DACs: External Power vs USB Power

This question originally appeared on reddit/headphones. I’m re-posting a longer response below, as the discussion commonly arises.

“Is an external power supply . . . an inherently easier design?”

Designing a sufficiently low noise supply from a USB +5V rail is economical and easy. Most manufacturers build entry-level DACs with this approach, relying on 3.3V regulation and filtering to clean up the USB supply. A decent regulator will achieve -50 to -90dB PSRR alone (frequency dependent), so unless the USB +5V rail is disastrous, the 3.3V DAC supply cleans up nicely.

An external AC power adapter requires rectification and voltage regulation to step down to clean, low DC voltage free of 60Hz hum. Then you have to battle thermal constraints from the large voltage drop. More circuitry and engineering effort goes into accepting external AC power compared to USB, so the end result is always higher cost (those 15V power adapters are also not free, nor is the extra 1lb in shipping weight). The benefit of external power is consistent noise performance from one system to the next.

A well designed DAC fed by USB power usually hits published performance, but there can be exceptions. Dig through feedback of any USB powered DAC and you’ll find reports of audible degradation. USB power is unpredictable. I’ve argued in the past that consistency for 99%+ of customers is adequate. Some agreed, and some vehemently disagreed with me. If you’re the 1% or so with a noisy USB system, you need a USB hub, or a DAC that doesn’t rely on USB power. Having been on both sides of the fence, I’d rather maximize trust with customers by relying on external powered designs. We made this commitment when announcing OL DAC and EL DAC. But in cost constrained designs, external power is not an option.

How to Connect a DAC to Powered Speakers, Xbox One, or PS4

Your DAC came with a basic setup guide and manual, but we regularly hear from owners with uncertainty. So we decided to sit down and play “Will it connect?” with some of our gear and share practical examples.

For help connecting a DAC to your phone or tablet, please see How to Connect Android, iPad, or iPhone to a DAC.

Powered Speakers

Everyone loves the convenience of powered speakers, and JDS Labs customers often want to make full use of their DACs with their headphone and speaker systems. Below are the most common connections.

Unbalanced Inputs: RCA or 3.5mm

RCA cables are definitely the easiest way to connect most DACs to a set of powered speakers. Simply run an RCA cable from your DAC’s RCA outputs to the RCA inputs of your speakers. Make sure everything is powered on and you’re good to go!

If your DAC and speakers use 3.5mm jacks, simply use an auxiliary cord.

To connect a 3.5mm jack to RCA jacks, use a 3.5mm to RCA adapter cable. While measurable crosstalk performance is best via RCA cabling, there is no audible penalty by using an adapter.

Both?

The Audioengine A2+ speakers pictured above provide several inputs, including 3.5mm, RCA, and even their own integrated USB DAC. It’s generally best to use RCA cables to connect a DAC. Please refer to your speakers’ manual for more help.

Listening to Headphones or Speakers

If your desktop audio system includes a JDS Labs Element or EL Amp, you can seamlessly transition between your powered speakers and headphones. Plug in your speakers via RCA and headphones via front-mounted ¼” jack, then press the power button to toggle between your speakers and cans.

For other headphone amps and DACs, you can manually unplug your DAC and reconnect to speakers as needed, or use an OL Switcher to transition between setups with a switch.

Balanced Inputs

RCA DAC output to XLR Input

Balanced speaker inputs, either XLR or TRS, can be connected to an unbalanced (single-ended) DAC.

XLR Inputs

To connect a DAC with RCA outputs to a balanced XLR input, such as JBL LSR305‘s, simply use two XLR to RCA cables (one cable per speaker). That’s it!

TRS Inputs

TRS jacks, also referred to as ¼” inputs, are trickier. In a balanced system, the pinout may or may not be known. The positive (non-inverting) and negative (non-inverting) balanced signals may be opposite in some systems, so only make use of TRS inputs if you can determine the exact pinout. Once you have determined your speaker input pinout, use a ¼” TRS to RCA splitter paired with RCA cables to access only the positive portion of the balanced signal.

Here’s the trick: Ignore the colors at the TRS splitter! You must connect the positive signal of your Left speaker to the Left RCA jack of your DAC, and connect the positive signal of your Right speaker to the Right RCA jack of your DAC. This means you’ll have either two reds, or two whites connecting to the DAC. Ignore the inverting signal. In other words, you will be left with one unused connector at the splitter of each speaker. It’s messy. For this reason, we recommend using XLR to RCA cables if at all possible.


