A few friends of mine had a mini Head-Fi meet today. Impressions:
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JDSlabs C5: I'm buying one. Bass boost=bueno. Stepped volume is A-OK for listening to my music quietly on my GR07, and no noise unless it's on 100% volume.

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I like the M100s a lot (with the C5). They have good soundstage and a solid bass.

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Headfonia review is up: http://www.headfonia.com/jdslabs-the-next-level-the-c5/

There review is exactly what we have said already, however I never had the C421 so cannot comment on that. 

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putente said:

Headfonia review is up: http://www.headfonia.com/jdslabs-the-next-level-the-c5/

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Interesting review. I often find myself disagreeing with a lot of Headfonia reviews, but that's just me.

nice review and a honest one

interesting review.
 
I assume that he has the OPA2227 C421, where as i had the AD8620, as you see in my comparison the C421 is more aggressive and in your face and the C5 more laid back.

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ostewart said:

interesting review.
 
I assume that he has the OPA2227 C421, where as i had the AD8620, as you see in my comparison the C421 is more aggressive and in your face and the C5 more laid back.

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A while ago I read a post from someone saying the same thing (maybe in this thread, I'm not sure now) as that review, comparing the c421 (OPA2227) and the new C5...

So maybe I do not need to buy C5 because Mike wrote that C5 is more forward than C421 and when pairing my HD598 with C4 I have already felt it is forward. Do not need it to get more forward. Besides I am a fan of slow midrange.

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loveknight said:

So maybe I do not need to buy C5 because Mike wrote that C5 is more forward than C421 and when pairing my HD598 with C4 I have already felt it is forward. Do not need it to get more forward. Besides I am a fan of slow midrange.

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While I'd like to see Headfonia post glowing reviews of everything we build, I have to commend Mike on sticking to his subjective taste. He enjoys the high output impedance of c421, and doesn't appreciate the Objective2. That's a problem, since high output-Z yields unique results for every headphone. Hence, c421 reviews were mixed. 
 
C5 is well received so far, and I couldn't say the same of c421 (it was either loved or hated). Many customers who tried both O2 and c421 kept their O2 and returned c421. We're seeing the opposite trend with C5.
 
Production: We approved C5 samples from the next batch this morning. Shipping is on schedule for April 12.

I with miceblue here, often finding myself being on the opposite side of Headfonia review. Not always, but more than enough to know I can't reference my own experience to their. I hope there is enough C5 this time around as I am going to order soon and don't want to wait for the next batch

I think once again personal taste comes in play. I truly appreciate the pairing with er4s and ck100pro and the fast charging time.

jseaber said:

Production: We approved C5 samples from the next batch this morning. Shipping is on schedule for April 12.

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That's great news as I placed my order a couple of days ago.

Has anyone tried the C5 with Sennheiser HD25's?  I know I saw at least one request earlier in the thread, but I don't think anyone has said they have.  I'm very curious.  I have the C421/OPA2227 with my HD25-1 II's (source: iTouch 4G, SendStation LOD, L8 cable) and I'm generally very happy with the setup.  The HD25's are pretty forward to begin with, so the slightly laid back C421 keeps them from being obnoxiously forward while still maintaining a great PRaT for Rock and Metal and so on.  However, I know that my 70-ohm HD25's are under the 8x multiplier rule of thumb for output impedance with the C421 which was around 10 or 11 ohm.  I'd be curious to hear what the much lower 2-ohm output impedance C5 with the same opamp and so on would sound like in comparison with the rest of my equipment.  Maybe I'll get a chance to try one at a meet up one day.  Or if anyone here has some helpful thoughts?
 
Also:  I've seen some conflicting reports on the bass boost, whether it's +6dB, +6.5dB, or +8dB.  Checking the JDS product page features tab, it says this:
"Bass Boost: +6.5dB @ 80 Hz"
 
If that's right, and the c421 page is also correct in saying "Bass Boost, +8dB peak", then that means the C5 bass boost is less aggressive than the C421's?  Is that right?  I quite like the bass boost on my c421, I leave it on almost all the time and rarely find it too powerful, so I'm not sure I'd like the 1.5dB reduction.  John, is the c421 centered at 80Hz as well?
 
EDIT:  replaced "dac" with "opamp" above.

mutnat said:

Has anyone tried the C5 with Sennheiser HD25's?  I know I saw at least one request earlier in the thread, but I don't think anyone has said they have.  I'm very curious.  I have the C421/OPA2227 with my HD25-1 II's (source: iTouch 4G, SendStation LOD, L8 cable) and I'm generally very happy with the setup.  The HD25's are pretty forward to begin with, so the slightly laid back C421 keeps them from being obnoxiously forward while still maintaining a great PRaT for Rock and Metal and so on.  However, I know that my 70-ohm HD25's are under the 8x multiplier rule of thumb for output impedance with the C421 which was around 10 or 11 ohm.  I'd be curious to hear what the much lower 2-ohm output impedance C5 with the same opamp and so on would sound like in comparison with the rest of my equipment.  Maybe I'll get a chance to try one at a meet up one day.  Or if anyone here has some helpful thoughts?

Also:  I've seen some conflicting reports on the bass boost, whether it's +6dB, +6.5dB, or +8dB.  Checking the JDS product page features tab, it says this:
"Bass Boost: +6.5dB @ 80 Hz"

If that's right, and the c421 page is also correct in saying "Bass Boost, +8dB peak", then that means the C5 bass boost is less aggressive than the C421's?  Is that right?  I quite like the bass boost on my c421, I leave it on almost all the time and rarely find it too powerful, so I'm not sure I'd like the 1.5dB reduction.  John, is the c421 centered at 80Hz as well?

EDIT:  replaced "dac" with "opamp" above.

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Yes it's a +6.5 dB bass boost.

The higher damping factor would likely affect the bass region the most on the headphone. Check out Tyll's recent article on the effects of the damping factor: http://www.innerfidelity.com/content/meridian-explorer-case-study-effects-output-impedance

From the past few months, I've seen a trend that people seem to ask how X sounds with headphone Y. Instead of asking how X sounds with Y, I think it would be more useful if people described how X sounds in general. I've used the C5 with multiple headphones and I've heard the same sings I listed before between it and the O2, no matter which headphone it is.


I pretty much know what I'm going to write in my review of the C5, including some improvements, but I'm still putting it off until I get the darn AVR programmer to work properly. >.>

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mutnat said:

If that's right, and the c421 page is also correct in saying "Bass Boost, +8dB peak", then that means the C5 bass boost is less aggressive than the C421's?  Is that right?  I quite like the bass boost on my c421, I leave it on almost all the time and rarely find it too powerful, so I'm not sure I'd like the 1.5dB reduction.  John, is the c421 centered at 80Hz as well?
 
EDIT:  replaced "dac" with "opamp" above.

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Bass boost of C5 is actually stronger. Neither amp's bass boost curve is centered at 80Hz; c421's "peak" was below 80Hz. You can find the curve on our release article.