Measurements Of Chord Mojo

[DonH56]

I believe the Chord dacs are still 1 bit dacs, so I think they still need noise shaping, but they can change pulse width unlike delta sigma dacs.

We must be crossing wires. DS DACs can modulate the pulse width; depends upon the architecture, though.

 

[March Audio]

There's a thread on CA discussing early battery failures in Mojos:
https://www.computeraudiophile.com/forums/topic/37976-chord-mojo-fails-after-18-months-battery-warranty-defects-liability /?tab=comments#comment-757121

Yeah, Its just a failure waiting to happen to my mind.

 

[March Audio]

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

 

[mindbomb]

We must be crossing wires. DS DACs can modulate the pulse width; depends upon the architecture, though.

Okay, I didn't know that. On computeraudiophile, there is a translation of an interview the Chord guy gave to a Taiwanese magazine, where he says " Pulse arrays DAC, this split D-A conversion is different from delta sigma and multi-bit R2R modulation...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."

Different from delta sigma and r2r and with a constant conversion rate means pwm, right?

 

[FrantzM]

Hard to wrap my mind around the opinion of all DAC sounding the same.. Same with amps. Hard to see how a Krell KMA200 sound like an Emotiva or a Spectral DMA 180.. All these measure well but IIRC, they sound different , very much so, in my experience. Placebo? perhaps... woudl like an experience, a test or account of such to convince me ...
I have several DACs and they seem to sound different on my headphones...

 

[dc655321]

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

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?

 

[DonH56]

Okay, I didn't know that. On computeraudiophile, there is a translation of an interview the Chord guy gave to a Taiwanese magazine, where he says " Pulse arrays DAC, this split D-A conversion is different from delta sigma and multi-bit R2R modulation...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."

Different from delta sigma and r2r and with a constant conversion rate means pwm, right?

Sorry, I do not know what a "pulse array" is... I have a hard time grasping how any DAC is immune to jitter but I do not know what this one is doing.

 

[DonH56]

Hard to wrap my mind around the opinion of all DAC sounding the same.. Same with amps. Hard to see how a Krell KMA200 sound like an Emotiva or a Spectral DMA 180.. All these measure well but IIRC, they sound different , very much so, in my experience. Placebo? perhaps... woudl like an experience, a test or account of such to convince me ...
I have several DACs and they seem to sound different on my headphones...

Without getting too far into the debate, I will note a few things:

• The output buffers and filtering after the actual DAC chip inside the box can significantly influence the sound.
• Amir's measurements show quite a variation in performance, with some being much better than others, and some are more sensitive to noise from the power supply or signal inputs.
• Amplifiers have to deal with a much wider range of loads than DACs. Speaker sensitivity and input impedance varies widely and heavily influences how an amplifier sounds when connected to any given speaker.
• Amplifiers have many different topologies and design trades that can influence the sound in various ways, from noise floor (SNR) to gain structure to output impedance to power level etc. etc. etc.

So I am not surprised people hear differences among DAC, though I suspect in general it is much less than they would find in a DBT, and ditto amplifiers but less so (i.e. I would expect it to be easier to pick out different amplifiers in a DBT). In any event I gave up trying to convince anybody of anything long ago though I still lose my mind and get into such "religious" debates now and then.

FWIWFM - Don

 

[dc655321]

Also interesting - Audacity spectra of the first ~110 seconds of each track (Clapton only).
Note the dB-scale and Peak fields.

 

[Sal1950]

Hard to wrap my mind around the opinion of all DAC sounding the same..

The best answer for me is, in this day and age they shouldn't sound different. But for many reasons from weird load variations, to purposeful "house sound" tuning by some manufacturers, they can and do.
But I would venture that 95% of the cases where sound variations can be backed up by DBT's and are not delusions, the reasons will be identifiable-measurable when done properly, as in what Amir does here.

 

[amirm]

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.

 

[Blumlein 88]

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 only have the first comparison tracks so far. The Mojo is about 3/4 db louder. That would explain them sounding a wee bit different. Level matching and all that. This fits with what DC655321 was also seeing.

It is closer to .7 db on the left channel and mostly right near .8 db on the right channel. Try adjusting the level of one of the files the right amount and see if the difference goes away.

The Meridian file is a bit over 30 ppm slower, but that is inconsequential. The frequency response of the Meridian droops (if you can call it that) by .05 db from 40 hz to 10 khz. I think that is also inconsequential.

 

[March Audio]

Hard to wrap my mind around the opinion of all DAC sounding the same.. Same with amps. Hard to see how a Krell KMA200 sound like an Emotiva or a Spectral DMA 180.. All these measure well but IIRC, they sound different , very much so, in my experience. Placebo? perhaps... woudl like an experience, a test or account of such to convince me ...
I have several DACs and they seem to sound different on my headphones...

Why do you have trouble with that idea? I actually think components do sound different, but that difference, especially in the case of dacs, is usually very, very, very much smaller than audiophiles allude to. To the point of being inconsequential most of the time.

Measurements do uncover performance differences. As mentioned above operational conditions for amplifiers will vary considerably more so expect to hear and measure bigger differences.

 

[March Audio]

I only have the first comparison tracks so far. The Mojo is about 3/4 db louder. That would explain them sounding a wee bit different. Level matching and all that. This fits with what DC655321 was also seeing.

It is closer to .7 db on the left channel and mostly right near .8 db on the right channel. Try adjusting the level of one of the files the right amount and see if the difference goes away.

The Meridian file is a bit over 30 ppm slower, but that is inconsequential. The frequency response of the Meridian droops (if you can call it that) by .05 db from 40 hz to 10 khz. I think that is also inconsequential.

I recorded these files a long time ago and didnt check them yesterday, but I was under the impression they were level matched. Its a absolute requirement and 3 dB is a big difference. I will check and re record.

 

[dc655321]

I recorded these files a long time ago and didnt check them yesterday, but I was under the impression they were level matched. Its a absolute requirement and 3 dB is a big difference. I will check and re record.

Perhaps @Blumlein 88 meant 3/4=0.75 dB, and not a range of [3,4] dB?
Subjectively, it was not that big of a difference.

 

[Blumlein 88]

I recorded these files a long time ago and didnt check them yesterday, but I was under the impression they were level matched. Its a absolute requirement and 3 dB is a big difference. I will check and re record.

Whoa! 3/4 db was .75 db. Not 3 or 4 db. So a bit over .7 db which is enough to make one sound better than the other, but far less than 3 db.

I now have the second set of tracks and they show the same imbalance in loudness at the same level.

PS-looks like dc655321 was a few seconds ahead of me posting.

I don't know that re-recording is necessary. Normalizing the two files or adjusting one to match the other in a sound editor should do it.

 

[March Audio]

OK, here are the amplitude statistics from Adobe Audition.

Clapton. Original

Mojo

Explorer

So it looks like about a 0.7dB spread which is too much for close comparison. Lets get that closer

 

[March Audio]

Whoa! 3/4 db was .75 db. Not 3 or 4 db. So a bit over .7 db which is enough to make one sound better than the other, but far less than 3 db.

Hehe Doh

 

[March Audio]

First track corrected to the originals level. There is a slight imbalance in the ADC or DAC between the two channels so I adjusted (both channels by the same amount) but to keep both within +-0.1dB of the original and each other.

Mojo

Explorer2

So those files are updated if you want to re-download them. I will adjust the others later

 

[Blumlein 88]

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.