Optical Sources

Xbox One

Connect your DAC to the Xbox One using the Optical jack on the rear. Make sure all is turned on and you’re looking at your Xbox One dashboard. Follow this selection path through the Settings Menu:

Audio and Video → Audio Options

Make sure you’ve selected Optical Output and Uncompressed Stereo and enjoy!

PS4

Connect your DAC to the PS4 using the Optical jack on the rear. Make sure all is turned on and you’re looking at your PS4 dashboard, then follow this selection path through the Settings Menu:

Sound and Screen → Audio Output Settings → Primary Output Port

Make sure you’ve selected Digital Out (Optical) and set the audio format to Linear PCM.

The PS4 is a little finicky and will also output audio via HDMI even after all of these steps. After scouring the internet and troubleshooting in the office, the best solution for this is muting the device outputting audio via HDMI.

PS4 is also known to limit output volume. If you plan to listen to your DAC with a PS4, please tell us when placing your order. We can force your DAC’s firmware to require PS4 to set 100% output volume.


Feel free to reply below or email us with any questions!

Element vs Objective2

Recent discussions reminded me that misconceptions also surround Element, such as:

    • ‘Element is an O2+ODAC in a nicer box / Element has an ODAC inside’
      • False: While both are designed for transparency, performance and features differ: 1.5W vs 0.6W output power is substantial.
    • ‘Element clips’
      • False: Of course not! Like any good design, gain is configured to avoid clipping.
    • ‘Element is warm/dark/bright/muddy, V-shaped . . .’
      • False: Element is held to the same standard of transparency as all of our designs.
    • ‘The Element’s DAC uses AKM’s reference schematic’
      • False: Element has zero AKM chips inside. EL DAC is AKM based. Neither are reference designs.

Element is my favorite amp+DAC. I’m listening to it now, and keep another at home. It’s my endgame. We’ve updated the design three times since 2015, and until now, have shied away from drawing comparison. I originally expected that a direct comparison would encourage mixups, as the Objective line has such a deep community history. Turns out, the community compares Element to the older Objective line anyway. Okay, let’s compare. They look like this:

The Element Objective2+ODAC
Headphone Jack 1/4 in 1/8 in (default)
Auto Line Output YES NO
Mute Protection YES NO
Amplifier Output Stage LME49600 NJM4556
Amplifier Gain 1.0/4.7x 1.0/3.3x
PCB Stackup 4 Layers 2 Layers
Max Power @ 32 ohms 1.5 W 0.6 W

 

Amplifier Performance

AMPLIFIER SPECS The Element Objective2+ODAC
Frequency Response, 20-20kHz +/- 0.1 dB +/- 0.1 dB
THD+N 1kHz, 2VRMS Input 0.0009% 0.0016%
IMD CCIF 19/20kHz 150 Ω 0.0002% 0.0002%
IMD SMPTE 150 Ω 0.0004% 0.0004%
Noise, A-Weighted, 1.0x Max Vol -110 dBu -109 dBu
Crosstalk @ 1kHz, -14dBFS, 150 Ω -86 dB -78 dB
Output Impedance 0.1 Ω 0.54 Ω
Channel Balance +/- 0.56 dB +/- 0.6 dB
Max Power @ 600 ohms 140 mW 88 mW
Max Power @ 32 ohms 1500 mW 613 mW

Benchmarks and screenshots were taken for this article with stated test parameters to ensure fair comparison (some published test parameters differ for Objective2 and Element).


Amplifier Frequency Response, 10-22kHz

Amplifier THD+N, 1VRMS input, 20-20kHz, 32 Ω

Amplifier Noise, A-Weighted, 1.0x Gain @ Max Volume

Amplifier IMD CCIF, 19+20kHz

Amplifier IMD SMPTE

Amplifier Crosstalk @ 1kHz, -14dBFS, 150 Ω

Digital-to-Analog Converter Performance

DAC SPECS The Element Objective2+ODAC
Frequency Response +/- 0.15 dB +/- 0.04 dB
THD+N, 20-20kHz < 0.0031 % < 0.0029 %
Noise, A-Weighted -102 dBu -103 dBu
Dynamic Range (A-Weighted) > 112 dB > 112 dB
Crosstalk @ 1kHz, -10dBFS (RCA) -100 dB -86.4 dB
Sum of Jitter Components @ 11025 Hz -113 dB -112.3 dB
IMD CCIF, -6.03 dBFS, 19/20kHz, 24/96k 0.0011% 0.0015%
IMD SMPTE -2VRMS, 24/96k 0.0012% 0.0015%
Linearity @ -90dBFS -0.02 dB -0.08 dB

The DAC chipset is indeed the same, however, there is no physical ODAC RevB inside of an Element. The two boards were prototyped at similar times, and we happened to release ODAC RevB just before announcing Element. In fact, the prototyping success of Element’s DAC was strong encouragement to produce ODAC RevB with the same chipset.

