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.
We build amazing headphone amplifiers and DACs. Obviously, this niche market appeals to owners of nice headphones. More interesting is a look at Google Trends for the search phrase “headphones”:
It’s clear that headphone popularity has grown in the past 3-4 years (and the average consumer searches for Beats by Dre…). Easy to explain is the annual spike in headphone interest around the December holiday season, followed by a return to normal interest by summer.
Since interest in headphones directly correlates to interest in headphone amps and DACs, we’ve learned to use summer for two things:
Building our company
Enjoying the summer!
Upgrading our Office
We moved into a 950 sq. ft. office in May 2012. We knew orders were growing at 300% annually in 2011, and hoped that our 2012 office would be large enough to last for 1-2 years. We ran out of space in 3 months. Our inventory room was packed full, our soldering benches were feet away from our CNC machine (noisy and messy), our shipping station doubled as an assembly table, and we had no room for additional desks in our front office. Our product display table and couch turned into a lunch table and conference “room” for visitors. We even resorted to storing an engine hoist in our restroom. At least the rent was low!
We began looking for a larger facility as soon as the 2012 holiday rush ended. There was a slight difficulty: We require an unusual mix of office and warehouse space. Large machines, dock access, and concrete floors are normally found in huge warehouses. We needed all of this, plus professional office space in a relatively small space.
In March, we were pleased to find a 2500 sq.ft. office just days away from undergoing a construction makeover. We signed a lease and moved into our fully customized facility on June 1st.
Frequently accessed inventory is now footsteps away from our two main soldering benches. Nick also spent a laborious weekend assembling a massive table for assembly and a 7ft tall shipping station.
Not pictured: About 60% of this room is unused for now. Room to grow!
Soldering and laser engraving stations are equipped with 4″ industrial fume exhaust lines.
Building a Machine Shop
Last year we bought a Tormach PCNC 770 as our first foray into the world of machining. Within 12 months, we’d machined over 5000 parts on the Tormach. Notice it’s absent from the picture above.
As much as we valued the ability to machine our own parts, the PCNC 770 turned into the weakest link of our production process. We frequently found ourselves waiting for parts to be machined. It struggled to keep up with our busiest weeks, so Nick was forced to work 12+ hour days in December and January.
Plus, moving a CNC (even the entry level Tormach 770) is no trivial matter. Industrial movers quoted 10% of the cost of the Tormach just to relocate it from our old office to our new facility. I didn’t want to invest more in a machine that was holding us back.
Nick found a lightly used 2012 Haas Mini Mill 2 the week before our move. At 7.5x the horsepower and 4x the speed of a Tormach, we placed the PCNC770 for sale and upgraded to a Mini Mill 2.
The Tormach was capable of producing about 45 Objective2 front plates per day. We’re now able to machine 135 of these parts in the same amount of time (3x faster).
To give you an idea of how quickly the Mini Mill 2 moves, here’s the first 30 seconds of machining a batch of endplates
And here’s the entire, 3-step process compressed into less than 3 minutes:
** 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’sObjective2 in the past year, you must have noticed that its power jack is discontinued. Alternatives to Kobiconn 163-7620-E do 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).
Zooming in on the power jack (J1), you can see that plenty of copper surrounds its 2.3mm holes:
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:
Hole Count Plated
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:
Tool names gain a prefix of ‘0’ throughout the rest of the drill file, and T08 appears with three coordinates on lines 250-253:
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:
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 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.
Disclaimer: This article has no audio related content. We hope the following manufacturing information will be useful to others.
A couple years ago, we naively expected that aluminum manufactures would perfectly interpret our engineering drawings and produce beautiful, black parts. After rejecting 4500+ aluminum cases in these past two years, I can tell you with certainty that this guy gives a false impression. There’s much more to fabricating a nice aluminum product than simple anodizing. Photos below are a chronicle of our progress.
Our raw cases arrive from the aluminum manufacturer looking something like this:
Rough, huh? Sometimes we see deeper scratches and dents, and parts can even arrive covered in grease and oil.
Anodizing fixes none of this! Any scratches or defects visible before anodizing will remain visible after anodizing.
Brushed + Anodized Aluminum
We added brushed finishing to c421 after realizing that we couldn’t expect aluminum manufacturers to deliver parts in perfect condition:
Brushing solved the immediately visible problem in our first manufacturing attempts, but created new issues. The texture of production parts was rougher than samples. And here’s what happens with a heavy brush intensity:
Relatively fast to perform
Generally low cost
Brushed appearance is popular
Since brushing a part is essentially like rubbing sandpaper against its surface, brushing can alter part tolerances (see above image).
