Announcement of The Element has reminded us that output power is widely misunderstood. Most confusion can be resolved by understanding that Volume sets Power.
In the world of audio, Power is the amount of energy that an amplifier can deliver into a specific load (ohms), at a specific frequency (Hz), for a specific duration (seconds), with a specific threshold of noise and distortion. And as we’ll explain, a speaker or headphone needs only enough power to reach your desired listening volume. Listening volume is set by your personal preferences and the efficiency of the driver. Onto the math:
Power in wattage is formally defined as: P = V2/Z
V = Signal Voltage, in Volts Root Mean Square (VRMS)
Z = Impedance of the load, technically consisting of Z = (R + jX). For amplifier measurements, the reactive portion X is assumed to be 0, so Z = R. The value of R is specified by the headphone manufacturer in ohms, Ω.
Signal Voltage, V, is determined by the source strength and amplifier gain. Thus:
V = Gain*Vsource
Gain is set by the amplifier. Many models feature multiple gain levels that you are able able to physically select. Vsource is simply the strength of the DAC or audio player with unit VRMS.
Minimum power in milliwatts (mW) required to reach a specific Sound Pressure Level (dBSPL) is: Pmin = 10(x-η)/10
x = Your desired listening volume in dBSPL
η = Efficiency of the headphone, in dB/mW
Next, it’s key to understand that an audio source generates only as much voltage as you select with the volume control (digital or analog), and that volume is only as strong as the particular music you’re playing. Low listening volume means Vsource is small, and high volume means Vsource is big.
From these equations, one can see that power is a function of volume. Output voltage is dictated by the strength of the input signal (from DAC or external device), which is then multiplied by the amplifier’s gain. More voltage means more volume, which means more output power.
As a purely hypothetical example, a 2.1VRMS DAC operating at 100% volume, playing music recorded at full scale, connected to an amplifier with gain of 4.7 also at 100% volume, into a 32 ohm headphone would yield P = (4.7*2.1)(4.7*2.1)/32 = 3.044W = 3044 mW. But, thermal and current (mA) limitations mean that an amplifier will be driven into distortion at some threshold, and that threshold depends on operating frequency and how long the amplifier has been subjected to the test. This is why we must conduct real world measurements and define test criteria.
Power Test Criteria
Standard audio Power measurements are taken at 1kHz with a maximum THD+N of <= 1%. Well, 1% distortion is rather obvious, and unacceptable for high fidelity listening. We set stricter standards.
JDS Labs conducts all Maximum Output Power tests into purely resistive loads at 1kHz, while maintaining THD+N <= 0.005% for a continuous duration of at least 45 minutes. Peak Output Power is the same as Maximum Output Power, but restricted to a duration of 10 seconds, still maintaining THD+N <= 0.005%.
Headphone Power Requirements
You do not need to crunch numbers to determine suitability of an amp for your headphones. Simply find the impedance (ohms) and sensitivity (dB/mW) specifications of your headphones, then refer to our SPL Chart:
Most users are satisfied when their headphones can reach 110dB. If you listen to quiet recordings or demand extreme volumes, look at the 115dB column. If an amplifier’s output power exceeds this number at your headphone’s rated impedance, it’s sufficiently powerful.
Since an amplifier only generates as much power as you set by listening volume, there is absolutely no concern of a headphone amplifier being too powerful for a set of headphones or IEMs. You can only damage headphones when you intentionally turn volume so high that the sound distorts. Your ears will let you know when this point has been reached.
That said, an amplifier can have excessive gain. O2+ODAC and The Element both ship with low gain of 1.0x (unity) for low volume listening, and a higher gain for achieving maximum volume/power. Use low gain for most listening. Switch to high gain only when you’re unable to reach desired listening volumes at low gain.
Audio specifications and output power have been thoroughly covered over the past century. Should you have further interest, we recommend the following articles:
JDS Labs has worked tirelessly to share this day with fellow headphone enthusiasts. We are proud to introduce The Element:
We designed The Element to enjoy our headphones without compromise. Its amplifier renders shocking power, driven by an ultra clean DAC, all housed in a precision machined chassis with a comfortable knob. The Element beautifully drives headphones of all technologies and sizes.
Mass production began six weeks ago and is now complete, pending final assembly (engraving, quality control, and packaging). Accessories are in transit with expected arrival later this week. We’ll share updates here, as well as on the item page.
June 22 Update – All accessories have arrived and engraving is 90% complete for batch #1. Knobs remain in anodizing. Preorders placed through jdslabs.com will begin shipping June 30. We expect to conclude all shipments by mid-July at the latest.
June 29 Update – The first batch of knobs have arrived. Final assembly and Q/C is underway. We remain on schedule to begin shipping tomorrow, June 30th.
