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Review: JDS Labs O2 (Black edition) + O2/ODAC discussion - Page 31

post #451 of 539
Quote:
Originally Posted by ostewart View Post

The iCan can definitely compete plus it has RCA in, 6.3mm out and bass boost + 3D sound options.

Check out clieOS's review on it. He says its the only other amp he's had that was on par with the O2


I am having trouble getting pricing information and specs on the iFi products. From their website, it would seem that it has some nice features, but is not as powerful as the O2. I don't really plan to make any new audio purchases for a very long while, but when I do, they will probably be planar's again.

post #452 of 539
Thread Starter 
It doesn't quite output as much mW per ohm but has variable gain so don't worry about power as it can drive the HE-500 and LCD2 easily.

Price in gbp is £225 I think. Not sure in $
post #453 of 539

Can you explain how gain substitutes for Power? Haven't heard that one before.

post #454 of 539
Thread Starter 

it doesn't substitute for power, but amplifies the signal more (i know it can introduce distortion), so less power + more gain should equal same volume....

 

Also if it can drive the HE-500 and LCD2 then it obviously doesn't lack power.

post #455 of 539
Thread Starter 

iCan: 400mW of output power (@32 Ohms)

O2: 613mW of output power (@33Ohms)

 

so the O2 puts out more power, i already know that. But power isn't everything.

 

Not my review:

http://noblehifi.blogspot.co.uk/2013/05/ifi-ican-review.html

 

But mine is the new version with adjustable gain.

post #456 of 539

Put simply, power is the result of applying voltage to a load. You control the output voltage with your volume control. If you set the volume control low, the headphones will for example receive 10 mW max even if the amp *could* provide more power.

 

The max output voltage is the input voltage (from your source, 2V in case of ODAC) multiplied by the gain.

post #457 of 539
Thread Starter 
Thank you. I'm not as knowledgeable as you when it comes to electronics.
I just know how it sounds and if I like it or not...
post #458 of 539
Quote:
Originally Posted by xnor View Post
 

Put simply, power is the result of applying voltage to a load. You control the output voltage with your volume control. If you set the volume control low, the headphones will for example receive 10 mW max even if the amp *could* provide more power.

 

The max output voltage is the input voltage (from your source, 2V in case of ODAC) multiplied by the gain.


I see. But any amp would therefore be limited, no matter the gain, but the amount of voltage it could provide. So, for example, the Ifi Can would tap out at 9 volts while the O2 (on adapter), can swing 12 volts. Right? A lot of amps seem capable of providing a lot of power at low impedance, but high impedance loads can be a very different story. I think the fact that high impedance phones can also be very efficient fools people into believing that Amp A is "just as good" as Amp B, even when it in fact provides less power.

post #459 of 539
Quote:
Originally Posted by MrMateoHead View Post
 


I see. But any amp would therefore be limited, no matter the gain, but the amount of voltage it could provide.

Well yeah. Primary limit would be the gain itself, after that the internal power supply will limit the voltage swing. If you overdo the gain (iCAN 20 dB setting = 10x) with a hot source (e.g. 2 V ODAC) you will get nasty clipping. High gain doesn't mean high or clean power.

 

On the other hand, difficult low-impedance loads (where current requirements are more problematic than voltage) will also cause the output power to be limited.

 

Quote:
 So, for example, the Ifi Can would tap out at 9 volts while the O2 (on adapter), can swing 12 volts. Right?

I like to always use RMS numbers: The iCAN seems to be able to output 5 V, the O2 can output about 7 V with the right gain. Thats 40 / 80 mW into 600 ohms respectively.

 

At 32 ohm the iCAN can output about 400 mW (= 3.5 V), while the O2 outputs over 600 mW (= 4.5 V). There are no 32 ohm headphones afaik that need nearly that amount of power, but you can see the limiting.

 

Quote:
A lot of amps seem capable of providing a lot of power at low impedance, but high impedance loads can be a very different story. I think the fact that high impedance phones can also be very efficient fools people into believing that Amp A is "just as good" as Amp B, even when it in fact provides less power.

Yeah, voltage swing can be a problem with high-impedance headphones (thinking of portable devices with 1 V output ...). But all it takes is the right gain setting and an amp that can handle it.

post #460 of 539

You know one thing I love about the O2 on my setup?

I can go from a recording with the HD-650 and it sounds really warm and full sounding and the next track is ultra thin, metallic and too trebly (sounding like an AD700 due to recording). Like there is no bass and this is the HD-650! Other tracks give you bloated bass, but again it's IN the recording and not due to my HD-650 (confirmed this many times).

 

I got similar results on the T90 and on my modded Q701. You really feel like you're hearing what exactly is on the recording. Same deal on my Micro Amp.

 

Well..I guess i'm listening to a 128kbps Jpop recording..how'd that get in there. On some DACs you can't even hear Itunes samples as being bad.

 

Some amps will not give you this kind of result...I'm guessing it's a combination of my DAC and Amp. Actually, probably more like the DAC without the AMP screwing with things.

 

Right now I don't have an ODAC but am using the Headroom Micro DAC (CS4398). It's very revealing to my ears and even more so than the Modi.

 

It's amazing how with this setup now there is such a massive variation in how each recording sounds..and this is on the HD-650!!

 

 

BTW someone mentioned the iFi iCAN earlier. I'm getting to try one tomorrow! Can't wait.

post #461 of 539
Thread Starter 
You'll enjoy the iCan I think. I'll be reviewing it soon. Just listening to it a lot now
post #462 of 539

Is swapping opamps in O2 a good idea? No harm in doing so?

 

Has anyone tried it previously? 

 

Any feedback on swapping opamps such as 2132, 49720HA, 2017, 4562 is welcome. I shall be using it through power supply.


Edited by shyamelge - 12/12/13 at 7:12am
post #463 of 539
The op-amps in the O2 have been chosen carefully and the whole thing is optimized for input bias, gains, load impedance, quiescent current, speed, bandwidth, compensation (to ensure stability!), power supply voltage ....

If you have a favorite op-amp that you like to stick into anything that's pin compatible ... don't. As he-who-must-not-be-named said:
Quote:
“when you have only a hammer everything looks like a nail”. But that just doesn’t work for op amps.


Swapping op-amps should always be considered as a risk, unless you have the equipment to measure stability etc.
Edited by xnor - 12/12/13 at 8:16am
post #464 of 539

Thank you for your advise and the quote.

post #465 of 539

I have to agree, i built an eBay dac kit and replaced the 5532 with a 4562 and it transformed it, but with the O2 its best to leave well alone. The designer wrote an entie article on the subject where he tested various different opamps and picked the best ones for the job. If your going to do anything replace the chips with the DD versions are they are slightly quiter, but i doubt but you will ever hear the difference.

 

On the other hand look up agdr's posts on diyaudio, he is continuing to develop the amp and has some interesting upgrades in the works..

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