[alphaphoenix]

Quote:

Would you guys recommend getting a c421 or Objective2 to go with an ODAC?  Or is there another DAC that you would recommend all together?

 The C421 and ODAC pairs very, very well, both aesthetically and sonically.  My Yuin PK1 never sounded so good:
 
 

 

[Ultrainferno]

I have to give that a try...
 

 

[guhmo]

Wow, that combo looks good!

 

[DanBa]

The Android-powered smartphone Samsung Galaxy S III interworks with the ODAC:
http://www.head-fi.org/t/595071/android-phones-and-usb-dacs-how-to-increase-the-issues-priority-with-google/60#post_8468969
http://pastebin.com/Jjq4xnT3
 
Samsung Galaxy S III > digital audio stream >> USB OTG cable >> USB DAC "ODAC" >> amp "O2" >> headphone

 

[sashaw]

Quote:

 The C421 and ODAC pairs very, very well, both aesthetically and sonically.  My Yuin PK1 never sounded so good:
 
 

 
Where do you get this ODAC? 

 

[alphaphoenix]

Same place as the JDS Labs C421.

 

[AstralStorm]

Folks, what's the output impedance and real crosstalk performance of C421?
 
(The measurements on JDSLabs page are useless - they don't have anything better than RMAA with a cheap soundcard?!)

 

[elbastardo]

Better specs posted here:
 
http://www.sonicelectronix.com/item_46564_JDS-Labs-Inc-C421-C421-v1.01-Headphone-Amplifier.html
 
Quote:

Folks, what's the output impedance and real crosstalk performance of C421?
 
(The measurements on JDSLabs page are useless - they don't have anything better than RMAA with a cheap soundcard?!)

 

[AstralStorm]

This says 0.1 Ohm, but the thread: http://www.head-fi.org/t/615766/impression-jds-labs-c421-opa2227-vs-ad8620-featuring-cmoybb-o2-t5-and-uha-4
 
Now that says 10.6 Ohm. 10 Ohm is unfortunately unacceptable for the annoyingly hard to drive IEM that is SE-5.
So, I've no choice other than fixing E17... (or rather, gambling it on the mail)
O2 is not portable really.

 

[ClieOS]

This says 0.1 Ohm, but the thread: http://www.head-fi.org/t/615766/impression-jds-labs-c421-opa2227-vs-ad8620-featuring-cmoybb-o2-t5-and-uha-4

Now that says 10.6 Ohm. 10 Ohm is unfortunately unacceptable for the annoyingly hard to drive IEM that is SE-5.
So, I've no choice other than fixing E17... (or rather, gambling it on the mail)
O2 is not portable really.

You can ask JDS to forfeit the ferrite which will of course worsen the EMI isolation, but you will get back the low output impedance. As my own pet DIY project, I am going to experience a variety of ferrite and see if a solution can be found where EMI isolation is still acceptable and output impedance can be lowered.

 

[jseaber]

Quote:

You can ask JDS to forfeit the ferrite which will of course worsen the EMI isolation, but you will get back the low output impedance. As my own pet DIY project, I am going to experience a variety of ferrite and see if a solution can be found where EMI isolation is still acceptable and output impedance can be lowered.

 
Bypassing the output impedance (ferrites) shouldn't greatly impact audible interference. They improve phase response at high frequencies, blocking theoretical high frequency instability and interference. But these issues shouldn't be audible anyway.
 
The 4-layer PCB is primarly responsible for EMI rejection and the great SNR.
 
 

Folks, what's the output impedance and real crosstalk performance of C421?
 
(The measurements on JDSLabs page are useless - they don't have anything better than RMAA with a cheap soundcard?!)

 
I won't defend RMAA, but we certainly did not use a "cheap soundcard". The RMAA test setup utilized a reference grade engineering sample of a high-end ADC and DAC. Most of our design reality checks are made on a Tektronix 100MHz digital scope w/FFT analysis function. Our reference ADC may not be a $10k audio analyzer, but I wouldn't call it useless. It at least provides a worst case picture of specifications. FFT analysis on a scope isn't as convenient or insightful as a dedicated audio analyzer. But again, it's not useless. Engineering is about designing the best solutions within a given set of constraints.
 
Output impedance is 10.5 ohm. As mentioned above, we can set output-Z to 0.1 ohms if you will be using lower impedance sets and/or don't like the specification.

 

[mmayer167]

I am really liking my c421 with the 2227 op. It is a little meatier sounding and maybe a bit more sparkly than the O2 at times. Detail retrieval is excellent and as good as the o2 imo. But, the previous statement may be due to the c421 seeming a bit more snappy in the treble. This amp is definitely worth it paired with the ODAC! Killer combo, looks, size, function, and build are excellent. It handles the Paradox, which can be hungry at times, pretty well (with bass boost on). The D2000 are excellent out of it as well, at times the treble can be hot with the Denon since I think the odac is a bit treble hot mixing with the Denon smiley face freq (note: my d2k are partial markl modded). For me the O2 still wins when I want truth, but dang is the c421 enjoyable.
 
Thought I would jot down some impressions after 5 days with the c421. 
 
-M

 

[AstralStorm]

Quote:

I won't defend RMAA, but we certainly did not use a "cheap soundcard". The RMAA test setup utilized a reference grade engineering sample of a high-end ADC and DAC. Most of our design reality checks are made on a Tektronix 100MHz digital scope w/FFT analysis function. Our reference ADC may not be a $10k audio analyzer, but I wouldn't call it useless. It at least provides a worst case picture of specifications. FFT analysis on a scope isn't as convenient or insightful as a dedicated audio analyzer. But again, it's not useless. Engineering is about designing the best solutions within a given set of constraints.
 
Output impedance is 10.5 ohm. As mentioned above, we can set output-Z to 0.1 ohms if you will be using lower impedance sets and/or don't like the specification.

 
That sounds decent, I'll strongly consider this amplifier then. (I'm getting a certain Audiotrak Prodigy Cube instead for non-portable use right now.)
Using the ferrite... sounds to me like overcompensation at gain stage. Shouldn't be necessary indeed, including for the purpose of evening out phase response.
 
Rather than the use of RMAA, I'm more worried that -57 dB crosstalk is the best your measurement setup can do...
Heck, my old Aureon Space could do better than that and that's not exactly pro audio.

 

[rudi0504]

I have both amp O2 and C421 with op smp 8620 from Jds lab

In my opinion : with standard version to drive UM Miracle , I prefer Jds lab C 421
Jds lab C 421 with Opamp 8520 sound : more open and better bass.

With upgrade version O2 : with op amp 627 and black gate resistor , O2 sounding much better

 

[ClieOS]

I have both amp O2 and C421 with op smp 8620 from Jds lab
With upgrade version O2 : with op amp 627 and black gate resistor , O2 sounding much better

You mean BlackGate capacitor. Those are a bit overhyped IMO.