[ginetto61]

  Hi guys,
Just a short follow-up on SQ stock MX-U8 ...
Stock MX-U8 sounds a lot better than stock U12.
We will see if U12 still can hold first place if MX-U8 is modded the same way I did with U12.
 
To be continued,,,,,,
 

Hi !  thanks a lot !
Bought one now ...
 
just to add that i was not completely satisfied with the stock U12.
I found it better anyway using a usb power supply that isolates it from the pc and provide cleaner power
So i think that some of the pc noise can "contaminate" the unit through the usb port
A very tawdry design flaw indeed ... with just a little more care that unit could be much much better
with almost no cost added .. just a connection on the pcb should work
(but i am not a designer so i would not dare to mess with the internals)
 
A usb to spdif converter that does not provide usb isolation is deficient by design
 
i have first a technical question about the MX-U8
Do you know if the usb input is isolated from the pc power ?
Anyway as i said at the beginning i bought one because i understand that even stock is better.
 
I have come to the conclusion that the usb to spdif conversion can make or break the sound indeed.
With a good converter just any decent pc and dac can give nice sounds indeed.
I will read your reports with the greatest interest.
Thanks a lot and keep us posted on your findings
Kind regards,  gino

 

[Jamiee]

My experience with the MX-U8 so far is that it does NOT require 5V USB power to operate.
 
I confirmed this using my Light Harmonic "Lightspeed" USB cable (separate data and power leads) by disconnecting the power lead from the PC's USB port (Actually a JCAT USB card fed by JCAT Battery PSU).  The MX-U8 continued to run without problem.

 

[ginetto61]

  My experience with the MX-U8 so far is that it does NOT require 5V USB power to operate.
 
I confirmed this using my Light Harmonic "Lightspeed" USB cable (separate data and power leads) by disconnecting the power lead from the PC's USB port (Actually a JCAT USB card fed by JCAT Battery PSU).  The MX-U8 continued to run without problem.

 
Hi and thanks a lot indeed.
 
This "feature" is an extremely good news and tells me that the unit has been designed very well indeed
The evil is in the details (that only details sometimes are not)
 
This is for me the very 1st requirement for a usb to spdif interface, isolation from the pc power.
The 1st thing i learned is how dirty is the power inside the pc.  So isolation is fundamental.
I could have done this also with a pci to toslink card ... maybe.
I am sincerely crossing my fingers on this ... it could be a decisive upgrade of my system this very nice unit.
I have carried out some tests and the usb to spdif converter can make a huge difference in sound really.
The U12 with a usb power supply is good.  I did not allow it to break in properly.
Maybe is much better than what i used to think.
But seriously i am excited and i am waiting to receive the MX-U8.
It could solve all my issues with the sound from the PC
Thanks a lot again,  gino

 

[pakultra]

Update on U12 USB power isolation mod:
 
I just did these to get my U12 completely and safely isolated from usb power:
 
1) Desoldered USB B socket and flush cut its Vcc and ground pins, covered them with insulation tape and then re-soldered it . This makes sure that U12 is safe to work with regular USB cable too;
 
2) Removed relay to cut off the 80 mA dc current running through U12's board to minimize power pollution as well as to save 0.5 watt power consumption per hour;
 
3) Replaced my diode with a 470k pullup resistor to further reduce XMOS's vcc input current consumption. A 820k resistor didn't work. Based on this I estimate that Vcc pin is consuming about 2 uA now. I am still waiting for a firmware update to make this pullup resistor redundant and to cut that 2uA consumption to 0 uA.
 
After these mods, the last bit of fatigue from my system is Gone! I didn't know that even 80 mA dc current running through the board can make the system less quite.

 

[Sonic Defender]

If I want to get an MX-U8, is there a ready made USB cable that will connect it to my laptop that only does data, not power? It sounds like there would be an advantage to not passing the power signal into the converter. Thanks for any suggestions.

 

[ginetto61]

Originally Posted by pakultra /img/forum/go_quote.gif
Update on U12 USB power isolation mod:
I just did these to get my U12 completely and safely isolated from usb power:
1) Desoldered USB B socket and flush cut its Vcc and ground pins, covered them with insulation tape and then re-soldered it . This makes sure that U12 is safe to work with regular USB cable too.

 
Hi and sorry but in this way it will not work.  I used the cable in the pic below that disconnects the usb power lines from the pc and the U12 did not switch on. It did not wake up let's say.   
To make the unit work i had to connect this special cable to the usb power supply also shown in the picture in the background . It is a Teradak U9.
 

 

 
2) Removed relay to cut off the 80 mA dc current running through U12's board to minimize power pollution as well as to save 0.5 watt power consumption per hour;

After the removal i have to make some jumpers ? some connection or the unit is working without problem without the relay ?
Moreover i have noticed that many high end digital units with toroidal transformer have a mains filter before the toroid like this Bricasti M1.
 

