[tlcocks]

Do you use with Dap or iphone?

Iphone

 

[prakasitp]

Iphone

I have problem with iphone 13 pro and 14 pro but no problem with iphone 8 plus.

which iphone model that do you use?

 

[tlcocks]

I have problem with iphone 13 pro and 14 pro but no problem with iphone 8 plus.

which iphone model that do you use?

iPhone SE (2020)

 

[jsk ksj]

What is happening when the mojo2 boots?

I see the flashing lights, but curious about what's happening.

Sure it has been asked before, so if you have a link...

 

[ducnsh]

What is happening when the mojo2 boots?

I see the flashing lights, but curious about what's happening.

Sure it has been asked before, so if you have a link...

I think it is the boot sequence that initializes the hardware and checks the operation before usage.

 

[ra990]

What is happening when the mojo2 boots?

I see the flashing lights, but curious about what's happening.

Sure it has been asked before, so if you have a link...

It goes through each of the EQ bands and shows you what is set.

 

[Rob Watts]

What is happening when the mojo2 boots?

I see the flashing lights, but curious about what's happening.

Sure it has been asked before, so if you have a link...

The technical reason for the 16 second rainbow mode is so that the digital DC servo stabilises. This takes around 15 seconds to trim the DC voltage down from several volts to uV levels. Once that is done, the OP relays are turned on, and this ensures a click free start-up.

It goes through each of the EQ bands and shows you what is set.

Correct. Thought it was a good idea to see what had been set last time one used it whilst DC levels are stabilised.

 

[ducnsh]

The technical reason for the 16 second rainbow mode is so that the digital DC servo stabilises. This takes around 15 seconds to trim the DC voltage down from several volts to uV levels. Once that is done, the OP relays are turned on, and this ensures a click free start-up.



Correct. Thought it was a good idea to see what had been set last time one used it whilst DC levels are stabilised.

Thanks for sharing, Mr.Watts, could you share the technical difficulties when reducing the noise floor? Currently, it is 2.7uV on the Mojo2, is it possible to reduce it more? I asked because I love the sound of Mojo2 and Hugo2 but both produce some slight hiss with 64Audio IEMs (which I love too), tested with Nio, Trio, and 12t. To deal with it, I use iFi iEmatch, it works flawlessly, not only reducing the noise floor but also improving the useful volume range (and increasing the dynamics too) but I am just curious can the noise floor be reduced more?

 

[Earbones]

Hey Rob, bit of an off-topic question, but something I’ve been wondering…

The last three IEMs I’ve bought all came on cables terminated in 4.4mm balanced… two of them are nice enough cables that I’ve no inclination to swap them out, even though I’ve largely been ambivalent towards balanced connections. Seems like 4.4mm may be moving from merely a popular option to the default audiophile connection, at least with some manufacturers.

Things certainly are not there yet, and it may never be, but then again I definitely wouldn’t take a bet that 4.4mm will never be the audiophile default.

If that day comes, will you be rethinking Chord’s stance on balanced connections? If not from the standpoint that it’s “better” (I for one don’t believe it necessarily is), but just from a general desire for out-of-the-box compatibility with the majority of IEM/headphone manufacturers at that point?

 

[Currawong]

Thanks for sharing, Mr.Watts, could you share the technical difficulties when reducing the noise floor? Currently, it is 2.7uV on the Mojo2, is it possible to reduce it more? I asked because I love the sound of Mojo2 and Hugo2 but both produce some slight hiss with 64Audio IEMs (which I love too), tested with Nio, Trio, and 12t. To deal with it, I use iFi iEmatch, it works flawlessly, not only reducing the noise floor but also improving the useful volume range (and increasing the dynamics too) but I am just curious can the noise floor be reduced more?

I've noticed manufacturers setting the output impedance to about 1 Ohm in their DAPs lately. This can reduce hiss, but I don't think is high enough to affect IEMs that have wild frequency-vs-impedance differences.

 

[Rob Watts]

Thanks for sharing, Mr.Watts, could you share the technical difficulties when reducing the noise floor? Currently, it is 2.7uV on the Mojo2, is it possible to reduce it more? I asked because I love the sound of Mojo2 and Hugo2 but both produce some slight hiss with 64Audio IEMs (which I love too), tested with Nio, Trio, and 12t. To deal with it, I use iFi iEmatch, it works flawlessly, not only reducing the noise floor but also improving the useful volume range (and increasing the dynamics too) but I am just curious can the noise floor be reduced more?

