Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › O2 AMP + ODAC
New Posts  All Forums:Forum Nav:

O2 AMP + ODAC - Page 47

post #691 of 3771

Forgot to add a

  • Audio forums propensity for hyperbole

 

Got to filter what you read and adjust expectations accordingly.

post #692 of 3771
Quote:
Originally Posted by mikeaj View Post

Forgot to add a

  • Audio forums propensity for hyperbole

 

Got to filter what you read and adjust expectations accordingly.


That reminds me. How come no one's reviewing the Schiit stack (Magni/Modi) with measurements? 

post #693 of 3771
Quote:
Originally Posted by proton007 View Post

Quote:
Originally Posted by mikeaj View Post

Forgot to add a

  • Audio forums propensity for hyperbole

 

Got to filter what you read and adjust expectations accordingly.


That reminds me. How come no one's reviewing the Schiit stack (Magni/Modi) with measurements? 

purrin did. Conclusion was that there were some differences despite measuring nearly identical. Another Head-Fier in this thread said they're too close in sound that the Schiit Stack would be a better buy for your money (if you want a desktop setup).

post #694 of 3771
Quote:
Originally Posted by miceblue View Post

purrin did. Conclusion was that there were some differences despite measuring nearly identical. Another Head-Fier in this thread said they're too close in sound that the Schiit Stack would be a better buy for your money (if you want a desktop setup).


I've read those, I'm referring to the comprehensive O2 style review, with technical measurements.

post #695 of 3771

I'd like to see something like this atleast:

 

Frequency Response 
THD 1 Khz 150 Ohms 
THD 1 Khz 15 Ohms 
THD 20 hz 15 Ohms 
THD 20 Khz 15 Ohms 
IMD CCIF 15 Ohms 
IMD SMPTE 0.002% 
Noise (ref 400 mV)
Max Output 15 Ohms 
Max Output 33 Ohms 
Max Output 150 Ohms 
Output Impedance
Crosstalk 15 Ohms 
Channel Balance

post #696 of 3771
Quote:

Originally Posted by mikeaj View Post
 

Those are acoustic measurements via HE-500 headphones.  All differences are more-or-less masked by the headphones and maybe the microphone.

 

I suspect the microphone. Especially at higher frequencies, a cheap electret microphone can have higher distortion than a headphone, particularly an expensive planar magnetic one. It appears that purrin's acoustic THD measurements tend to have a fairly constant 2nd order distortion of a couple tenths of a percent at least, which may come from the microphone.

 

Quote:
Originally Posted by mikeaj View Post
but couldn't you see any undue amp / headphone interactions by measuring the signal that's across the headphone terminals, thus avoiding all the inaccuracies with most acoustic measurement setups?

 

There are people who believe that the exact same signal across the headphone terminals does not guarantee the same sound.

 

Quote:
Originally Posted by mikeaj View Post
Also note that I don't think his gear is good enough for electrical measurements of higher-end amps, particularly with easier loads.

 

It does not take expensive gear to achieve measurement quality that is good enough that if it becomes a bottleneck, then the parameter measured is clearly below any reasonable threshold of audibility anyway. However, one must really pay attention to avoid mistakes in the measurement and analysis that cause large errors, like testing amplifiers without a load, ground loops (very common), incorrect measurement of AC voltage with poor DMMs, using the ADC under conditions it does not perform well or even acceptably (like too low or too high input voltage), buggy/limited software (e.g. RMAA), and more. It is also important to know and understand the specifications and performance of the test gear itself, and how it can make the results inaccurate (sometimes it is possible to compensate "bad" measurements with that knowledge). From my experience doing PC based measurements, it takes quite some work to overcome all those issues, including writing software myself, and building various DIY circuits that work around the limitations of the sound card line input (voltage dividers, pre-amplifiers, differential amplifiers, etc.).


Edited by stv014 - 1/14/13 at 5:59am
post #697 of 3771

If you read the designers blog you can see that this person spent many, many hours designing and engineering the layout of the amp and the dac.....implementation plays a very, very important role, parts selection although important seems less relevant than how the part is used and layed out physically on a pc board etc...

 

Alex

post #698 of 3771
Quote:
Originally Posted by MrMateoHead View Post

 

Or is there some extremely good reason why consumers are supposed to shell out money blindly?

 

Hmmm... trust their ears?? tongue.gif

post #699 of 3771

Thats why the design points and specs that the O2 has caused such a stir about are very important baselines...with so many opinions, glittering generalities and glowing adjectives the specs provide a baseline to base all of our other opionions on....

 

Alex

post #700 of 3771

I was reading about the simple half wave rectifier power supply in the O2.......its amazing that a simple, not complex power supply...not even a full wave bridge circuit.

 

The proof is 131 dB of S/N and 0.0009% THD on battery or AC power.

 

Absolutely amazing.....

 

Alex

post #701 of 3771

Hi folks,i am in quite a problem with my early arrived O2-Odac combo,and so early i thing i almost F***** up my unit.I did paste the question from another O2 related thread.

___________________________________________________

I hope you technical guys can tell me some positive thoughts..

 

I did received Friday my very first O2-Odac combo.I did ordered them on September ,but then my first package has been lost,then before to JDS send me another unit i had to wait for some complaining form to USPS and then another month to the new package to arrive here.well i did learn something more about patience ,hehe.

 

So,when i received my combo i've gone to Capital city to find an adapter for the amp,but the first night i have been home with the combo i let the adapter on the 110V switch whereas my home town support 220V.Well for the first days i thought the batteries or the plug where not having a good connection because the O2 were able to work for a couple of minutes before stopping working.

 

But then,i realize my stupidest misuse:The wrong switch on the voltage input.

Now,i did call the manufacturer of the adapter and they told me that possibly the adapter would blew just after 30 minutes on the wrong switch input (well it has been all night plugged in ,and the amp turned on).

My first worries were about the adapter but now i am afraid more about the amp,because they told me too that if the output voltage in my case is wrong the amp could receive more or less for about  28 volts,which i know is very high for the amp,so i hope i did not damaged my beloved and so long awaited amp.

If this could help you,as i sad before,the amp just work for a few minutes before stopping working,due i suppose to the low charge of the batteries inside.

I hope i have been clear as English is not my native language.

Thank you very much guys

post #702 of 3771

What upset me right now is that i have been looking for a new Head-Rig ,but at the moment i am being very busy i just can have listening session sometimes on Sundays....And i already messed up.blink.gif

post #703 of 3771

Why not order the adapter on JDSLab's website?

post #704 of 3771

I think its because his normal voltage is 220vac, the ac adapater on JDS site are 110VAC.

 

There are several European 220vac ac adapters you can find that will meet the ac voltage req's...check the DIY Audio site..

 

Alex

post #705 of 3771

28 VAC input?

 

The power supply regulators and capacitors are rated for 35V max, checking the datasheets of the default parts.  28VAC gets 39.6V from 0 to peak, with a slight drop well under 1V from the diode.  So yeah, the filter caps wouldn't be happy seeing that 39V.  Not sure how long it takes to cook these parts.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › O2 AMP + ODAC