Tag Archives: NwAvGuy

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.

Fixing Objective2’s Power Jack

** We’re moving to a new office on Friday, May 31st. Orders placed after 10am CST tomorrow (5/31) will ship Monday! **

If you’ve assembled NwAvGuy’s Objective2 in the past year, you must have noticed that its power jack is discontinued. Alternatives to Kobiconn 163-7620-E do not fit.

One of many alternative 2.1x5.5mm DC jacks -- Does not fit!Substitute power jack for O2. Does not fit.

NwAvGuy last reached out to us on July 1, 2012 before mysteriously disappearing. Two months earlier, he’d discussed revising the O2 PCB. The discussion is archived for those interested: NwAvGuy Emails

From:Northwest AvGuy
Sent: Tuesday, May 01, 2012 12:30 PM
To: John Seaber
Subject: John: O2 Power Jack

Have you found an alternate power jack for the O2, are you modifying jacks to fit, or do have enough of the old ones for now? I’m getting more questions about the discontinued jack and trying to decide what the best solution is.

If I revise the PCB artwork I would fix the jack footprint and move the via under the corner of the gain switch. Are you aware of any other necessary board revisions?

On Tue, May 1, 2012 at 11:57 AM, JDS Labs Inc. wrote:

We source unique parts in large quantities, so we have enough power jacks to last all year.

Kobiconn 163-179PH-EX is close. Dimensions aren’t a perfect match to 163-7620-E, but it should fit existing O2 boards and front plates [Edit: 163-179PH does not fit]. Breaking mechanical compatibility with the original board/plates would be a mess.

No other revisions should be necessary!

On Tue, May 1, 2012 at 2:08 PM, Northwest AvGuy wrote:

Thanks for the reply. Yeah, I have a sample of the 179PH already and, as I posted on the O2 Summary comments, two of the tabs are a bit too big. A revised board shouldn’t change form, fit, or function of the assembled board.

Just beware before ordering a large number of PCBs the artwork may be revised so you might want to check in with me first.

We believed NwAvGuy would eventually update O2. Now that almost a year has elapsed, we can only hope he’s doing okay.

We’ve spent the past few months seeking substitute power jacks. No success. Jack manufacturer Kycon quoted a custom part, with tooling and minimum order quantity totaling $25k-$100k. Not worth it! The last thing we want to do is violate NwAvGuy’s work by disregarding the O2’s no-derivatives license. We’ll gladly respect any wishes he may have if he’s able to return in the future. Until that time comes, we’ve decided it’s time to proceed with NwAvGuy’s intention of sustaining O2 as a viable DIY project. That means the O2 PCB must accept common power jacks.

NwAvGuy only supplied Gerbers for the O2, which makes the design nearly impossible to modify without re-drawing the schematic and PCB from scratch (definitely unacceptable).

O2 v1.1a PCB Gerbers
Original O2 v1.1a PCB Gerbers

Zooming in on the power jack (J1), you can see that plenty of copper surrounds its 2.3mm holes:

O2_original_zoom
Original O2 v1.1a PCB Close-up

Most power jacks have pin widths of 3.0mm, instead of the small 2.3mm pins used by 163-7620-E. So, we only need to increase hole diameter at J1 by 0.7mm.

NwAvGuy left us with wonderful documentation. You can find this table in the O2 readme, and tool “T8” looks like the drill bit relevant to jack J1:

Tool Hole Size Hole Type Hole Count Plated
T1 28mil (0.7112mm) Round 104
T2 32mil (0.8128mm) Round 44
T3 42mil (1.0668mm) Round 23
T4 53mil (1.3462mm) Round 24
T5 55mil (1.397mm) Round 8
T6 62mil (1.5748mm) Round 12
T7 68mil (1.7272mm) Round 12
T8 91mil (2.3114mm) Round 3
T9 125mil (3.175mm) Round 3
Totals 233

To test this idea, I searched the drill file for “T8”. The first instance occurs at line 13, where this table is defined explicitly in Gcode:

M48
;Layer_Color=9474304
;FILE_FORMAT=2:4
INCH,LZ
;TYPE=PLATED
T1F00S00C0.0280
T2F00S00C0.0320
T3F00S00C0.0420
T4F00S00C0.0530
T5F00S00C0.0550
T6F00S00C0.0620
T7F00S00C0.0700
T8F00S00C0.0910
T9F00S00C0.1250
%

Tool names gain a prefix of ‘0’ throughout the rest of the drill file, and T08 appears with three coordinates on lines 250-253:

T08
X017Y-005452
Y-00305
X015189Y-00431

To confirm that T8 is the appropriate drill bit for the DC jack, I set T8 to an arbitrarily large size on line 13 and checked the visible result:

Changed drill size in NC Drill file to use arbitrarily large holes
Arbitrarily large T8 drill size confirms T8 is only related to O2’s DC jack

This test proved that T8 only affects holes at the DC jack. Thus, I changed T8 in the drill file to our desired hole diameter of 120mils (3.05mm). Here’s the visible result, showing successful 3mm, plated holes at the power jack:

O2 v1.1b PCB: Equal to NwAvGuy's v1.1a, with J1 holes enlarged from 2.31mm to 3.05mm
New O2 v1.1b PCB: Equal to NwAvGuy’s v1.1a, with J1 hole sizes increased from 2.31mm to 3.05mm

O2 v1.1b PCB fabricated and confirmed perfect!

