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m8oman
192
Oct 13, 2016
Question to Mr. Grace, or any other in the company. (Please ignore replying to this same question in the Head-fi M9XX thread if you reply to this here)
In the early days of the first m9XX drop on Massdrop's discussion thread, before the first shipment to consumers ... You wrote a post describing the m9XX in great technical detail. In that you made mention of something that only has meaning for me today.
Because I'm now in the early days of trying to talk myself into dropping the serious plunk of change necessary to buy the m905 to serve as the center piece controller for my headphone rig, with digital passthru, unbalanced and balanced in, and can drive several amps balanced and control volume uniquely for each. And was awarded an A+ rating by Sterophile. But I digress...
What was said was that the amp in the m9XX was very similar (if not pretty much the same?) to the one used in the m905. Wondering if you or someone can elaborate on this some more.
It's obvious the m905 has a more robust PS behind it which one assumes produces more power to the headphone out. Is that also thru the use of a discrete follower to provide more current? Does it swing a higher voltage too? Or any other differences worth mentioning are welcome. In comparison to the m9XX would help as I own that so have a frame of reference.
In regards to the DAC that gets a A+ from Stereophile. That pretty much stands on its own. But if you want to elaborate on what I could be in store for over the m9XX's vaunted performance, I won't dissuade you. :)
Much thanx!
m8omanHi m8oman, The m905 headphone amplifier is very similar to the m9XX. We actually started with the m905 circuitry when beginning the m9XX development. But given that the m9XX comes with size, power, and cost constraints we had to strip things down a bit.
The main things that changed are as follows. Power supply: The m905 has a bigger power supply and much more available current. This allows the m905 to deliver more power to current hungry headphones. The voltage rails are similar the the m9XX (when in high power mode) so there is not a big difference in power for high impedance phones.
Clocks: The m905 contains our s-Lock VCXO (voltage controlled crystal oscillator) which is state of the art in low jitter low/phase noise PLLs. There was simply no room in the box or in the budget for this in the m9XX. Note that a pll is only needed when you are listening to SPDF, AES, or TO TOSLINK. Both products use asynchronous mode USB streaming so the DAC becomes the master clock and no PLL is required.
Amplifier: While the amplifier topology is nearly identical between the two We spent some time researching how to get the output impedance really low on the m9XX.
Volume Control: The since the m905 has analog as well as digital inputs the volume controls are in the analog domain. This does present a slight advantage over digital volume controls since the DAC can always be using the maximum number of bits. That said, the m9XX digital volume control works very well even at very low levels.
DAC: The m905 DAC is based on the Burr-Brown PCM1796 and the THAT1570 dual transimpedance amplifier as the current to voltage converter. This is a very high performance circuit intended for the most critical monitoring in the music production environment. I think the m9XX comes pretty close to this level of transparency but I think you will be very pleased with the sound of the m905!
I hope this helps! Michael
m8oman
192
Oct 15, 2016
Michael_GraceYou may have already read this on Head-fi, but I'll echo it here...
Michael, this helps immensely. Much thanks for taking the time providing the detail.
The only reason I didn't get on the horn with your shop after reading this is it is Mrs. M8o's birthday. Spending the significant chunk of change on myself on her special day, without warning no less, didn't seem ... wise. ;)
felix_felicis
4
Oct 17, 2016
Michael_GraceHi Mr. Grace,
I was thinking about purchasing this Amp for use with the Fostex X00 headphones. However, I'm very new to pro audio equipment and have another question... since this is also listed as an DAC, could I use it as a DAC for studio monitors (specifically, Yamaha HS8's)? It looks like the HS8's take TRS or XLR inputs, and it looks like the Grace m9XX connects using TRS, but I don't know if it would benefit sound going out to speakers.
My goal is to use both the Fostex headphones and the Yamaha studio monitors for a digital piano. I will have MIDI going from the piano to my PC (running pianoteq), and I assume I will need to connect my PC to a DAC to connect to the speakers. But I'd also like to connect the PC to an Amp for when I'm playing with headphones if the Amp will improve my experience (I've read good things about the m9XX paired with the Fostex X00's). If this product can be both a DAC/Amp for headphones and a DAC for studio monitors, that would be ideal. I would love to minimize the amount of hardware and extra wires I need around my setup.
