[salla45]

   
 
There was an early post that had some pictures that Chord might be developing attachments to make life easier for Android and iPhone users, so that they don't have to put up with messy OTG cables. Not sure if it's coming out though.

yeah, that was interesting. Also suggested that there would be a sort of modular series of attachments to come in future. Pretty exciting. Transport maybe? Explains also somewhat the chunky basic shape, allowing for longer overall aspect with addons.

 

[h1f1add1cted]

   
The so-called "impedance" value of IEM is just a nominal value that is not constant across all frequencies and don't mean much above 10kHz.
A 50 ohm impedance IEM could have 2 ohm response at 5kHz, etc.
If you look at graphs on Innerfidelity etc, some IEMs effectively act as a short or open at higher frequencies based on the driver and crossover configurations.
 
The main point here is that Mojo is behaving differently to other common high powered headphone amps, and it would be good to get some insight from Chord about why this might be the case. If the testing method is to be blamed or whatever, it's still showing differences between Mojo and other amps nonetheless.

Thanks for your reply I know, with multiple driver IEM we can have really different impedance curve which needs a source with below 1 ohms output impedance for a ruler flat frequency. But the Mojo is pretty much below 1 ohms, with 0.075 ohms, this is the only big question mark I have. The same 8 driver IEM, with different dac/amp with 0.5 ohms (which is good, but the Mojo is better!) has a ruler flat frequency compared to the Mojo which has this slight treble roll off, this can't be from the ultra low output impedance from the Mojo. The reason is someting other. 0.075 ohms wins versus 0.5 ohms but in this case not, now the question is why. I don't have a problem with this, I would never use any other dac/amp for my IEMs / CIEMs in terms of SQ the Mojo wins over all devices I know, but a detailed answer would be nice.

 

[Currawong]

   To me the small treble roll off is not a big number sure, but I don't get it why this happens with this crazy awesome low 0.075 ohms output impedance from Mojo. This "normally" only happens with source which provide over 1 ohms output impedance with multiple driver IEM.

 
I'd have to find it, but Rob Watts posted that it had something to do with his very simple output stage.

 

[OK-Guy]

 
The main point here is that Mojo is behaving differently to other common high powered headphone amps, and it would be good to get some insight from Chord about why this might be the case. If the testing method is to be blamed or whatever, it's still showing differences between Mojo and other amps nonetheless.

 
the DAC & Amp in the Mojo are one of the same (same as Hugo), there is no separate Amp section, hth. 

 

[h1f1add1cted]

   
 
There was an early post that had some pictures that Chord might be developing attachments to make life easier for Android and iPhone users, so that they don't have to put up with messy OTG cables. Not sure if it's coming out though.

I use this short (DIY) USB OTG cables for the Mojo and my Android devices:
 

 
You an buy this kind of cable from i.e. FiiO: http://www.aliexpress.com/store/product/FiiO-OTG-cable/1473108_32240751500.html no need for generic bulky USB OTG cables.

 

[sandalaudio]

   
the DAC & Amp in the Mojo are one of the same (same as Hugo), there is no separate Amp section, hth. 

 
Sorry. I should re-word it as the "current buffer stage" on the Mojo then.
 
Don't get me wrong. Mojo sounds amazing.

 

[OK-Guy]

   
Sorry. I should re-word it as the "current buffer stage" on the Mojo then.
 
Don't get me wrong. Mojo sounds amazing.

 
I keep seeing that the Mojo sounds amazing, lots of happy Customers by the looks.
 
Unfortunately I don't do 'technical' that's above my pay-grade, I just roll-out old answers that I've been advised on previously, hth... 

 

 

[headwhacker]

  Thanks for your reply I know, with multiple driver IEM we can have really different impedance curve which needs a source with below 1 ohms output impedance for a ruler flat frequency. But the Mojo is pretty much below 1 ohms, with 0.075 ohms, this is the only big question mark I have. The same 8 driver IEM, with different dac/amp with 0.5 ohms (which is good, but the Mojo is better!) has a ruler flat frequency compared to the Mojo which has this slight treble roll off, this can't be from the ultra low output impedance from the Mojo. The reason is someting other. 0.075 ohms wins versus 0.5 ohms but in this case not, now the question is why. I don't have a problem with this, I would never use any other dac/amp for my IEMs / CIEMs in terms of SQ the Mojo wins over all devices I know, but a detailed answer would be nice.

 
I don't use IEMS much as I used to and don't really perceive the treble roll-off in Mojo with my cans. I really love how the Mojo sounds with my cans. Nevertheless,  I'm also interested to know what is causing the roll off even if it's small and difficult to perceive. Thanks for sharing your findings.

 

[mjdutton]

   
 
 
I did my tests again, it's no measuring error. I did the tests with RMAA and Audacity as usual I did this kind of tests like all the years before.

 
The impedance of the load has zero impact (see my examples),  I always have a ruler flat frequency, the only impact has the amount of drivers see below:
 
 

 
Again the small bass roll off is not from Mojo it's the sound card itself. The only truth is the slight treble roll off of which only happens with multi driver IEM, the impedance has zero impact like my 14 ohms IEM still straight flat line.