Each project we’ve embarked upon in the past eight years has been a step towards a better listening experience. The cMoyBB delivers better bass. NwAvGuy’s Objective2 and ODAC projects invigorated the headphone community in 2011, inviting disruptive leaps in headphone amp/DAC performance. While our manufacturing efforts have helped propel O2 to its #1 Desktop Amp community rating at Head-Fi.org, everyone recognizes the glaring problem with O2. It’s ugly. The mechanical design was an afterthought—a bare minimum solution to put the circuit in a box.
Years before JDS Labs, I often browsed impressive HiFi systems that I either could not afford, or lacked the resources to skillfully assemble. The average DIY amp in the early 2000’s demanded access to a machinist, and of course basic mechanical and electrical assembly knowledge. Whether commercial or DIY, a well designed enclosure is a work of art.
The Element places equal emphasis on external and internal design. We began with an ergonomic volume knob size and position (commonly found in pro gear), then designed an enclosure to accommodate the knob, and very last created the amplifier and DAC to fit the enclosure.
On Pushing Boundaries
Some of our competitors have scoffed in disbelief that a niche audio company can sustainably build a product like The Element. We’ve heard that it’s priced too low. We’ve heard that our volumes need to be in the millions. We’ve heard that we’ll ultimately fail and give up.
We thoroughly understand the pressures. The Element is an insane mechanical design–to most. One impressed applications engineer described our initial concept of The Element as, “This is the way it should be. Let the design test the limits of the machines and the machinists.”
The Element’s contoured chassis requires six sided machining, plus three machining processes for its volume knob, another operation for its custom buttons, as well as injection molding for its soft bottom surface. These requirements were beyond the capabilities of our single CNC in early 2014. Contract shops quoted labor costs that would have doubled The Element’s target price. It’s simply not feasible while following ordinary supplier/manufacturer business models.
So, we made a judgement call last year. Rather than dismiss our vision, we chose to do what we’ve done best since 2007. Our head manufacturing engineer, Nick, retooled the company and developed a viable, in-house production process for The Element. Our machine shop now generates truckloads of locally recyclable aluminum chips. More on this another day.
Prototypes of The Element have been on my home and office desks for months, and I cannot stop smiling as it drives a set of Audeze LCD-XCs.
The enclosure was merely our starting point. As with the exterior design, we set strict performance standards of transparency and tremendous output power.
Linear regulators provide 30VDC to clean LME49600 buffer amplification stages, with peak output power in excess of 1.5W at 32 ohms. The Element drives all balanced armature, dynamic, and planar magnetic headphones with ease. A 3-inch volume knob and and dual gain levels make fine level adjustments possible.
Digital-to-Analog Conversion The Element processes digital audio through an SA9023 controller and PCM5102A DAC. While the PCM5102A supports 32-bit, 384kHz audio, we’ve intentionally selected a UAC1 controller for maximum software and OS compatibility. DSD and 32-bit driver support remain unjustified. Quantization error of 24-bit audio yields a theoretical dynamic range of 144dB, several orders of magnitude beyond an audibly ideal dynamic range of >110dB. In other words, we value a clean implementation and real world performance over a superfluous feature-set.
Tactile Buttons and Logical Relays
We also designed The Element to interact as nicely as it looks and sounds. Custom, tactile buttons control power and dual gain functions. An onboard microcontroller operates failsafe relays which mute the output for 500ms during startup and shutdown, producing headphone silence (no DC offset, pops, or thumps).
The Element was a mess in early prototyping! We started from scratch three times and produced over 125 development revisions of the PCB to achieve desired transparency, power, and functionality. That said, we’ll keep the technical discussion to a minimum. Know that the following specification tables are backed by the same test procedures as other JDS Labs products and Objective series designs.
All benchmarks are conducted on our Prism dScope Series III Audio Analyzer. Certain tests require additional data from a Tektronix 100MHz digital oscilloscope or Fluke 287.
Max Continuous Output Power is conservatively measured at 1kHz with THD+N below 0.005% for 45+ minutes of sine wave output. This endurance test places great stress on any amplifier. Many amps, including O2, overheat during extended 32 ohm sine tests (THD skyrockets and ICs may incur damage). The Element runs stable.
The Peak Output Power test demonstrates the highest power observed under the same conditions for less than 10 seconds. This approach gives a better view of the amplifier’s capability during real world usage.
The Element performs well in all areas: low noise, low output impedance, low harmonic and intermodulation distortion, and high output power.
