Chord Mojo as a static HiFi DAC

[inbox4]

Does anyone use a Mojo in their hifi system?

I'm considering buying one as an upgrade to the DAC built into my Musical Fidelity M6si amp and using the Mojo permanently in my hifi. I don't plan to ever move it or connect a pair of headphones to it.

I would like to get a wall plug to micro usb phone charger to permanently connect it to the mains so I can use it exactly as I would a standard hifi DAC like Arcam's irDAC for example.

I would like to hear opinions on whether the Mojo would work well in this configuration as it is essentially a mobile, headphone amp/ DAC. If anyone is able to comment on whether the Mojo would be a worthy upgrade on the DAC in my amp, that would to great too.

 

[expat_mike]

Does anyone use a Mojo in their hifi system?

I'm considering buying one as an upgrade to the DAC built into my Musical Fidelity M6si amp and using the Mojo permanently in my hifi. I don't plan to ever move it or connect a pair of headphones to it.

I would like to get a wall plug to micro usb phone charger to permanently connect it to the mains so I can use it exactly as I would a standard hifi DAC like Arcam's irDAC for example.

I would like to hear opinions on whether the Mojo would work well in this configuration as it is essentially a mobile, headphone amp/ DAC. If anyone is able to comment on whether the Mojo would be a worthy upgrade on the DAC in my amp, that would to great too.

I recently got a Mojo but have not yet tried it as the permanent DAC in my hifi - but I do intend to experiment with this. Many people do successfully use Mojo as their system DAC, as described in some of the posts in this forum thread http://www.head-fi.org/t/784602/chord-mojo-the-official-thread-please-read-the-3rd-post . If you read the third post, click on the section

Setting Mojo to Line-Level (e.g. for use with a Preamplifier or Active Loudspeakers, etc.)

Setting Mojo to Line-Level (e.g. for use with a Preamplifier or Active Loudspeakers, etc.)

This section contains details about how to set the line level output to the desired voltage.

Regarding wall chargers, the Mojo needs one that supplies 1A minimum, and try and ensure that the charger does not output any ripple current (because that can create issues by causing the inductors inside the Mojo power circuits to vibrate, resulting in a faint buzzing noise). I think that there are several chargers recommended within the thread, but there are over 18000 posts, so use the forum search function.

If you like the Mojo sound (or rather lack of coloration), then an alternative option would be to use the 2Qute DAC, feeding your power amp.

 

[inbox4]

Very helpful, thank you. I will search the site. Do you know of any recommended chargers off the top of your head?

 

[expat_mike]

Very helpful, thank you. I will search the site. Do you know of any recommended chargers off the top of your head?

Post #4 on the same thread gives a few more details about using wall chargers connected permanently, in the sectionIs it alright to leave Mojo plugged in, 24/7?[/b] (Click to hide)

Regarding charger makes, Samsung and Apple phone chargers are often mentioned as working well (providing they supply 1A minimum). I have only used the fast charger that was supplied with my OPPO HA-2, and that works ok as well.

 

[inbox4]

Expat_Mike: What do you think of something like this?

https://www.amazon.co.uk/Charger-Supply-Raspberry-Pi-Computer/dp/B00DM2YF90/ref=sr_1_6?ie=UTF8&qid=1465381458&sr=8-6&keywords=raspberry+pi+mains+adapter

Does anyone else have any opinions on using a Mojo in this way?

 

[Hugh56]

I still unable to find an answer in the forum on whether the Mojo is actually compatible with an external amp. Can it be connected to a Nait. How do i overcome the volume level. Has any body tried this dac with a nait.

 

[expat_mike]

I still unable to find an answer in the forum on whether the Mojo is actually compatible with an external amp. Can it be connected to a Nait. How do i overcome the volume level. Has any body tried this dac with a nait.

Setting Mojo to Line-Level (e.g. for use with a Preamplifier or Active Loudspeakers, etc.)[/b] (Click to hide)
To set the output level to 3V ( line level ) for connection to a preamplifier press both volume buttonstogether when switching on the unit. Both volume balls will illuminate light blue. This mode is not[/b]remembered so when you switch off it will reset back to the previous volume stored for safety reasons.[/b] Quote:Originally Posted by Ra97oR[/b]
Quote:Originally Posted by s7uart[/b]
Quote:Originally Posted by nntnam[/b]

Has anyone experienced the Mojo keeping its 3V setting even after turning off and on again? It happened twice to me. Fist time, it almost killed my Fitear 335. Luckily I notice the huge hiss at the beginning of the song and unplugged it quickly. Second time, I saw the volume balls was illuminated in violet and had to decrease the volume (usually they are pink-ish).

The Mojo remembers what volume you had last and does not reset when you turn it off.

Line out mode is an exception, unless you have pressed a volume button while in it. Then the volume you set will be saved, if you did not change volume in Line out mode, it will not save to 3V for obvious reasons.[/b]

To set the output level to 1.9V RMS, first follow the above guidance, to attain 3V, and then continue further, with the following:

Quote:Originally Posted by Rob Watts[/b]

Yes 4 clicks down will set it to 1.9v (both balls indigo). Each step is always a 1 dB change.

Quote:Originally Posted by Rob Watts[/b]
Quote:Originally Posted by vapman[/b]

Please no worries!

However, iwas wondering if you could answer, the Mojo on line level mode - does this still run thru the Mojo's amp? from how i understand your earlier descriptions, buth the amping and DAC is done in the FPGA?

thus there is no way to truly use it as a dac without double amping?

Line level mode is just a volume preset for the volume control - nothing else changes.

