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Audio-Gd Master 7 - Discrete Fully Balanced DAC (PCM1704)

Discussion in 'High-end Audio Forum' started by darknightdk, Sep 3, 2012.
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  1. borrego
    With a few more days of burn in I am quite satisfied with the sound quality of the M7S Amanero input with the Icron Ranger + OPA2140 DC Servo opamps. I believe I will skip upgrading to any USB-I2S DDC no matter what new chip/clock it will be using as it is still USB Audio 2.0 the limiting factor. Let see in a few years if the next wave of Thunderbolt-I2S interface or HDMI 2.X audio (directly output from video card supporting 8K and 22.2 channel audio) shall give a definite advantage over my current setup. As the M7S is limited to192kHz PCM in 8XOS mode, the current Amanero is still capable for this data rate. I can understand DSD128 and above streaming can easily overrun the current Amanero.

    I am too lazy opening the M7S setting jumpers to try 4XOS or NOS. I compared 8XOS and 4XOS by playing some 352kHz materials with/without using J. River doing downsampling to 176kHz. (as PCM1704 auto switches to lower oversampling when playing above 192kHz), and I like 8XOS with J. River downsampling better. 4XOS makes each intrument sounding bigger, like sitting closer to stage. I prefer the more precised imaging of 8XOS, which is more "capatible" to different genres/masterings of music.
    Last edited: Dec 2, 2018
  2. FredA
    Same here. Os8 is my fav overall. I can recommend the singxer f-1 as external i2s ddc. You have to install an rj45 output cable (diy). I use a special power cable with usb b female socket to feed both power and signal. All in all, the cost is around 300$.
  3. DACLadder
    @borrego Enjoy the M7S. I sure did recently with V3A OS 8x. Eventually working my way up to OS 8x on the R7 as well. OS 8x tickles the warmer highs of the M7S very well. A bit much for the R7 until warmed up for hours. Bass and dynamics good on both models.
  4. FredA
    The r-7 really needs close to 24 hours to sound at its best, no even kidding.
  5. batfier
    not sure I got it, but the main points for DDC (like singxer su-1) for me are galvanic isolation, reclocking and in my case also multiple digital outputs to feed different dacs.

    it's not a bandwidth topic, so I wonder what thunderbolt will add to the game?

    same with hdmi2.x. assuming you will still have the m7s in use, you can not use it directly, as on m7s side it's only a physical hdmi plug but a different protocol.

    in both cases increasing the bandwidth means increasing the frequencies which usually comes with a cost (technically).

    but anyhow, you said you are happy with the current setup. that a goooood thing. enjoy it and the music as long you can and it before it bugs you again and you will start again to think, it might be possible to get an even better sound, by doing.... :wink:
  6. batfier

    just received my reborn r-7 (fully upgraded r2r7) back form magna hifi. after knowing about the efforts and risk you had during your upgrade, I'm happy, I did it this way, also including warranty. so thanks again for letting us/me know about your experiences.

    regarding the 24 hours "warmup" time, I can not really comment on it. because of longer times between my hearing sessions, I usually switch it on when I need it. in the first hour (may be two) there are definitely some improvements for me, but then it stays for me on that level.

    to my understanding the whole warmup thing is about equal/stable temperatures in the unit, as resistors are sensitive to temp and their accuracy is critical to the concept of r2r dacs.

    in a dac chip equal temp is much easier and faster to archive, because of its very small size.
    r2r7/r7 using lots of discrete parts distributed on the pcb. getting them all to a stable temperature, will take some time.

    but I could imagine that the location/surrounding of the unit will have an effect as well on the time the unit needs to sound its best. with a lot of free floating air the unit is able to distribute some more "heat", because of bigger delta temp.

    in my case the unit sits in a rack/shelf (only front/ back is open, but there is some cm/inch space around the unit in all directions), so may be the slightly limited heat transport helps to faster distributed the heat/temp more equally in the unit.
  7. FredA

    Yes, that’s my understanding. But there is another component to the warm-up: in an open location, the output stage requires 4-6 hours to have the right balance. This is in fact the time the m7 would need to sound at its best. Same for the master-1.
  8. borrego
    I meant USB output from the computer is the limitation. Thus I shall not upgrade to any USB to I2S inyerface like the SU1. I hope there will be better I2S interface in the next few years, like Thunderbolt to I2S, or HDMI to I2S.

    The bandwidth statement was about the Amanero chip. The are audio-gd R7 users saying the Amanero chip will not handle signal above DSD64 well.

    My Icron Ranger already solves the issues of galvanic isolation, reclocking, plus extra data buffer. It is already the most any device can do maximizing USB. The next worthy DDC upgrade for me has to be anything but USB.
    FredA likes this.
  9. DACLadder
    @borrego How is the M7S working out for you? I bought a new DDC (Gustard U16) and checking it out with the M7S today. The U16 sounds really great with both the M7S and R7 DACs (HDMI I2S). Both DACs V3A firmware.
    Last edited: Dec 19, 2018
  10. borrego
    I have accumulated listening my M7S for about 50 hours since it arrived. Most of the listening was done with speakers. I think all the XO inside the DAC has become mostly stablised, and so had the sound. I am not saying it would not improve further with more burn-in but I think the sound signature has mostly stablised.

    I am still on the 8xOS, Dither on, PLL off, USB sync off, V3A firmware setting. I like the sound very much. It keeps mostly the same sound signature as my Reference 5.32 mod, with wider sound stage, higher resolution (especially in bass frequency), and better dynamics. The improvements are more obvious when listening to speakers.

    The OPA2140 opamps I put in make the M7S warm up super fast. I think it reaches "good enough" sound in 10 minutes, "optimal" sound in about 30 minutes. I can tell my M7S now warm up faster than my SA31SE, EPA-007 headphone amps, and the Electrocompaniet AW180 Chinese clone power amp.

    I checked the shipping log of audio-gd in the past month and found they have only shipped one M7S (to me) and one HE7S. So I might very well be one of the two owners of the very last production PCM1704 DACs. :->
    Last edited: Dec 20, 2018
    motberg, FredA and DACLadder like this.
  11. borrego
    Last edited: Dec 29, 2018
    motberg likes this.
  12. borrego
    Yesterday I took my Metrum Aurix out from storage and hooked up to the M7S. The Metrum Aurix is virtually a simple current buffer design and it would only sound as good as the output buffer circuit of the feeding source. With the Aurix I can immediately tell the M7S's Class A single ended output buffer circuit is superior to the Class A push-pull buffer circuit design of my Reference 5.32. The Aurix sounds quit a bit less grainy when being fed from the M7S comparing from the Reference 5.32. I am not sure if the OPA2140 DC servo opamp I put in the M7S also has something to do with the smoother sound. Having said that, the Reference 5.32 sound output was completely without any grain when connecting to all my other headphone amps except with the Aurix.
  13. borrego
    Accusilicon XOs received. Not sure when I will have these installed because of my super busy day job. For now I prefer listening to my M7S system after returning home tired than spending time on another 500hrs of burn-in.

  14. DACLadder
    Congrats! My factory S7 (M7S) has never sounded better after the Accusilion swap. You can always pre-burn the XOs on a bench to avoid burn-in variations in sound. But doesn't take too many days to sound equal or better than stock XOs.
    borrego likes this.
  15. PeterCraig
    Anyone else here enjoying the Master 7 with the Singxer SU-6.

    Anyone compare a M7 with SU-6 with one of the newer R8 or R7 dacs?

    I'm sure they are completely different fish, but the M7 really shines with the SU-6 :dt880smile: Smooth as silk treble, and I'm using Beyerdynamic T1.
    motberg likes this.
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