 
Could this filter be beneficial also with the Gustard ?
Thanks a lot again,  gino 

 

[Sonic Defender]

Wouldn't the MX-U8 simply ignore the power from the computer USB anyway meaning I can just continue using my current cheap USB cable with the U8? I'm not a believer in cables for the most part so using a super cheap printer USB cable has always worked for me.

 

[pakultra]

 

Originally Posted by pakultra /img/forum/go_quote.gif
Update on U12 USB power isolation mod:
I just did these to get my U12 completely and safely isolated from usb power:
1) Desoldered USB B socket and flush cut its Vcc and ground pins, covered them with insulation tape and then re-soldered it . This makes sure that U12 is safe to work with regular USB cable too.

 
Hi and sorry but in this way it will not work.  I used the cable in the pic below that disconnects the usb power lines from the pc and the U12 did not switch on. It did not wake up let's say.   
To make the unit work i had to connect this special cable to the usb power supply also shown in the picture in the background . It is a Teradak U9.
 

 

 
2) Removed relay to cut off the 80 mA dc current running through U12's board to minimize power pollution as well as to save 0.5 watt power consumption per hour;

After the removal i have to make some jumpers ? some connection or the unit is working without problem without the relay ?
Moreover i have noticed that many high end digital units with toroidal transformer have a mains filter before the toroid like this Bricasti M1.
 

 
Could this filter be beneficial also with the Gustard ?
Thanks a lot again,  gino 

 
@Gino Sorry I didn't write it clearly. My update was based on what I already did in post #1480 on page 99. In post #1480, I wrote about Steps 1, 2 and 3 to mod U12. This update can be regarded as steps 4, 5 and 6.
 
A main's filter is always good. But there is no room to add one inside U12. 
 
 
Cheers

 
pakultra

 

[Gino]

Please use proper forum nickname when addressing people with @. I get email prompts that aren't meant for me. Thanks.

 

[pakultra]

  Please use proper forum nickname when addressing people with @. I get email prompts that aren't meant for me. Thanks.

Sorry, my mistake...

 

[ginetto61]

    @Gino Sorry I didn't write it clearly. My update was based on what I already did in post #1480 on page 99. In post #1480, I wrote about Steps 1, 2 and 3 to mod U12. This update can be regarded as steps 4, 5 and 6.
A main's filter is always good. But there is no room to add one inside U12. 
 
Cheers

 
pakultra

 
Hi Pakultra !  thanks a lot for the very kind and valuable reply
People in Gustard should hire you as a consultant/beta tester.  
Many basically really good project/design like the U12 could be even better with just some more attention to details (that sometimes impact functionality and performance)
I think that one of the basic requirements for a usb to spdif converter is that it should provide isolation from the pc power.
Lately someone told me about also noise in the data lines .. but this is less detrimental (i hope).
Anyway i would love to modify my unit but i am worried to damage it. I am still undecided.  
You did a really great job and the outcome shows. 
You are right about the lack of space inside. This is unfortunate.
I like to peep inside units and i see two things in the best digital units, in some of them at least.

• transformer with separate primary and secondary (i.e. not toroidals)
• rf mains filter at the input

 
just to show this is the type of transformer that i would like to see in a digital unit, with primary and secondary windings separated
 

 
I don'y know why it is labelled " Signal transformer" ... this is a mains transformer
However this kind of transformers  usually provides a very good filtering effect on HF noise coming from the mains. 
The toroidals tend to let everything pass through .... this HF/RF noise has very bad effects with digital.  
Much less with analog and there toroidals are just fine. 
The quality of power supply is fundamental. 
At the point that i would try even batteries with this units that generate the clock (even if to be perfectly honest the Apogee Big Ben, a very good clock generator,
has a high quality SMPS 

 ... so maybe i am overestimating things)
So if instead a toroidal is used i see often, but not always, a RF filter before it. 
This below is a dac from Weiss ... another great brand indeed. 
You can spot a mains filter on the upper right corner ..
 

 
Thanks a lot again.  Kind regards,  gino

 

[pakultra]

 

    @Gino Sorry I didn't write it clearly. My update was based on what I already did in post #1480 on page 99. In post #1480, I wrote about Steps 1, 2 and 3 to mod U12. This update can be regarded as steps 4, 5 and 6.
A main's filter is always good. But there is no room to add one inside U12. 
 
Cheers

 
pakultra

 
Hi Pakultra !  thanks a lot for the very kind and valuable reply
People in Gustard should hire you as a consultant/beta tester.  
Many basically really good project/design like the U12 could be even better with just some more attention to details (that sometimes impact functionality and performance)
I think that one of the basic requirements for a usb to spdif converter is that it should provide isolation from the pc power.
Lately someone told me about also noise in the data lines .. but this is less detrimental (i hope).
Anyway i would love to modify my unit but i am worried to damage it. I am still undecided.  
You did a really great job and the outcome shows. 
You are right about the lack of space inside. This is unfortunate.
I like to peep inside units and i see two things in the best digital units, in some of them at least.

