It's Like the Objective 2's Younger Sibling

A Review On: JDS Labs C5 Headphone Amplifier

JDS Labs C5 Headphone Amplifier

Rated # 8 in Portable Amps
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Review Details:
Audio Quality
Purchased on:
Price paid: $189.00
Posted · Updated · 42180 Views · 8 Comments

Pros: Similar sound signature to the Objective 2, re-programmable digital potentiometer, bass boost, engaging midrange, little to no channel imbalance

Cons: Situational bass boost, fatiguing at times, volume increments are a *bit* too large

Okay, a serious question not related to the review: what is the difference between the "Audio Quality" rating and the "Quality" rating, and how is the "Quality" rating different from the "Design" rating? blink.gif *scratches head*

Anyway, back to the review.



I did a video review for the C5 on YouTube if you are interested in an auditory/visual review:





What's in the Package?

  • JDS Labs C5 wrapped in an anti-static bag
  • Mini-USB to USB 2.0 cable with gold connectors
  • 4 clear adhesive rubber feet
  • JDS Labs business card
  • User manuel with objective measurements


It's a pretty basic package, but it gets the job done. The C5 also comes with the standard JDS Labs 2-year warranty against manufacturing defects.


I did an unboxing video on YouTube if you are interested (probably not, hahaha).





Custom Orders

There are also 2 things you can get customised when your order your C5; all you need to do is fill out the "order notes" section before you make your purchase:

  • Specify if you want an alternative endplate colour (black or silver, as shown in the images below)
  • Specify if you want a custom laser etching (in the images below, the text to the left and right of the JDS Labs logo were custom ordered)



^ those were not Photoshopped






I would say the C5's design and user interface are near perfect as a portable headphone amplifier for my preferences. There are 5 things I don't like about the design, but all them are pretty minor to me:

  • There are 2 places that I know of where cell phone coverage is very poor/non-existent. In these areas, when the C5 is connected to my iPhone, I encounter some RFI noise (the *boo boop, boo boop, boo boop, boo boop, boo boop* sounds). However, I have only heard this noise with poor/non-existent cell phone reception, so you probably won't hear this noise with normal use.
  • The battery life lasts around 10-11 hours from a full charge in my tests. It's enough for me but others might want a few more hours from their portable amp.
  • The "low gain" is a 2.3x gain, which can be too loud for quiet listening sessions when using sensitive headphones/earphones.
  • The potentiometer's volume increments are sometimes too large for me and I would prefer to have something between the 2 volume steps
  • The bass boost is pretty substantial and there is only 1 setting for it. Perhaps a 2-setting bass boost would have been more appropriate. *see the bass boost section below for more details*



Now on to the good things about the C5's design:

  • The C5's battery can fully charge from an empty battery in around 2.5 hours
  • The digital potentiometer is very well implemented and can be re-programmed (the potentiometer is pretty flush against the frontplate so it's hard to accidentally adjust the volume in your pocket; the gain is also toggled by pushing in the potentiometer)
  • The potentiometer has very little, i.e. non-audible, channel imbalance even on the first level volume (there are 62 levels of volume, 63 if you include mute)
  • There is very little background hiss with the C5 under normal volume levels (at higher volume levels you can hear a slight hiss when you adjust the potentiometer)
  • The C5 loads the volume and gain settings from the previous session upon turning it on
  • The switches are all very sturdy-feeling and they have a very satisfying *click* sound when switched. No cheap-feeling switches here.
  • The source and headphone inputs are both on the front plate but spaced far enough apart that cables don't get in the way of the rest of the front-panel interface. The headphone jack is closer to the outside, so right-angled jacks have more freedom to rotate.
  • The PCB itself can be re-oriented within the C5's enclosure due to the rail system inside the case



  • The size of the device itself is small and pocketable. It's a bit thicker and wider than an iPhone 4S, but shorter in height.




