Is Someone Playing Fast & Loose With Measurements?

[The Computer Audiophile]

Hi Guys - I haven't paid much attention to the measurements published by LH Labs, a division of Light Harmonic, but they were recently called to my attention by AudioQuest. Much of this is beyond my technical expertise, but the information is certainly interesting. Hopefully we can get comments from both sides to help us figure out what's fact and what's fiction. Below is information claimed by LH Labs and refuted by AudioQuest.

 

 

Please let me know if any of the information I posted is incorrect or misleading, I can update the data anytime. I just want to get to the facts. Thanks guys.

 

 

 

 

[TABLE]

[TR]

[TD]Date: 8/16/2013 Testing: GEEK vs. the Others[/TD]

[TD][/TD]

[TD][/TD]

[/TR]

[TR]

[TD]Item[/TD]

[TD]LH Claims[/TD]

[TD]AudioQuest Claims[/TD]

[/TR]

[TR]

[TD]Volume Control[/TD]

[TD]Software[/TD]

[TD]Software Controlled Analog[/TD]

[/TR]

[TR]

[TD]Output impedance[/TD]

[TD]12 (note 1)[/TD]

[TD]0.65 ohms (note 2)[/TD]

[/TR]

[TR]

[TD]Amplifier Type[/TD]

[TD]Class A/B[/TD]

[TD]Class A[/TD]

[/TR]

[TR]

[TD]THD+N[/TD]

[TD]0.041% (note 2)[/TD]

[TD]0.041% (note 2)[/TD]

[/TR]

[TR]

[TD]Max Native Bitstream[/TD]

[TD]None[/TD]

[TD]Sample Rate Equal (note 3)[/TD]

[/TR]

[/TABLE]

1. 12 ohms is specified in the DragonFly manual as the minimum load to meet the specifications. Not the output impedance.

2. Stereophile a Source Interlink Publication Vol 35, Number 10 October 2012, tests by John Atkinson pages 143-148, review by Art Dudley. Link to measurements

3. Sample Rate Equal, implies that the correct fixed oscillator that is a base 2 multiple of the selected sample rate.

 

 

 

 

[TABLE]

[TR]

[TD]Date: 9/5/2013 Testing: GEEK vs. the Others, v2[/TD]

[TD]LH Claims[/TD]

[TD]AudioQuest Claims[/TD]

[/TR]

[TR]

[TD]Output Impedance[/TD]

[TD]5.9 ohms[/TD]

[TD]0.65 ohms (note 2)[/TD]

[/TR]

[TR]

[TD]Maximum Output V[/TD]

[TD]2.106 and 2.105 (note 4)[/TD]

[TD]1.86V (note 2)[/TD]

[/TR]

[TR]

[TD]THD+N[/TD]

[TD]5.038965 and 4.860163%[/TD]

[TD]0.041% (note 2)[/TD]

[/TR]

[/TABLE]

 

4. The DragonFly is only capable of these output voltages when the testing level is greater than a gain of 0dBFs. Meaning the tester is deliberately clipping the signal before it reaches the DragonFly.

 

 

 

 

 

 

[TABLE]

[TR]

[TD]Date: 3/15/2014 Testing: Geek Out vs. the Others, 3rd Installment[/TD]

[TD]LH Claims[/TD]

[TD]AudioQuest Claims[/TD]

[/TR]

[TR]

[TD]Noise Floor[/TD]

[TD]~ -120dB[/TD]

[TD]See Sine1KHz-44.1Khz-AC-and-Battery[/TD]

[/TR]

[TR]

[TD][/TD]

[TD][/TD]

[TD]See Sine1Khz-96Khz-ACPower[/TD]

[/TR]

[TR]

[TD]Volume Control[/TD]

[TD]It doesn’t appear to[/TD]

[TD]Computer Controlled Analog (Note 5)[/TD]

[/TR]

[TR]

[TD][/TD]

[TD]have computer-[/TD]

[TD]not Digital volume control (note 5)[/TD]

[/TR]

[TR]

[TD][/TD]

[TD]controlled digital[/TD]

