[miketlse]

totally. The "oh it comes in via the USB" excuse is laughable; as if designing for that shouldn't be a fundamental consideration. "oh, the water leak only comes into your house through the water pipes, otherwise your house is leakproof!"

You obviously believe me to be an idiot, but I have followed this thread for 2300 pages, so have read all the issues and cures that have been proposed and proven/disproved by the many Mojo owners.
Try using optical input instead - you will find that the RFI disappears. If the RFI was entering via the volume balls, the RFI would still be present.

 

[GrussGott]

You obviously believe me to be an idiot, but I have followed this thread for 2300 pages, so have read all the issues and cures that have been proposed and proven/disproved by the many Mojo owners.
Try using optical input instead - you will find that the RFI disappears. If the RFI was entering via the volume balls, the RFI would still be present.

Quite the opposite: I think you're being observationally practical to a fault (or trying to make cleverly framed, dissembled excuses for a flawed product). You're providing the observation of why the flaw happens and potential fixes, but you should know that comes across as excusing the miss. If the product is susceptible to interference during it's intended methods of use, it's a flawed product, i.e., the Mojo is a flawed product.

That's not a bad thing if it's a recognized flaw and there's a fix released or even a new version coming with a fix. Few if any products are flawless, so denial of design flaws is the more serious offense.

As usual, it's the cover-up, not the crime that's the worst part.

 

[Deftone]

What would cause the poor RF problems with Mojos USB port? USB chip implementation? USB connector quality?

I’m not an engineer but I am wondering why you never really hear about it with other dac amp units.

 

[DavidWeinberg]

Very bummed. I had a defective CCK cable and was on my way to the Apple store to get another under the Apple warranty. As I was walking from my car, I plugged the CCK cable into the Mojo. It didn't stay in. I looked closer and noticed that the USB socket on the Mojo had become dislodged and is now inside the unit. The CCK cable is now my small worry. The Mojo, that is something else (and it's only six months old). I'll work with my dealer and Chord to see what can be done. But for something like this to happen to a unit I generally handle with care while in transit, very bummed...

 

[SomeGuyDude]

You obviously believe me to be an idiot, but I have followed this thread for 2300 pages, so have read all the issues and cures that have been proposed and proven/disproved by the many Mojo owners.
Try using optical input instead - you will find that the RFI disappears. If the RFI was entering via the volume balls, the RFI would still be present.

They're saying that it's a dumb excuse because this is ostensibly a portable amp, which means its stated goal is to be plugged into a phone with headphones plugged into it. That's what it's built for. If the primary function of a device results in RFI interference, that's bad design.

I love my Mojo to bits, but the interference with a cell phone considering the accessory pack includes rubber bands to strap it TO a phone is damn near inexcusable.

 

[Light - Man]

Guys, Mike is only trying to help by giving a practical solution that he has tried and tested, he is not trying to defend Chord or represent them in any way.

The official Chord response seems to be - no comment and no solution other than what Mike has suggested.

 

[styks]

Guys, Mike is only trying to help by giving a practical solution that he has tried and tested, he is not trying to defend Chord or represent them in any way.

The official Chord response seems to be - no comment and no solution other than what Mike has suggested.

I personally dont feel that, and if i believe my gut, I understand why Mike is posting as he is, trying to help, and I for one thank him for that.

It's obvious there is so much irritaion regarding this, folks jump in attacking anything they may percieve as a Chord defence, also understandable to a degree. I always try and remember to start a post by saying, "now im not trying to defend ## but this what i think may be happening" or like that .... Then folks know exactly where your comming from, unless your known to be affiliated with the company of course! Ha ha ha.
One must also realise that there are generally more negative comments posted than there are positive. We shout about whats wrong rather keenly, and it escalates. With possitive comments it doesnt happen to the same degree, its very human and of course understandable! .....

Question is i think. Did Chord test for RFI from what was likely to be the most commonly used source. If they did it was obviously to costly, time consuming, or too difficult it resolve. ...... If they didnt test for RFI well thats an even worse failure.

As an radio amatuer opperator the onus is on us to ensure we do not create RFI for our neighbours, even if it means adding filters/chokes etc to their equipment, (if they agree if course) to cure the problem, at our expense. If we're unable to do that, we have to " stop " transmitting on those frequencies!

We all know that cellular frequencies can interfere with our car radios, some are suseptable some not.
The manufacturers know that cell phones will be used in close proximity and that they have no control over installaion.
The more expensive systems are designed well to reject interference, and even work with our phones, seamlessly, flawlessly, (unless fitted really badly) and normally do just that. ..... Cheaper ones, well you take pot luck!

Chord should've ensured this did not happen, especially given what its designed for. The reason for the "no comment" is in my opinion the same as saying, yes we ballsed that up! ..... They can't say anything else.

 

[Rob Watts]

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.

 

[turkayguner]

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.

Thanks for this info. Would you mind if I ask which brand/model is the phone you are using Mr Watts?

 

[RiseFall123]

Hi,

1) anyone knows if RFI issue is related also to ipad?

2) what jack to rca cable is adviced for an laptop to amp use (line level mode)?

