[GrussGott]

It's a Motorola Moto X style. Although it's never happened to me, again it's YMWV! That's why this whole RFI business has been so very frustrating... Fortunately, in the long term this problem will disappear, as the next gen mobile phones will not low frequency modulate the RF.

Rob on your next trip to silicon valley I recommend you stop at any large device manufacturer (like the people making the phone you have and a zillion other portable devices), and I mean any, because it's an RFI issue and that's been confirmed. I would recommend a large grey-beard company that makes routers, switches, networking equip, etc and recently IP phones, cameras, and other consumer devices. They are experts are at this.

I'm not a device engineer but I've been in their labs 100s of times and they can recreate the issue on any device you point to in 30 seconds and show you what they do to prevent it.

 

[Hikoki]

Hi everyone. I am thinking about getting the Mojo and using it as an outboard DAC and/or headamp. I have an Ifi iCan I have been using with the DT880 600ohm feeding it from Chromecast Audio and its internal DAC. I have recently tested the Schiit Modi Multibit as a external DAC, however, I didn't perceive much if any difference in SQ. Which surprised me. Now, does anyone on here have an experience with Chromecast Audio and the Mojo? If so, has this had an impact on the sound quality?
Thanks for any feedback,
Ivan

 

[GrussGott]

Hi everyone. I am thinking about getting the Mojo and using it as an outboard DAC and/or headamp. I have an Ifi iCan I have been using with the DT880 600ohm feeding it from Chromecast Audio and its internal DAC. I have recently tested the Schiit Modi Multibit as a external DAC, however, I didn't perceive much if any difference in SQ. Which surprised me. Now, does anyone on here have an experience with Chromecast Audio and the Mojo? If so, has this had an impact on the sound quality?
Thanks for any feedback,
Ivan

Mojo is a mobile solution (thus the "mo"), Mimby is a desktop solution so if you're looking for a desktop solution ....

Chromecast has issues with HiFi audio: here and here and here - and shouldn't be used for HiFi

It’s not fair to Google to connect a € 39 streaming device to a € 900 stereo. Google never even hinted it could be used like that ... It is an ideal way for youngsters to play music from their phone to a speaker ... But if your want just a little bit of audio quality, this is not the way to go. Any streamer I have reviewed sounds many times better. And to be fair to Google, cost many times more.​

 

[Arpiben]

Rob on your next trip to silicon valley I recommend you stop at any large device manufacturer (like the people making the phone you have and a zillion other portable devices), and I mean any, because it's an RFI issue and that's been confirmed. I would recommend a large grey-beard company that makes routers, switches, networking equip, etc and recently IP phones, cameras, and other consumer devices. They are experts are at this.

I'm not a device engineer but I've been in their labs 100s of times and they can recreate the issue on any device you point to in 30 seconds and show you what they do to prevent it.

I will be the first one interested in the solutions they may have to protect speakers, loudspeakers and headphones when you bring a mobile phone at a few inches

 

[GrussGott]

I will be the first one interested in the solutions they may have to protect speakers, loudspeakers and headphones when you bring a mobile phone at a few inches

that's the EXACT use-case I saw them demonstrate a zillion times. Like if you're on a conf call and someone sets a cell phone down by the speakerphone.

 

[435279]

@Rob Watts I respect and admire your DAC technology, it's the best out there by far, reading these comments it seems you may a bit to learn regarding RF noise though. If you could get together with some RF experts during the design of the Mojo 2 we could have the perfect portable DAC.

As I said above currently listening to iFi Nano BL via my HTC 10, streaming over 4G and its totally immune from any background noise.

 

[Arpiben]

that's the EXACT use-case I saw them demonstrate a zillion times. Like if you're on a conf call and someone sets a cell phone down by the speakerphone.

Therefore you may also complain about headphones and loudspeakers EMI susceptibility.
That said if you want to keep your mobile on air a bit of copper foil should keep EMI away.
For different reasons, I do keep my mobile with WiFi Off and in Airplane mode when using it as a DAP.

 

[styks]

No that is not the situation, we did not balls up RFI.

Chord and I have been working very hard on this issue, and spent a lot of time and effort trying to improve the RFI. So the first mod improved Wi-Fi, and this went into the production model. But people kept complaining, so I tried iss3, with RF improvements.

Iss 3 had no benefit.

So I tried iss 4.
This had no benefit.

Iss 5 - this too had no benefit.

At this stage I had tried everything conceivable to improve RFI, so I handed the design to a RF engineer, who builds RF OP stages for mobiles.
He suggested some changes.
I took his ideas on board, and actually improved upon them, with filters that knocked out every single mobile phone freq across the World. And then I beefed it up with three of these filters.

