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Testing audiophile claims and myths - Page 109

post #1621 of 3264
Quote:
Originally Posted by Speedskater View Post

So then it doesn't matter if the damping factor is greater than 10?

 

It can make a small difference, but something like increasing it from 100 to 1000 is likely inaudible.

post #1622 of 3264
Quote:
Originally Posted by Steve Eddy View Post

Meaningful? What can one expect going from a damping factor of say, 1,000 to 1?

 

In a test where I used a source with 100 Ω impedance to drive a DT880 Pro (a damping factor of 2.5), the distortion that appeared on the voltage on the headphones was roughly a tenth of the distortion in the acoustic output. Eliminating that is not much of an improvement, but it is better than nothing. The headphone is also not a particularly reactive one, with the HD650 used in the Benchmark output impedance paper, there was relatively more distortion when taking the higher damping factor (10) into account.

Another example at InnerFidelity: DT48E (25 Ω) at near-zero and 120 Ω output impedance. There is a few dB of difference in the THD+N vs. frequency graphs here, although I am not sure how accurate/reliable they are.

post #1623 of 3264
Quote:
Originally Posted by Steve Eddy View Post

 

Meaningful? What can one expect going from a damping factor of say, 1,000 to 1?

 

se

>45 dB increase at low frequencies according to benchmark when going from an output impedance of 0.01 ohms to 30 ohms using an MDR-V6 (60 ohm) as load. That's only THD though.

post #1624 of 3264
Quote:
Originally Posted by xnor View Post

>45 dB increase at low frequencies according to benchmark

 

Of course, that is measured on the input voltage to the headphones, rather than the actual sound output with a microphone, where the difference would be much less.

post #1625 of 3264

I was having a discussion with an EE over source components .. a believer, and I explained how difficult it is these days to find a source component that doesn't measure flat and have low noise. His argument :

 

"I can show you two source components that measure similar distortion figures (less than 0.005%) and they sound very different. Distortion measurements are only done at certain fundamental frequencies (like 1kHz) and only tells you a very small part of the total story. Distortion measurements don't consider factors like the phase response of digital filters or the result of phase shifts after the low pass filters at the upper octaves."

post #1626 of 3264
Quote:
Originally Posted by Yahzi View Post
"I can show you two source components that measure similar distortion figures (less than 0.005%) and they sound very different. Distortion measurements are only done at certain fundamental frequencies (like 1kHz) and only tells you a very small part of the total story. Distortion measurements don't consider factors like the phase response of digital filters or the result of phase shifts after the low pass filters at the upper octaves."

 

What if distortion is tested at all audio frequencies and multiple levels, and the phase response of the digital filter is tested too, showing that the phase shift should be inaudible, like here ? It is true that the available information is often limited to a few numbers (maybe even just copied from the data sheet of the DAC chip, rather than actually measured), but that is not always the case, and when more detailed testing is done, it may still not show why the sound would be "very different", at least in sighted subjective reviews.


Edited by stv014 - 11/20/12 at 4:49am
post #1627 of 3264

I mentioned level matching source components to my EE, and he replied with :

 

"All digital source components are level matched, using a 1kHz sine wave, to 1V RMS analogue. The reference WAV test tone is created to be at a level of -1dB from absolute, sampled at 96kHz with 24 bit depth. Not trying to be funny but I've been doing this for a while".

post #1628 of 3264
Quote:
Originally Posted by Yahzi View Post

I mentioned level matching source components to my EE, and he replied with :

 

"All digital source components are level matched, using a 1kHz sine wave, to 1V RMS analogue. The reference WAV test tone is created to be at a level of -1dB from absolute, sampled at 96kHz with 24 bit depth. Not trying to be funny but I've been doing this for a while".

 

You EE chap(?) is wrong. I have measured the output levels from 3 different DAC and/or CDP combinations there can be anywhere up to a 0.5V difference in line levels !  Also look at some StereoPhile measurements on digital components they frequently show big variations away from the nominal !

 

i.e 

 

Quote:
The CD-4.1x's maximum output level at 1kHz was 2.45V, an audible 1.8dB higher than the CD standard's 2V RMS.
 
 
The maximum output level from both the ERC-2's balanced and single-ended outputs was 2.25V, which is 1dB higher than the CD standard's 2V. If not accounted for, this will tilt A/B comparisons in the Emotiva's favor
 
The maximum output of the 650D was 2.1V RMS from both its balanced and unbalanced outputs
 
The maximum output at 1kHz from the tubed outputs, with the volume control set to "26," was 5.1V balanced and 2.53V unbalanced. Switching in the FET buffer stage raised these levels to 5.3V and 2.63V, respectively, owing to the lower output impedance of this stage
 
etc etc etc
 

Edited by nick_charles - 11/20/12 at 8:39am
post #1629 of 3264

Well they used to be level matched (more or less) but that was then and this is now.  Back in the days when they all ran on AC power the very common output was 2V.

post #1630 of 3264
Quote:
Originally Posted by Yahzi View Post

I was having a discussion with an EE over source components .. a believer, and I explained how difficult it is these days to find a source component that doesn't measure flat and have low noise. His argument :

 

"I can show you two source components that measure similar distortion figures (less than 0.005%) and they sound very different. 

 

 

Ask your EE how he did his comparisons, sighted or blind ?

post #1631 of 3264
Quote:
Originally Posted by Speedskater View Post

Well they used to be level matched (more or less) but that was then and this is now.  Back in the days when they all ran on AC power the very common output was 2V.

 

2 Vrms is still a commonly used standard line level. The problem is that it is not implemented accurately enough for reliable ABX testing without having to adjust levels. A difference of at most 0.1 dB is acceptable in a blind test (in fact, someone at the hydrogenaudio.org forums was even able to ABX that with fast software switching between samples), and, to meet the 0.1 dB requirement even in the worst case, the line levels would have to be 2 Vrms +/- 0.05 dB. In reality, +/- 1 dB variation is common. I have two "2 Vrms" sound cards, one outputs ~1.94 at 0 dBFS, and the other (the more expensive, by the way) one outputs 2.15 Vrms.

post #1632 of 3264
Quote:
Originally Posted by Speedskater View Post

Well they used to be level matched (more or less) but that was then and this is now.  Back in the days when they all ran on AC power the very common output was 2V.

Even CD player reviews done 25 years ago show these differences.

post #1633 of 3264
Quote:
Originally Posted by nick_charles 
Ask your EE how he did his comparisons, sighted or blind ?

I'll find out. I suspect it's a sighted evaluation which should invalidate the comparison and the anecdotal reports that follow. biggrin.gif
post #1634 of 3264

By the way, even variations in source output impedance can cause greater than 0.1 dB difference, even if the output levels are the same unloaded. For example, if there are two exactly 2 Vrms sources with 100 and 500 Ω output impedance, then the actual input voltage to an amplifier with 10 kΩ input impedance will be 1.98 and 1.90 Vrms, respectively (0.34 dB difference).

post #1635 of 3264

Oops, I didn't read the fine print.

It's 2 Volts (more or less) not anywhere near close enough for an ABX test.

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