[TD]See file DragonFly-Enumeration[/TD]

[/TR]

[TR]

[TD][/TD]

[TD]volume attenuation,[/TD]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[TD]which may cause[/TD]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[TD]issues with software[/TD]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[TD]that doesn’t have it’s[/TD]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[TD]own implementation.[/TD]

[TD][/TD]

[/TR]

[TR]

[TD][/TD]

[TD][/TD]

[TD][/TD]

[/TR]

[TR]

[TD]Output voltage[/TD]

[TD]2.077 and 2.076Vrms[/TD]

[TD]1.8609V, 1.85965Vrms see Sine1KHz-96KHz-100percent -Notes 7&8[/TD]

[/TR]

[TR]

[TD]THD+N[/TD]

[TD]5.086305 and 5.26774%[/TD]

[TD]See file #4 0.76905 and 0.7072%[/TD]

[/TR]

[TR]

[TD]Channel Separation[/TD]

[TD]-62.003dB[/TD]

[TD]-65dB (note 2)[/TD]

[/TR]

[TR]

[TD]5KHz Square Wave[/TD]

[TD]Why wasn’t a scope used?[/TD]

[TD]See file TEK-5Khz (Note 6)[/TD]

[/TR]

[TR]

[TD]0dBFS 1KHz Sine[/TD]

[TD][/TD]

[TD]See Sine1KHz-96KHz-100percent[/TD]

[/TR]

[TR]

[TD]Jitter?[/TD]

[TD]Why No Jitter Testing?[/TD]

[TD]See file JTEST-DragonFly[/TD]

[/TR]

[/TABLE]

 

5. Digital volume controls reduce the sample size. Analog volume controls retain the full sample and control volume in the analog domain.

6. The Ap525 should not be used as an oscilloscope. These have very limited processing range. The only true test is using a good calibrated oscilloscope for this kind of testing.

7. The only way to get 2.077Vrms out of the DragonFly was to send a 100% signal then add another 10% (meaning the sine wave is distorted before it reaches the DragonFly).

8. As you can see from file Sine1KHz-96K-110percent.gif The testing done by LH/Geek was causing clipping distortion before it left the computer. This is the only way to get 2.077vrms output

 

 

 

Sine1Khz-96Khz-ACPower

 

 

 

 

 

 

 

Sine1KHz-96KHz-100percent

 

 

 

 

 

 

 

Sine1KHz-96K-110percent

 

 

 

 

 

 

 

Sine1KHz-44.1Khz-AC-and-Battery

 

 

 

 

 

 

 

 

JTEST-DragonFly

 

 

 

 

 

 

 

 

TEK-5KHz

 

 

 

[The Computer Audiophile]

Or, send me a unit and I'll have it measured by a third party.

[The Computer Audiophile]

Speaking of playing "fast and loose", how about the title of this thread Chris? It is suggestive that LH intentionally fudged the numbers or at best was grossly negligent. I don't think this is fair to LH. Why assume the worst before you find out all the details?

 

None of us were present during LH's testing. Larry has provided screenshots and background details- he has been totally transparent. To take issue with the testing methodology is one thing, to suggest LH is dishonest or reckless without having proof is another.

Hi Blake - The title is meant to attract attention through the use of creative liberty without being too suggestive. If you look at this the other way, AudioQuest could be playing fast & loose with the measurements. The truth is I simply don't know because it's outside the realm of my knowledge. Thus, the reason I posted the following statement in the opening thread, "Please let me know if any of the information I posted is incorrect or misleading, I can update the data anytime. I just want to get to the facts. Thanks guys."

 

If I had to guess, now that some people have weighed in and LH has responded, I'd say LH's numbers are very misleading, LH isn't being transparent, and conducted testing in an unethical manor. LH is a smart company with qualified engineers. It's strange that the iDSD measurements published can only be obtained by running the battery flat, using a very low impedance load, and adding excess dither. It seems LH is playing dumb on some items as well.