  • The aluminum enclosure has a matte-finish with a texture similar to that of a chalkboard (not a fingerprint magnet)






As a whole, the C5 sounds very clean, detailed, and clear, similar to the Objective 2 (my current reference amplifier). It is the cleanest-sounding portable headphone amplifier I have heard so far and I think it is well worth the $189 USD investment.


Here are my comparisons between the O2 and the C5:

  • O2 gives the sense of a larger soundstage with more air between instruments (a school cafeteria); the C5 sounds more boxed-in (a school classroom)
  • O2 sounds a bit more dynamic; the C5 sounds a little duller (not boring dull, but instruments don't sound as "full" and don't offer the kind of grand sound you get from the O2)
  • O2 has a more laid-back upper-midrange/lower-treble (relative to the C5); the C5 sounds a bit brighter and more fatiguing
  • Relating to the above point, the C5 has a midrange that is is a bit more forward and engaging; the O2 sounds more laid-back


To sum it up, the C5 sounds like a brighter O2 with a more forward upper-midrange and the soundstage, both width and depth, are reduced; hence why I call it the O2's younger sibling. For a portable headphone amplifier, I think the C5 does very well for what it is in terms of sound and I would recommend it to someone looking for a reference portable headphone amplifier in the ~$200 USD range. I actually prefer the more upfront upper-midrange of the C5 at times compared to the O2 since they are more engaging to me and I often have the urge to sing along to the music (in comparison I would just listen to the music with the O2).


I forgot to mention, but the high gain mode has a slightly different sound profile from the low gain mode. The bass becomes a bit boomier and the treble becomes a bit softer. If you're looking for a less fatiguing listening experience, this is a great option if the higher gain (6.5x) isn't a problem for you such as when you're mobile listening. The difference in sound is more noticeable when you compare the C5 with low gain and bass boost on to when you have high gain and bass boost.



Speaking of the bass boost, I think it would be appropriate to describe how it sounds. If you've heard the digiZoid ZO2 before, the C5's bass boost is similar to a green-yellow setting from what I recall in memory. In layman's terms, it's a very deep and substantial sub-bass boost. It won't be for everyone due to its large increase in bass, but I didn't find it to colour the midrange all that much, similar to the ZO2. Despite the large bass boost, I actually do use it while mobile listening with the V-MODA Crossfade M-100 since it provides that extra bit of bass to enjoy even on a noisy bus ride. It's the kind of bass I call "theater bass" since it gives you the sense of bass rumble one would experience in a movie theater. The C5 + bass boost + AKG K 701 = awwwwwesome movie-watching experience





Re-Programming the Digital Potentiometer

Now this is a unique feature that I haven't heard about in any other piece of audiophile equipment before. I'm sure there's something out there that has such a feature, but I personally haven't heard of any.


I made a video on YouTube explaining this process and at the end of the video I demonstrate how I modified the C5's potentiometer:


By using an ISP programming tool in conjunction with Arduino software, you are able to re-program how the C5's digital potentiometer behaves. Unfortunately I have not gotten this process to work in Windows 7 (both 64 and 32-bit), but I did get it to work in OS X Mountain Lion (I am running version 10.8.4). It is possible to solder a surface mount LED onto the C5's board but I since I don't have a soldering iron small enough to do the job, I decided to utilise the C5's existing power LED.


You will need the following to re-program the C5:


Before you can re-program the C5, you need to solder the header pins into the PCB. Additionally, the header pins are too long to fit within the C5's enclosure, so you will need to trim them slightly. Slightly trimming the pins should not affect they're ability to connect to the ISP programmer.




When connecting the ISP programmer to the C5, make sure the orientation of the cable is correct. In the image above, the pin labeled 1 on the PCB corresponds to the red cable in the image below.



You can download the firmware/code for the C5 from JDS Labs' C5 blog post (they are releasing the firmware under a Creative Commons Attribution-ShareAlike 3.0 Unported license):


If you haven't programmed in Arduino before, such as myself before looking at the C5's code, the programming language is similar to C.


