C5D is a high-performance portable headphone amplifier featuring digital volume control, multi-position bass boost, dual gain, and asynchronous digital-to-analog conversion compatible with iPad, iPhone, and all UAC1 compatible operating systems.
Pros - Transparent amplification, transparent 20 ENOB DAC performance, Great Build, Works with iOS and Android,
Cons - No dedicated line out from the DAC without sacrificing analog input, Battery life is a bit short
I’d like to thank John Seaber and the folks at JDS Labs for the C5D loaner unit.
The C5D ships with a 1.5 foot USB mini-B cable, a set of four rubber stick-on feet and an instruction manual. A Spartan lineup, to be sure, but it gets the job done.
Design and Build Quality
Identical to the C5 in shape and size, though with a couple of added features, including a switch around back to allow the C5D to charge from a connected USB source or run strictly from battery power and a two-stage bass boost switch on the front with two boost options, instead of the single boost option in the original version of the C5.
Though I thought the switch that allows one to disable the charging circuit of the C5D and run on battery power alone was a rather frivolous feature at first, I quickly learned that it’s a hugely beneficial when using the DAC with my iPhone. I connected another USB DAC/portable amplifier I have, the MUSE PD1+, to my iPhone and it advised me that the connected accessory couldn’t be used because it consumed too much power, despite having its own battery. So a point for JDS Labs for realizing the necessity of such a feature.
Clad in an aluminum casing, the C5D feels sturdy and reliable, like it could easily handle being thrown into a bag or pocket every day and endure like a champ. Of course, I handled my demo unit with care but its solid feel instills confidence in long-term durability.
Unfortunately, my demo unit shipped with a weak battery so I wasn’t able to evaluate its performance accurately.
iPhone 5S – Apple Camera Connection Kit
Google Nexus 7 FHD – USB Audio Player Pro – USB OTG Cable
If you’ve read my review of the JDS Labs C5, just apply everything I said there to the C5D, as its amp section is audibly identical to my ears, namely, excellent. The C5D, like the C5, is designed for sensitive headphones and IEMs, so its power output isn’t very high compared to other portable amplifiers like the Fiio E12 but despite that, it is still able to drive high impedance and low efficiency loads like my Sennheiser HD 600 and HiFiMan HE-400 to nice and loud levels without sounding strained, like some other portable amplifiers will with headphones like these.
The all-in-one design of the C5D makes it very portable and usable around the office. I’ve been using it almost exclusively with my iPhone 5S, loaded with a mix of high-resolution lossy AAC and MP3s and performance has been stellar.
It is a bit disappointing that the C5D doesn’t have line-out functionality built in, just in case you wanted to use it as a dedicated DAC for a more powerful amplifier (like the O2, for example) but I didn’t find myself wanting for more than the C5D was capable of delivering. Of course, this may change if I ever get my hands on a set of power-hungry planars or 600 ohm Beyerdynamics. JDS Labs offers a conversion service to change the line-in jack to a dedicated line-out from the DAC but the downside of this is that you lose the ability to connect analog sources.
Another minor flaw is the audible “pop” that comes from the amplifier when it’s switched on. Not a big deal but it’s worth noting.
Yep, that’s it.
The C5D supports 24 bit/96KHz decoding over USB and performs excellently in that capacity. Listening to a few 24 bit high-res test tracks I loaded onto my Nexus 7, the C5D sounded lovely with my Sennheiser HD 600s, so much so that I had to tear myself away from my listening in order to go to bed that night. That being said, whether or not there is any tangible benefit to carrying around 24/96 high-res files is up for you to decide as the audible differences between two lossless 16 and 24 bit files are negligible at best.
But I digress. The important thing here is that the C5D is more than capable of decoding high-res files and amplifying them at a level that will make your headphones sing. Compared head to head with my O2 + ODAC, the C5D was practically identical, subjectively speaking, which is very high praise in my book.