I have been trying a number of headphones over the last week and did notice a change in the high frequency that might be caused by the roll off that you mentioned.  I'm very happy with the sound, but am some what confused when Mr Watts say there is a roll off with low impedance headphone by design, and JF is adamant that it is totally flat.  They both need to sing off the same hymn sheet and perhaps a mention in the user guide would be useful.  It does mean that HiFi Worlds measurements (Frequency response (-1dB)   4Hz-31kHz) are incorrect without a qualifying statement.

 

[JaZZ]

 

  The Westone UM-Pro30 has 56 ohms (at 1 kHz), so typical IEMs with lower impedance will have a drop-off in the range of ~1.8 dB at 20 kHz, unfortunately with a distinctive start above 10 kHz already. Provided that your measurings don't suffer from the same errors that have happened to h1f1add1cted according to John Franks.

  Yes, well it's just load sensing, so there's no reason to say one kind of amp performs better than the other. Having the output clamped to constant voltage is not necessarily the best solution anyway.
It's just that unless Chord gives us some insight to how the headphone amp works, I'm sure a lot of people would go frantic that it's not a ruler flat response. I think the same thing happened to Hugo a while ago, and yet nobody's complaining that it's a bad sounding headphone amp...

 
I did my tests again, it's no measuring error. I did the tests with RMAA and Audacity as usual I did this kind of tests like all the years before.
 
The impedance of the load has zero impact (see my examples),  I always have a ruler flat frequency, the only impact has the amount of drivers see below:
 

 
Again the small bass roll off is not from Mojo it's the sound card itself. The only truth is the slight treble roll off of which only happens with multi driver IEM, the impedance has zero impact like my 14 ohms IEM still straight flat line.

 
Well, that now is a contradiction to Sandalaudio's Measurements.
 
Quote:

  The so-called "impedance" value of IEM is just a nominal value that is not constant across all frequencies and don't mean much above 10kHz.
A 50 ohm impedance IEM could have 2 ohm response at 5kHz, etc.
If you look at graphs on Innerfidelity etc, some IEMs effectively act as a short or open at higher frequencies based on the driver and crossover configurations.
 
The main point here is that Mojo is behaving differently to other common high powered headphone amps, and it would be good to get some insight from Chord about why this might be the case. If the testing method is to be blamed or whatever, it's still showing differences between Mojo and other amps nonetheless.

 
Yes, multi-driver IEMs usually have acoustic low-pass filters, which means several drivers running in parallel at high frequencies electrically, making for an impedance drop. But according to your measurements the modded Etymotic ER-4 rated 14 ohms should have lead to a high-frequeny drop off (despite the impedance rise reaching 75 ohms at 20 kHz with the original P), which isn't the case with h1f1add1cted's curves.
 

  -1.5dB at 20 kHz is effectively inaudible with music IMO, but it is interesting all the same. 

 
Maybe; but –0.7 dB at 12 kHz is audible. – That's not to say the Mojo's headphone out is bad, though.

 

[JaZZ]

 

 
The main point here is that Mojo is behaving differently to other common high powered headphone amps, and it would be good to get some insight from Chord about why this might be the case. If the testing method is to be blamed or whatever, it's still showing differences between Mojo and other amps nonetheless.

 
the DAC & Amp in the Mojo are one of the same (same as Hugo), there is no separate Amp section, hth. 

 
Yet they don't sound the same. I'd like to know if the Hugo has the same measurable drop-off at low impedances, but it definitely sounds more extended.

 

[x RELIC x]

Yet they don't sound the same. I'd like to know if the Hugo has the same measurable drop-off at low impedances, but it definitely sounds more extended.

Rob has said he purposefully smoothed the Mojo's output SQ compared to the Hugo given the Mojo's intended portable use.

 

[TomGi]

Until now, I listen mainly the Mojo on amplified monitor speakers (as for my Hugo).
 
And why ? Because Mojo (and consequently Hugo) is for my taste amongst the best DAC I listen (Benchmark, Dangerous Music, Mytek, RME, Bel Canto).
 
I use it as converter/monitor (digital) volume control plugged directly on the amplified monitors.
 
The input impedance of monitor speakers is often close to a constant value of 10kOhm.
 
I measured the impulse response (left and right analog outputs are identical: green curve) of the Mojo with a load impedance of about 4kOms (the microphone's impedance of the input of my sound card) and for this use, it is perfect for different tested settings of the volume.
 
 

 

[OK-Guy]

^ what he said ^... I can't improve on Relic's post.

 

[JaZZ]

 

Yet they don't sound the same. I'd like to know if the Hugo has the same measurable drop-off at low impedances, but it definitely sounds more extended.

Rob has said he purposefully smoothed the Mojo's output SQ compared to the Hugo given the Mojo's intended portable use.

 
True, I remember that. Now how is this done? On other occasions it was stated both ouput stages be identical. I just wonder how (and if) the Mojo's audible drop-off compared to the Hugo can be measured. BTW, I also have to apply a 0.2 dB decrease between 100 and 300 Hz to make it sound more similar to the Hugo, beside the treble increase.
 
But don't get me wrong: I like the Sound of the Mojo nonetheless.