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Showing 1 of 1093 conversations about:
Ormia
31
Nov 3, 2015
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After reading some of Purrin's review (on Super Best Audio Friends) I'm starting to have second thoughts...
Nov 3, 2015
avitron142
134
Nov 3, 2015
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OrmiaWhat, the one about crossfeed? He hasn't said anything else about the m9XX (to my knowledge) - that's not exactly a review.
Nov 3, 2015
Ormia
31
Nov 3, 2015
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avitron142Comparing distortion measurements of m9xx, GOV2, and Schitt Stack, iDSD nano (http://www.superbestaudiofriends.org/index.php?threads/measurements-mid-fi-dac-amp-comb-units-grace-schiit-ifi-lh-jds-etc.427/). More harmonic distortions in m9xx compared to some of the other amp/dacs, but I guess still well below (at least -70dB rel. to the the fundamental freq) human hearing thresholds. I'm starting to wonder if its better for me to get 02+DAC or Schitt Stack and save at least $200.
Nov 3, 2015
DeathbyMusic
157
Nov 3, 2015
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avitron142Even if it was a review he'd probably say the same thing.
Nov 3, 2015
avitron142
134
Nov 3, 2015
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DeathbyMusicMy point is people here are relying on preliminary impressions instead of looking at actual reviews. It's ironic is all. I spent countless hours comparing headphone pairings, DAC/amps, etc. And then the deciding factor is what somebody else would have "probably" said.
Nov 3, 2015
avitron142
134
Nov 3, 2015
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OrmiaIf when you buy a DAC/amp you hear measurements through your headphones, maybe :D Otherwise, try to ask somebody who's heard both and have an opinion about which one you should get. Which headphone you're using matters a lot in this.
Nov 3, 2015
DeathbyMusic
157
Nov 3, 2015
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avitron142Well, 3 days left on the drop. I might reconsider, but for now, I'm back behind the fence. Doing research on iFi iDSD micro and maybe a few other options out there when I see them.
Nov 3, 2015
DeathbyMusic
157
Nov 3, 2015
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It's not that. I've bought stuff in the past that have been raved about only to find that it doesn't work for me. I own a pair of Fidue A83 and they get the bench treatment while I use my TF10 most of the time. I'm just not sure if the m9xx will work for me, and with so little reviews on the net to base it on, there isn't a easy way to get an overall picture of the device's performance. The only way to know if I would like this or not is to try it, but of course, I can't know that right now. And Massdrop has a no-return policy so it's not like I can decide on a whim knowing I can return it after. I admit that I pulled on the Ei.xx almost immediately without thinking so yeah, this isn't exactly fair for the m9xx. I'm not out yet. Just weighing my options.
Nov 3, 2015
Michael_Grace
432
Grace Design
Nov 5, 2015
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OrmiaWhen I looked at Purrin's plots I was pretty sure something was amiss. I have spent plenty of time doing bench tests on the m9XX and have never seen any of the spurs that show up in his plots. I have been in contact with Purrin and we are trying to sort out where the problem lies. It may be a test setup/grounding issue or it is possible there is a problem with his unit. In the mean time I have duplicated his test parameters on our Audio Precision here at the factory and the results are here: http://www.gracedesign.com/support/m9XX_FFT_plots_301_ohm_.55V_output.pdf
All harmonics or inter-modulation artifacts are less than -100dB below the fundamental in any of the measurements. Note that the noise floor of the Audio Precision is about 15-20dB lower than the QA400 so there are harmonics visible in these plots that are masked by noise in Purrin's measurements. Also note that there the m9XX is still not the lowest distortion device. But that is due to the intentional choice of amplifiers for other desirable characteristics such as slew rate and output impedance. -Michael
Nov 5, 2015
fuzzybaffy
28
Nov 5, 2015
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Michael_GraceNice, thank you! I was hoping Grace would respond to this issue. Now I feel a lot better. I joined the drop anyway, but it's definitely nice to hear from a rep.