As both a portable amplifier and DAC, the JDS Labs C5D is superb. Though its published battery life is relatively short compared to some other portable amplifiers, the C5D’s feature set and overall performance more than make up for it. I wish its DAC had a dedicated line out for use with more powerful amplifiers but that’s taking the C5D out of its element to a certain degree. It’s meant to be used in a portable setting and in that capacity, it excels, though I would hardly say someone was crazy for using it as an all-in one desktop amplifier and DAC option. The C5D has the audio quality to perform well in that respect but I’d still recommend the slightly more expensive O2 + ODAC for desktop use.
At $250, JDS Labs’ C5D certainly an investment and one that only audiophiles can easily justify but if you’re looking for stellar audio performance from any and everything that supports an external USB DAC or a simple line-out, the C5D is likely one of the best portable amplifiers in the business and definitely the best I’ve ever heard.
Cons - Battery life, slightly confusing modes of operation, a bit fatiguing
This was provided to me from JDS Labs as a free review unit, so I need to give a big, big, big thank you to JDS Labs for their generosity!
You might be able to see in the photos that my unit has some blemishes in the aluminum case. These will not appear in normal units.
Since Head-Fi doesn't display the rating details from the reviewer, but rather the community average, here are my ratings:
Value - 4.5/5
Audio Quality - 4.5/5
Quality - 5/5
Design - 4/5
I still wonder what the differences are between the Audio Quality, Quality, and Design criteria...
Anyway, onwards to the review!
At $250 USD, the C5D offers good sound quality while still having a lot of applications of use.
This is quite a good selection of features for a mobile user!
^ My standard portable rig (iPhone 5G + C5D + V-MODA Crossfade M-100)
For what you get with the C5D's package, and the different ways you can use it, the C5D is a nifty device for anyone who travels or moves around a lot.
4.5/5 (Excellent) for Value
[rule] Audio Quality
Moving on to the sound quality, I would say the C5D as a whole has a fairly transparent sound signature, with just the slightest bit of warmth.
The C5D shares the same amplifier design as that of the C5 model (amp only), so the C5D's sound is very similar to the C5. When A/B-ing the C5 next to the C5D, they sound nearly identical, which is to be expected, but I hear a slightly deeper bass extension with the C5D (bass boost off in both cases). This is a very minimal difference relatively speaking, but it's nice to hear bass guitars having a slightly more realistic sound with the AKG K 701 when using the C5D.
So in short, the C5D's amp section sounds fairly transparent, carrying a similar sonic signature to the Objective 2 amp. In comparison to the O2, the O2, like the C5, has a larger sense of a soundstage, the instrument separation is better, and the midrange is a bit laid-back in presentation (the C5D's amp brings the midrange a bit forward, so it's more engaging to the listener). On the other hand, carrying the O2 around is often an inconvenience and the C5D is a nice alternative for those who need a portable amplifier that sounds transparent.
Some people suggested that JDS Labs make a 3-way bass boost switch since the original C5 bass boost switch added too much bass. JDS Labs decided to take those suggestions and incorporate them into the C5D, and newer C5 units as of December 2013. When the 3-way bass boost switch is in the middle, the bass boost is fully enabled, giving a very large sub-bass bass boost. This works great in some cases such as mobile listening when there is a lot of background noise, or if you want to have the rumbly-like feeling when listening to a movie in a theater. If you use high gain with the full bass boost, the bass boost is actually more than on low gain, giving you 4 levels of a bass boost in essence. On the other hand, the full bass boost is sometimes too much for some music genres, so having the bass boost switched to the top position for half the bass boost amount can come in handy.
The only dedicated DAC I have at hand is the Objective DAC, so most of my impressions are based on comparisons between the two. With that, the C5D's DAC section adds a bit of warmth and thus thickness to the music. The overall presentation is also a bit more intimate, so the soundstage like the amp section is a bit on the small side, but it's also more engaging while listening to music and the sense of soundstage depth is more apparent compared to the ODAC's more wide soundstage. The ODAC in comparison sounds a bit more spacious and open, while also being laid-back; the music is just there. Both are good in their own ways, but I actually prefer the C5D's sound since the ODAC almost sounds metallic next to it (using the C5D as the amp in both cases).
