[ZappaMan]

Thanks for all of your input.
I didn't know about the timing issues with USB-SPDIF converter.

I see the following options to connect a source with the mojo:

(a) Android Smartphone which connects to the Mojo via USB cable. Additional investment required: USB OTG micro B - B cable (5$ to 150$)
(b) DAP which connects to the Mojo via an optical cable. Additional investment required: Ibasso DX80 (cheapest DAP I found with optical out) for 200 USD used + 15-100$ for the Toslink cable (e.g. the lifatec toslink cable for 90$).
(c) USB-SPDIF converter which connects the source via USB first and then via optical or coaxial to the Mojo. Additional investment required: I have seen USB-SPDIF converters ranging from 20$ to 120$ for the Schiit Eitr to....
(d) Chord Poly which connects to the Mojo via optical cable (I read somewhere that the data transfer from poly to Mojo is via optical but I can't find that reference any more). Additional investment required: 400$ used.
(e) Less viable options: PC (Lenovo Laptop) is not really an option because it has more noise than a smartphone and no optical out. The conventional/cheap DAPs I have (Sansa Clip, Sony, Samsung; all no optical out) don't seem to provide any benefit over (a) and have worse UI.

Advantages and disadvantages as I see them for the options above:
(a)
+ cheapest
+ most compact (no additional unit)
- noisy USB cable which may decrease SQ, the theory is that of course bits are bits but RF noise is audible, see FAQ in https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/ (Spoiler: Is one the the inputs better than the other?)

(b)
+ optical cable should sound best (compared to coax and usb) also acc. to Rob Watts (designer of Mojo), see http://www.the-ear.net/how-to/rob-watts-chord-mojo-tech
- more expensive than (a) by ~ 200$.
- a little less compact than (a) because of an additional unit

(c)
- I am confused by the above feedback: My original assumption was that what matters is that there is an optical input to the mojo and nothing else really matters and a USB-SPDIF converter would provide for that. But if there is a timing issue as described here https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-2386#post-14149141 and other issues as described here https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-2386#post-14149215 then this might not be an option because it's more expensive than (a) but might produce worse SQ than (a).
+ But it could be a great solution as there are compact, inexpensive USB-SPDIF converters. The effect on SQ of such an USB-SPDIF converter is just unclear to me at this point.
- If quality of these units matters in some way and it's not only as simple as "SQ is great as long as there is an optical cable feeding the mojo" than the selection of quality units gets smaller and less compact possibly, the Schiit Eitr for example is already not really portable anymore.

(d)
+ Should sound at least as good as (b) given that it uses an optical connection to transfer data to the mojo (I forgot where I read that. Would be nice if someone had a link to confirm that). I am not sure if there are other factors that effect sound quality built into the Poly other than the fact that the mojo is fed by an optical connection.
- This post https://www.head-fi.org/threads/chord-electronics-☆-poly-☆-wireless-microsd-module-for-mojo-☆★►useful-info-on-1st-page-◄★☆.831347/page-34#post-13161612 put forth a few arguments that the Poly could be noisy in itself and effect SQ negatively. I have not seen a rebuttal to that. Has anyone?
- more expensive than (a) by ~ 300$.
- a little less compact than (a) because of an additional unit

My criteria are (from important to not so important but still relevant): Audible sound quality, compactness (I live in hotels mostly), price.

Regards poly using optical, according to roon, it says it’s using a usb aspect. So I think it’s not using optical - otherwise how would it play dsd etc.. only know a little so could have it wrong.

 

[Mython]

 

[majo123]

I use a opus1 with optical to mojo and also a cayin n3 coax to mojo , I have to say I prefer the opus1 optical to mojo although the cayin n3 coax to mojo does come close its not quite as clean sounding to my ears.
The opus 1 is a great optical source to the mojo with dual card slots and also a great dap on its own too, going for about 250 dollars at musicteck.

 

[miketlse]

In https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-2385#post-14145488 you mention a critique by @Mojo ideas

Here is one of the replies by JF regarding RFI.
If he was wrong, then people would now be saying that Mojo/poly results in degraded sound, but people are posting the opposite, for example.

 

[haduel]

I guess you are implying that the optical is a dummy?

I just can remember where I read that the Poly connects to the Mojo via optical but I consider that false now given all of your opposite convictions.

 

[Mython]

I guess you are implying that the optical is a dummy?

I just can remember where I read that the Poly connects to the Mojo via optical but I consider that false now given all of your opposite convictions.

