Measurements Of Chord Mojo

[March Audio]

Very interesting. Thanks for providing the sample files.
Had a listen to the Clapton song via mac os x --> SMSL iDEA --> FLC8s iem.
Perhaps it was placebo, but I thought I heard the mojo sample as being warmer - i.e. the bass guitar stood out to me as more forward.

Curious why the file sizes are different though?
The "mojo files" are slightly, but consistently larger...
Just digital silence?

This mirrors my own opinion and thanks for doing those other plots because that seems to add evidence to suport my second thoughts that the Mojo has a very slight emphasis on some of the higher frequency sounds, maybe some sounds seem a bit more "sparkly". Needs to be investigated more before jumping to conclusions though, the difference in those plots seems too big too me.

I realise both our comments here can lead people, but it can always be tested blind with different tracks later.

 

[March Audio]

Haven't listened to all your files, and all are sighted so far. Even then, these are so darn close, there just isn't a big difference to get bent out of shape over for general listening. Haven't tried ABX on them or over headphones. My only complaint, yes now a complaint, is you should have kept the identities of the copies hidden for a bit.

See above, we can do further tests. But you are absolutely right, if audiophiles are claiming night and day differences between DACs then they are deluding themselves.....and this is after is been re-recorded by an ADC which will add its own distortion.

 

[Blumlein 88]

Here is a spreadsheet of a 2k FFT I exported. It is from 30 seconds centered on about the 1 minute mark in the 1st track. You see the level for each bin which at 96 khz is about 46 hz wide. You see in column I the difference once I subtract for a .71 db difference between the files. This is left channel only. The left hand pane holds the lower frequencies. The right hand pane holds the higher frequencies near 18 khz. You see there is a nearly linear difference in frequency response that reaches about .05 or .06 db by 18 khz. So the FR of these two files is essentially the same.

So if you determine one does have a more sparkly or warmer sound it doesn't seem that it is because of frequency response.

BTW I've tested this method out several different ways. As long as the level in the bin is 40 db above the noise floor in that bin it works surprisingly well with surprising accuracy. It lets you compare frequency response if all you have is music played thru two devices or one device and the original sound file.

 

[March Audio]

Yep I was doing a very similar thing across the whole track, 10Hz to 19kHz with a 65k FFT. Biggest individual bin difference between Mojo and Explorer was .24 dB. Thats not audible in itself of course. The plot didnt show any real slope, so as you suggest it shouldnt create any significant FR colouration. A lower resolution FFT will probably present clearer trend data, but we can surely be only talking about 0.1dB difference.

Of course we can also do proper FR sweeps on the DACs.

 

[Sal1950]

This mirrors my own opinion and thanks for doing those other plots because that seems to add evidence to suport my second thoughts that the Mojo has a very slight emphasis on some of the higher frequency sounds, maybe some sounds seem a bit more "sparkly".

A purposely injected "house sound" ?, that now looks to be fairly easily measured.
Typical marketing con-job of how they have the magic dust and know how infuse gear with better magic as the price goes up.

 

[stalepie]

OK, luckily I realised I had recorded the Mojo and Meridian Explorer2 as an experiment over a year ago using my TI EVM4222 board. So the link below has 3 versions of three tracks. Of each track there is the original, and replayed by Mojo and Explorer2. The originals are all 44K 16 bit and the recordings are 96K 24 bit. I can tell a difference between the Mojo and the Explorer. See what you think and tell me about the differences you hear.

http://alanmarch.hopto.org/sharing/3re1FgOSQ

I couldn't hear a difference when using my headphones (DT-1350) with the first track, though I see a slight difference in the waveforms when zooming in:

https://imgur.com/a/OFwOP

 

[March Audio]

OK, all the files have been amplitude corrected exactly to match the PK amplitude of the original including correcting the minor channel imbalance .

http://alanmarch.hopto.org/sharing/3re1FgOSQ

 

[Blumlein 88]

OK, all the files have been amplitude corrected exactly to match the PK amplitude of the original including correcting the minor channel imbalance .

http://alanmarch.hopto.org/sharing/3re1FgOSQ

So do these sound different to you now?

 

[March Audio]

So do these sound different to you now?

I am going to say yes, but that needs to be substantiated with some foobar abx.

I will also record the same tracks with the Motu 8A and see if that makes the difference easier or more difficult to hear and post them here.

 

[Wombat]

If the recorded tracks sound different thru' the same device then the recordings need as much(if not more) scrutiny as the device, not ignoring subjectivity of course.

With the stated level of uncertainty, why bother?