So background noise comes from a number of different areas - DAC noise (from switching activity), reference voltage noise, op-amp or transistor noise, resistor noise (thermal noise from or Johnson-Nyquist noise) and lastly the overall gain.

DAC noise is normally significant, and a major source of noise floor modulation, but is negligible with my pulse array DAC, so I don't need to worry about that.

Reference noise is usually hidden by cancelling techniques, which only works with no signal - this is another major source of noise floor modulation, but doesn't normally create significant background noise as I use ultra low noise (and crucially below 0.001 ohm) discrete reference circuitry, so in my case again this problem is eliminated.

Op-amp or transistor noise depends upon the input voltage noise. The best you can get is 1nV/rt Hz - that's 0.15 uV on the amp input. This noise level is very expensive, with Mojo 2 it's set to 2.2nV/rt Hz or 0.33 uV input noise.

Resistor noise depends upon how much distortion you are prepared for. There comes a point when you reduce circuit resistance when halving it (giving only a 3dB improvement in thermal noise) quadruples distortion, so one has to be ultra careful in setting this parameter.

Overall gain is crucial. Double the gain, you double the noise. But if you want a decent OP voltage, you need high gain. Mojo 2 can deliver 5.2v RMS (that's 7.35v peak) which is a lot of voltage, so this will increase the background noise. Using attenuators on the OP reduces noise by reducing the overall gain - but they add output impedance, so will make the IEM or HP sound softer and warmer, as the transducer is not so well damped. Attenuators also degrade transparency by adding more parts in the signal path, and create dynamic SQ problems.

When I design a DAC I have created a calculation tool, and can calculate all of the above effects. But it is all about compromises, and getting the right mix is not straightforward. Life would be an awful lot easier if IEM manufacturers did not have such crazy sensitivity. I have to deal with 114dB/mW Shure IEM and at the other end potentially a 83dB/mW Susvara... Of course virtually nobody will use a Susvara on Mojo 2, but you get the idea.

Hey Rob, bit of an off-topic question, but something I’ve been wondering…

The last three IEMs I’ve bought all came on cables terminated in 4.4mm balanced… two of them are nice enough cables that I’ve no inclination to swap them out, even though I’ve largely been ambivalent towards balanced connections. Seems like 4.4mm may be moving from merely a popular option to the default audiophile connection, at least with some manufacturers.

Things certainly are not there yet, and it may never be, but then again I definitely wouldn’t take a bet that 4.4mm will never be the audiophile default.

If that day comes, will you be rethinking Chord’s stance on balanced connections? If not from the standpoint that it’s “better” (I for one don’t believe it necessarily is), but just from a general desire for out-of-the-box compatibility with the majority of IEM/headphone manufacturers at that point?

Sure, we constantly re-appraise what is going on. That said, the 4.4mm connector is very expensive - it doesn't matter when you are using a $2 chip in a $600 DAC, but using an FPGA solution is comparatively hideously expensive, so every extra cent counts with Mojo 2.

I've noticed manufacturers setting the output impedance to about 1 Ohm in their DAPs lately. This can reduce hiss, but I don't think is high enough to affect IEMs that have wild frequency-vs-impedance differences.

Only increasing the OP impedance won't directly reduce background or fixed noise - unless say your load is comparable to the OP impedance. Then it will sound very soft and with out of control bass. Unless you are thinking about attenuators, so a 99 ohm followed by 1 ohm will attenuate the noise by 40dB, but also attenuate the available driving voltage by 40dB - plus all the other SQ problems I mentioned above.

 

[ducnsh]

So background noise comes from a number of different areas - DAC noise (from switching activity), reference voltage noise, op-amp or transistor noise, resistor noise (thermal noise from or Johnson-Nyquist noise) and lastly the overall gain.

DAC noise is normally significant, and a major source of noise floor modulation, but is negligible with my pulse array DAC, so I don't need to worry about that.