Frequency Response 20Hz-20kHz
+/- 0.1 dB
THD+N @ 1kHz 150 Ω
IMD CCIF 19/20kHz 150 Ω
IMD SMPTE 150 Ω
Crosstalk @ 150 Ω
+/- 0.56 dB
Max Continuous Output, 600Ω
Max Continuous Output, 150Ω
Max Continuous Output, 32Ω
Peak Output Power, 32Ω
Frequency Response 20Hz-20kHz
THD+N 100 Hz -0.15 dBFS
THD+N 20 Hz -0.15 dBFS
THD+N 10 kHz -0.15 dBFS
IMD CCIF 19/20 kHz -6.03 dBFS
IMD SMPTE -6.03 dBFS
Noise A-Weighted dBu 24/96
Dynamic Range (A-Weighted)
> 112 dB
Linearity Error -90 dBFS 24/96
Crosstalk -10 dBFS 100K RCA
USB Jitter Components 11025Hz
Maximum Output Line Out 100K
We hope this article has given you a glimpse of our excitement towards The Element. Let the introduction of this bold new system empower you to hear what you’ve been missing.
Today we’re announcing a chipset update to ODAC. Revision B improves general reliability, while meeting or exceeding the original performance criteria set forth by NwAvGuy.
This announcement will come as a surprise to many, considering ODAC was declared as the be-all and end-all of DAC transparency by a now absent engineer. This article explains who owns the ODAC design, why an update is prudent, and how ODAC Revision B’s objectivity has been exhaustively verified.
Scroll towards the end for benchmarks, or read on for the full story.
ODAC was released on May 9, 2012, shortly before NwAvGuy vanished from the community. While his name is closely tied to ODAC, it’s critical to understand that ODAC was jointly developed by NwAvGuy and Yoyodyne Consulting.
Yoyodyne generated ODAC’s schematic and PCB, and NwAvGuy provided prototyping feedback and performance analysis. Yoyodyne also generated the project title, “ODAC” in 2011 and has remained responsible for all production engineering and distribution of the project to end retailers like JDS Labs and our counterparts.
In other words, ODAC was benchmarked and certified Objective by NwAvGuy; Yoyodyne generated the design and controls its manufacturing to this day.
NwAvGuy’s name has been intentionally omitted from ODAC RevB, so as not to imply an ongoing collaboration.
Why Update ODAC?!
Our job is to deliver perfect audio performance to every user. We’ve hit this goal for 99.5% of ODAC users out of the box, and have found a way push ODAC’s reliability and objectivity to an even higher standard.
To better convey ODAC’s position, Yoyodyne has shared worldwide distribution data. ODAC’s popularity continues to grow. Over twice as many ODACs shipped in 2014 compared to 2012, with a total of 12,000 units in circulation:
Increasing demand over time is amazingly rare for electronic production, and is a testament to ODAC’s positive reception.
Although ODAC has proven itself in the audio community, JDS Labs and fellow retailers have observed lower than expected yield (<1% DOA units), higher than expected long-term failure rates (< 2%), and an ongoing USB hub issue that NwAvGuy did not have an opportunity to address before his 2012 departure.
One of the first bits of ODAC feedback we received in 2012 revealed odd behavior: severe distortion, completely resolved by a USB hub. This peculiarity would ultimately affect less than 0.5% of all users, and the simple USB hub solution became well known within the audio community (later published to ODAC’s operating instructions). We invested in a dScope Series III audio analyzer in 2012 and verified ODAC’s performance.
The behavior was later identified as a power supply regulation design choice made by NwAvGuy. ODAC performs consistently with all devices, unless the host USB bus has remarkably low ESR ceramic capacitors placed too closely to the USB 5V output pin (rare). When ODAC is connected to such a host computer, ODAC’s 3.6V linear regulator performance plummets from 100% stable operation to extreme oscillation, which turns the perfect audio signal into garbage (lots of very audible distortion). There is no in-between. The regulator is either 100% stable, or 0% stable. Consequently, we’ve offered support for this rare behavior since 2012.
So, ODAC performs as described for about 99.5% of users. As demand grows, that USB bug becomes increasingly pronounced. Add in 1-2% DOA and long-term ES9023 failures, and ODAC retailers have growing collections of bad ICs. DOA boards are easy to catch via quality control, but long-term failures require frustrating warranty service.
Meanwhile, JDS Labs and Yoyodyne have engineered solutions to each reliability concern, meaning we can make ODAC reliable and objective for virtually 100% of users.
Yoyodyne produced a series of ODAC RevB variants in 2014 with reliability fixes. JDS Labs benchmarked each prototype to ensure equal or better performance compared to the original ODAC. Although the update was ready in late 2014, ODAC production runs occur about once annually. This long production cycle is best for the project, as it minimizes supply constraints and keeps distribution flowing smoothly to several O2/ODAC manufacturers.
I think the community hoped NwAvGuy would return and publish necessary updates to O2/ODAC/ODA himself. At this point, a reliability update is the best judgement we can make for ODAC’s long-term success. Keep in mind that O2 is protected from derivatives by its license; ODAC is coordinated by Yoyodyne and nondisclosure agreements with its IC suppliers. Even so, we do not want to modify ODAC. Subjective bias is not trivial in the audio business.