 

[March Audio]

If the recorded tracks sound different thru' the same device then the recordings need as much(if not more) scrutiny as the device, not ignoring subjectivity of course.

With the stated level of uncertainty, why bother?

Not sure what you mean by this.

Scenerio is simple.

I believe the Mojo sounds slightly different to many DACs. This is a subjective observation which I have not scientifically explored. I am always very cautious about subjective conclusions as there are so many pitfalls.

The recordings were made not for this purpose and had a slight difference in volume level due to the finite graduation in dac output volume control. This has been corrected. I still believe I can hear the difference, although it is not as obvious as when listening directly. This could be for several obvious reasons like effect of headphone load or the level of transparancy of the ADC (the original sounds subtly but noticeably different to both recordings to me). However the ADC is a consistent factor and if sufficiently transparent should not stop you differentiating between the dacs, assuming there is a sufficient difference to hear.

Without an ABX I could easily be kidding myself. I probably am. These are all exploreable variables, its not a futile exercise as you seem to imply, and of course a simple switch box can also be employed for direct testing. The recordings were presented because I was asked, and because its interesting and helpful to get others involved.

Why bother? Its a fascinating question to try and answer. We have seen with the testing performed on this site that there many very affordable dacs that are technically very competent. The crux of what we do here is to objectively identify worthy kit that ultimately is subjectivly satisfying. So we need to at least try and establish if we can hear differences between dacs that are of a decent level of technical performance regardless of price differential. Otherwise the limit of what we can acheive here is identifying the odd bit of kit that performs like Schiit..I mean shit.....interchangeable words of the same meaning

 

[Wombat]

As you were. Senior moment here.

 

[Kyle / MrHeeHo]

I have a Chord Mojo and I’ve noticed that when plugged into an Apple idevice through the latest version of their Camera Conversion Kit Chord products will sometimes cut out for an instant, I haven’t run into that with competing products that also require the CCK. IMO it’d be something worth looking into if possible.

 

[restorer-john]

The DA conversion rate of Pulse arrays is constant. This feature make it immune to the effect of signal jitter, and naturally, will not lead to any harmonic distortion and background distortion caused by the jitter

The early Philips 'one bit' D/As were PDM whereas the majority of others (Japanese) were PWM. The description above appears to suggest PDM.

Technics also designated their early MASH D/As as PDM. PDM is essentially immune to jitter and ran around 45MHz IIRC.

 

[Arnold Krueger]

The difference between stuff I measure is very obvious until I level match. It is remarkable how the difference vanishes when I do that. Or at least becomes very small.

Interesting that level matching is mission impossible for so many people when these are readily available:

https://www.ebay.com/itm/Little-Bea...Pre-Amplifier-XLR-RCA-Controller/272630670340

 

[amirm]

How do you level match with a single volume control Arny?

Also passive volume controls like that impact the frequency response at different levels. And some introduce channel imbalance.

 

[Jimster480]

Awesome review man!

 

[March Audio]

So do these sound different to you now?

I am going to say yes, but that needs to be substantiated with some foobar abx.

I will also record the same tracks with the Motu 8A and see if that makes the difference easier or more difficult to hear and post them here.

Hi Blumlein 88 , I finally performed this ABX test, only tried the once but here is the result:

foo_abx 2.0.4 report
foobar2000 v1.4 beta 11
2018-04-15 20:34:36

File A: 01 - Before You Accuse Me.flac
SHA1: d25ca7e4d5881a3dc1b9aa892f40203b675086b9
File B: 02 - Before you Accuse Me Chord Mojo.flac
SHA1: 564af148a0856ff60cdaf8a664f6eb853350d6b5

Output:
DS : Digital Output (Chord Async USB 44.1kHz-768kHz)
Crossfading: NO

20:34:36 : Test started.
20:41:39 : 01/01
20:47:25 : 02/02
20:48:27 : 02/03
20:49:12 : 03/04
20:50:36 : 03/05
20:51:22 : 03/06
20:52:04 : 04/07
20:52:22 : 05/08
20:52:57 : 06/09
20:53:29 : 07/10
20:54:00 : 08/11
20:54:17 : 09/12
20:54:33 : 10/13
20:54:52 : 10/14
20:55:18 : 10/15
20:55:31 : 10/16
20:55:31 : Test finished.

----------
Total: 10/16
Probability that you were guessing: 22.7%

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[amirm]

I hate results like that. You think you got it and all of a sudden the mojo is gone and you keep getting it wrong.

 

[March Audio]

I hate results like that. You think you got it and all of a sudden the mojo is gone and you keep getting it wrong.

Yeah, Im going to try with some different tracks and see if I can be more consistent.