By Elias Gwinn
June 24, 2011
Apple’s iPad has become a favorite device for many people - to surf the web, watch videos and movies, read the news, etc. However, only a few have used it as a source for high-quality digital audio. This is about to change.
A simple USB adapter made by Apple can enable the iPad to connect directly to a DAC1 USB, DAC1 PRE, or DAC1 HDR. The USB adaptor is called the 'Camera Connection Kit.' It connects to the iPad via the dock connector. This $29 adapter can be purchased here: Camera Connection kit
Using this adapter, the iPad can transparently stream high-resolution digital audio to the USB input of DAC1 converters. Even more remarkable, the iPad is able to wirelessly stream a 96-kHz, 24-bit audio file via Wi-Fi without losing sonic quality. (Wireless streaming is achieved using iTunes 'Home Sharing' - a mechanism that enables media to be streamed between multiple devices on a common Wi-Fi network. Read more information about this below.)
This revelation is very exciting for many reasons. This setup has no sonic degradation or tradeoffs. Setup is instantaneous, and requires no drivers. It is a low-cost alternative to buying another computer to act as a music server. And now, with the recent announcement of Apple’s iCloud, the capabilities of this setup will expand to encompass more of your media experience.
Sonically speaking, this setup will stand up to even the most discerning audiophile scrutiny. We've done significant testing to verify the audio quality when using this adapter.
Our tests show that:
To demonstrate that the stream was not being down-sampled, we used a 30 kHz audio test tone (-5 dB FS amplitude, 96-kHz sample rate, 24-bit resolution). If the iPad was down-sampling to 48 kHz, the cutoff (Nyquist) frequency would drop to 24 kHz. In this case, the 30 kHz tone would disappear. Our tests show that the 30 kHz tone is properly reproduced.
Here is the graph from our test:
In this graph, there are three measurements of the same 30 kHz digital tone going through the DAC1 USB. The red measurement is the 30 kHz tone coming from the iPad. The cyan measurement is from the Macbook via optical. The blue measurement is from the Macbook via USB. As you can see, they each perform identically, achieving full 96-kHz, 24-bit performance.
In all three cases, it is also evident that Benchmark’s UltraLock™ jitter-immunity system is very effective against any jitter coming from these devices. As can be seen from the measurements above, no jitter-induced sidebands could be detected. (This test is capable of resolving jitter-induced distortion at levels as low as 140 dB below peak output levels.)
Remarkably, this connection requires almost no setup configuration. You simply insert the USB adaptor into the iPad's dock connector and connect it to the DAC1 via a normal USB cable. That's it! Now you can play audio from any application on your iPad and achieve the high quality digital-to-analog conversation of the DAC1. Benchmark’s driverless AdvancedUSB™ system makes this possible.
The user may notice that the iPad's volume control is disabled when using this setup. This is ideal, as the highest dynamic range will be acheived using the analog volume control of the DAC1 rather then a digital volume control. (This whitepaper explains why dynamic range is maximized when using the DAC1’s analog volume control versus a digital volume control: Volume Control Technologies)
To setup wireless streaming from a computer to the iPad, you must engage 'Home Sharing'. To do this, the computer and the iPad must be on the same Wi-Fi network. Follow this link to read detailed step-by-step setup instructions: http://support.apple.com/kb/HT4557
The equipment used for testing is as follows:
The AP measurements were made using a 32,000 point FFT with 16x power averaging and Equiripple windowing. Other details of the AP setup can be seen in the image below.
"Greater love hath no man than this, that a man lay down his life for his friends." - John 15:13
On the evening of July 17, 2022, my oldest son David Paul Siau gave the ultimate sacrifice of love when he knowingly gave his life to save those he loved. He took three shots from a 12 gauge shotgun so that his wife, children and sister could be spared.
David is survived by his wife Christy Siau and their two oldest children, ages 6 and 3. His 18-month old daughter McKenzie was killed within moments of David. I have no doubt that David and McKenzie entered into God’s glory hand in hand.
My daughter-in-law Christy Siau was shot and nearly killed in the incident. We are grateful that she is now out of the hospital making a full recovery.
In the end, my daughter Christina Siau fought the attacker with a knife and prevailed. She sustained many knife injuries and it is a miracle that she lived. She is now out of the hospital and making a full recovery.
We ask your prayers for the healing of physical and emotional scars. We have been overwhelmed by the love people have shown to our family during this difficult time.
Secrets contributor Sumit Chawla recently caught up with Benchmark’s VP and Chief Designer, John Siau to get a little more in-depth on several subjects.
Q: "Benchmark is one of the few companies that publishes an extensive set of measurements, but you also balance that with subjective testing. Can you talk about the equipment, the listening room, and the process for subjective testing?"
Q: "Was there ever a time where you learned something from a subjective test that was not captured by measurements?"
Q: "You conducted some listening tests to determine whether distortion in the “First Watt” was audible. What test material did you use for this, and what did you find?"
Q: "The AHB2 amplifier incorporates THX Audio Achromatic Amplifier technology. When and how did the partnership with THX come about?"
Q: "Linear power supplies have been and remain quite popular in high-end devices. You favor switch-mode power supplies. When and why did you make this switch?"
... and more!
At Benchmark, listening is the final exam that determines if a design passes from engineering to production. When all of the measurements show that a product is working flawlessly, we spend time listening for issues that may not have shown up on the test station. If we hear something, we go back and figure out how to measure what we heard. We then add this test to our arsenal of measurements.
Benchmark's listening room is equipped with a variety of signal sources, amplifiers and loudspeakers, including the selection of nearfield monitors shown in the photo. It is also equipped with ABX switch boxes that can be used to switch sources while the music is playing.
Benchmark's lab is equipped with Audio Precision test stations that include the top-of-the-line APx555 and the older AP2722 and AP2522. We don't just use these test stations for R&D - every product must pass a full set of tests on one of our Audio Precision test stations before it ships from our factory in Syracuse, NY.