All of that being said, we’re confident ODAC RevB is a perfect reliability update. The newer DAC IC has proven reliable in other projects. In addition to thorough benchmarks, we’ve shipped ODAC RevB to a few users seeking support for their original ODACs. Feedback is perfect. We also shared ODAC RevB at the 2015 AXPONA tradeshow and allowed some random visitors to perform A/B tests. No one could differentiate.
ODAC RevB resolves all reliability inadequacies of the original ODAC, while meeting or exceeding original transparency requirements.
ODAC RevB utilizes the same PCB footprint and is a physical drop-in replacement to all existing ODAC and O2+ODAC assemblies. Revision B’s stronger output voltage of 2.10VRMS must also be accompanied by a slight DAC volume or gain adjustment when used in O2+ODAC; optimal gain is now 1.0/3.33x.
Analog filters and power supply passive components remain identical to the original board. The new chipset consists of an SA9023+PCM5102A, and the LDO has been updated to a ceramic stable Analog Devices ADP151 equivalent part. Fixes include:
Added 16x vias to USB support pads to improve mechanical strength of mini-USB jack
New chipset and locked EEPROM to prevent IC failures
Fixed USB supply stability, affecting < 0.5% of systems
Minor performance improvements (audibly equivalent)
ObjectiveDAC was designed for measurable and audible perfection. Reduced performance from ODAC RevB would be absolutely unacceptable, so we took great care in checking our work.
Engineering test methods impact test results. While THD+N, frequency response, and crosstalk are straightforward, even these basic tests are impacted by audio analyzer setup parameters and real world hardware setup. Certain ferrites on the mini-USB cable improve dynamic range by up to 10dB versus an ordinary USB cable. More complex tests like Jitter and IMD produce surprisingly different results based on signal strength, averaging, etc.. As Yoyodyne and I analyzed performance of the original ODAC through a TDK ZCAT2035-0930 ferrite equipped USB cable via dScope audio analyzers, it was clear that NwAvGuy had utilized averaging and custom dScope routines. We would never be able to definitively duplicate his work due to unknown averaging, scripting variables, and exact ferrite type.
To ensure a fair comparison, we measured a randomly selected ODAC production unit to establish baseline requirements. Measurements were repeated with two additional, randomly selected units to confirm consistency. The exact same cable and test scripts were then repeated with ODAC revB. All tests are performed under a standard 100k load.
In particular, please note that many of our measurements are taken at different signal strengths and sampling rates than used by NwAvGuy. Our table results are also taken without averaging; instead, we observe worst case performance over the course of 5 seconds of data collection.
So do not be surprised that our baseline ODAC measurements reflect lower performance than NwAvGuy’s nicely averaged 2012 results!
Frequency Response, 20-20kHz
THD+N 100 Hz, -0.15dBFS
THD+N 20 Hz -0.15dBFS
THD+N 10 kHz -0.15dBFS
– 103 dBu
Dynamic Range (A-Weighted)
> 111 dB
> 112 dB
Dynamic Range (Un-Weighted)
> 107 dB
> 109 dB
Crosstalk @ 1kHz, -10dBFS (3.5mm)
Sum of Jitter Components @ 11025 Hz, -1dBFS
IMD CCIF, -6.03 dBFS, 19/20kHz, 24/96k
IMD SMPTE -2 dBFS, 24/96k
Linearity @ -90dBFS
Frequency Response: NwAvGuy’s DAC Transparency Guideline calls for response of +/- 0.1 dB from 20 Hz – 19 kHz. RevB is slightly flatter than the original ODAC, exceeding the proposed transparency requirement for the complete audible range, 20 Hz – 20 kHz.
THD+N: The original ODAC measures 0.0056% at 10kHz -0.15dBFS using our worst case scenario measurements (see above table). RevB manages just 0.0024% under the same condition.
Shown below are THD+N -1dBFS, 8x averaged sweeps of each channel, directly comparing ODAC to ODAC RevB . The original ODAC’s right channel closely resembles NwAvGuy’s 2012 THD+N sweep, with a peak of 0.005% at 9kHz, and 0.004% at 10kHz. Note that the Left channel of the original ODAC differs from its Right channel in our sweeps. This observation is consistent across each unit tested from 2013 and 2014 production batches, despite no channel differences visible in 2012 benchmarks. RevB’s THD+N is consistent between Left and Right channels.
Revision B also cuts THD+N in half at 10kHz, and remains below 0.0030% across the entire audible spectrum for each channel. Both versions are well below NwAvGuy’s suggested transparency limits (green line).
Full-Scale Performance:Rumor suggests that PCM5102 clips at full scale. We first investigated this concern in 2013 with the then newly released PCM5102A. Empirical results show clean sine output at all frequencies. ODAC’s ES9023 reaches 1.99VRMS, and RevB’s PCM5102A generates 2.07VRMS at 0dBFS.
