Chord Mojo DAC-amp ☆★►FAQ in 3rd post!◄★☆
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Libertad

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Are your mojos getting hot i used mine in a gaming session on warframe while using foobar2000 for music and it got really hot. Im using it while feeding it power from a 1amp charger is this normal?
 
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Takeanidea

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  Are your mojos getting hot i used mine in a gaming session on warframe while using foobar2000 for music and it got really hot. Im using it while feeding it power from a 1amp charger is this normal?
Totally normal nothing to worry about at all
 
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Torq

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Just a thought. Why do other DAC/headphone amps have amp sections when Hugo/Mojo get by without one, and many including Chord say it is more transparent? Have Chord got the patent for ampless amps :)
 
Off the shelf DAC chips, which is what is in the vast majority of other DAC products, aren't necessarily intended to drive transducers directly and, as a result, will tend to have lower maximum output current and/or voltage swing.  Buffers and op-amps, or discrete equivalents (i.e. the "amp section") are then needed to accommodate more demanding loads. 
 
Rob's designs don't use off-the-shelf converters so don't have the same constraints.
 
Or that's my understanding of it at least.  For some reason I thought there was a series of discrete transistors in the Mojo's output section as well, but I could well be mixing things up and/or reading slides incorrectly.
 
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  Totally normal nothing to worry about at all
thank you very much for the quick reply
 using optical out on my pc (fist time ever using it) and i have to say it sounds at least to me just ever so slightly smoother in a good way compared to usb
 
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x RELIC x

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Just a thought. Why do other DAC/headphone amps have amp sections when Hugo/Mojo get by without one, and many including Chord say it is more transparent? Have Chord got the patent for ampless amps :)
Off the shelf DAC chips, which is what is in the vast majority of other DAC products, aren't necessarily intended to drive transducers directly and, as a result, will tend to have lower maximum output current and/or voltage swing.  Buffers and op-amps, or discrete equivalents (i.e. the "amp section") are then needed to accommodate more demanding loads. 

Rob's designs don't use off-the-shelf converters so don't have the same constraints.

Or that's my understanding of it at least.  For some reason I thought there was a series of discrete transistors in the Mojo's output section as well, but I could well be mixing things up and/or reading slides incorrectly.

I would echo what Torq said, but I'm not going to pretend to be an EE here. Being the designer of the entire device and not using off the shelf components has advantages to create a device with a specific design goal and to meet the challenges that are presented along the way. Rob said he had quite a few challenges with the Mojo design and it took some time to overcome them. I'm glad he stayed the course.

As far as the actual analogue stage is concerned he said he used six small transistors in parallel instead of three large devices as being the only real difference in the OP stage from the Hugo. It's still not a seperate amp as is in traditional systems. It's much more simple.
 
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shigzeo

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Here's a great Japanese axiom that may explain Mojo's brilliance: "Simple is best".
 
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prismstorm

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  yes it will re-sample everything to whatever you set in the Audio Midi Setup before sending it to Mojo. That is why the color never change in Mojo even if the actual sample rate of the file varies.
So it's entirely normal that when used as a DAC for iMac the Mojo's ability to display different colors according to sample rate differences is effectively disabled and it will simply forever be at the color corresponding to the maximum rate you set it on in the MIDI setup.
 
Should I set it to the maximum (7xxHz) just for maximum leeway or just to 192 since that's the top rate for most tracks? Is there an advantage to picking one over the other or does it simply not matter. 
 
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lextek

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Versatile little thing. Just messing around with different sources. Sounds OK from the AppleTV. I'm sure the $2 optical cable has something to do with it, but not bad.
 
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Can you tell what cable please? I bought a USB-audio quality cable to use with Meridian Explorer. I A-B tested it with a standard £1 cable and really struggled to hear any change. It doesn't mean that I am a sceptic or in the camp of opposition. It means that maybe my headphones and the ME didn't have enough quality to discern any change. It left me sceptical as to whether it was worth buying an audio quality USB cable with the Mojo.
I also have the Meridian Explorer and have explored (pardon the pun) "audio-quality" USB cables and other USB power solutions, and can confidently say that these things make a huge difference to the Explorer's sound quality. My educated guess in this is, since the ME is powered by the source device, it is dependent on the source's power cleanliness. The "audio-quality" USB cable alone should be designed differently than your $5 printer cable where the power lines are wound separately from the data lines, thus reducing whatever interference it may cause to each other. By adding special USB linear power, thus separating the dirty USB power from your source computer, will take things to another level. The improvements are so obvious that it doesn't take an expensive headphone for anyone to notice the difference.
 