Reference noise is usually hidden by cancelling techniques, which only works with no signal - this is another major source of noise floor modulation, but doesn't normally create significant background noise as I use ultra low noise (and crucially below 0.001 ohm) discrete reference circuitry, so in my case again this problem is eliminated.

Op-amp or transistor noise depends upon the input voltage noise. The best you can get is 1nV/rt Hz - that's 0.15 uV on the amp input. This noise level is very expensive, with Mojo 2 it's set to 2.2nV/rt Hz or 0.33 uV input noise.

Resistor noise depends upon how much distortion you are prepared for. There comes a point when you reduce circuit resistance when halving it (giving only a 3dB improvement in thermal noise) quadruples distortion, so one has to be ultra careful in setting this parameter.

Overall gain is crucial. Double the gain, you double the noise. But if you want a decent OP voltage, you need high gain. Mojo 2 can deliver 5.2v RMS (that's 7.35v peak) which is a lot of voltage, so this will increase the background noise. Using attenuators on the OP reduces noise by reducing the overall gain - but they add output impedance, so will make the IEM or HP sound softer and warmer, as the transducer is not so well damped. Attenuators also degrade transparency by adding more parts in the signal path, and create dynamic SQ problems.

When I design a DAC I have created a calculation tool, and can calculate all of the above effects. But it is all about compromises, and getting the right mix is not straightforward. Life would be an awful lot easier if IEM manufacturers did not have such crazy sensitivity. I have to deal with 114dB/mW Shure IEM and at the other end potentially a 83dB/mW Susvara... Of course virtually nobody will use a Susvara on Mojo 2, but you get the idea.



Sure, we constantly re-appraise what is going on. That said, the 4.4mm connector is very expensive - it doesn't matter when you are using a $2 chip in a $600 DAC, but using an FPGA solution is comparatively hideously expensive, so every extra cent counts with Mojo 2.



Only increasing the OP impedance won't directly reduce background or fixed noise - unless say your load is comparable to the OP impedance. Then it will sound very soft and with out of control bass. Unless you are thinking about attenuators, so a 99 ohm followed by 1 ohm will attenuate the noise by 40dB, but also attenuate the available driving voltage by 40dB - plus all the other SQ problems I mentioned above.

Many thanks for your explanation, I know that there is no perfect design, there is always a trade-off for a certain design, Mojo and Hugo are portable devices that can be used with both IEM and HP, and I really appreciate that. But if it can be, I am really looking forward to a design that sacrifices some power (or have the gain option) to deal with the hiss on IEMs. Again, thank you again for sharing, I just want to share my expectation on the next Chord portable device as a user who had both Mojo2 and Hugo2 .

 

[Solarium]

HD800S need bit of a high impedance output to warm them up. To simulate this with Mojo, increase subbass eq +5db, increse basseq + 1db, decrease midhi -1db (or -2db) and top high -1db. Mojo 2 has very good control for a portable with the Sennheisers, it just more of a tonality issue.

that's great! Will try this. I just got it and it's definitely "anemic" compared to my IER-Z1R's which are pretty bassy.

Also, are the EQ settings automatically saved per headphone or would I have to change it back every time I use the IEM's?

 

[ducnsh]

that's great! Will try this. I just got it and it's definitely "anemic" compared to my IER-Z1R's which are pretty bassy.

Also, are the EQ settings automatically saved per headphone or would I have to change it back every time I use the IEM's?

Mojo does not have multiple EQ profiles, it always saves the last one, so you have to change it manually

 

[davehutch]

Can I ask about the suitability of the Mojo 2 as a DAC only, feeding a separate headphone amp?
I've bought the Mojo 2 and I'm considering getting a small tube headphone amp (Schiit Vali 2++) and I was wondering about the fact that the output of the Mojo 2 is designed to drive headphones, not act as a line-level signal to feed a pre-amp.
I thought that the voltage and output impedance needed to be particular values, as found in a standard line-out such as RCA connectors, rather than the headphone amp output from the Mojo 2.
Is this not a case of amping an amp (which I've always heard is something that should be avoided)? Maybe @Rob Watts could give me some guidance if you have time?

I found this post which suggests that the output is actually not a headphone amp in the traditional sense but rather a high-level DAC analogue output so I should be fine.
Can anyone confirm?