RevB’s full-scale performance is remarkably similar to the original ODAC. Notice that both DACs produce THD > 0.005% at 0dBFS due to FFT summing phenomenon at full-scale:
Elevated THD at 0dBFS is consistent for all DACs we’ve measured, and is the reason engineers (including NwAvGuy) typically conduct DAC benchmarks at -1dBFS or -3dBFS. Simply put, digital to analog conversion is less ideal at 0dBFS. Any reasonable recording should be free of such peaks. At any rate, it’s ideal to slightly reduce DAC volume when listening to recordings containing frequent 0dB peaks.
Noise: The newer PCM5102A DAC automatically enters a soft mute condition in the absence of an audio signal, pushing the measurable noise floor to an impressive -115dBu (near the dScope’s measurable limit). Therefore, noise was also measured with an applied -180dBFS, 20kHz signal, revealing the active state noise floor. RevB manages -103 dBu, slightly superior to the original ODAC’s -102 dBu. All noise components of RevB are well below the transparency requirement of -110dB for both mute conditions.
Dynamic Range: RevB improves A-weighted dynamic range by about 2dB, and achieves a cleaner noise floor.
Crosstalk: The PCM5102A’s soft mute function causes a standard crosstalk measurement to produce abnormally impressive results, as one channel is digitally muted. Thus, crosstalk looks substantially superior at all frequencies for RevB. Crosstalk measurements are similar between ODAC and ODAC RevB with a sufficiently small signal applied to the “muted” channel. Also note that the 20kHz “Ch A” test point is invalid for all four curves, as the dScope script conducts the test too quickly during relay initialization. “Ch B” curves at 20kHz are accurate.
Jitter: Testing is conducted using an 11025Hz, -1dBFS signal with 8x averaging.
Reliability fixes only necessitated a new power supply LDO and DAC IC. We swapped the USB controller for two reasons. First, the SA9023 provides 16/88.2kHz support. Second, its jitter performance is noticeably superior to the older TE7022L. We actually tested a TE7022L+PCM5102A prototype in effort to stay closer to the original ODAC. The SA9023 was ultimately a finer choice. Keep in mind that even the TE7022L produced audibly insignificant jitter (components below -110 dB). Hopefully 16/88.2kHz functionality adds value to some.
IMD SMPTE: The 60Hz/7kHz IMD test returns similar measurements for both DACs: 0.0008% using a -2dBFS signal referenced to 2VRMS.
ODAC produces audibly negligible sidebands (below -120dB) within a few thousand Hz of 7kHz, whereas RevB’s distortion shows less jitter but higher amplitude components around the same tone. Note that all of these components are more than an order of magnitude below the audible transparency limit of -90dBFS (green line).
IMD CCIF: Twin tone amplitude is closely matched in the IMD CCIF 19/20kHz test. The test returns numerically superior measurements for RevB due to smaller 1kHz components.
Sidebands are slightly more pronounced from RevB. While sidebands are higher, NwAvGuy prescribed a maximum sideband limit of -90dBr with 2VRMS reference for frequencies below 19kHz, and -80dBr above 20kHz to achieve transparency. RevB meets expectations.
The dScope is internally limited to -6.03dBFS for the Twin-tone script. Yoyodyne points out that NwAvGuy displayed a sum of powers and utilized custom scripts when conducting IMD measurements (-6dB + -6dB = -3dB).
Linearity: Both versions demonstrate excellent linearity from -1dBFS, down to their respective noise floors.
Price and Availability
ODAC RevB begins shipping in all JDS Labs ODAC products ordered after 9:00AM CST on Monday, May 11 with unchanged pricing:
Custom engraving is free with any new JDS Labs amplifier or DAC ordered through jdslabs.com. It’s a fun process, both for us, and for you.
When you click the “Engrave” button during checkout, our production staff receives and pastes your custom text or image into Adobe Illustrator, then prints to one of our two laser engraving machines. Here’s our new Trotec laser engraver in action:
A full image takes just 2-3 minutes, and custom text takes only seconds.
Engraving image quality is comparable to that of a black and white laser printer. The key difference is print media. With a laser printer, black toner prints onto white paper. With a laser engraver, the result is always white onto all anodized aluminum, regardless of aluminum color.
Like a laser printer, black and white images engrave perfectly:
A monochrome image with a black background needs to be inverted. Our production staff uses their best judgement and corrects images as necessary, for example:
Laser engravers handle shaded images acceptably. This customer did not realize his image contained shading, and was surprised to see the result. [Note: We use calibrated IPS monitors. Check your screen brightness if you cannot see shading in the dark images!]
A gradient test pattern reveals engraver shading limitations:
Color images and photographs can be engraved reasonably well even with limited shading:
In summary, custom engraving works best with monochrome images.
There are three basic requirements to connect a USB DAC to any Android or iDevice:
Power: The DAC must not consume more power than the phone or tablet permits.
Support: The phone or tablet must be able to stream digital audio over USB.