An aggressive brushed finish can create a rough, undesirable texture.
When we began designing C5, we knew that enclosure quality needed to match the awesome new circuit board. Brushed cases had to go. Our local anodizer suggested a very fine bead blast (aka, “peening”).
Bead blasting is essentially like a pressure washer that uses “abrasive media” instead of water. Any media can be used: walnut shells, sand, and glass beads are common. Pick a media, a pressure, a distance from the part, and then blast the surface. Most shops say it’s an art.
Ultra fine glass beads produce a soft appearance similar to Apple’s Macbook:
Bead blasting dulls the part finish. While appearance is excellent before and after anodizing, surface texture oddly changes after anodizing. In some cases, the texture is comparable to a chalkboard.
We also noticed that black parts turned out especially dull, unlike other colors.
With the right bead blasting media and pressure, a bead blasted part looks excellent
Part tolerances are not altered
Requires significant sampling/experimentation from your metal finishing shop
Cost is 50-100% higher than brushing
Most shops manually blast parts, which can lead to surface inconsistencies
Especially rough parts must be tumbled prior to blasting (even higher cost)
Anodizing yields a matte appearance, especially unsuitable for black
Bead Blasting + Bright Dipping + Anodizing
Aluminum parts are normally caustic etched immediately prior to anodizing. If you substitute etching for a process called Bright Dipping, dullness is magically replaced by a brilliant appearance and pleasant texture.
The bright dipped parts shown above are not actually brighter. At another angle, you can see instead that light reflects more brilliantly at all angles. Notice the bright dipped pieces appear darker in this photo:
Excellent surface appearance
Excellent surface texture
Cost is comparable to standard anodizing
Bright dipping is extremely corrosive, so it’s rarely offered in the United States
Carries all other downsides of regular bead blasting (see above)
Hopefully this helps someone in their manufacturing adventures. Special thanks to Tom at Archway Anodize for making our experiments possible!
Lately we’ve received several phone calls which start like this:
Customer: “Hi, I’m new to high end audio. Does [insert product] have a DAC in it? Do I need a DAC?”
From these discussions, two observations are clear.
DACs are suddenly “hot” on the market.
The majority of prospective DAC buyers, especially those new to the scene, have almost no idea what a DAC does.
We sell one of the best reference grade DACs in the world, so this is concerning to me. I’d never shell out $100+ to buy something I didn’t fully understand, and the average customer is no different. He’s turning to Google to gain a better understanding of these mystical “Digital-to-Analog Converters”. Unfortunately, the same people who call keep telling me that they can only find bad/mixed information.
What is a DAC?
Put simply, a DAC is the chip which turns your digital music into something you can physically hear. Every digital audio player (laptop, cell phone, tablet, iPod, etc.) already has an internal DAC and a weak headphone amp.
In terms of the audio chain: [Digital audio source] –> [DAC] –> [Amp] –> Headphones
Why use an external DAC?
If you’re shopping for a DAC, your goal is either to fix poor audio performance, or you’re in the much greater pursuit of reference quality audio. Either way, you’re seeking peace of mind that your audio is audibly perfect.
iPOD DACs: I think most of these are a waste of money as most modern iPods already have very respectable DACs in them. For example, the iPod Touch 3G’s DAC outperforms the one in the popular NuForce uDAC-2.
PC DACS: […] a lot of PC’s have respectable DACs in them. If the problem is your headphones not getting loud enough, just an amp may be enough.
My advice to new users mirrors NwAvGuy’s recommendations. If you want better audio, start with nicer headphones and a headphone amp. An external DAC is a great investment when your source is noticeably poor (background hiss, device interference, etc.).
When you connect a headphone amplifier to an audio player, the amp relieves your audio source from its difficult job of driving headphones. The source now sees an easy load from the external amp. Assuming you’ve selected a high quality headphone amplifier, output power improves, output impedance issues are resolved, THD+N improves (due to the easier load), and background hiss is minimized through input attenuation at the amp. In other words, a headphone amplifier solves the most audible problems.
A high performance DAC ensures that your headphone amp receives a high quality input signal. Since signal quality of most DACs is already excellent, further improvements from an external DAC tend to be minimal.
Lifehacker polled users last month for the Best DAC. The ODAC was nominated, and a tube based amp+DAC won the poll. Considering the $1000 pricetag of the winning nomination, lifehacker correctly identified that they’d actually created a poll of aesthetics. Results are more correctly titled, Most Popular Digital-to-Analog Converter. So, what is the best DAC??