 

I also don't follow the logic of LH. Saying the measurements are kosher, then saying c'mon guys we posted these in our forum not in a magazine (my paraphrase) is strange to me. It's almost like they have some guilt but are saying everything is OK because they are in their forum. On the other side, if the measurements were all above board why even attempt to delineate a difference between a magazine or their own website. I don't follow the logic.

 

Larry's quote:

 

"We publish that testing result inside our Geek Force forum. And we just hope our Geek Out backers knows how good their perk will be. Why suddenly it looks like this becomes a media focus? We didn't quote it here or in Audiostream"

 

So, the measurements are good enough to publish in the Geek Force forum, but not on AudioStream? I don't follow the logic.

 

 

Some other issue I've now seen that seem somewhat sinister.

 

- On 8/16/13 LH claim AQ output impedance is 12ohm and then on 9/513 they claim 5.9; neither claim is correct.

 

- On 8/16 LH list distortion as .041% but later list it at 5(+)%. Which even if they had the DF 1.0 is significantly higher than what JA measured and reported.

 

- The only way to approximate Geek’s claims (see Sine1Khz-96K-100percent) is by overdriving the signal.

[The Computer Audiophile]

None of us were present during LH's testing. Larry has provided screenshots and background details- he has been totally transparent. To take issue with the testing methodology is one thing, to suggest LH is dishonest or reckless without having proof is another.

The beauty of empirical data and scientific measurements is they should be repeatable. If LH explained how it got the iDSD to perform like it did, thus allowing others to replicate the testing all would be cool. But as I said before, one way to get the iDSD to measure like LH's tests is to run the battery flat, use a very low impedance load, and add excess dither.

[The Computer Audiophile]

Blake - I don't win by proving one company wrong or supporting one company over another. I and the CA readers win by getting the facts out in the open.

 

I have nothing against LH. In fact we've been talking about an ad campaign on CA for a few months. One way to ruin my relationship with LH is to show favoritism. That's not good for anyone, even AudioQuest.

[The Computer Audiophile]

Chris, your take seems quite plausible to me.

That's all I can glean from what I've seen and read. If there are more facts that lead me in another direction I'll be happy change my opinion. As we all know my opinion isn't fact, it's just an opinion.

[The Computer Audiophile]

Still can't get it, the reason(s) why...

 

1. But are we now dictated by some audio company to do something?

2. Why bring their wars here? Let them play it by themselves.

3. And why they point out a single company? If they're complaining, publish theirs (testing) right?

As previous stated by others, third party testing, include also others DACs.

Hi Mickey - I'm not sure what you mean in point number 1. Your point number 2 is very valid. I thought about it long and hard before posting this thread. I decided that the topic of DACs is very important to CA readers and it's very important for CA readers to have facts before spending hard earned money. If I can help get to the bottom of this discrepancy I will have provided a service to the CA readers. No matter how this ends up, everybody wins with more information. As to point number 3 I believe this testing is provided in the original post and by John Atkinson at Stereophile.

[The Computer Audiophile]

Wow... Really Chris?

 

If it is outside of your realm of expertise then how about refraining from accusing LH of being "unethical" and "misleading". As the MC of this forum your name carries a lot of weight to be this reckless and accusatory. As stated previously even your title is baited.

 

And I don't like how this appears to be an orchestrated smear campaign as all of this stuff hit CA and AudioStream at the same time with supporting collateral and talking points ready to go.

Hi Junker - I definitely hear you. I had no idea Michael was going to publish about this as well. I likely would have refrained if I knew that, as the service of getting to the facts would have been carried out by him. I also elected to use the forum rather than a front page article for this topic. While the testing is outside my skill set, the facts of publishing incorrect results once, then updating them to be another incorrect value is simple to understand. Any layman can look at that and think something is up. I was provided information about the iDSD suggesting the only way to get LH's results are running the battery low, etc... I can understand that. Thus, let's figure how else to get those results. LH could help us here.

[The Computer Audiophile]

Hi Guys - If you want to discuss business practices of LH or any company please start a new thread. I don't want this potentially volatile thread to turn into a bash LH thread.

[The Computer Audiophile]

I don't have a big ass scope ...

 

That's the technical term correct? :~)