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*Comparison and Review* Magni/Modi vs O2/ODAC - Page 27

post #391 of 428
Quote:
Originally Posted by xnor View Post
 

Well sensitivity ranges from 102 (for the rev2, but we only have 1 data point) to roughly 109 dB SPL @ 1V. The ODAC outputs 2 V, so you can add 6 dB to that plus the gain of the amp.

 

As you can see, if you want 110 dB peaks you don't need much gain in your amp if any at all.

 

 

I don't agree with the "you need a very powerful amp" / "1W minimum" at all. It's nonsense.

If you listen to compressed music (pop, rock, metal etc.) then a fraction of this power is enough to cause serious permanent hearing damage only by listening to a few tracks.

If you listen to highly dynamic classical music, for example, then there can be short, loud peaks but on average the level will be much lower than with compressed music, so you'll never need 1W of continuous output power.

 

 

The Audeze guys speak of music with 60 dB dynamic range. That is realistic, but what's weird is that they also set the noise floor to 60 dB SPL. A 60 dB noise floor? What concert hall has a noise floor that is as loud as someone talking into your face?

Silence in a concert hall is maybe around 30 dB SPL. Even if the orchestra produced highly dynamic sound in a well-optimized concert hall with a range of 70 to 80 dB it would still only be 30 + 80 = 110 dB SPL peak.

 

 

So even if you pick the more inefficient rev2, listen to music with an annoying dynamic range of 80 dB and turn the volume up so that peaks will reach 110 dB SPL you only need about 100 milliwatts max. On average the amp won't have to output more than <10 milliwatts. The O2 outputs over 600 mW for 33 to 80 ohms.

 

 

 

edit: Only with something like the HE-6 you'll need a much more powerful amp, maybe even a speaker amp. If you read reviews of HE-6 & EF-6 you will see how bias affects what these people hear. "It's very clear sound" etc. but measurements by the German Audio magazine have shown a signal-to-noise ratio of only 75 dB. That means that fine details of the highly dynamic music mentioned above would be "overshadowed" by the noise produced by the amp.

 

Very insightful, thank you.

post #392 of 428
Quote:
Originally Posted by xnor View Post
 

Absolutely not. The HE-400 is more sensitive and efficient than the HE-500, which is not hard to drive itself.

 

With the ODAC/O2 you might even be fine with no (0 dB) gain, and less gain is better.

With that last phrase, are you saying that you should always use lowest gain settings that are loud enough for your ears?

post #393 of 428

Yes. I consider the optimal volume control range (in which you listen most of the time) to be between 10 and 2 o'clock.

post #394 of 428

I agree, generally speaking the less gain an amp runs the quieter it is, and less prone to distortion.  As above, if you need to wind the volume past 12 o'clock you could probably do with a bit more gain. Aim for ~50% on the volume dial as the maximum volume you will use.

post #395 of 428
Having less gain makes sense from a technical standpoint, but with my STX, I prefer high gain and 20% volume to medium gain and 50% volume. Could it be that I subjectively enjoy the distortion more?
post #396 of 428

Even at the higher gain settings with the O2 your not going to get any audible hiss......if there is some its from your recording.

 

Alex

post #397 of 428
Quote:
Originally Posted by adydula View Post
 

Even at the higher gain settings with the O2 your not going to get any audible hiss......if there is some its from your recording.

 

Alex


(or from a noisier DAC/audio out such as that implemented in the STX). The O2 is a 'black' amp, but back when I had it plugged in to my Realtek Audio chipset in my laptop, there was hiss at high volume with nothing playing.

post #398 of 428

Of course. Good amps/DACs don't improve the signal, they just degrade it as little as possible. In other words: even a perfect amp could not improve/reduce the noise generated by the DAC, it just wouldn't add more noise. ;) 

 

Part of the high performance of the O2 is the fact that the volume control comes after the gain stage. So the noise generated by the gain stage will be attenuated if you turn the volume control down.


Edited by xnor - 11/10/13 at 9:20am
post #399 of 428
Quote:
Originally Posted by Acknown3 View Post

Having less gain makes sense from a technical standpoint, but with my STX, I prefer high gain and 20% volume to medium gain and 50% volume. Could it be that I subjectively enjoy the distortion more?

 

The STX has entirely digital volume and gain control, and therefore the software "gain switch" does not affect the noise floor or the distortion of the headphone output at matched levels at all. The only things that do affect the noise floor are:

- software problems on Windows (16-bit volume control, etc.)

- hardware problems like interference, bad power supply, or ground loops

- the sample rate (48/96/192 kHz is 6-7 dB less noisy than 44.1/88.2/176.4 kHz because of the re-clocking performed by the C-Media chip in the latter case)

- the impedance and efficiency of your headphones (use 250+ Ω HD6xx, DTxx0, etc., and there should be no audible noise, with the additional benefits of a high damping factor and low distortion)

 

If high gain sounds better to you, that can be because of two possible reasons: either you did not match the volume properly (and therefore provided another example of how higher gain fools people into thinking the sound quality has improved, when in fact it did not), or there is some problem in the Windows drivers (for example, under certain circumstances, software dynamic compression is applied to the audio output to avoid clipping, but that should not normally happen at 50% volume).


Edited by stv014 - 11/11/13 at 1:29am
post #400 of 428
Quote:
Originally Posted by mcandmar View Post
 

I agree, generally speaking the less gain an amp runs the quieter it is, and less prone to distortion.  As above, if you need to wind the volume past 12 o'clock you could probably do with a bit more gain. Aim for ~50% on the volume dial as the maximum volume you will use.

 

There is nothing wrong with using low gain on the O2, and more than 50% volume.

post #401 of 428

Yup agree there I almost always used unity gain and crank the volume control to where it is needed.

 

Alex

post #402 of 428

Well i use unity gain in my O2 and half volume is my comfort level with Grados, with Sennheisers i use 2.5x gain as half volume is also the most i can comfortably listen to.  Reason for aiming for 50% on the volume pot is because that is the sweet spot for channel balance.

post #403 of 428

This may be a stupid question but I'm considering the Magni and noticed it only uses stereo RCA's for input. If I connect an Xonar DGX with a mini to RCA to the Magni will I lose the Dolby Headphone 5.1 surround effect since the signal is being "split into stereo"?

post #404 of 428

The headphone surround effect is encoded into the stereo output of the sound card. But you need to select "Headphones" instead of "2 Speakers" in the Xonar Audio Center, and enable Dolby Headphone. Note that some Xonar cards that have separate (amplified) headphone and line outputs (specifically, the Essence ST/STX) do not support Dolby Headphone on the line outputs.

post #405 of 428

how do O2 and Magni compare to headphone amps using the 6102?

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