Now whether all these matter to the Mojo, is quite another matter. Since the Mojo has its own internal battery, all these external USB cable and power solutions should, in theory, not have any effect. I haven't been able to try out any of the so called "audio-quality" USB cables for the Mojo due to the lack of them with micro-USB terminations.
 
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Are you using a cell phone or tablet as your source?

If so, put it in airplane mode and see if that helps.

Otherwise, what source are you using, how is it connected to the Mojo and what headphones/IEMs are you using?

The "hiss" being described by most that are hearing it is extremely quiet (so quiet that even with the most sensitive IEMs it's below what is considered the lower threshold for normal/average hearing).
 
I am using the AK120 Titan via optical out and using the MH335DW.
 
And as I stated, it is not hissing, it is a buzzing. It happens even when the Mojo isnt connected to any source, and it is more prominent on the right channel and its not very slight, its actually very noticeable and can even be heard in the opening of songs where the music is a bit softer (not just in quiet passages). Is this a defect? should I bring it back? 
 
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I would echo what Torq said, but I'm not going to pretend to be an EE here. Being the designer of the entire device and not using off the shelf components has advantages to create a device with a specific design goal and to meet the challenges that are presented along the way. Rob said he had quite a few challenges with the Mojo design and it took some time to overcome them. I'm glad he stayed the course.

As far as the actual analogue stage is concerned he said he used six small transistors in parallel instead of three large devices as being the only real difference in the OP stage from the Hugo. It's still not a seperate amp as is in traditional systems. It's much more simple.
 
Now to say it has no analog stage  or straight from the DAC might be pushing it too far. Even transistors are still analog stage, just perhaps no gain stage is involved (as it is taken care mostly in the digital domain as well as the DAC output) but only buffer stage is implemented. I'll think typically you will find other manufacturer describe this as having a 'discrete output', which means no opamp is used.
 
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Now to say it has no analog stage  or straight from the DAC might be pushing it too far. Even transistors are still analog stage, just perhaps no gain stage is involved (as it is taken care mostly in the digital domain as well as the DAC output) but only buffer stage is implemented. I'll think typically you will find other manufacturer describe this as having a 'discrete output', which means no opamp is used.

ClieOS, I've always said its the analogue stage after the DAC. Not once did I say that it has no analogue stage. I said its different from 'typical' DAC/amp designs and it can't be bypassed in the Mojo (or the Hugo).

Edit: Besides the transistors Rob said the Mojo is very much the same as the Hugo. You can read his take on his implementation here:

http://www.head-fi.org/t/702787/chord-hugo/1830#post_10459450

From his post in the link, apologies if I oversimplified:

3. The lack of DAC RF OP noise means that the analogue section can be made radically simpler as the analogue filter requirements are smaller. Now in analogue terms, making it simpler, with everything else being constant, gives more transparency. You really can hear every solder joint, every passive component, and every active stage. Now Hugo has a single active stage - a very high performance op-amp with a discrete op-stage as a hybrid with a single global feedback path. This arrangement means that you have a single active stage, two resistors and two capacitors in the direct signal path - and that is it. Note: there is no headphone drive. Normal high performance DAC's have 3 op-amp stages, followed by a separate headphone amp. So to conclude - Hugo's analogue path is not a simple couple of op-amps chucked together, it is fundamentally simpler than all other headphone amp solutions.

This brings me on to my biggest annoyance - the claim that Hugo's amp is merely good. Firstly, no body can possibly know how good the headphone amp in Hugo is, because there is not a separate headphone stage as such - its integrated into the DAC function directly. You can't remove the sound of the headphone amp from the sound of the DAC, it's one and the same.
 
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  So it's entirely normal that when used as a DAC for iMac the Mojo's ability to display different colors according to sample rate differences is effectively disabled and it will simply forever be at the color corresponding to the maximum rate you set it on in the MIDI setup.
 
Should I set it to the maximum (7xxHz) just for maximum leeway or just to 192 since that's the top rate for most tracks? Is there an advantage to picking one over the other or does it simply not matter. 
 
Entirely up to you. 
 
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Just a thought. Why do other DAC/headphone amps have amp sections when Hugo/Mojo get by without one, and many including Chord say it is more transparent? Have Chord got the patent for ampless amps :)

I wrote up what I gathered from Rob on post 5198 :)
 
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