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AMI MUSIK DDH-1 specific technical questions
AMI MUSIK DS5 specific technical questions
Please download the instruction here.
Please download the instruction here.
To play DSD128 the player must be able to change the Mac Audio settings to 352.8Khz. Please make sure that your DSD128 player changes the current sample rate to 352.8Khz before playing a DSD128 file.
The AMI MUSIK DS5 support up to 24bit/192kHz and thus, you should not select 384kHz in Mac. In Windows, it is possible to remove the 384Khz from the list of the available formats in the system because the players, such foobar, to play DSD would use ASIO or they would join directly to the WDM driver ignoring the Windows Audio Settings. In Mac the driver needs to declare all the available format to be used by a player (even though the hardware could not support it). Therefore, the main reason is that in Windows ignore the players while Mac does not.
The output level of PCM and DSD is pair matched at 2.2VRMS. The volume is digital and control the CS4398 DAC IC digital volume itself. The solution is 24bit. When playing PCM and DSD, the DSD level is lower. Therefore, there is a problem when having DSD and PCM file within the same play list. For AMI MUSIK DS5, we have designed our product to have pair matching output.
AMI products generic technical questions
This section discusses some software-related issues discovered in the past and provides some tips on problem analysis and possible solutions or workarounds. Note that the discussion in this section applies to scenarios where the driver has been configured for low audio latency (see also FAQ on compatibility and stability issues). (1) Kernel Mode Processing (background info) A USB audio driver must be able to process incoming and outgoing isochronous data streams in real time. The driver gets called periodically by the operating system kernel to perform its processing. The period of the calls is determined by the buffer size the driver uses to exchange data with the USB. This buffer size is adjustable and is referred to as "Streaming Buffer Size" or "Streaming Buffer Depth", If one of the processing calls is delayed by more than one buffer size interval, data loss will occur. Delayed processing calls are the most common source for audible signal distortions. This problem is referred to as DPC latency issue. Deferred procedure call (DPC) is Microsoft’s term for processing callbacks issued by the kernel. In this context, "DPC latency" is not to be confused with audio latency which is not directly related. Because Windows is not a real-time operating system the Windows kernel cannot guarantee that a driver gets called in time. Any kernel-mode software component, including other device drivers, can monopolize the CPU which prevents the kernel to perform its periodic processing in time. A typical situation is that a device driver gets called by the kernel (e.g. from a timer service) to check the state of its hardware. The driver keeps the CPU busy for several milliseconds by spinning in a loop and polling hardware status, for example. The kernel cannot call any other driver before this driver returns control. If the misbehaving driver keeps the CPU busy for an interval that exceeds the streaming buffer depth of the audio driver, the audio driver experiences a delayed processing call which leads to an interruption in the audio data stream. Note that at this level of kernel-mode processing there is no priority based multithreading. The Windows kernel executes calls into various device drivers sequentially which may lead to delayed calls as described above. The design is based on the assumption that no driver stalls the CPU and any call into a driver returns quickly. Microsoft documentation states that drivers should spend no more than 100 microseconds in any processing call issued by the kernel. While most device drivers fulfill this requirement there are a couple of misbehaving drivers in the market. If such a driver is used in parallel with an audio driver then audio dropouts can occur. Note also that a multi-core CPU is not a solution to the problem. This is because the kernel (and bus drivers) arbitrarily assigns kernel processing calls (DPCs) to CPU cores. A device driver cannot reserve a CPU core for its own (time-critical) processing. (2) Misbehaving This section lists some potential sources of DPC latency issues. The information is based on AMI’’s own experience and on user feedback. 1) W-LAN or Ethernet device drivers Quite often it can be observed that device drivers for W-LAN adapters monopolize the CPU in kernel mode as described in the previous section. A few Ethernet drivers do also have such issues. AMI’s dpclat utility (see next section) can be used to analyze the system behavior when WLAN is enabled or disabled. Solution: Try to find an updated W-LAN driver, or try an older version of the driver. If no suited driver can be found, disable W-LAN (or Ethernet) while audio streaming is running. 2) On-access virus scanners or personal firewall software Normally, this kind of software includes some kernel-mode component to perform filtering or scanning work in the kernel. Often, such components keep the CPU busy for long periods which causes kernel processing calls (DPCs) to be delayed. AMI’s dpclat utility (see next section) can be used to analyze the system behavior when on-access scanning (or filtering) is enabled or disabled. Solution: Disable or uninstall the software. Try using a different product with similar functionality. 3) Windows in-box drivers Basically, it can be stated that the set of device drivers that ships with Windows behaves well. If DPC latency problems occur then they are typically caused by third party drivers that are to be installed for hardware which Windows does not support by default. So if a hardware component is supported by an in-box driver then this driver is to be preferred and a third party driver should not be installed. 