Could you also answer a question I had about the m9xx (I know it's easy to miss it in the discussion)? How much of the m9xx is DAC vs. amp? In other words, is it mostly a DAC with a small amp section put in, or is it mostly an amp with a small DAC section put in, or is it mostly split 50/50 down the middle? I'm assuming it's mostly a DAC with small amp section because there aren't any audio-ins. Either way, I was hoping to find out so I know which upgrade path to take in the future...
Nov 5, 2015
m8oman
192
Nov 5, 2015
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Michael_GraceThat's a relief. I saw the measurement. Love seeing one without those large high-order harmonics even more!
Nov 5, 2015
Ormia
31
Nov 5, 2015
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Michael_GraceHi Michael,
That's awesome! I'm glad to see that the higher harmonics are significantly lower than than the fundamental. Thanks!
Nov 5, 2015
DeathbyMusic
157
Nov 5, 2015
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Michael_GraceHi,
I already emailed someone at Grace Design, and with the drop end so close, I need an answer. I asked if you could include some sort of certification or at least some kind of indication on the invoice that states that the m9XX is made in the USA. It may help foreign buyers whose countries have FTA with the US. Please get back to me regarding this.
Nov 5, 2015
Michael_Grace
432
Grace Design
Nov 5, 2015
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DeathbyMusicHi DeathbyMusic, Sorry for the delay but we will be able to provide you with a NAFTA certificate of origin if that will suffice. -Michael
Nov 5, 2015
Ormia
31
Nov 5, 2015
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Michael_GraceHi Michael,
I think it would be helpful if you can offer an explanation of the results to non-engineers and people without DSP training. This would help some people here interpret the results.
How did you generate the pure tones? What levels were these input signal presented. Are the measurements linear across the entire dB range? How did you measure the output? Did you measure the output signals from the headphone jacks or the RCA?
Thanks for diligently standing behind your product. I really look forward to this purchase.
Nov 5, 2015
Michael_Grace
432
Grace Design
Nov 5, 2015
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OrmiaHi Ormira, The tones were generated digitally by our Audio Precision 2700 series instrument and recorded via spdf to an M-Audio Microtrack II recorder. The files were then transferred to a MacBook Pro running jRiver 19. All tones were recorded at 0dBFS. This process is tested bit accurate using the AP bit tests. The m9XX volume control was set at 79.0 for single tone files and 80.5 for two tone files. The m9XX was powered from the production USB power supply using the supplied 10ft USB cable. The unit tested in the plots was one of three pulled from the production line. All three were very similar but this one had slightly higher 2nd order harmonic content.
The measurements were taken from the headphone outputs with the 301 Ohm load was connected at the input to the Audio Precision. A separate ground wire was connected from ground of the 1/4" plug to the chassis ground on the Audio Precision.
I am afraid I don't understand the following question: "Are the measurements linear across the entire dB range?" Cheers, Michael
Nov 5, 2015
Ormia
31
Nov 5, 2015
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Michael_GraceHi Michael,
That's an excellent description of what you did!
What I meant about linearity is whether the relative amplitude differences between the fundamental and harmonics would remain the same if you changed the volume setting on the device and made the same measurements.
Best Regards, Ormia
Nov 5, 2015
Michael_Grace
432
Grace Design
Nov 5, 2015
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OrmiaOh I see, The answer is yes and no. With a 300 ohm load the harmonic percentage stays about the same up to about 2V out (volume 90). This is still relatively low power though. When the output amplifier kicks in to high gain mode the 2nd harmonic will rise about 6dB. With lower impedance phones the power goes up and so does the distortion. Worst case scenario is 5.5V out with 20 Ohms (about 1.5Watts) The 2nd is about -78dB and the 3rd about -68dB.
Nov 5, 2015
m8oman
192
Nov 6, 2015
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Michael_GraceLoving the composition of the harmonics. Should sound 'tube like' when driven hard.
Nov 6, 2015
DeathbyMusic
157
Nov 6, 2015
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Michael_GraceThe drop will end in 19 hours. I will send you a separate email directly regarding the NAFTA certificate.
Nov 6, 2015
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