Some people have wondered how the O2/ODAC combo sounds next to the C5D. Carrying the C5's sound for the amp section, and an engaging and warm DAC, they have different sounds overall. To be honest, I like the C5D over the O2/ODAC combo for its musical sound and naturalness, but the O2/ODAC sounds more technical having better microdetails, soundstage size, and instrument separation. I guess I have just now discovered the definition of how a system can sound "musical."
In terms of what I've used the C5D with, I liked the Alpha Dog, Mad Dog, AKG K 701, and even the HE-4 with them. Obviously the HE-4 won't sound at its best with the C5D, but I was pleasantly surprised at how well the combo sounded.
^ Comparing the C5D with the ODAC/O2 while using the Alpha Dog
^ Mad Dog with the C5D connected to the iPhone 4S as an external amplifier
^ Using the HE-4 with the C5D
^ Using the C5D as an external amplifier with the FiiO X5
With a fairly natural and transparent sound, an engaging midrange, and a bass boost option for different listening environments and/or music genres, the C5D a great companion for mobile users. It may be a bit fatiguing to some though due to the more forward midrange, which may sound a bit bright (similar to the C5).
4.5/5 (Excellent) for Audio Quality.
I'm not sure what this arbitrary category is for, honestly. I'll explain it in the Design section below, but the overall feel and appearance of the C5D is excellent; this thing is well-designed and well-built. As from the Audio Quality section above too, the audio quality is excellent.
To top it off, JDS Lab's customer service has always been of the highest quality as well. I can send them an e-mail inquiry at 10 PM and I'll receive a reply back from them before midnight. They offer explanations and walk through problems with you, so communication is very quick, personal, and professional. JDS Labs' first batch of C5D units had a sound imperfection that caused a humming sound to be heard in some circumstances. Although they caught the error after shipping the units, they were very communicative with their customers, acknowledged the problem publicly, and offered to replace the units. This is just one slice of JDS Labs' manufacturing process and they employ a bunch of quality control inspections when making their products. When you receive a unit from JDS Labs, you know you're receiving a high-quality product.
The C5D represents perfection in terms of quality before and after reaching the end-user.
5/5 (Perfect) for Quality
The C5D's design is pretty basic on the outside. The front panel has the input and output jacks, the battery life LED indicator, the bass boost switch, and the digital potentiometer. The back panel contains the power and battery mode switches, and the miniUSB port. The endplates are held on by two screws, so they are removable. JDS Labs also offers silver endplates, so you can change the colour scheme of the C5D a bit.
The whole enclosure is made of aluminum, so it's quite sturdy and solid-feeling. Additionally, JDS Labs offers a laser etching service for free with the C5D, so you can put your own custom artwork or text on the top or bottom of the enclosure. This is certainly a unique opportunity to have your unit customised since I don't know of any other company that offers this service with their devices! In terms of physical size, the C5D is about the same length and width as an iPod Classic or iPhone 4S, so it's a pretty small footprint overall.
Another unique thing about the C5D is that its digital potentiometer, LED indicators, and DAC filter type can be re-programmed through the Arduino software. While programming is certainly not in my expertise, I do encourage looking at the C5D's code and learning a bit about the Arduino platform. A lot of cool things can be done with the Arduino, and learning and understanding the Arduino code for the C5D can lead to some fun side-projects. I reprogrammed the C5D so that it has 5 modes of operation:
DAC circuit "off", low gain, volume change via potentiometer, solid LED, press gain to switch to next mode
DAC circuit "off", high gain, volume change via potentiometer, blinking LED, press gain to switch to next mode
DAC circuit on, low gain, volume change via potentiometer, faster blinking LED, press gain to switch to next mode
DAC circuit on, high gain, volume change via potentiometer, even faster blinking LED, press gain to switch to next mode
DAC circuit on, high gain, DAC filter change via potentiometer, fastest-blinking LED, press gain to switch back to mode 3
I also made the volume setting reset back to low-gain, volume level 1/63 every time the C5D is powered on so that I don't blast my ears with the previously-remembered settings.