Fits
CUI PJ-002A power jack (3.0mm pins): Fits new v1.1b PCB
O2 v1.1a in Green, O2 v1.1b in Purple.
Original O2 v1.1a in Green, Modified O2 v1.1b in Purple.

AVAILABILITY

Modified O2 PCBs are Now in Stock. You may also download the v1.1b Gerbers for your own use.

SUMMARY

O2 v1.1b is a straightforward manufacturing alteration to the O2 v1.1a circuit board. Specifically, holes of the power jack, J1, have been enlarged to accommodate standard power jacks. All aspects of the Objective2 remain unchanged from NwAvGuy’s work. The PCB layout is identical. Performance is identical. Even the silkscreen still shows “v1.1a” (admittedly confusing). The O2 v1.1b PCB merely allows builders to assemble O2 without encountering frustration from the DC jack.

 

Endplate Experiments & RCA Jacks for ODAC

** Scheduled Maintenance: We’re moving our server tomorrow night at 1:00AM CST, Saturday, July 14th. Anticipated downtime is 1-4 hours. JDSLabs.com may be difficult to access in some parts of the world for the next 24-48 hours while our new IP address propagates. **

CNC Experiments

Nick has spent the past three weeks making noise, breaking drill bits, and splashing super fun blue coolant all over the office. Most people don’t pick up mechanical engineering and machining as new “skills” in just three weeks, but we do what we have to here.

First batch of reasonable test parts, despite artwork mistakes and over-sized screw holes

With the basics of CNC’ing out of the way, our attention has turned back to the reason we bought the CNC in the the first place. We want brilliant quality, and we want our parts now.

We’ve specified brushed aluminum on our endplates since they were first designed. It turns out that most aluminum suppliers do not offer brushing. The process is a time consuming and challenging task even for most machine shops. That was a disappointing discovery!

Our endplates will still be brushed, but this sourcing realization led us to experiment with the aluminum. The test pieces shown above were machined at our shop on Friday afternoon, then plated on Monday morning in downtown St. Louis. Clear alodine and black anodizing finishes both look fantastic. And it was all done in under 2 business days. 🙂

O2+ODAC Rear Panel with 3.5mm Output

Rear B2-080BK endplate with 3.5mm ODAC output

Although we don’t recommend that you install a 3.5mm output jack on your O2+ODAC, some customers have requested to do so anyway. This is for you: Machined O2+ODAC Endplate w/3.5mm output. These are made from stock endplates included with the Box B2-080 cases, thus, the price is lower than other endplates.

RCA Jacks for ODAC

RCA jack on an O2 Endplate. Hey, it fits!

Okay, this isn’t an ODAC or even a reasonable device. But it is a proof of concept for our Standalone ODAC w/RCA outputs.

We’ve avoided RCA outputs on the Standalone ODAC for several reasons. RCA jacks take longer to assemble and cost more than a 3.5mm jack, but this has been irrelevant to our decision.

We haven’t offered RCA jacks on the ODAC due to virtually identical performance: Why complicate a product with multiple variations and increased build cost at no benefit? The 3.5mm jack on the ODAC circuit board is wired to the same line output header as used by RCA jacks. Some customers have asked, “Aren’t 3.5mm cables more lossy than RCA?”. As NwAvGuy has stated, characteristic impedance is a non-issue in unbalanced audio systems. There are no impedance mismatches to be concerned with, and there are no significant losses resulting from the use of a 3.5mm cable. Crosstalk might change negligibly (1-3dB), but overall, it’s a myth that RCA cables are less lossy than 3.5mm cords. Case in point, why would NwAvGuy (an audio benchmark and measurement fanatic) have designed the ODAC with a 3.5mm jack if it were “lossy”? He wouldn’t have! I’m sure NwAvGuy can provide benchmarks if badgered.

3.5mm to RCA Cable
3.5mm to RCA Cable

Moreover, you can use a common 3.5mm to RCA cable for direct connection of a 3.5mm device to an RCA device.

With all of that said, it’s easier to build products customers want, than to convince everyone that what we’re building is the best solution.

So last week we set out to fit RCA jacks into our Standalone ODAC enclosure. I had briefly collaborated with Stefan of Head ‘n’ HiFi earlier this year on the Standalone ODAC case. We’d been asked by NwAvGuy’s contractor to lead the design and distribution of a standardized ODAC case for the DIY community. I wanted ultimate enclosure quality, and was willing to wait until late July for a custom case fabricated in the USA.

However, Stefan wanted cases immediately, and didn’t think he could fit RCA jacks into our thin case, with only 10mm to work with (a typical RCA jack is 9.5mm). Stefan’s a nice guy, but we had to agree to disagree on our design goals. Product excellence is more important than expedited delivery and cost, especially when a product will stick around for years to come.

Despite the tiny clearance, we’ve managed to design ODAC endplates that will accept 2x RCA jacks and still fit into our thin ODAC enclosure, without losing ground isolation. This is only possible due to a beautiful, black anodized finish. More pictures are coming soon. For now, imagine the gold RCA jack pictured above on our Standalone ODAC.

ODACs are scheduled to arrive July 19-25. All Standalone ODACs will ship by the end of July.