Cables: You must use an appropriate cable for your device.
Below we’ll show how you can connect a USB DAC to most Androids, iPads, and iPhones.
All iPad, iPhone, and most Android devices enforce a peripheral power consumption limit. If you have a self-powered DAC like C5D, this requirement is easily satisfied since the DAC only consumes power from its own battery.
Connecting a more common, power hungry DAC is still possible! USB devices declare their power consumption in software, during USB enumeration (connection). Therefore, it’s easy to trick a phone or tablet by connecting the DAC to a small USB hub. With the right USB hub, your phone only reads the low power consumption of the USB hub, and not the larger power consumption of the DAC.
For example, directly connecting ODAC to an iPhone or iPad does not work. ODAC consumes about 20mA, while iPhone/iPad permits a maximum current consumption of around 5mA in software. With a portable USB hub connected, ODAC now works!
Power consumption has not actually changed here since we’re using a non-powered USB hub; ODAC still draws power from the iPhone.
A powered USB hub would be more ideal, but this experiment shows it’s possible to fool the software power limitations. Also note that a USB hub will only work with your phone or tablet if it reports itself as “self-powered”. Not all portable USB hubs report their power consumption this way. We’ve had success with Plugable’s USB 2.0 2-Port hub, but it’s worth mentioning that some customers have received Plugable hubs that do not work. Again, a powered hub is the best choice.
History Lesson: It’s safe to bypass the tiny power consumption limit of your iDevice. Maximum power consumption of iPad was much higher in iOS4 and earlier, so most standard DACs worked out of the box with iPad back then. Apple later reduced the software power limit causing standard DACs and other peripherals to only connect when used with a powered USB hub.
Android Devices – DAC Connections
Cables: Any USB On-the-Go (OTG) cable will suffice. Android devices use a micro USB port, while most DACs rely on mini USB. A micro-to-mini OTG cable makes a perfect connection.
Support: Digital audio support with Android continues to improve. While only some Android devices support digital audio out of the box, nearly all Androids can connect to a DAC using USB Audio Player Pro. And if you’re adventurous, Cyanogenmod is known to enable streaming digital audio systemwide (all apps) for most devices.
Tip:Even with the proper cable and support, Android sometimes needs a reboot. Make sure to turn your DAC on and connect it to your phone/tablet, then reboot Android. This will give Android a chance to initialize the DAC.
Apple unlocked digital audio support under iOS 7, so all iPhone and iPad devices painlessly connect to self-powered DACs. Support is excellent.
Unlike Android, Apple’s proprietary cables are the only point of confusion. There are presently four possible connections, and only three of four work.
Lightning to USB Cables
The best solution for now is Apple’s Lightning to USB Camera Adapter, part number MD821ZM. This cable conveniently provides a USB port from your iPhone/iPad, allowing you to connect a short mini-USB cable to your DAC.
One might expect that Apple’s Lightning to Micro USB adapter (MD820ZM) and a short USB cable would also work. We’ve confirmed this adapter is NOT usable with DACs! Apparently it was made only for charging.
Apple 30-Pin to USB Cables
For iPhone and iPads with an older 30-pin dock connector, you’ll need Apple’s 30-pin Camera Connection Kit (CCK), Apple part number MC531ZM.
Note that iOS 7 is mandatory to use a DAC, meaning these adapters are suitable for iPad, iPhone, and iPod Touch running iOS 7. There’s currently no standard digital audio support for iPod Classic or iPod Nano, as they do not support iOS 7.
If you already have a 30-pin CCK and a Lightning-to-30-pin Adapter (MD823ZM), it’s possible to pair these two connectors together to form a bulky Lightning to USB adapter:
Addendum: You can use any mini USB cable with the above Apple accessories. The stock, 1.5ft cable provided with C5D will work, or you may choose a shorter cable. Some users also prefer to strap their devices together with silicon bands for better organization:
Generic Lightning Cables
Now you’re probably asking yourself, “Why doesn’t someone make a short Lightning to mini-USB cable?!”
It was a quick task for us to find a great manufacturer for our custom Android OTG cables. Sourcing the equivalent Lightning-to-mini-USB cable is vastly more challenging. Apple controls the accessory market under its MFi Program. JDS Labs has applied twice in the past 3 years and has yet to receive a go ahead. This leaves us with three options: We can either source generic Lightning cables from non-MFi certified manufacturers, or we can partner with an MFi approved developer, or we can continue to wait for our own MFi certification.
We’ve found several overseas vendors willing to product custom Lightning cables, but we have no interest in breaking Apple’s MFi agreement or distributing cables which may not always work. So, generic cables are not an option. We’ll continue seeking a path of MFi approved production.
Power – Use a self-powered DAC. For other DACs, you can use a self-powered USB hub.
Support – iOS7 fully supports streaming digital audio!