• transformer with separate primary and secondary (i.e. not toroidals)
• rf mains filter at the input

 
just to show this is the type of transformer that i would like to see in a digital unit, with primary and secondary windings separated
 

 
I don'y know why it is labelled " Signal transformer" ... this is a mains transformer
However this kind of transformers  usually provides a very good filtering effect on HF noise coming from the mains. 
The toroidals tend to let everything pass through .... this HF/RF noise has very bad effects with digital.  
Much less with analog and there toroidals are just fine. 
The quality of power supply is fundamental. 
At the point that i would try even batteries with this units that generate the clock (even if to be perfectly honest the Apogee Big Ben, a very good clock generator,
has a high quality SMPS 

 ... so maybe i am overestimating things)
So if instead a toroidal is used i see often, but not always, a RF filter before it. 
This below is a dac from Weiss ... another great brand indeed. 
You can spot a mains filter on the upper right corner ..
 

 
Thanks a lot again.  Kind regards,  gino

@ginetto61 You are most welcome

  I fully agree with you on the transformer choice and the need of a filter for better power supply. However, the separate winding transformers have more leakage and they need to be placed further away from sensitive circuits, in the case of U12, that means they have to be put outside the U12 case. I already have a Blue Circle Audio mains filter, so once my U12 is isolated from PC, it is very quite and non-fatiguing.
 
Unfortunately, modding is always a little risky. The other day when I was trying to remove the relay, the board became so hot that the bypass ceramic capacitor right beside the relay dropped off to my desk! This surprised me. Luckily, the relay did come off almost at the same time, so I still considered it a success. That specific capacitor was useless anyhow since I bypassed the relay. Still, I carefully picked it up and soldered it back just to make the board look as original as possible. lol 
 
If you ever decide to mod your board, I'd be glad to help as much as I can.
 
I already have a 0.8uv power supply kit at hand. This kit has a good Murata hybrid mains filter that rejects both common and differential noises. I am expecting my R-core transformer to arrive anytime now. Once I get it, I will build an external power supply for my U12, with separate 5+ and 3.3+ outputs. 
 
Cheers
 
pakultra

 

 

[ginetto61]

@ginetto61 You are most welcome

  I fully agree with you on the transformer choice and the need of a filter for better power supply.
However, the separate winding transformers have more leakage and they need to be placed further away from sensitive circuits, in the case of U12, that means they have to be put outside the U12 case.
 

 
Hi and thanks a lot again. You are right. The unit that have that kind of transformer are usually full size and the trans itself is placed far away from the circuits.   The EMI emission is stronger than with toroids.
Actually the space in the U12 is very limited and toroids are the best choice ...​

 
I already have a Blue Circle Audio mains filter, so once my U12 is isolated from PC, it is very quite and non-fatiguing. 

 
i think that this is more than enough indeed.  Great brand Blue Circle Audio ... not so famous in EU but i read a lot about their products and their beautiful sound. 
Which specific model do you have ?  i am thinking about this option.  Or at least a in line filter for the converter, assuming that the dac being pro is already better isolated, 
 

Unfortunately, modding is always a little risky. The other day when I was trying to remove the relay, the board became so hot that the bypass ceramic capacitor right beside the relay dropped off to my desk! This surprised me. Luckily, the relay did come off almost at the same time, so I still considered it a success. That specific capacitor was useless anyhow since I bypassed the relay. Still, I carefully picked it up and soldered it back just to make the board look as original as possible. lol 
If you ever decide to mod your board, I'd be glad to help as much as I can.
I already have a 0.8uv power supply kit at hand. This kit has a good Murata hybrid mains filter that rejects both common and differential noises. I am expecting my R-core transformer to arrive anytime now.
Once I get it, I will build an external power supply for my U12, with separate 5+ and 3.3+ outputs. 
Cheers
pakultra

 

 
thanks a lot again for your kind offer.  But it is a little too far from me.  I have to learn some basic first.
Anyway my late discover of the Teradak U9 usb power supply has given me confidence to get a decent sound. 
Now it is still a little harsh but more musical.  Also the components are still quite new. 
For the future i would like to take out the U12 internals and put them in a bigger box maybe with a different transformer 

 (sorry it is an obsession now) and with your mods on the usb port.
I really do not know why they did not think to this.  For instance i have a Cambridge Audio Dacmagic and it works also with a data only usb cable
So this means to me that the usb input is isolated. I found it quite ok but a little flat.  I read that a better transformer could be beneficial.
Thanks a lot again.  
Regards,  gino   

 

[pakultra]

I am using The PLC FX-2  (six outlet model) from Blue Circle Audio:
 

 
http://www.bluecircle.com/page151.html
 
Not fancy but very functional.
 
Cheers

 
pakultra

 

[Sonic Defender]

@pakultra, how expensive was the FX-2? I live about two hours away from where they make the Blue Circle gear, but they are slow to return calls! Thanks brother.