Over the years, I’ve grouped users into three categories:
Subjective audiophiles. Users who mainly ignore specifications and instead base their opinions on their own listening impressions, and/or impressions of other audiophiles.
Objective audiophiles. Users who primarily consider benchmark performance when evaluating an audio device.
Common users. New audio enthusiasts and everyone else, including non-audiophiles. These people aren’t sure what to expect from high end audio.
Jitter and DAC resolution these days are so excellent that the majority of common users and audiophiles we’ve talked to admit that they struggle to differentiate between one DAC and another. Unless your audio source delivers low quality to begin with, this is expected: You shouldn’t hear a reference grade DAC. That’s the point!
Therefore, there’s no such thing as the Best DAC on the market. Most modern DACs are equally capable of providing excellent audio. If you’re after higher quality sound, start with nice headphones and a headphone amp. If you’re after audio perfection, consider a reference quality DAC as well.
Enclosures: In stock, awaiting anodizing February 19-22
Barring unforeseen catastrophic failures, C5 preorders will ship no later than February 28. Review samples and distributor orders will ship on February 22.
Wed., March 13 Update: The C5 preorder sold out this morning. Mass production began two weeks ago, so C5 will be in stock in just 2-4 weeks.
View All Status Updates
Tues., March 12 Update: 99% of preorders have shipped! New Slate C5’s ship immediately. New Red C5’s will ship next Tuesday, March 19.
Mon., March 11 Update: Slate anodizing remains on schedule for completion tomorrow morning. Our anodizer says this batch is turning out as desired.
Fri., March 8 Update: Over 75% of preorders have shipped (all Red and Silver). All Slate preorders are scheduled to ship by Tuesday evening.
Thurs., March 7 Update: We inspected and approved a new batch of enclosures today, and now expect to complete preorder shipments within 3 business days.
Tues., March 5 Update: We have encountered an “unforeseen catastrophic failure” as I wrote on February 16th. The enclosure delay mentioned last week was caused by our local metal finishing shop. Their job is to apply the smooth, blasted finish to C5 (bead blasting). As of last Tuesday, they realized they’d blasted our C5 cases with the wrong parameters. Already one week late, they called on 2/26 and promised to start over and deliver perfect pieces by Thursday, 2/28. All seemed fine, until we anodized those pieces. Our anodizer called this morning apologetically. His shop follows this blog and is well aware of the significance and beauty of C5. Every single piece from the “fixed” batch was not fixed. Anodizing had revealed severe cosmetic defects–all pieces from 2/28 were junk.
I drove to the blasting facility this afternoon and handed them two C5 enclosures: one from the first batch, and one from the 2/28 batch. The production manager was as shocked as we are, and will begin another batch in the morning with strict supervision.
It’s an absolute shame that one shop foiled our ambitions to ship early. As soon as we realized the possibility of failure, we began identical blasting production at a second metal finishing shop, for redundancy.
The Good News:
We have a strong supply of raw enclosures; without delays, metal finishing normally takes just 2-5 business days.
Over 61.5% of C5 preorders have already shipped
For those affected by the delay (mainly Silver and Slate preorders), we promise to upgrade all USPS First Class shipments to USPS Priority. Please do not hesitate to contact us if we can be more helpful!
Mon., March 4 Update: All Red C5’s have shipped. All outstanding preorders will ship by Wednesday.
Thurs., Feb 28 Update: Enclosure anodizing is in progress, and we still expect to ship on Monday afternoon.
Wed., Feb 27 Update: A large batch of C5 enclosures will enter anodizing by 1PM Thursday (a 1-2 day process). Preorders will resume shipping on Monday afternoon.
Tues., Feb 26 Update: Over 25% of C5 preorders have shipped. All PCBs have been tested and are awaiting final enclosure assembly. Our enclosure finishing contractors called this morning to report a 2-3 day delay, so remaining C5 orders will ship Feb 28 thru March 6.
C5 is not a response to the Objective2, nor to competitors’ products. C5 began as a fun project in 2012 to build a smarter headphone amplifier to solve the single greatest hindrance we see in DIY audio: the analog volume potentiometer.
C5 is built for portable users who need a small amp with USB recharging, exceptionally low noise, sufficient output power, long battery life, and most importantly, a super fine volume control to handle sensitive headphones and IEM’s.