3) if in a hifi integration i can keep it under charge or ut will damage uts batteries in this way?

4) under charge is true that it will become warm so much?

5) anybody here use it in a hifi system (like a stand alone dac) for an everyday use? If so, is so uncomfortable as i read?

 

[435279]

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.

It can't be as simple as that Rob, I suffer with Mojo's notorious interference issue too, I'm using an HTC10. Two other portable DAC amps I have that are immune from this issue are the DragonFly Red and the iFi Nano BL both are basically noise free and both have aluminium cases.

I also can't use my Mojo on my PC desk, the PC is on a shelf directly below and I get a fair amount of noise in that case too.

 

[miketlse]

Hi,

1) anyone knows if RFI issue is related also to ipad?

2) what jack to rca cable is adviced for an laptop to amp use (line level mode)? In principle you just need a cable of this type https://www.head-fi.org/threads/cho...in-3rd-post-◄★☆.784602/page-891#post-12423100 . As to brand, I use a cheap cable without issue, but some owners will happily spend hundreds of $/£/euros on a cable, so personal preference is a big factor.

3) if in a hifi integration i can keep it under charge or ut will damage uts batteries in this way? Chord posted a few days ago, that their advice is not to leave the battery permanently charged 24/7, so switch the mojo off when not in use.

4) under charge is true that it will become warm so much?
The heat buildup is greatest, if you are listening to mojo plus charging from a near empty battery. The heat buildup is minimised, if you fully charge the mojo before starting to listen. If you live in a hot season/climate, the ambient temperature will be greatest, and the mojo will run hotter and the thermal shutdowns may operate. In this case standing the mojo on its edge, will improve the heat transfer, and reduce the temperature.
rob watts said: ↑
If you fully charge Mojo then use it in a desktop it will not switch off; the power dissipation that the charger uses in matching the current drawn by Mojo is negligible. You are only at risk when charging & using at red - & indeed as Mython says putting Mojo on its side will solve that issue too.

Just to give you some numbers - fully charged and matching Mojo's current draw the power dissipation is 107 mW for the charger circuit. That will increase running temperature by less than 1 deg C. But at flashing red it is 910 mW for the power dissipation in the charger.

Now I could fix this by using a switcher based charger rather than a linear one - but these inject too much RF noise onto the battery. This would impair sound quality, & Mojo's design goals was that plugging in the charger would have no significant change in SQ - which would not happen if I used a switcher based charger. I am not prepared to damage SQ as to me this is the most important aspect just for a tiny improvement in usability.

5) anybody here use it in a hifi system (like a stand alone dac) for an everyday use? If so, is so uncomfortable as i read?

I used it at home, connected to my pc for a year, without issues.

 

[turkayguner]

Hi,

1) anyone knows if RFI issue is related also to ipad?

2) what jack to rca cable is adviced for an laptop to amp use (line level mode)?

3) if in a hifi integration i can keep it under charge or ut will damage uts batteries in this way?

4) under charge is true that it will become warm so much?

5) anybody here use it in a hifi system (like a stand alone dac) for an everyday use? If so, is so uncomfortable as i read?

1) I had no noise issues with any wifi source to date including non-cellular iPad mini 4th gen.

2) You cannot send analog signal to Mojo, it only accepts digital signals.

3) It is okay if you switch it off after using and charge only when the battery is empty. Not recommended to leave it on 7x24 plugged in for the longevity of the battery.

4) Yes it gets pretty warm if you charge and use at the same time.

5) I use it at home and also on the go. I have no issues at all.

 

[Rob Watts]

Thanks for this info. Would you mind if I ask which brand/model is the phone you are using Mr Watts?

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.

 

[GreenBow]

I also had a dying battery after 1½ year of moderate use, say between 500 to 600 hours of use in total over 1½ years. I am using the Mojo 2x per day while commuting. What worked for me is charging it to full, disconnect the charger and then let the Mojo play continuously with headphones connected, but without my USB source connected. To my surpise it played about 8 hours. Next I used the Mojo during commuting and it turned out I get at least 7 hours playing time as I am used to.
What a relief, happy that I do not have to buy a new battery.

I hope that others with a battery issue will have the same luck.

I tried this and it's worked.

My Mojo was giving me eight hours and ten minutes when new. ... I don't use it too often. I have a Meridian Explorer which shares workload with my Mojo, (which is used as a desktop DAC).

However just recently I noticed the battery seemed to run out quicker. Two or three times I thought this, so I decided to time my Mojo play time. It was now doing seven hours and fifteen minutes, (having dropped from eight hours and ten minutes).

Anyway Rudivanb, I tried your method for battery time improvement and it worked. ... To recap for other readers. Fully charge Mojo. .. Remove all cables. ... Plug in headphones... . Power on Mojo... Leave it switched on and let it exhaust its battery set up like this.

After I did this once. My Mojo went from 7 hours and fifteen minutes, to eight hours exactly next time I used it for music. .. I ran it through a cycle like this again to see if I could get eight hours ten minutes again. I forgot to time playback, but I will do it again.


Thank you, Head-fier Rudivanb.