[Mython]

 

Rob has discussed the (relative**) immunity of optical connections to RF, and the influences of undesirable RF on analogue circuitry. A USB cable may well be carrying a digital signal, but it can also, inadvertently, carry RF noise which may manage to influence analogue components on the PCB (any DAC; not just Mojo).  (**relative since although the connection itself is 'immune', it does not immunise the DAC circuitry from other avenues of RF intrusion, so an optically-connected DAC should not casually be assumed to be immune from RF intrusion)


I quoted some of Rob's comments on this topic, in the 'informative posts' section of post #3; a couple of which are as follows:
 

Can anyone pls let me know what does mean by "......USB cables that have ferrites in the cable is a good idea ....."?
From where i can buy such a cable?
Pls help me?

 
 
 
yes, it means a cable with one of these ferrite bands around it:
 
https://www.amazon.com/eBoot-Pieces-Ferrite-Suppressor-Diameter/dp/B01E5E5IY4
 

 
Some cables already have one fitted, others can very easily be fitted with one, manually, as they just clip-on

 

[rkt31]

@sharon124, you can find plastic shell encased ferrite core online according to the dia of the cable. these can be placed on the cable .

 

[sharon124]

Ok.. Got it.. Thank you so much...seems it easy solution..

 

[Mython]

Remember to measure your USB cable thickness and choose the closest size of ferrite core, to clip onto it - otherwise, it'll drive you nuts, sliding back&forth, along the cable

 

[sharon124]

Remember to measure your USB cable thickness and choose the closest size of ferrite core, to clip onto it - otherwise, it'll drive you nuts, sliding back&forth, along the cable :wink_face:

One more question.. If we consider the usb cable come with mojo, is it ok if i connect one chock near the mojo side connector? Or it will need to connect two chorks at both end of cable?

 

[EagleWings]

What is the worst thing that can happen to Mojo, if I am being careless with connecting my Fiio X3ii to the Mojo using the TRRS-TRS coax cable? There are 6 possibilities as shown in the picture. 1-A is the ideal and the correct connection. What about the other 5 scenarios? I wouldn't do the 3-A and 3-B. But it is a possibility when I have friends over and they want to give Mojo a try.
 
 

 
Thanks for your help!

 

[appabahn]

Finally found way to post photos, I think.

A different approach to mobile carry, allowing flexibility in sitting, standing, kneeling, etc.
I wear iem's over ear, down back and route through belt loops to control pressure at USB connectors and limit cable bind.

 

[jmills8]

Finally found way to post photos, I think.

A different approach to mobile carry, allowing flexibility in sitting, standing, kneeling, etc.
I wear iem's over ear, down back and route through belt loops to control pressure at USB connectors and limit cable bind.

You in a war or something?

 

[Mython]

 

Remember to measure your USB cable thickness and choose the closest size of ferrite core, to clip onto it - otherwise, it'll drive you nuts, sliding back&forth, along the cable

One more question.. If we consider the usb cable come with mojo, is it ok if i connect one chock near the mojo side connector? Or it will need to connect two chorks at both end of cable?

 
Just one choke should be sufficient (more than one will not cause any harm, but there's just no need, unless your USB cable is several metres long

)
 
Generally, I think they tend to be applied at the source end, but just experiment and see which end you prefer.
 
Ultimately, it's not a big deal. Just try it and see what suits you best.

 

[jmills8]

Not like this

 

[miketlse]

One more question.. If we consider the usb cable come with mojo, is it ok if i connect one chock near the mojo side connector? Or it will need to connect two chorks at both end of cable?

 
Some people manage with one choke, but others like to have a choke at each end of the cable. The chokes are relatively cheap so you can try both options, and find the one that suits you.

 

[rhythm]

But for the interpolation filter in a DAC there is absolutely no uncertainty...

How about spline interpolation (https://en.wikipedia.org/wiki/Spline_interpolation)? Does it make sense to do it in a FPGA?

 

[Rob Watts]

  How about spline interpolation (https://en.wikipedia.org/wiki/Spline_interpolation)? Does it make sense to do it in a FPGA?

No that will create significant timing errors. Theory is very simple - use a filter that has as close as possible to an ideal sinc impulse response, and you will better recover the original un-sampled signal. If its a perfect sinc response, it will recover it perfectly for all bandwidth limited signals. No other form of interpolation filter will do this - to perfectly recover the signal it must be a sinc impulse response.
 
An FPGA can do anything you like, so long as the desired function will fit with timing closure.
 
Rob 

 

[Slaphead]

An FPGA can do anything you like, so long as the desired function will fit with timing closure.

Rob 

Rob, I've got a question regarding the use of FPGAs in Chord devices, especially relating to the Mojo.

I don't really know the cost to volume ratio of FPGAs compared to ASICs, but I'm led to believe that an ASIC is possibly a more economical solution in terms of high volume production and in terms of power consumption (at least with small enough manufacturing processes)

I totally understand that an FPGA is an advantage when it comes to "time to market", and it makes significant economical sense with the majority of Chord products in that they are relatively low volume and high end. However given that the Mojo appears to be the big thing these days, selling by the bucket load, would it not make sense to order bulk ASICs based on your design, given that your design is pretty much set in stone now.

If the truth be told I don't know how transferable your FPGA design is to an ASIC, but as it's logic gates in both I'm guessing it's achievable.

 

[Mython]

 

An FPGA can do anything you like, so long as the desired function will fit with timing closure.

Rob 

Rob, I've got a question regarding the use of FPGAs in Chord devices, especially relating to the Mojo.

I don't really know the cost to volume ratio of FPGAs compared to ASICs, but I'm led to believe that an ASIC is possibly a more economical solution in terms of high volume production and in terms of power consumption (at least with small enough manufacturing processes)

I totally understand that an FPGA is an advantage when it comes to "time to market", and it makes significant economical sense with the majority of Chord products in that they are relatively low volume and high end. However given that the Mojo appears to be the big thing these days, selling by the bucket load, would it not make sense to order bulk ASICs based on your design, given that your design is pretty much set in stone now.

If the truth be told I don't know how transferable your FPGA design is to an ASIC, but as it's logic gates in both I'm guessing it's achievable.

 
 
I don't know much about that, but wouldn't it mean having to disclose the proprietary (and currently-encrypte-against-reverse-engineering) code structure to the silicon fabricator?