The internals of the C5D (the DAC circuitry is underneath the battery):
Another part of the design for the C5D is making it USB Audio Class 1 (UAC1) compatible, which basically means no external drivers are necessary to get it running. This is both a pro and a con. This is a con in the sense that the DAC chip is purposely limited in function (no 24/192, 32/384, nor DSD playback), but this is a pro as well because it allows the C5D to be compatible with more devices without needing to install drivers. Additionally, the C5D is self-powered, so this makes the DAC portion usable to iOS 7 devices with the Apple Camera Connection Kit and Android devices using the USB On-The-Go feature.
^ C5D connected to the iPhone 4S as a USB DAC with the Apple Camera Connection Kit
^ With the USB On-The-Go cable, you can connect the C5D to an Android device if it's supported
Objectively, the C5D has great jitter, THD+N, dynamic range, and crosstalk performance measurements (available here: http://blog.jdslabs.com/?p=722).
The one major complaint I have about the design of the C5D is its battery life. When only using the amp section of the C5D, I get around 8 hours of battery life. This isn't a lot, but it's not too little either, so it's only an "okay" battery life. On the other hand, when using the C5D as an external DAC/amp with my iPhone 4S, I get around 6 hours of battery life. This isn't a lot either, but it is more on the short side. I would have liked to have a longer battery life since this is my primary mobile soundcard/amp. Additionally, the C5D does tend to get a bit warm when in your pocket, so I'm curious as to whether or not the circuit can be designed to be more energy efficient in the future, which may also increase the battery life. I only recently programmed the C5D to have the DAC circuit "off," so I haven't had the chance to test the battery life with that "disabled." I say "off" and "disabled" because power is actually still flowing through the DAC circuit I believe, but not enough for the DAC to be detected by devices (in the Arduino code, it's LOW or HIGH). I sent an e-mail to John Seaber of JDS Labs though and he said the battery life is increased compared to the stock C5D (which has the DAC always on HIGH), but not as long as the standalone C5 battery life (around 10-11 hours).
Another small complaint I have for the C5D is its mode of operation with the battery mode switch. The C5D can operate in "battery" or "charge" mode. When connecting the C5D to a computer via USB, it would make sense to have the battery charge at the same time (thus using "charge" mode). On the other hand, when connecting the C5D to a mobile device/phone via USB, it would make sense to have the battery be used instead of draining the mobile device's battery to charge the C5D's battery (thus using the "battery" mode). When using the C5D as an amplifier with a line-out connection on the other hand, the mode of operation doesn't matter. It's just a bit confusing sometimes to toggle the mode when switching from a mobile device DAC/amp to a computer external soundcard (switching from "battery" mode to "charge" mode, unless you plan to drain the C5D's battery when using it this way).
One last final complaint I have is the bass-boost switch (both on the newer C5 models and the C5D). No bass-boost is the top-most position of the switch, maximum bass-boost is in the middle position, and medium bass-boost is at the bottom position. It takes some getting used to, but it's not intuitive at first.
On a positive note, I have not encountered any RFI noise at all while using the C5D. If you plan to strap this to your phone, you probably won't hear any of the annoying "buh buh, buh buh, buh buh, bburrr-urrr-urr" sounds, and if you do, it'll be minimal.
The C5D's design is great overall, but the relatively short battery life is something that can be improved.
4/5 (Great) for Design
For its size, the C5D packs a lot in such a small package. If you're looking for a nice portable amp/DAC combo, I think the C5D is an excellent value at $250. It has a fairly transparent and musical sound, and it holds its own ground next to my reference ODAC/O2 combo. Being self-powered, the C5D can be used with Android and iOS devices alike, and that's something someone may value.
Size comparisons of the C5D to the C5 and O2:
I want to give another BIG thank you to JDS Labs again for sending me this free review unit. Also, I want to thank you, the reader, for taking the time to read through this review.
If you have any questions or concerns, please feel free to leave a comment below.