The C5D, as Mike has already pointed out has the best build quality ever since JDSLabs started making the C421 amplifiers. It looks and feels really nice, you can clearly see they’ve been investing in quality improvement. The digital volume control works like a charm, you just have to realize it’s different from most volume controls. I often forget about the left-right thing, resulting in even louder sound when I wanted to turn it down. The C5D is very light too compared to the Cypherlabs Theorem (my reference/standard portable unit) and so I always left the house with the C5D stacked on top of the Theorem. For all my idevices I have to admit using the Theorem as DAC, I just didn’t have the right cables or didn’t want to be out with the CCK (Camera Connection Kit). So basically you could use the C5D with some Apple devices but it just isn’t the same thing as using a Cypherlabs or Centrance unit, therefor I won’t call the C5D a real idevice. Quality and price-wise the Theorems of this world are still miles ahead.
As a result my impressions are purely based on pc listening (dac/amp) and using the Theorem as idevice dac and C5D as an amp. For A/B testing the C5 vs the C5D, I used Fiio’s HS2 Signal Switch unit, which is excellent for comparisons like this.
After a few weeks of using the C5D on the go and at work I have to say I mainly used the unit when listening to my (custom) in ears like the Eterna Rev 1, Cosmic Ears BA4 and RHA MA750i. Whenever I used full size headphones like the LCD-2 and the Sennheiser HD650 at the office, I always fell back to the Theorem. Don’t get me wrong here, the C5D has more than enough juice, or gain as you will, to power both units, it’s just that I’m missing some dynamics and “life” for these headphones. I guess our ears have been too spoiled lately with really great (and expensive) units.
One of the best features of the C5D and the JDSLabs products is the Bass Boost. In this latest version you even get three settings in stead of the normal on-off setting you had before. I usually find the toggle to be in setting 2 or 3 but it’s always on. This is one of the main reasons as well why I used my iems with the the C5D, extra bass and mid range warmth. Unlike Mike who clearly prefers the max BB setting, I find the bass to be a little over-powering with some music at that setting. It seems I’ve become less of a “bass head” over the last few years but with these different settings you will have at least one that suits your preference.
Apart for some slight differences in the numbers, the amp part of the C5 and the C5D is supposed to be the same. However while A/B testing them you can clearly notice a difference in the amp section. The C5D seems to have less space and air in the music, making it seem like a more congested sound compared to the C5, which sounds clearer and more resolving. The bass bump Mike talked about really is there. I know I’m saying a lot of the things that Mike already said, but I can only confirm I am hearing the same. So for me personally, just looking at the amp section, I would choose the C5 sound over the C5D. There however is a big but: I don’t think it is fair to just look at the amp section of both units as the C5D is a DAC/AMP combo and so it should be evaluated as one.
After A/B testing both units I only used the C5D as a combo with my laptop. Headphones I used were mostly the Cosmic Ears BA4 and Philips Fidelio L2. I remember when I first listened to JDSLabs’ C421 a long time ago, the unit was so much fun to listen to and it was so nicely musical. The C5D as a combo still gives that exact same feeling and it has a very high toe-tapping/fun factor, it’s very easy to enjoy your music. I think the combination of the dac part and the amp section in the C5D is a winner, together they deliver a dark background and clean sound where musicality comes first. Sure it might not be the most detailed or revealing unit with the biggest sound stage but it is hard not to enjoy.