USB Impedance

Notice that Element is built on a 4-layer PCB, while ODAC uses a 2-layer board. Differential USB signals require a characteristic impedance of 90 ohms, and this spec is only tightly controlled on a 4L board. Ideal USB characteristic impedance improves jitter and increases reliability of USB connections when using long cables (6ft+).

If there’s interest, I’ll also publish a deeper look at each DAC (Element, EL DAC, and ODAC). Feel free to ask questions!

ODAC vs OL DAC

“Hey, I was just wondering what the major differences were between the ODAC and the OL DAC.”

This fine question continues to pop up in emails, on the phone, on reddit, on Head-Fi, etc.

I was excited to push OL DAC into the wild last November for a number of reasons. I’ve always placed great trust in JDS Labs customers, finding them to be knowledgeable value hunters, and OL DAC set a new bar. Alas, we omitted too many details at release, like why we created another transparent DAC in the first place. Rumors took off. My favorite assumptions include:

  • ODAC and OL DAC are the same circuit in different boxes (False)
  • OL DAC costs less, so performance must be lower (False)

In short, the DACs share few similarities, aside from comparable transparency.

ODAC OL DAC
DAC IC PCM5102A AK4490EQ
Powered By USB AC Adapter
USB Input YES YES
TOSLINK Input NO YES
Configurable Filters NO YES

 

ODAC vs OL DAC

OL DAC clearly has the upper hand in terms of performance.:

SPECIFICATIONS ODAC RevB OL DAC
Frequency Response  +/- 0.04 dB  +/- 0.15 dB
THD+N, 20-20kHz < 0.0029 % < 0.0010 %
Noise, A-Weighted -103 dBu -109 dBu
Dynamic Range (A-Weighted)  > 112 dB > 114 dB
Crosstalk @ 1kHz, -10dBFS (RCA) -86.4 dB -108 dB
Sum of Jitter Components @ 11025 Hz -112.3 dB -116 dB
IMD CCIF, -6.03 dBFS, 19/20kHz, 24/96k 0.0015% 0.00033%
IMD SMPTE -2VRMS, 24/96k 0.0015% 0.00031%
Linearity @ -90dBFS -0.08 dB +/- 0.01 dB

 

THD+N Sweep (24/96kHz, 20-20kHz)

THD+N, 20-20kHz, 96k Sampling Rate, USB Input
THD+N, 20-20kHz, 96k Sampling Rate, USB Input (ODAC vs OL DAC)

 

Noise, A-Weighted

Frequency Response (24/96kHz, 20-20kHz)

IMD CCIF

IMD SMPTE

Linearity

USB Jitter @ 11025Hz

Crosstalk

 

Why Another Transparent DAC?

ODAC was interesting five years ago for its claim of transparency at only $149. DAC performance and features improve every year; OL DAC is the logical successor. While there’s no need for “greater transparency”, few can argue with getting more for less.

There remains one potential advantage to choose a Standalone ODAC–running from USB power can be useful in certain scenarios. Thus, we decided to maintain ODAC and OL DAC concurrently. Confusing? Yes, sorry about that.

OL DAC: The People’s Filter

Understanding some customers’ want for customization, we placed an Easter egg in OL DAC  for you to filter the sound however you see fit!

oldacdipswitch

If you wish to experiment with the sound signature of your OL DAC, we left pads for a 3-position DIP switch on the PCBs, Omron Part# A6SN-3104. Ask for it when ordering and we’ll be glad to pre-install, and remember to sign up so you get new post notifications, you will also be participation on the wooden watches giveaway we will be doing.

Edit: AKM provides a summary of the available filters:

AK4490EQ Interpolation Filters [Source: AKM]
AK4490EQ Interpolation Filters [Source: AKM]

Announcing EL DAC, EL Amp, OL DAC, and OL Switcher by JDS Labs

Today’s announcement of the Element Line and Objective Line makes most sense when viewed alongside our mission:

JDS Labs enables exceptional listening experiences, with underlying objectivity in our designs and transparency in our interactions.

