 6 moon config, with audirvana upsampling to 352/384 using a 1 million sample window, i now have yet a new winner. It's everything the sound was with the smooth firmware and same config, only more dynamic and accurate. Microdynamics to die for. Could be too smooth or laidback for some. Bass is firm, mids are rich and treble is silky and accurate.

    It's no joke, the accurate fw really plays more accurately. You don't need to crank up the volume, the dynamics are also clearly superior with it. It gives you the impression that it plays louder, so you can turn down the volume and still get the rythm correct.

    On important note, i noticed something was picking static electricity in my setup (the air is so dry in the house, static electricity builds up quickly). I found the problem: the intona and its plastic case. I wrapped it up in aluminium foild for now and ordered copper tape to stick all over the interior of the case soon. Since i did this, i noticed the sound is more relaxed.

    Bottom line: i will never go back to the smooth fw. With the default config, i think i would still prefer the smooth fw, but otherwise it's the accurate one all the way. I will try it with dsd within the next week. I expect great sound.
    Last edited: Jan 4, 2018
  14. Currawong Contributor
    I thought I wouldn't go back from the accurate firmware as well, but it is too brutal with less than perfect recordings in my set-up, so I'm back to the default firmware.
  15. FredA
    Same for me with default config last time i tried but not at all when doing my own upsampling with the new firmware. I enjoy the old jazz records, even the poorest ones, because dynamics still come through. That said, my amps are tuned to be bit forgiving. So far, i would say the accurate fw is smooth the way i use it. Comparable to the smooth one under the same conditions, just clearly more dynamic.

    The idea from my perspective is the root cause is not the dac module, it's just playing accurately what it is sent. I think that the oversampling done by the dsp can be fine-tuned to take into account how accurately the dac module performs. Maybe it's simply that it boosts dynamics to compensate for a previously lacking conversion. I think with a dsp correction with this regard, the smooth firmware could become obsolete, IMO, ending with a better sounding dac in default mode. Same conclusion on headphones (he-560) driven by the nfb-1amp. No fatigue and great listening experience.

    Have you tried dsd with the accurate fw, by the way? If so, how was it?
    Last edited: Jan 4, 2018
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