You can find out what USB modes any USB devise supports using a "USB prober" (it's a program you run on your computer that "asks" the attached USB device what modes it supports).
You can assume that, if a DAC supports asynch, then it will be used (the official terms are "isochronous" and "asynchronous isochronous").
There's a company named Thesycon who makes custom USB drivers.
If you go to their website at http://www.thesycon.de you can download a FREE USB prober program and a latency monitor (both for Windows).
(Look under FREE SOFTWARE.)
Unfortunately, there's a truly MASSIVE amount of bad information, non-information, and just plain myths and legends, floating around on this subject.
And, sadly, that's about 1000% true when it comes to the various USB tweaks floating around.
Most of the tweaks currently available are absolutely useless for most people in most situations - although a few of them may occasionally help in some situations.
Unfortunately, many currently available tweaks are just plain snake oil, and many others fix real problems, but problems that are incredibly uncommon, and most of us will never experience.
In general, the biggest "upstream tweak" you can undertake is your source itself....
- make sure your actual source is providing uncompressed audio (for example, ALL music from Spotify uses lossy compression, so the game is over)
- make sure you store all your audio in LOSSLESS formats (FLAC, WAV, and ALAC = good; AAC and MP3 = bad)
- make sure your source operating system doesn't perform or allow any unnecessary conversions (in Windows, use WASAPI mode; on a MAC, use something that supports "bit-perfect playback")
- if you use some sort of streaming process like DLNA, MAKE SURE IT DELIVERS A LOSSLESS UNCONVERTED AUDIO STREAM (check your configuration options; and make sure they tell you one way or the other)
The other thing you need to understand is that, at many steps in the process, there is no way to actually analyze the data or detect errors; while, in others, errors are almost impossible.
Here are a few common examples.....
Jitter is an error in timing.
A digital audio file is a list of numbers stored in a file.
Therefore, A DIGITAL AUDIO FILE CANNOT HAVE JITTER AND JITTER CANNOT DIRECTLY AFFECT A DIGITAL AUDIO FILE.
And, jitter on your CD transport can ONLY affect anything if it's so bad that it causes read errors on the disc (see below).
A clock is added to the file whenever it is transported or converted, and jitter that is present AT THE POINT OF CONVERSION is critical, because it directly affects the analog output.
However, the only way jitter on any of the steps before that would matter would be if it was so bad that it caused data errors.
Physical CD drives have very powerful error correction.
The Red Book audio CD format includes two levels of hardware error correction.
There is actual extra data stored on the CD which is used to confirm that the data you read is perfect, and which can be used to PERFECTLY repair errors if it is not.
Because of this, ERRORS OCCURRING ON THE CD DISC ITSELF ARE REPAIRED BY THE DRIVE AND THE DATA IT SENDS OUT IS PERFECT.
Just to be clear on that..... it doesn't matter if there are errors on the disc, or when the drive reads the disc, because they are repaired PERFECTLY inside the drive.
And, when repairable errors are repaired, the result is PERFECT.... NOT ALMOST PERFECT..... NOT NEARLY PERFECT.... TRULY PERFECT.
A disc with recoverable errors will NOT sound the tiniest bit different than a disc without recoverable errors.
(There is a third level of imperfect error correction, called interpolation, which most CD drives also offer... but which is only implemented in cases of severe damage. Interpolation is audible.)
In fact, when you RIP a CD using most modern computer programs, a final level of checking is performed.... a checksum of each song is compared to a public database.
This provides a final confirmation that THE RIP IS TOTALLY ABSOLUTELY PERFECT.
Again... to be clear....
A PERFECT RIP MADE ON A $20 DRIVE IS EXACTLY THE SAME AS A PERFECT RIP MADE ON A $20,000 DRIVE. PERIOD. END.
Actually measuring jitter is very complex, and requires complex and expensive test equipment.
Most so-called jitter measurements are actually inferred (they detect audio distortion caused by jitter and not jitter itself).
You also need to realize that the PCM data stream itself does NOT include checksum information.
This means that a device, like a DAC, or the RMC-1, can tell you the sample rate and bit depth of the audio data it receives.
However, it has no way of actually knowing that the data itself is correct.
However, assuming that the USB connection is functioning properly, there's really not much opportunity for the data to become damaged.
Virtually all of the tweaks that actually do anything whatsoever do one of two things:
1)
They reduce jitter on the data stream being sent to the DAC; this ONLY matters if your DAC doesn't include some internal method for eliminating jitter.
Because of this, these sorts of tweaks can make a big difference with certain DACs, especially some older ones, but make no difference whatsoever with many others.
2)
They can reduce power supply noise on the USB input.
A USB line carries power form the computer, and the power supplies in computers are notoriously noisy, so some DACs have a problem with noise on the USB power supply lines.
This has spawned a whole bunch of devices and cables intended to help with this situation.
The unfortunate reality is that many of these devices actually just plain don't work.
Also, they aren't going to make any difference if you don't have the problem to begin with.
(Audiophiles are very prone to purchasing expensive solutions to problems they don't have in the vain hope of getting some intangible improvement.)
So, back to the topic at hand, the upcoming RMC-1. Is anyone at Emotiva willing to say whether the RMC-1 will display features about the incoming Data Stream Transport other than the format of the Digital Audio Data itself? For instance, will the USB display include information like Isochronous vs. Asynchronous, Error Rate, Late Packet Rate, etc.?
Actually, for that matter, does anyone know of any DAC which tells you things about the quality of the underlaying Digital Audio Data Transport?
The reason I ask is because there's an article on
Computer Audiophile titled
My Quest for a New DAC - Introduction to the Series where the author spends most of the article talking about how he spent more money upgrading the Digital Data Path upstream of the DAC than on the DAC itself — claiming that each piecemeal portion of that set of upgrades significantly improved the quality of reproduction. (sigh) I asked him if his DAC (an
Ayre Codex) was running in Isochronous or Asynchronous USB Mode. But in retrospect, I'm not actually sure how one would tell. This is what motivated me to ask if the RMC-1 will display features about the Digital Data Transport (Mode, Errors, Jitter (where appropriate), Missed Data, etc.) and not just the Digital Audio Data Format (PCM, DSD, etc. x Sample Rate, Bit Depth, etc.)
Casey
Room size ; house rental ;ceiling style all have contributions as too niche status and how we are handicapped..