JDS Labs is strongly associated with audio measurements these days–perhaps to an excessive degree. Still, the subjective experience certainly matters. Each amp and DAC we’ve offered over the past nine years has in some way made headphone listening more worthwhile. Enjoyable audio equipment just happens to measure well, so we take measurements seriously.

Expanding Connectivity for Desktop Audio

EL Amp + EL DAC
EL Amp + EL DAC

Expanded connectivity for Desktop Audio is the theme we’ve been working towards lately. I listen to powered speakers at my desk whenever I have the chance, and transition to headphones at other times. Many of our customers listen the same way, and agree that a single system should be able to interface with headphones and speakers. Sometimes a system doesn’t involve a USB connection. Thus, optical and coaxial S/PDIF inputs are long overdue. Element Line and Objective Line each provide means to switch between listening to headphones or to powered speakers. Introducing:

  • EL DAC – Self-powered USB UAC2, TOSLINK, and transformer isolated coaxial S/PDIF
  • EL Amp – 1.5W @ 32Ω Headphone Amp with RCA pass-through Line-Output
  • OL DAC – Self-powered USB UAC1 and TOSLINK
  • OL Switcher – 2 Input : 2 Output Passive Preamp
Custom Objective2 + OL DAC + OL Switcher
Custom Objective2 + OL DAC + OL Switcher

Performance Characteristics

EL DAC OL DAC
Frequency Response 20Hz-20kHz +/- 0.15 dB +/- 0.15 dB
THD+N 20Hz-20kHz < 0.0011% < 0.001%
IMD CCIF 19/20 kHz -6.03 dBFS 0.00017% 0.00033%
IMD SMPTE -6.03 dBFS 0.00061% 0.00031%
Noise (A-Weighted) -109 dBu -109 dBu
Dynamic Range (A-Weighted) 117 dB 114 dB
Linearity Error -90 dBFS -0.01 dB -0.01 dB
Crosstalk -10 dBFS 100K RCA -108 dB -108 dB
USB Jitter Components 11025Hz -116 dB -116 dB
Maximum DAC Line-Output, 100K 2.00 VRMS 2.00 VRMS

AKM AK4490

EL DAC and OL DAC both utilize an AK4490EQ digital-to-analog converter. Measurable performance is spectacular compared to the older PCM5102A, at similar cost. While it’s accepted that ODAC achieves baseline audible transparency, a look at THD+N shows why we’ve moved to AK4490. Note the order of magnitude improvement across the frequency band (log scale):

THD+N of AK4490EQ vs PCM5102A (EL DAC vs ODAC RevB)
THD+N of AK4490EQ vs PCM5102A (EL DAC vs ODAC RevB)

UAC2

Support for 24/96kHz audio via USB Audio Class 1 (UAC1) is all you need for audible transparency. For simplicity and maximum value, OL DAC is a UAC1 device, which requires no third-party USB drivers.

EL DAC is the first JDS Labs DAC to support USB Audio Class 2 (UAC2). We’ve caved for two reasons. First, 24/192k and beyond is often requested by customers we hear from at audio meets. Second, Microsoft will soon provide native UAC2 drivers in Windows 10. We’ve promised UAC2 support as soon as the market fully embraces it, and that time is upon us. Until native Win10 drivers are available, EL DAC uses SaviAudio’s Bravo drivers with ASIO support.

Interpolation Filters

Both EL and OL DAC use default filter parameters for AK4490. The alternative filters achieve less satisfactory measurements, especially in terms of high frequency response. If you wish to experiment, we left pads for DIP switches on the PCBs,  Omron P/N A6SN-3104. Ask and we’ll be glad to pre-install.

OL DAC - Printed Circuit Board
OL DAC – Printed Circuit Board

100% Self-Powered

Clean power is one of the keys to achieving high performance audio. As confident as I am in the USB powered regulation performance of past JDS Labs designs, we take feedback seriously, and feedback indicates limited trust in USB power. Also, operating system power management behavior continues to change, creating a continuing battle for support.

I’m glad to report that EL DAC and OL DAC are 100% self-powered. All of our future designs will be self-powered as well. [Nov 25th Edit: To clarify, “self-powered” means the DACs receive power from an AC outlet. Zero (0) power is consumed from the USB cable/hub/PC.]