Analog Potentiometers’ True Performance
I interviewed an electrical engineer in January. He’d applied here after discovering the Objective2, and during our discussion, he asked, “What’s there left to design? The O2 is audibly perfect. How can you build anything better than that?”
Easy, there’s no such thing as a perfect product. Every design has its unique goals and constraints.
Our Chinese competitor says the Alps RK097 analog pots are “still the best” solution, presumably based on low cost and decent benchmark performance. NwAvGuy dismissed digital potentiometers as too expensive to implement with good performance, while acknowledging the major shortfall of the Alps pot he settled on for the Objective2:
THE CHANNEL BALANCE PROBLEM: Devices with conventional volume controls may have audible channel imbalance at very low volumes [i.e., one side is much louder than the other –JDS]. It’s extremely difficult to manufacture volume control potentiometers that maintain tight channel balance below about -40 dB (referenced to full volume). — NwAvGuy
In this article he briefly describes how imbalance can be resolved with proper excess gain. The excess gain problem is primarily why we’ve custom built cMoyBBs for over five years. That is, setting a suitable gain usually avoids channel imbalance. Usually–until you’re sitting in a quiet room and want to listen at low volumes, or until you try a set of high efficiency headphones. Even at 1.0x gain, you’ll encounter major channel imbalance from your so-called high performance analog headphone amplifier in such situations.
Let’s take a look at channel balance of c421, measured by the dScope as I slowly turn the knob from maximum to minimum position:
The yellow line represents the left channel; pink represents the right channel. Lines resting exactly on top of each other indicate audibly perfect balance (no deviation in L and R volume).
c421’s Alps RK10J imbalance grows after just -12dB. The problem becomes severe by -22dB, and it’s quite useless by -30dB. If you called or emailed in the past year, you know we didn’t recommended c421 for IEM’s. If you tried c421 without seeking our advice, you either listen above the imbalanced region, or you returned the product.
Here’s an Alps RK097 implemented in the cMoyBB (Objective2 uses the same series potentiometer):
Channel balance of the RK097 fairs much better, due to its larger mechanical size. You can see 1-2dB deviations at -25dB, with otherwise decent balance down to -40 to -50dB. And that’s where things get nasty. I only managed to turn the knob at a single point when the dScope cycled to measure the imbalanced region, which is exactly the problem IEM users face. You can either turn the knob to mute, or to a point of imbalance, or to a level louder than you’d prefer.
Even with the RK097, we still receive a few emails and phone calls each month about channel imbalance. So what good is a HiFi amplifier when it actually hurts your listening experience?
For years, audiophiles feared digital volume controls. Software based digital volume control is the worst, causing you to “lose bits”–the audio signal itself is digitally divided and becomes less precise. Bad!
Early digital potentiometers solved the basic mechanical problems of analog potentiometers. A digital potentiometer is electrically equivalent to an analog potentiometer. Both feature High, Low, and Wiper terminals. The potentiometer is mechanically or digitally set to determine the ratio of High:Low resistance. However, bad digital pots added a large amount of capacitance to the Wiper, and thus, audiophiles frowned at the resulting THD+N (often 0.1% or worse).
It’s 2013, and it’s finally time to say goodbye to the analog potentiometer. C5 features 64 steps of audibly perfect digital attenuation:
C5 presents only +/-0.1dB of deviation all the way down to -50dB, and only +/-0.55dB at -60dB! [Yes, you can only see 28 steps here, as I’m manually racing the dScope test duration by making larger volume transitions.]
In other words, C5’s digital attenuation achieves perfect audible balance at volumes -20dB lower than the analog Alps RK097. Remember that audio sounds twice as loud every 10dB, so this is no small improvement.
Reference Level Performance
C5 began as an experiment, and even I was skeptical that we could outmatch c421’s THD+N with a digital potentiometer. Thus, we bought a dScope III and set no project deadline and no budget. We’d either continue shipping c421’s, or continue experimenting.
By January 2013, it was clear that C5 was electrically complete. We quietly put C5 PCB’s into production instead of another batch of c421’s. C5 had not only hit our THD+N goal, it had matched the O2!