Thanks for any insight you can provide.
(PS I see >200 requests... does that mean we can expect another drop for this product soon?)
AlexVallejo
87
Oct 17, 2016
felix_felicisHi Felix, You can connect your HS8's to the m9xx via the RCA line outputs and using an RCA to 1/4" adapter like this one: www.ebay.com/itm/Female-RCA-Phono-to-Male-1-4-6-35mm-Mono-Jack-Audio-Adapter-Gold-Plated-/250599779551 You can connect your X00's to the left headphone jack on the m9xx to use it at the same time as speakers, or connect them to the right jack to mute speakers when using headphones.
felix_felicis
4
Nov 3, 2016
AlexVallejoThanks Alex! And to add two more newbie questions, from what I can read, there's no reason to expect sound quality would degrade at all/in any recognizable way using a 1/4" adaptor--correct? Thanks for the link to a cheap one by the way!
Second, does running audio through a DAC like this cause any noticeable latency? When playing from a digital piano, a few milliseconds of latency is tolerable (because it's basically undetectable) but if the DAC added even 10ms of latency above what would be produced if I just ran the audio straight from my computer, it might not be worth it.
AlexVallejo
87
Nov 3, 2016
felix_felicisSound quality shouldn't really change when using good working adapters. The buffers in the m9xx are fixed at a decent size which isn't totally ideal for low latency audio playback. It is done that way to have reliable audio streaming. I just tried it using Reaper and a virtual synth and it felt pretty quick so you might not have any problems with latency. Our m920 and m905 have adjustable buffers so they can get down to sub-millisecond latency.
felix_felicis
4
Nov 7, 2016
m8oman@DeLuca @AlexVallejo Thanks for the info! That's super helpful.
@AlexVallejo If you can clarify some things for me it will go a long way towards helping me figure out whether to purchase or not: * what is "a decent size" buffer? Can you estimate milliseconds? * do DACs contain their own drivers for processing digital signal, and if so does this DAC come installed with ASIO drivers? * if you have a couple minutes, would you mind testing pianoteq lag? Painoteq is published by a reputable company, has a trial version that is super easy to install and run, it's only about 40-50Mb, and you don't need a MIDI keyboard, you can just click the keys within the program. Ultimately, if you get sound in your headphones or speakers without a perceivable lag (for me, that tend to be once the latency exceeds 12-15 milliseconds, I definitely don't need sub-millisecond latency), then I think I'm in. If you're able to notice a delay I probably need to look at a different product.
If anyone else can comment on ASIO drivers or running virtual/MIDI instruments through the m9xx I'd appreciate advice. Big question is: can I play piano with virtual piano software through this DAC without lag?
AlexVallejo
87
Nov 8, 2016
m8omanBuffer size is 800 samples at 44.1kHz, about 18ms. U2 mode has an ASIO driver. Using pianoteq it is just the slightest bit noticeable latency, might not be ideal for live playing but might be okay for just playing around.
felix_felicis
4
Nov 9, 2016
AlexVallejoJust to clarify, there is slight noticeable latency using U2 mode and ASIO drivers? I still may end up purchasing the DAC/AMP anyway, it just seems like an excellent product. Sorry I'm asking these questions at the last minute. And thanks for checking pianoteq for me
AlexVallejo
87
Nov 9, 2016
felix_felicisIt might feel a bit funny if you are used to playing a real piano.
felix_felicis
4
Nov 26, 2016
m8omanAlex, thanks for the replies a couple weeks ago. One more question:
I understand your statement about a latency of ~18ms with a buffer size of 800 samples at a 44.1kHz sample rate. Fortunately, if the *buffer* is fixed at 800 samples that is no problem, as long as the DAC can adjust to increased sample rate. The Grace Design sheets I found say the DAC accomodates up to 384kHz sample rates, so 192kHz should be no problem.
I have pianoteq pro, which can achieve a sample rate of 192kHz. At 192kHz, an 800-sample buffer has a latency of <4.5ms, which is very playable. Is there any reason I wouldn't be able to send a 192kHz output from pianoteq to the DAC? Can the DAC receive 192kHz or at least 96kHz sample rates running U2 mode with ASIO drivers?
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