So I was now convinced it would kill the problem.

But - iss 6 had NO BENEFIT again - what was alarming was it made no difference whatsoever.

But then realisation occurred: the RFI problem IS NOT RFI.

Why did I come to this conclusion? Because RF treatment has no effect at all, but people were claiming that mild steel helped. Mild steel has no screening effect on RF, but screens for low frequency magnetic problems. The RFI issue is in fact the phone having poor low frequency magnetic fields as the RF is modulated. This explains why most phones have no problems whatsoever, but other phones have big issues, when the actual RF transmission power is identical.

So to help with the issue you can:

1. Get a better phone with low external magnetic fields.
2. Use a case that has mild steel plates on the surface between Mojo and the phone.
3. Keep the mobile some distance away from Mojo.

Note that this issue is not just a Chord issue, as this noise affects other DAC amps too. Note too that it's not an issue with all phones - I have personally never ever heard RFI on Mojo or Hugo 2.

Errm interesting. So not all phones are equal. Do they have to comply with EMF standards / regulations?
So you say EMF production from some is greater than others? Low frequency, are you saying these emmisions produced are venturing out of the bands, outside of the cellphone frequencies, spurious emmisions?
Could you explain further please, I'd like to look into the problem, I have friends with sensitive equipment that may be able to measure / show these spurious emmisions.
I'll certainly contact Samsung, my phone is fairly modern, an S5. ..... They musy be told of the problem if the emmisions are not clean or within specified guide lines.

Have you difinitive proof of what you say?

Would be possible to use some sort of magnetic shielding, some material with similar properties to mild steel but lighter? ..... I'm quite interested in this, ill do some research into shielding against EMF.

There must be a way of sheidling against it now you know what the problem is? .... A MK7!
GIRON Magnetic Shielding Film, maybe? .... Many foils available, but i guess you have considered this?

 

[miketlse]

Errm interesting. So not all phones are equal. Do they have to comply with EMF standards / regulations?
So you say EMF production from some is greater than others? Low frequency, are you saying these emmisions produced are venturing out of the bands, outside of the cellphone frequencies, spurious emmisions?
Could you explain further please, I'd like to look into the problem, I have friends with sensitive equipment that may be able to measure / show these spurious emmisions.
I'll certainly contact Samsung, my phone is fairly modern, an S5. ..... They musy be told of the problem if the emmisions are not clean or within specified guide lines.

Have you difinitive proof of what you say?

Would be possible to use some sort of magnetic shielding, some material with similar properties to mild steel but lighter? ..... I'm quite interested in this, ill do some research into shielding against EMF.

There must be a way of sheidling against it now you know what the problem is? .... A MK7!
GIRON Magnetic Shielding Film, maybe? .... Many foils available, but i guess you have considered this?

18 months ago @psikey was reporting that slipping a thin ferrite sheet inside his phone protector (plus adding a ferrite choke) removed the RFI issue for him. https://www.head-fi.org/threads/cho...n-3rd-post-◄★☆.784602/page-1188#post-12591852

 

[styks]

Therefore you may also complain about headphones and loudspeakers EMI susceptibility.
That said if you want to keep your mobile on air a bit of copper foil should keep EMI away.
For different reasons, I do keep my mobile with WiFi Off and in Airplane mode when using it as a DAP.

No never complained about that, never really had that problem tbh, tell a lie, i had old hifi speakers a while back that were susceptible. I managed to shield those fairly well, my transmitters were not as clean as they should've been, I was quite green then.
Yes thought about copper foil, much of my equipent has copper foil shielding within, + ferrites, etc etc.
As it happens my phone is always in airplane mode, no sim in it most if the time either. Its a dedicated source only.
I only popoed a sim in it to test interference for a member.

 

[styks]

18 months ago @psikey was reporting that slipping a thin ferrite sheet inside his phone protector (plus adding a ferrite choke) removed the RFI issue for him. https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-1188#post-12591852

Thank you for the link, ill have a read.
Good news, I'm glad he sorted it successfully. Im guessing he paired them, stack ive heard it called. I'll go read.
Is there room inside the Mojo for foil or ferrite shielding? If you shield the most sensitive components, would possibly help?

 

[Rob Watts]

@Rob Watts I respect and admire your DAC technology, it's the best out there by far, reading these comments it seems you may a bit to learn regarding RF noise though. If you could get together with some RF experts during the design of the Mojo 2 we could have the perfect portable DAC.

As I said above currently listening to iFi Nano BL via my HTC 10, streaming over 4G and its totally immune from any background noise.