Long story short, I re-programmed the C5's potentiometer such that I have 3 modes of operation (for an actual demonstration of these 3 modes, please refer to the YouTube link I posted above):

  • Low gain mode, normal volume speed toggle, no flashing LED
  • Low gain mode, slow volume speed toggle, fast-blinking LED
  • High gain mode, slower volume speed toggle, faster-blinking LED


In addition I have the C5 set the gain and volume levels to low and 1 respectively so I don't blast my ears if I had loud volume levels during the last listening session.


Why slower volume speed toggles? To allow a more precise volume adjustment while holding the potentiometer down (which I do in my pocket when mobile listening).

Why blinking LEDs? To have a visual indication of when I am on a different mode






All in all, I really do find the C5 to be a fantastic portable headphone amplifier in the ~$200 USD range. It sounds fantastic and is reference-worthy in my experience; the bass boost does wonders depending on the headphone, music, and listening environment; the unit itself can be customised specifically for you with a laser etching; the ability to re-program the digital potentiometer is a novel concept to me for audiophile gear and I think it can lead to some very cool results if you spend the time tweaking it (as demonstrated above).


To bring this review to a close, I have had some of the best customer experiences with JDS Labs since they are quick to reply to any e-mails you send them and their responses are very helpful and direct. Whatever the "Quality" rating is for the review details, the customer service of JDS Labs deserves some recognition and that in part is why I gave the quality of the C5 a full green bar.





Thank You!

Thank you for taking the time to read or glance through my review! smily_headphones1.gif 


Excellent review. As I have experienced several "glitches" with the V-Moda amps, I am considering the C5, but I wonder if it would be a step down since the C5 is just an amp with no DAC. How would you describe the improvement in sound through C5 vs. Iphone direct?
Hey there Craigster75! Versus the iPhone's headphone out, the soundstage with the C5 expands both in depth and width so you get a better sense of space in the track. Also the treble seems to be smoothed out and is less harsh/grainy-sounding. The midrange is a tad bit more forward so it's a bit more engaging.
I forgot to mention in the review, but the high gain mode has a slightly different sound profile from the low gain mode. The bass becomes a bit boomier and the treble becomes a bit softer. If you're looking for a less fatiguing listening experience, this is a great option if the higher gain (6.5x) isn't a problem for you such as when you're mobile listening.
I haven't tried an iPhone DAC before, but the difference in sound between the iPhone 4S + C5 isn't much different from my standard reference ODAC DAC + C5.
Would the Objective 2 be a better amp for a Grado SR80? I'm assuming since you say the 02 is not as bright, more laid-back in the treble and with a bigger soundstage than the C5.
I would say yes from a pure synergy perspective. If you need a more portable O2 on the other hand, then I would say the C5 is a good alternative. The C5's brightness isn't a huge difference, but it is noticeable when done in an A/B test with the O2.
Miceblue you ised this with your AKG's you said in your review. Did you think they were driven well? I might get tbis for ther Sennheiser HD 650 and that's also a 300 ohm headphone.
The AKG K 701 is rated at around 62 Ω, instead of 300 like the HD650, but yes I find the K 701 to sound great with the C5. The C5 should be fine with the HD650 though if you're looking for a portable amp to drive them.
Okay thanks for the response! Are you sure it should handle it? My E11 only gives it 30Mw right now and i think it needs a little more oomph to get a better sound.
From JDS Labs themselves:
"Correct, C5 is well suited for all of your headphones. Your HD-650′s are 103dB/mW @ 300 ohms, so they need about 16mW. C5 delivers 28mW into 600 ohms. This means it will provide more than twice the necessary power into HD-650′s."

From a calculated value:
300 ohms: V = 3.836 Vrms, Ipeak = 18.1 mA, P = 49.0 mW

A power value of 49 mW at 300 ohms should be able to drive the HD650 just fine (up to 115 dB SPL).

From FiiO's E11 webpage:
Drive ability 16~150Ω(recommend)