The first prototypes ran rather hot with full linear regulation. Heatsinks were mandatory for stability in USB mode, and enclosures turned into space heaters. So, we moved to a higher efficiency, split, multi-stage approach. All analog audio circuitry is powered exclusively by linear regulation, while the power hungry digital USB controller receives power from the same primary, linear regulator, through a clean buck regulator, followed by multiple stages of linear regulation. This experiment paid off. Not only does the circuit run much cooler, THD+N improved by over 5dB across the entire audio band, and it passed FCC/CE compliance testing on the first try. Super clean.

Power is Volume

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:

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.

Too 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.

Further Reading

Audio specifications and output power have been thoroughly covered over the past century. Should you have further interest, we recommend the following articles:

Introducing The Element by JDS Labs

JDS Labs has worked tirelessly to share this day with fellow headphone enthusiasts. We are proud to introduce The Element:the-element-top-down-wp

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.

Availability

The Element is available for Preorder via JDS Labs. The first batch will ship by June 30th.

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.
  • July 7 Update – All preorders placed through July 1 have shipped. A second batch of Elements are due for shipment in the next 3-10 business days.

Design Motivation

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-upright

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.

Circuitry

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.

Amplification
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).

Benchmark Performance

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.

Amplifier Performance

Frequency Response 20Hz-20kHz +/- 0.1 dB
THD+N @ 1kHz 150 Ω 0.0009%
IMD CCIF 19/20kHz 150 Ω 0.0004%
IMD SMPTE 150 Ω 0.0005%
Noise, A-Weighted -108 dBu
Crosstalk @ 150 Ω -67 dB
Output Impedance 0.1 Ω
Channel Balance +/- 0.56 dB
Max Continuous Output, 600Ω 140 mW
Max Continuous Output, 150Ω 505 mW
Max Continuous Output, 32Ω 1.1W
Peak Output Power, 32Ω > 1.5W

DAC Performance

Frequency Response 20Hz-20kHz +/- 0.15dB
THD+N 100 Hz -0.15 dBFS 0.0023%
THD+N 20 Hz -0.15 dBFS 0.0016%
THD+N 10 kHz -0.15 dBFS 0.0019%
IMD CCIF 19/20 kHz -6.03 dBFS 0.0011%
IMD SMPTE -6.03 dBFS 0.0012%
Noise A-Weighted dBu 24/96 -102 dBu
Dynamic Range (A-Weighted) > 112 dB
Linearity Error -90 dBFS 24/96 -0.02 dB
Crosstalk -10 dBFS 100K RCA -100 dB
USB Jitter Components 11025Hz -113dB
Maximum Output Line Out 100K 2.10 VRMS

 

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.

Releasing ODAC RevB

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.

ODAC-RevisionB-Web1600x1200

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 Ownership

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 judgment 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.

Change Log

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)

Test Methodology

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!

Performance

DAC SPECIFICATIONS ODAC ODAC RevB
Frequency Response, 20-20kHz +/-0.14 dB +/-0.04 dB
THD+N 100 Hz, -0.15dBFS 0.0022% 0.0013%
THD+N 20 Hz -0.15dBFS 0.0017% 0.0015%
THD+N 10 kHz -0.15dBFS 0.0056% 0.0024%
Noise, A-Weighted -102 dBu – 103 dBu
Dynamic Range (A-Weighted) > 111 dB > 112 dB
Dynamic Range (Un-Weighted) > 107 dB > 109 dB
Crosstalk @ 1kHz, -10dBFS (3.5mm) -80.4 dB -86.4 dB
Sum of Jitter Components @ 11025 Hz, -1dBFS -105.8 dB -112.3 dB
IMD CCIF, -6.03 dBFS, 19/20kHz, 24/96k 0.0027% 0.0005%
IMD SMPTE -2 dBFS, 24/96k 0.0008% 0.0008%
Linearity @ -90dBFS -0.09 dB -0.08 dB
Maximum output 2.00 VRMS 2.10 VRMS

 

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.

Crosstalk (RCA output) - ODAC vs ODAC RevB
Crosstalk (RCA output) – ODAC vs ODAC RevB

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:

Please note that product titles are unchanged, as performance is audibly the same for both versions of ODAC.

For orders placed outside of jdslabs.com, please contact your reseller for availability information. It will take some time for ODAC RevB to make its way to all end retailers.

Summary

ODAC RevB maximizes long-term DAC reliability,  adds 16/88.2kHz support, increases measurable performance, and most importantly, remains audibly transparent.

Custom Engraving Examples

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 Examples

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.