Cables – Use Apple Camera Connection Kit cable + mini USB cable
This morning we’re glad to resume production of C5D! UPS delivered parts at 10am and I’ve been listening to C5D for more than two hours with a smile on my face.
In case you missed the drama, we caught a tiny error in the first batch of C5D and temporarily halted production. Our terrific engineers, George Boudreau and Ken Mathews, collaboratively resolved the mistake in less than 48 hours. We owe them many thanks.
A few C5D’s shipped on Monday and Tuesday without the correction. We’re emailing affected customers today and will offer an easy exchange.
C5D shipments to distributors resume next week:
Headphone Bar / Canada
Munkong Gadget / Thailand
Headsound Audio / Germany
Kingsound Audio / Hong Kong
Noisy Motel / Australia
C5D samples also ship to reviewers by Monday.
If you’re curious, C5D is a complex device that makes use of 12 highly regulated, onboard power supplies.
Prior to the production fix, the first batch of C5D exhibited an extremely low level hum under USB data transfer. Hum vanished while music was not playing over USB, so it was easy to miss while listening. And by nature of its presence, it could never appear in Noise measurements, and was simply a tiny component of THD measurements (all excellent). This type of problem could only be found by an engineer actively looking for it. Conclusion: Subjective results matter as much as Objective measurements!
Working backwards, we disabled individual power supplies in C5D to isolate the issue. We found that when the USB controller placed its heavy load during data transfer (0.5W), it brought the primary +7V rail to 60% capacity. The +7V rail has been stable in C5, and the amplifier and DAC measure well independently. While powering both amp and DAC, the higher power draw pushed the rail slightly out of regulation. Line ripple increased by a factor of 10.
The solution was shockingly simple–we added a larger capacitor to the +7V rail (this capacitor will be hand soldered on the first batch of C5Ds). Ripple decreased more than 10x, to levels better than ever. Performance is restored. Low level hum is gone.
On a related note, we pushed a major site update to JDSLabs.com last night. Please call, email, tweet, or reply below if you encounter any browsing issues.
C5D Production Status
Design: 100% Complete
Benchmarks: 100% Complete
Production: Ships by November 22
C5D is entirely complete and ships immediately! We temporarily paused production to make a final tweak. Shipments resume no later than November 22.
C5D adds an outstanding PCM5102A DAC and extra bass boost level to our C5 headphone amplifier. Both C5 and C5D are built for portable users who demand exceptionally low noise, sufficient output power, and a super fine volume control to handle sensitive headphones and IEM’s.
Our goal for C5D is simple: Merge a reference grade DAC with C5, valuing performance and compatibility over superfluous features. C5D works natively with iPhone, iPad, and all devices and operating systems which support UAC1.
USB Audio Class 1 (UAC1) is the widely compatible standard for transmitting digital audio over USB. UAC2 is required to go beyond 24/96 audio, but UAC2 support remains limited and requires special drivers for Windows XP/7/8, etc. In other words, connecting a UAC2 DAC becomes more involved and potentially buggy.
It’s easy to understand why audiophiles develop specification wish lists such as 32/384kHz PCM via UAC2, or DSD, or asynchronous operation. The numbers and algorithms look really impressive. But ultimately, you can’t utilize 32/384 audio when your music collection is the bottleneck. It makes perfect sense from a marketing standpoint to enable the latest features on a new device. Fortunately, we’re engineers and not marketers.
C5D’s hardware actually supports DSD and 32-bit audio. We disabled both. UAC2 breaks compatibility with many portable devices, and C5D needs to work out of the box with phones and tablets. Plus, transparency is achievable through UAC1 and fully utilizing 24-bit depth can be unrealistic.
So instead of giving C5D compatibility limiting UAC2 features, it’s configured for awesome performance under UAC1. And we still managed some interesting characteristics–galvanic isolation, asynchronous operation, and a low latency jitter filter.
Reference D/A Conversion
C5D’s new DAC circuitry fits in previously unused space beneath the battery, so size remains identical to C5. The PCM5102A DAC and SA9027 controller pack incredible performance in this small space.
The large chip next to the USB jack is an Analog Devices ADuM3160. This IC serves two functions:
Enhanced ESD protection at the USB jack
Also next to the USB jack is a new toggle switch. Flipping this switch right allows C5D to charge. Flipping the switch left makes use of the ADuM3160’s air core transformer technology to operate C5D in self-power mode*. That is, the DAC runs from its own battery when connected to a portable USB audio player. This is known as galvanic isolation, and it cleverly prevents the DAC from being subjected to noise on the USB +5V rail.
Self-power mode also gives C5D maximum flexibility with portable devices since most smartphones and tablets disable USB devices that consume too much power.
* Full isolation is utilized with low power USB devices. C5D enters a hybrid self-powered mode when connected to strong USB devices, only consuming extra power. DAC performance is identical in all power modes.