Mojo connects to Poly via USB

Here are a few posts from the Poly thread:

An add on product that has been designed to mate with the original unit must actually do that It seemed logical to connect via the active HD USB and also to feed through the charging feed USB so that both units can be charged at the same time the outer two bosses are there only for lateral stability protecting both of the USBs. The connection works very well.

We've repeatedly tested this connecting and disconnecting the connection between the two units thousands of times. It's is very stable having two extremely strong carbon reenforced locating bosses that fit into the optical and minijack connectors this stabilises the two USB connectors and Poly also cups the Mojo further enhancing the connection

Because we are turning the Poly on and off by interrogating the USB input on the Mojo this is done by a tiny additional microprocessor this measures many parameters of the USB in Mojo

 

[daberti]

Elsewhere there are people saying that Chord DACs convert DSD internally to PCM.
Does this hold true?

Thanks

 

[paulgc]

I guess you are implying that the optical is a dummy?

I just can remember where I read that the Poly connects to the Mojo via optical but I consider that false now given all of your opposite convictions.

Optical and Coax assist supporting the PHYSICAL connection only. Taking strain off the Micro USBs.

 

[Mython]

Elsewhere there are people saying that Chord DACs convert DSD internally to PCM.
Does this hold true?

Thanks

I'm not absolutely 100% certain, but I'm 99.5% sure Mojo handles DSD exactly the same way Hugo1 does.

On that basis, you might find the following post of interest:


https://www.head-fi.org/threads/chord-hugo.702787/page-166#post-10494245



Hope this helps!

 

[daberti]

I'm not absolutely 100% certain, but I'm 99.5% sure Mojo handles DSD exactly the same way Hugo1 does.

On that basis, you might find the following post of interest:


https://www.head-fi.org/threads/chord-hugo.702787/page-166#post-10494245



Hope this helps!

The link to Hugo you kindly pointed me to HUGELY helped me.
Rob says "..in Hugo, we have a potentially much more serious problem with DSD, as Hugo has to do volume control and cross-feed EQ. This means it has to be converted to PCM.......".
Volume control is called into play also for Mojo (not cross-feed EQ though, which ain't there in first place).
So...yes, I'm 99.5% sure (until Rob corrects me of course) the DSD is DoP delivered to Mojo who (as well as Hugo) internally converts it to PCM.

Thanks again Mython, you gained a like

 

[stevedlu]

Imac's have a high quality spdif optical out built in to the headphone jack. Surprisingly the on board dac is not low quality by any means but of course cannot compete with mojo. It's optical out does in my opinion rival any convertor.

Actually they don't anymore. I bought a '17 iMac assuming it did. NOPE. Using a OWC Thunderbolt3 Dock Optical out now. Not a high quality spdif chipset...thankfully Chord DACs reclock spdif and it doesn't matter.

 

[x RELIC x]

So...yes, I'm 99.5% sure (until Rob corrects me of course) the DSD is DoP delivered to Mojo who (as well as Hugo) internally converts it to PCM.

Based on the part I quoted you should be aware that DoP has absolutely nothing to do with converting DSD to PCM. DoP (DSD over PCM) is a means of transmitting DSD without drivers (which is called Native DSD). There is absolutely no difference in the DSD bits played between the (poorly) named Native DSD and DoP. Any conversion, if Rob confirms there is conversion, is seperate and not representative of DoP at all.

If you already surmised this then please disregard my reply.

 

[musickid]

Mine was a late 2013. Think they stopped optical around 2016.

 

[daberti]

Based on the part I quoted you should be aware that DoP has absolutely nothing to do with converting DSD to PCM. DoP (DSD over PCM) is a means of transmitting DSD without drivers (which is called Native DSD). There is absolutely no difference in the DSD bits played between the (poorly) named Native DSD and DoP. Any conversion, if Rob confirms there is conversion, is seperate and not representative of DoP at all.

If you already surmised this then please disregard my reply.

RELIC, that was exactly what I meant to say. I.e.: Player=>DoP encapsulation (notably by means of DoP Standard 1.0 with 0xFA / 0x05 markers)=>Mojo.

I think that basing on what I wrote and/or reported above there's little space for doubts: ".....This means it has to be converted to PCM" (per Rob's own words).

 

[435279]

Why does it matter if DSD is converted to PCM if its done correctly? They are just two different ways of representing the same digital data, the content would be identical.