Mojo has an FPGA (which is digital logic only) a discrete DAC (turning digital signals to analogue via flip-flops and resistors) and a single output amplifier - and that is it.

Conventional DAC headphone amps use differential outputs and have two I to V converters (current to voltage), a differential to single ended converter, and an outputamplifier. Wrapped up with that is a analogue filter. So that's a lot of passive components and four amplifiers in the signal path.

Because Mojo's FPGA has extensive digital filtering (at 2048 FS) and has a noise shaper that runs at a very high rate (104MHz) and uses a discrete DAC, I can keep the analogue section radically simpler, and this is one reason why Mojo is so transparent compared to all other DAC amps.

Rob

Quote:Originally Posted by Rob Watts[/b]
Quote:Originally Posted by vapman[/b]

@xtr4 i understand the FPGA designs makes the dac and amp essentally the same... what im really trying to get at is, can the FPGA's amp functions be bypassed so it is used simply as a DAC, and the two 3.5mm outs are true line outputs to prevent double amping
amplifier to do the critical I to V conversion. Now it is possible to design a voltage only DAC (no amp at all), but they sound poor due to lots of problems - the largest being the huge amount of distortion you get doing it that way. Believe me, if I could make it simpler I would. The key that Mojo has is extremely low distortion and noise (0.00017% 3V 300 Ohms) but only one single amplifier in the signal path - and this amp combines headphone drive, filtering and I to V conversion in a single stage.

Rob

Setting Mojo to Line-Level (e.g. for use with a Preamplifier or Active Loudspeakers, etc.)[/b] (Click to hide)
To set the output level to 3V ( line level ) for connection to a preamplifier press both volume buttonstogether when switching on the unit. Both volume balls will illuminate light blue. This mode is not[/b]remembered so when you switch off it will reset back to the previous volume stored for safety reasons.[/b] Quote:Originally Posted by Ra97oR[/b]
Quote:Originally Posted by s7uart[/b]
Quote:Originally Posted by nntnam[/b]

Has anyone experienced the Mojo keeping its 3V setting even after turning off and on again? It happened twice to me. Fist time, it almost killed my Fitear 335. Luckily I notice the huge hiss at the beginning of the song and unplugged it quickly. Second time, I saw the volume balls was illuminated in violet and had to decrease the volume (usually they are pink-ish).

The Mojo remembers what volume you had last and does not reset when you turn it off.

Line out mode is an exception, unless you have pressed a volume button while in it. Then the volume you set will be saved, if you did not change volume in Line out mode, it will not save to 3V for obvious reasons.[/b]

To set the output level to 1.9V RMS, first follow the above guidance, to attain 3V, and then continue further, with the following:

Quote:Originally Posted by Rob Watts[/b]

Yes 4 clicks down will set it to 1.9v (both balls indigo). Each step is always a 1 dB change.

Quote:Originally Posted by Rob Watts[/b]
Quote:Originally Posted by vapman[/b]

Please no worries!

However, iwas wondering if you could answer, the Mojo on line level mode - does this still run thru the Mojo's amp? from how i understand your earlier descriptions, buth the amping and DAC is done in the FPGA?

thus there is no way to truly use it as a dac without double amping?

Line level mode is just a volume preset for the volume control - nothing else changes.

Mojo has an FPGA (which is digital logic only) a discrete DAC (turning digital signals to analogue via flip-flops and resistors) and a single output amplifier - and that is it.

Conventional DAC headphone amps use differential outputs and have two I to V converters (current to voltage), a differential to single ended converter, and an outputamplifier. Wrapped up with that is a analogue filter. So that's a lot of passive components and four amplifiers in the signal path.

Because Mojo's FPGA has extensive digital filtering (at 2048 FS) and has a noise shaper that runs at a very high rate (104MHz) and uses a discrete DAC, I can keep the analogue section radically simpler, and this is one reason why Mojo is so transparent compared to all other DAC amps.

Rob

Quote:Originally Posted by Rob Watts[/b]
Quote:Originally Posted by vapman[/b]

@xtr4 i understand the FPGA designs makes the dac and amp essentally the same... what im really trying to get at is, can the FPGA's amp functions be bypassed so it is used simply as a DAC, and the two 3.5mm outs are true line outputs to prevent double amping
amplifier to do the critical I to V conversion. Now it is possible to design a voltage only DAC (no amp at all), but they sound poor due to lots of problems - the largest being the huge amount of distortion you get doing it that way. Believe me, if I could make it simpler I would. The key that Mojo has is extremely low distortion and noise (0.00017% 3V 300 Ohms) but only one single amplifier in the signal path - and this amp combines headphone drive, filtering and I to V conversion in a single stage.

Rob

Regarding optional use of an additional amp[/b] (Click to hide)
Quote:Originally Posted by audionewbi[/b]

I just carried a quick amp test and my results are as follows:

Portaphile 627x:[/b] Sadly this amp proves to be the worst offender. Mojo has out classed this amp by a large margin.

Meir Audio quickstep:[/b] This amp did not alter the sound but to me there is no point in pairing it with quickstep as Mojo alone offers far more volume than paired with quickstep.

Wagnus Epsilon S:[/b] Expanded the soundstage which was nice but like the other amp the amp section is just nowhere as powerful as Mojo. I felt transparency also took a hit.

Analg2paper TR-07hp:[/b] This was the best pairing of the lot. Like other amps the transparency took a hit but the added bonus was the bass had a nicer reverb. To my ears the bass become extended the the decay was a lot more natural. The mid-bass to my ears was reduced and sub-bass become a little more prominent.

Summary: [/b]Add an amp if you like to color the sound and play around with the tuning, I see no real value in adding amp. So far I dont have any amp that is as powerful as mojo.