You clearly did not read my post about RFI - I gave the design to an RF expert, with full access to schematics and layout. He recommended changes, which I actually implemented in full, plus some, and it FAILED TO MAKE ANY DIFFERENCE whatsoever - not even the slightest change at all. This was after months of other work on the issue, again NO CHANGE whatsoever. Sorry to shout, but I get fed up sometimes with armchair "experts" pontificating, when they have absolutely no experience about electronic design - and particularly after we have spent a great deal of time and effort over this issue and involved experienced RF experts in the process too.

 

[Rob Watts]

Errm interesting. So not all phones are equal. Do they have to comply with EMF standards / regulations?
So you say EMF production from some is greater than others? Low frequency, are you saying these emmisions produced are venturing out of the bands, outside of the cellphone frequencies, spurious emmisions?
Could you explain further please, I'd like to look into the problem, I have friends with sensitive equipment that may be able to measure / show these spurious emmisions.
I'll certainly contact Samsung, my phone is fairly modern, an S5. ..... They musy be told of the problem if the emmisions are not clean or within specified guide lines.

Have you difinitive proof of what you say?

Would be possible to use some sort of magnetic shielding, some material with similar properties to mild steel but lighter? ..... I'm quite interested in this, ill do some research into shielding against EMF.

There must be a way of sheidling against it now you know what the problem is? .... A MK7!
GIRON Magnetic Shielding Film, maybe? .... Many foils available, but i guess you have considered this?

When the mobile phone communicates with the cell tower, it modulates the RF carrier - its this modulation that you hear as the chirping noise. This generates two components - the RF at whatever MHz, and a low frequency magnetic component, which falls away quite rapidly away from the mobile phone. This low frequency magnetic field is simply the nett current flowing within the phone from the battery, and is only at audio frequencies. The problem that Mojo has is it's strength - the small size, which means the unit gets closer to the magnetic field. If the mobile phone has a small magnetic loop internally, there are no problems.

To be honest, we have spent two years chasing our tails assuming it was RF - but now I am reasonably certain I have been looking in the wrong area (it's not RF) then we can look at other possible solutions. I am posting my findings about magnetic screening so others can experiment or offer suggestions.

 

[Hikoki]

Mojo is a mobile solution (thus the "mo"), Mimby is a desktop solution so if you're looking for a desktop solution ....

Chromecast has issues with HiFi audio: here and here and here - and shouldn't be used for HiFi

It’s not fair to Google to connect a € 39 streaming device to a € 900 stereo. Google never even hinted it could be used like that ... It is an ideal way for youngsters to play music from their phone to a speaker ... But if your want just a little bit of audio quality, this is not the way to go. Any streamer I have reviewed sounds many times better. And to be fair to Google, cost many times more.​

Grüß Gott and thanks for taking the time to reply. I and quite a number of CCA users don't subscribe to your and Darko' s point of view, though. To me, just like to many people on various forums this cheap little thing sounds ' hifi' enough even in direct comparison with much more expensive signal source gear. I personally own the Fio X5 player ( might not be hifi enough, though, or is it ?) and I haven't really perceived much difference if any in SQ comparing the Fiio and the CCA, definitely not of the horrifying caliber the reviewers in the links you provided suggested.
But hey, I wasn't even asking for the evaluation of the CCA in the first place. I just wanted to know if using the Mojo might make a difference even in this setup. Your reply sounded like you couldn't even imagine using the Mojo in combo with the CCA ( I also stream flac music from my NAS, mind you).
Sorry to say this, but I am of the opinion that somehow people can't stomach the fact this Google device only costs as little as $30.
Cheers
Ivan

 

[435279]

You clearly did not read my post about RFI - I gave the design to an RF expert, with full access to schematics and layout. He recommended changes, which I actually implemented in full, plus some, and it FAILED TO MAKE ANY DIFFERENCE whatsoever - not even the slightest change at all. This was after months of other work on the issue, again NO CHANGE whatsoever. Sorry to shout, but I get fed up sometimes with armchair "experts" pontificating, when they have absolutely no experience about electronic design - and particularly after we have spent a great deal of time and effort over this issue and involved experienced RF experts in the process too.

I don't want to get into an argument with you Rob, so this is my last post on this, I just wanted to defend my position, I did read your post, I would suggest your RF "expert" was not "expert" enough, or his efforts would have fixed the problem, in your words I don't want to shout, but "GET A BETTER EXPERT". Also how do you know what experience in electronic design I have? Its not "absolutely no experience", back in the day I did an HNC in electronics over three years, before I switched to software engineering.