scarfacegt
500+ Head-Fier
- Joined
- Nov 4, 2010
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Yes some owners do use it as a source for a pre-amp or amp.
There is a lot of info in the FAQ in post #3, so read that for a start, and feel free to ask any follow-on questions.
A key thing to remember, is that the line-out mode is just a short cut to the default 3V output. 3V can be a bit 'too hot' for some amplifiers, so if needed you can use the volume balls to adjust the voltage down a bit, for example to 1.9V which is close to the historical AV standard.
To set the output level to 3V ( line level ) for connection to a preamplifier press both volume buttons
together when switching on the unit. Both volume balls will illuminate light blue. This mode is not
remembered so when you switch off it will reset back to the previous volume stored for safety reasons.
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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.
To set the output level to 1.9V RMS, first follow the above guidance, to attain 3V, and then continue further, with the following:
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Yes 4 clicks down will set it to 1.9v (both balls indigo). Each step is always a 1 dB change.
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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 output amplifier. 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
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@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
Paste
No, you need at least one 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
For physically-connecting Mojo to active speakers, see: www.head-fi.org/t/784602/chord-mojo-the-official-thread-please-read-the-3rd-post/13350#post_12423100
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I just carried a quick amp test and my results are as follows:
Portaphile 627x: Sadly this amp proves to be the worst offender. Mojo has out classed this amp by a large margin.
Meir Audio quickstep: 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: 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: 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: 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.
Tnx for the help