+/- 0.02 dB
THD+N (20-20kHz, 150 Ω)
THD+N (20-20kHz, 32 Ω)
Crosstalk @ 150 Ω
Inter-channel Phase @ 1kHz
+/- 0.55 dB, all volume positions
Max Output @ 600Ω
Max Output @ 150Ω
Max Output @ 32Ω
Battery Run Time
2 Hrs to 80%, < 4 Hrs to 100%
–40°C to 85°C
0 to 85% Rel. Humidity
Dimensions (excluding switches)
99.5 x 61.5 x 14.0 mm (LxWxH)
Achieving high output power was not a primary goal of C5. Referring to its design objectives, portable users do not need inordinate amounts of power (note: P = V^2/R); you need run-time and just enough power. C5 has equal output power to that of c421, and we know from measurements and subjective results that c421 and C5 are well suited to driving 90+ dB/mW headphones. IEMs and common 32-250 ohm dynamic sets are okay for C5. It’s not meant for your planar orthodynamics. Therefore, instead of setting unnecessary supply voltage and output power, we set adequate supply voltage for moderately demanding headphones and achieved run-time of 14 hours.
Dual LDO Supply Regulation
C5 builds upon c421’s proven power stage by adding cutting edge TPS7A4700 and TPS7A3301 regulators to the supply rails. Hats off to HiFiDuino’s blog post for catching my attention back in September.
We wanted to place LDO’s in c421, but there was no way to control them, and without control, unsynchronized LDO’s produce unsafe turn-on transients. C5 is smarter than c421, so its firmware simultaneously enables the positive and negative LDO’s after the rest of the amp has initialized. You hear only a safe turn-on transient with C5, and reap the benefits of ultra-low supply noise.
Digital Stepped Attenuation (63 steps + mute)
Dual Gain: 2.3x or 6.5x, MOSFET controlled
Bass Boost: +6.5dB @ 80Hz
20-Minute Low Battery Indication
0.1% Thin Film Resistors
1200mAh, 3.7V Li-Ion Battery
Smart USB Charging
Ultra Low Noise +/-7V rails
3.5mm Input and Output Jacks
Gold Immersion, 4-Layer Printed Circuit Board
Atmega168A MCU w/Opensource Arduino Firmware
How to Use
Hold volume lever left to decrease volume, or right to increase volume.
Push volume control to toggle high/low
Toggle up for normal audio, toggle down for bass boost
A single LED conveys all of C5’s behaviors:
The C5 proof of concept began as an Arduino Pro with messy wires coupled to a c421: DIY style.
Writing firmware for a digital potentiometer is surely a hurdle for many in the DIY audio community. In pursuit of retiring analog potentiometers in DIY HiFi, we’re releasing C5’s firmware under the CC BY-SA 3.0 license. Note that a 6-pin header and ISP programmer are required to write to C5. Enjoy!
Happy New Year, everyone! 2012 was by far our best year ever, at 430% revenue growth over last year. Incredible!
No surprise to us, “Erik” at Headfonia.com named the O2+ODAC combo his personal Product of the Year:
“I have heard and seen more gear in 2012 than in all the years before combined. For me, the rise, and subsequent disappearance, of NwAvGuy has probably been the most prolific event this year. Like it or not, the release of his maximum-value Objective2/ODAC combo (designed in 2011 but properly distributed in 2012) really shook up the scene and therefore deserves it’s place as my personal Product of the Year 2012…”
Well put. While we can’t claim absolute responsibility here, we ramped up production of the Objective2 and O2+ODAC combos in 2012 and the effect has been nothing short of amazing. NwAvGuy completely changed our business plans for the year, as well as my perspective on product development and customer recommendations. As the Objective2 gained popularity, we gained even greater respect for NwAvGuy’s contributions to the DIY scene, especially in the way of subjective bias.
A little surprise: Yes, we have black O2’s and O2+ODAC combos in stock. These have been available for a while now upon special request. We’ll add greater store visibility for the Black Edition O2 as soon as our knob supplier catches up.
The end of the year is peak season for us, and that means two things. First, our production team is as busy as Santa’s elves. Second, we’re preparing for tax season. Part of this preparation is an annual Inventory count, in which we count everything in the office: chairs, computers, soldering irons, circuit boards, resistors, capacitors, IC’s, etc…
On the flip side of this enormously busy month, it’s equally important for us to reinvest spare cash in new equipment. We’d already acquired a CNC and laser engraver back in the summer. So in the name of NwAvGuy, we made one final acquisition in December–a PrismSound dScope Series III audio analyzer.
The dScope III is an amazingly powerful tool, which enables us to continue developing great products, with or without NwAvGuy.
We may find other uses for the dScope, aside from R&D. Rockford Fosgate ships unique test performance sheets with some of their car audio amps. Maybe some of you guys would like to see actual printouts of your new amplifier’s output? Tell us!