Notes from the Test Bench
By Bruce Hofer, Chairman & Co-Founder, Audio Precision
Since returning from my annual participation in Dr. Anderson’s very popular PhD level course on class-D amplifier design at the Danish Technical University near Copenhagen, I am really enjoying getting back to some serious design and new product development. Audio Precision continues its long tradition of providing new capabilities to the audio test and measurement industry. Indeed, later this month we are particularly proud to be introducing an entirely new member of our APx family, the APx582; along with v3.1 of our APx500 software.
The APx582 is designed with multi-channel amplifier designers in mind, with 8 analog inputs and 2 analog outputs. It provides an extremely attractive combination of features, performance, and price. Read more about it below.
Our new APx500 v3.1 software is loaded with many new features and refinements. For example, it includes the ability to connect directly with ASIO drivers used in professional PC audio interfaces. This means that designers of today's PC-based recording hardware can now test their products quickly, directly and completely with APx. We have also added standard noise waveforms to the generator without having to download and playback a .WAV file.
Stay tuned for even more exciting new developments in the future.
As always, I look forward to hearing from you. I am planning to be at the upcoming AES convention in San Francisco (unfortunately only for the first day), and also the Munich Electronica trade show later in November.
Output: Introducing APx582
APx582: High performance two channel analog output and eight channel analog input
Audio Precision is proud to announce a new member of the APx family of audio analyzers: the APx582.
The APx582 audio analyzer combines eight channels of analog input and two channels of analog output plus support for all of the APx digital interfaces (AES/SPDIF, I2S, HDMI, Bluetooth, PDM).
This configuration closely matches the inputs and outputs of modern multichannel audio devices which tend to have a maximum of two analog inputs plus HDMI or other I/O for multichannel or encoded audio.
Because it uses the output stage of an APx525, the APx582 supports several measurements that the APx585 does not have, including DIM/TIM distortion tests. it also supports several output impednaces (20, 50, 75, 100, 600 Ω). In addition, the AG52 advanced analog generator option ships as standard, so the APx582 has a higher maximum output (26 Vrms) and can generate the sharpest square waves in the industry.
At -108 dB (typical), APx582 system THD+N is better than an APx585, but not quite as low as an APx525 (typical -110 dB THD+N) (see below for specification summary)
Price is also in-between the two models, with a base price of $18,900 in the US. APx582 can be ordered beginning Oct 1, and starts shipping in late October.
Sound Advice: ASIO in APx500 v3.1
The newest release of APx500, v3.1, now supports direct connection to PC audio devices via ASIO, allowing for complete testing of high performance ASIO-compliant PC audio interfaces.
For users of the Windows operating system there have been several means of transporting digital audio to and from devices and applications. Consumer-level devices most frequently use the built-in DirectSound and Media Foundation APIs, but these exhibit higher latency than is required by professional users. Microsoft introduced high performance Core Audio APIs in Windows Vista and Windows 7, but prior to that (in 1996) Steinberg of Germany developed a solution called Audio Stream Input/Output (ASIO). ASIO facilitates a direct path from applications to audio hardware, ensuring that audio data is transferred at the highest possible speed without degradation or manipulation. Because of its long history, it is the de facto standard for professional audio in Windows-based systems.
ASIO in APx
With ASIO built in to APx500, measurements of ASIO-compliant audio interfaces may now be made directly on the PC running the measurement software, without passing through additional hardware.
The ASIO implementation in APx500 supports up to 16 simultaneous channels of input and/or output, allowing direct testing of multichannel interfaces that are connected directly to the PC running APx500. An APx audio analyzer must remain connected to the PC in order for ASIO to be used, regardless of the signal path configuration.
In order to interface with a DUT via ASIO, appropriate drivers for the DUT must be installed on the PC; unlike Windows Audio, the operating system has no means to detect and install these drivers. Once the ASIO drivers are installed, the DUT will become available to any audio application on the PC that supports ASIO, including APx500.
ASIO appears in the Signal Path exactly like any other interface option. When selected, an additional drop down menu appears, allowing you to select among multiple installed ASIO devices. You may select from several ASIO-related options once a device is selected.
Testing PC Audio Interfaces with ASIO
Complete testing of PC Audio Interfaces can now be performed, using signal paths that send or receive audio via USB or Firewire as well as those that employ the analog and digital I/O on the DUT itself. This allows the test environment to closely mirror the "real world" application of the DUTs.
Virtually any configuration of DUT signal path can be realized and measured. Finally, manufacturers of PC audio interfaces can completely test their devices from end to end.
ASIO devices are automatically enumerated when "ASIO" is selected as a connector.
You can select up to 16 channels to assign to APx (APx515 is limited to 2 channels).
Pricing and availability
ASIO is included at no charge for APx525 and APx585 families. For the APx 515 production test analyzer, ASIO is available as a software option (SW-ASIO) for $750 and supports any two channels of ASIO at one time. ASIO ships with APx v3.1 and will be released October 2012.
Test Results: AP News & Events
© 2012 Audio Precision, Inc.