Just weeks before we approved C5D for production, I received word that a code update could convert C5D from adaptive to asynchronous operation. Features are always second to performance at JDS Labs, so we repeated all benchmarks.
C5D jitter already measured extremely well in adaptive mode. We want to see a sharp signal in this test, with minimal sidebands (especially near the signal). Keeping the sum of matched components below -100dBFS prevents an audible impact. C5D in adaptive mode far surpasses this reference goal at -111dBFS:
Running asynchronously, jitter improves little more than the measurement’s margin of error:
Jitter measures slightly better at -112dB in async mode, and is the only standard test that revealed any difference from adaptive mode on C5D. All other benchmarks returned identical results. Thus, C5D ships in asynchronous mode.
Asynchronous mode and galvanic isolation together make C5D a rare UAC1 DAC. These features make it highly self-reliant, generating its own clock and power.
+/- 0.14 dB
IMD 19/20kHz, -7dBFS
> 109 dB A-Weighted
Linearity Error, -90dBFS 24/96
USB Jitter, Marked Sum
DAC measurements were obtained by hardwiring a line-output jack to C5D’s PCM5102A output for connection to our dScope Series III audio analyzer.
Frequency response is excellent, with negligible rolloff of 0.1dB in the final octave of human hearing.
THD+N measures well below our reference goal of 0.005% at all frequencies:
A-Weighted noise exceeds expectations with components at -110dBu, and overall noise better than -100dBu:
Dynamic range measures quite well at 109dB:
The DAC’s line output crosstalk measures at -86.1dB, outperforming our reference requirement of -80dBFS. Note that crosstalk is limited by 3.5mm cables in actual use (still excellent).
The IMD CCIF test checks DAC performance during simultaneously playback of 19kHz and 20kHz tones. C5D returns excellent results here, with minimal blurring between the high frequency signals (noise below -120dB). Total distortion measures well at a very low 0.0013%:
Low Latency Filter
The PCM5102A DAC used in C5D features a configurable low latency filter. In testing, we’ve observed no significantly audible difference. C5D ships with its Low Latency Filter set High.
C5D’s firmware is released freely under the Creative Commons BY-SA 3.0 license. Refer to line 55 if you wish to experiment with the PCM5102A’s LLF feature. Note that a programmer and pogo pins are required for DIY tinkering.
C5D’s amplifier and supporting power circuitry is identical to that of C5, with the exception of an additional bass boost level and smaller output resistors. Output impedance of C5D has improved to 0.62Ω. This specification change minimally impacts overall performance, and ensures neutral operation with low-impedance balanced armature IEMs.
+/- 0.1 dB
THD+N (20-20kHz, 150 Ω)
THD+N (20-20kHz, 32 Ω)
Crosstalk @ 150 Ω
Inter-channel Phase @ 1kHz
+/- 0.01 degrees
+/- 0.55 dB
Max Output @ 600Ω
Max Output @ 150Ω
Max Output @ 32 Ω
Battery Run Time
0°C to 60°C
0 to 85% Relative
99.5 x 61.5 x 14.0 mm
Triple Bass Boost
C5D’s bass boost has three positions: Off / Medium / High. The High position is identical to C5’s bass boost, with the Medium level residing audibly halfway between off and high. Below are C5D’s bass boost curves in low gain:
These curves relax at high gain, in effect producing four unique bass boost curves:
Camera Connection Kit and iOS7
Camera Connection Kit
ROM and OS must support UAC1
Mac OS X
We considered developing C5D for fully native operation with Android, and discovered the goal is presently futile. Even a DAC designed for native functionality via Android’s Open Accessory Protocol remains limited to 16-bit, 44.1kHz operation. And even then, support is not 100% guaranteed across all Android devices! Only an app like USB Audio Recorder Pro unlocks full 24-bit digital audio, by utilizing alternative drivers.
C5D works with every Android device we’ve tested under USB Audio Recorder Pro. We met a few Android users at the 2013 CanJam who successfully used C5D natively (i.e., with any app). Some Android phones and tablets output UAC1 natively. Others require special ROMs or apps.
Guaranteeing DAC operation with all Android devices is currently not realistic. Since Android is opensource, it’s definitely possible to enable 24-bit digital audio output on any Android device. Hopefully Google will make UAC1 output standard in future Android updates to simplify the user experience.
The good news: C5D is self-powered, so its power consumption is not a limitation. You’ll only need to enable digital audio output on your device if it’s not already available.
iPad and iPhone
C5D works out of the box with iPad and iPhone! Apple has finally enabled UAC1 output as of iOS7. You simply need a Camera Connection Kit cable. C5D is self-powered, so power consumption is of no concern.
We’re running half staff today and tomorrow while JDS Labs presents at CanJam. If you’re anywhere near Denver this weekend, CanJam at Rocky Mountain Audio Fest is the place to be. Check out our booth for freebies and a first look at our upcoming amp + DAC.