4) WHQL signed drivers The fact that a given third party device driver is WHQL certified is not a guarantee for correct DPC runtime behavior. WHQL tests currently do not enforce proper DPC behavior. (3) DPC Latency Checker Utility Thesycon (AMI MUSIK DDH-1’s original driver provider) provides a free utility that enables users to check the behavior of a given system. The utility performs a statistical analysis of kernel-mode processing calls which are called deferred procedure calls (DPC). For more information about the utility checkout http://www.thesycon.de/eng/latency_check.shtml To download the utility directly, use this link: http://www.thesycon.de/dpclat/dpclat.exe The dpclat utility should be executed when the audio device is not connected to the system. The utility shows the maximum delay of processing calls the audio driver may experience on the given system. If excessive DPC latencies can be observed then try to identify the culprit by using a trial and error approach. Disable/Enable devices in Device Manager (one at a time) and check whether the results shown by dpclat change. Unfortunately, dpclat does not allow to identify the kernel-mode component that is causing the problems directly. This is because this kind of analysis is very difficult to implement
USB audio devices have stronger requirements for USB hardware and software layers than other USB devices. A faulty hardware component, e.g. USB cable or USB port, may not have an impact on standard USB devices such as a FLASH drive but can be catastrophic for a USB audio device. USB hardware requirements are discussed in more detail in the section 4. Due to the real-time nature of USB audio streams there are also requirements for time characteristic of the operating system and third party software components installed on the system. Software components that make real-time behavior of the operating system worse are not compatible with audio streaming applications in general. However, in this context it’s important to note that real-time requirements depend directly on audio latency requirements. If low audio latency is required (e.g. to create a monitor mix in the PC and route it back to speakers) then the operating system must be able to fulfill resulting timing requirements of the driver. If audio latency is not critical (e.g. in case of music playback) then timing requirements of the driver are relaxed which increases compatibility with other applications and drivers significantly. AMI Muse DDH-1 driver allows users to adjust internal buffer depths to find a tradeoff between audio latency and compatibility with a given system. Below, two typical scenarios are discussed. (1) Low-latency applications Audio latency is critical if an audio signal is routed into the PC, processed in the PC and then routed back to speakers. A typical scenario is a monitor mix created by a multi-track recording application such as Cubase. For such applications the drivers streaming buffer depth should be set to 4 milliseconds or less. In this configuration a couple of issues can occur because the given system may not be able to handle the resulting real-time requirements. A discussion of possible problems and incompatibilities is given in section 3. (2) Normal-latency applications In case of a playback-only or recording-only scenario, audio latency is not critical. For such applications the driver’s streaming buffer depth should be set to 16 milliseconds or more. This will reduce the risk of audio distortions caused by other software components in the system significantly. Issues discussed in section 5 may still occur but this will happen in extreme cases only. If the driver is configured this way, it will be compatible with a larger number of Windows systems. Normally, it will not be necessary to optimize a system for audio steaming according to the hints given in "known software issue and possible solutions".
Some music players does not support native playback of music files. We would like to recommend you to install music players that support this feature as well as automatic sample rate switching and automatic sample rate detection.
All AMI products are USB 2.0 Audio Class 24/192kHz Asynchronous products, and thus, more care is needed in regards to connectivity. There are several factors that can affect the AMI products during music playback causing crackling noises or dropouts and/or freezing. (1) Please shut down all applications other than the audio playback interface. (2) Ensure that you are not connecting your AMI products to a USB hub. (3) Other sources that can affect USB Audio signal and cause distortion:
- USB Cables (Link to the specific content)
- PCB mounted USB ports (Link to the specific content)
- Front panel mounted USB ports (Link to the specific content
- W-LAN or Ethernet device drivers (Link to the specific content)
- On-access virus scanners or personal firewall software (Link to the specific content)
The USB Audio class uses isochronous transfer mode to transfer the audio signals on USB. Early USB implementations and chip sets did not support isochronous transfer mode correctly and had a couple of other issues. Therefore, it is necessary to define minimum chip set requirements. However, most users don’t know which chip set is inside of their PC or laptop and it may not be easy find out this. Hence, it makes sense to define a limit for the age of the computer. Based on this AMI defines the minimum PC hardware requirements as follows:
- PC or laptop manufactured after January 2006
- Intel Core 2 @1.6 GHz, or AMD equivalent
- 1 GB main memory
The AMI MUSIK DDH-1 Driver supports the operating system versions listed below. The driver and its installer have been tested on these systems.
- Microsoft Windows® XP incl. SP3 – Not recommended.
- Microsoft Windows® Vista (32/64 bit incl. SP2)
- Microsoft Windows® 7 (32/64bit)
- Microsoft Windows® 8 (32/64 bit)
- Apple Mac OS X (10.6.4 or later)
Generic Audio FAQ
Great Audio Quality Requires More Than USB 2.0 SupportNow that listening to music on computers is as commonplace as listening to music on the radio—and maybe more so—Audio Interfaces have also become commonplace. Today, anyone can enjoy high quality sound via a single “music server device,” which is a PC or Macintosh computer. But what are the technical limitations of these audio interfaces? Is it enough that an interface be USB 2.0 compatible? The numerous USB Audio Interfaces, which can be thought of as external sound cards, all contain Digital-to-Analog Converters (DACs). Regardless of the capability of the DAC, it must rely on USB to receive and deliver data—and USB was not designed for audio. Early USB DACs came with limitations and could not provide “real” hi-fi audio quality. The audio community recognized the problem and gathered to work on the “USB Audio Class” standard, which was finalized in 2006. The new standard should have solved the problem—but it didn’t. By the time the finalized USB Audio Class 2.0 was released, the USB 2.0 specification was already complete. And it used the earlier audio spec from USB 1.1. The saddling of USB 2.0 with the legacy USB 1.1 audio spec is one reason so many Audio Interfaces on the market claim support for USB 2.0, but are limited to 24bit/96kHz audio. Just because the USB jack supports USB 2.0, does not necessarily mean that the product supports the Asynchronous USB Audio Class 2.0. What, then, are the limitations of the USB 1.1 audio spec? USB 1.1 supports a maximum throughput of 10Mbps (megabits per second). For audio, you need to fix, or maintain, a particular frequency, and doing so prevents you from using the full 10Mbps. That is why USB 2.0 and USB 1.1 devices are limited to 24bit/96kHz audio. What are the advantages of Asynchronous USB Audio Class 2.0? The Asynchronous USB Audio Class 2.0 supports 480Mbps of audio data (in contrast to 10Mbps which cannot be fully utilized), delivering 24-bit audio with sample frequencies up to 192kHz (in contrast to 96kHz). You can see that while USB 2.0 or better support is a must, it is not an indicator of audio quality. When comparing Audio Interfaces and DACs, look for Asynchronous USB Audio Class 2.0 support (such as the AMI MUSIK DDH1), and check the Audio Interface delivers up to 24bit/192kHz audio. In fact, these are the types of audio interfaces that we are developing here at AMI International, Inc., such as the AMI MUSIK DDH-1 and the AMI MUSIK DS5.
What is DSD audio-- A Simple Explanation
Paul McGowen, of PS Audio, wrote a wonderful short explanation of what DSD audio is and how it differs from PCM audio. Here is an excerpt from his post on DSD audio or 1-bit audio and why it sounds closer to analog sound than PCM. 1-bit audio is simple to understand in concept. There are no samples, there are no words, there is no code. Instead there is a continuous streaming “train” of single identical bits that are either on or off. The more bits that are on, the higher the eventual output voltage becomes. The more bits that are off, the lower the eventual output voltage. We refer to this type of scheme as Pulse Density Modulation because when you have a greater number of on bits it appears as more densely populated. Here’s a picture that will help you visualize a 1-bit system. Note the blue areas are on and the white areas are off. Also note the periodicity between single bits is identical. The red sine wave overlaid on this image shows the results of more bits or fewer bits. Where there are no on bits (all white) the sine wave is at its lowest point – lots of on bits and it’s at its highest point. The speed of the bits is 64 times the sample rate of a CD and some DSD schemes run at 128 times faster than a CD. Here’s the interesting part of this: if you take a DSD stream and run it through a simple analog lowpass filter to smooth out the on/off transitions, you get music! This is amazing considering that if you do the same with PCM you get only noise. DSD is a lot closer to analog than PCM ever thought to be. You can read the entire article here and sign up for his newsletter here. We encourage you to visit his online magazine, PS Tracks, and sign up for his daily educational newsletter that is packed with information on the technical aspects of reproducing sound.
The AMI MUSIK DS5 is not replacing the AMI MUSIK DDH-1. It's adding DSD, but does not have the DDC feature or analog in features that the AMI MUSIK DDH-1 have for instance. Our prime motive is of course not to cannibalize our own product within each other, but rather providing a variety of choices to the audiophile community. Different design, different concept, and different flavor. One thing that will remain the same though, will be the quality of audio we deliver at a certain price point and trying to spread the world "luxury audio you can afford". We won’t go over the differences of the spec., components and features as this is very obvious. When we first developed the AMI MUSIK DDH-1, we wanted to come out with an all-round Hi-Fi audio product for your desktop supporting headphone amp, analog input, digital input, digital output, line out to support the various use. We made sure that overall is well balanced and providing the most without giving away audio quality. The cosmetics of the AMI MUSIK DDH-1 would be more functional and classic. The AMI MUSIK DS5 was developed at the end phase of AMI MUSIK DDH-1 development. And this time, we had DSD in mind as the main focus. We first planned a half rack size at a higher price, but as our goal is to provide affordable luxury audio, we shifted the direction to our main purpose and developed the product to a smaller size desktop DAC. Although focusing on DSD features supporting both SPDIF input and USB, we had to be careful that the sound quality did not bias to DSD side or PCM side, and thus, for the balance of it, we had to lower the output level, but instead focus on the tuning of the audio out by providing an overall well balanced output from high, mid to low. Hearing can be very subjective, however we can say that the AMI MUSIK DDH-1 handles dynamics with subtlety and power providing massively detailed & punchy sound, while the AMI MUSIK DS5 would provide, open, full-bodied, natural, unforced and transparent sound. We recommend to all our customers to age the unit. The more you age it the better the sound would get.
The AMI MUSIK DDH-1 is now officially released and available through our eStore and through our international partners worldwide. You can subscribe to our newsletter and/or follow us on social media (see the icons near the bottom of this page).
The AMI MUSIK DDH-1 is now officially released and available through our eStore and through our interational partner worldwide.