[Walderstorn]

Thanks Alex, i will try that with some wire from power cord and just cut off the black wire and the shielded (still have to see which was is this) and try to do it.

 

[abartels]

  Thanks Alex, i will try that with some wire from power cord and just cut off the black wire and the shielded (still have to see which was is this) and try to do it.

 
Hi Walderstorm,
 
Try to connect wire as pakultra did, AES transformer pin 1 to IEC320 ground as shown in picture pakultra posted, thats the easiest way to do.
 
Regards,
Alex

 

[Walderstorn]

What about the 2 other steps, not needed? one thing is the 1st step, seems very direct to the point but the  other i dont feel confortable to doing it, also because he said my friend could fry pc or the u12 if he by mistake used a normal usb cable.

 

[pakultra]

  Thanks a lot. It's works. I am using Oyaide NEO d+ Class S usb cable with isolated ground, Vcc and shield by...insulating tape! Big sound improvement, much cleaner.@

@Voltot
 
You are most welcome. Glad it worked for you too

 

[ginetto61]

Hi !  what about this USD isolator between the pc and the Gustard ? 
 
http://www.ebay.com/itm/111648127278
 

 
I bought one to try out. 
It has a power plug receptacle marked 6V-24V.  
Any decent PS would be better than the dirty pc usb lines i guess. 
What you think ?
Thanks,  gino 

 

[pakultra]

  @pakultra thank you very much but turned out to be much more complex than i thought it would be, definitely not something im confortable trying. I guess my friend (the owner of the u12) is screwed and he's probably going to sell it, since he finds it (and so do i) awful that they could've ignored this issue when manufacturing, seems like a huge oversight and i dont think a firmware update will be able to fix it.

@Walderstorn I understand how frustrated you and your friend feel about this design feature. I was, like you, also very unhappy and even a bit angry at it too. I was even about to return U12 the first day I received U12 when I found it refused to work with my usual data-only connection. But for me, it is probably more costly and troublesome to return it than to mod it.
 
U12 is originally hardware AND firmware designed Not to work without USB vcc. It's particularly frustrating that other than this design feature, U12 is an excellent piece of device.
 
I am 100% sure that a firmware revision can get rid of the need for step 3). Right now there a instruction in U12 firmware to tell XMOS to check for USB vcc and it tells XMOS to Not start working until Vcc is present. Once this specific Vcc checking instruction is removed in the firmware, XMOS will work regardless of whether Vcc is present. We have asked Gustard to update firmware and Gustard is happy to assist. But their main designer is busy these days, so it can be a few more days before we can hear back from them.
 
@all fellow forum members, do not mod U12 if you don't know the consequences of what you do. You are fully responsible for your own modding. If anything goes wrong, Do not blame me or others for sharing what we've found. Thank you.

 

[pakultra]

 

  Findings on U12 cap values:
 
I replaced my two 2200uf ultra-low impedance (14 mohm) Nichicon caps with two 5600uf ultra-low ESR panasonic FC caps for experiment. To my surprise, the breathtaking imaging is gone. Everything is a little laid back. To make sure I wasn't imagining differences, I put my 2200uf Nichicon back in, the imaging is back. It turns out that the original cap value of 2200uf is pretty optimal.
 
Some people insist that audio sounds better with smaller caps so that the circuit is powered more of the time directly by transformer instead of by capacitors. That's the reason I didn't increase the cap value when I replaced them. My experiments with 5600uf caps confirmed this.

 
Hi pakultra, the downside on modifying audio equipment is that you have to let the replaced components BURN-IN, so, put those Pana's back in and let it them burn-in for at least 100 hours!
You will be surprised what they finally bring you!
 
Cheers

 
Alex 

@Alex thank you for your advice. I will put bigger values back in and let them burn in. I was aware of this burn-in effect but I was just too impatient to wait for a whole week before U12 could sound good again. The effect of replacing original caps with 2200uf Nichicon 14 mohm was instant and immediate. Without a single minute of burn-in, I heard breathtaking imaging. I was expecting the same level of performance from the Pana's... I will order some 4700 uf Nichicon 11 mohm to see if there is a difference between the Nichicon and Pana's.
 
Cheers

 
pakultra

 

[pakultra]

 

 
@Walderstorn,
 
D+ and D- two wire data only connection is working now. No positive, no ground in usb wire, data wire shielding connected at U12 only and disconnected from PC.
 
Here is how I did it:
 
 
:
 

 
 
Warning: Do Not use regular usb cable after these mods. You might damage your U12 or PC if you use regular four wire usb cables. Absolutely no USB Positive connection at any time!
 
Regarding Step 3), please note that we hope Gustard will issue a firmware revision to disable XMOS's Vcc detection function. Once that is done, there will be no need for Step 3. Step 3 connects U12 + 5 with USB  Vcc, which is BAD and Dangerous! Take cautions here.
 
No wiring on the upper side of the pcb:
 

 
I replaced the spdif transformer and 2200 uf caps. There are no hookup wires on this side. U12 still look nice and clean.

 
Nice job pakultra, I didn't took time to measure all of the pins to find groundpin, AES transformer pin 1 is a good find, will remove wire on top and modify to this pin, look cleaner indeed.
 
About relay bypassing, It's a nice find, but I'm not very fond of this mod because of accidental connecting standard usb cable will destroy U12 or usb-port from pc.
 
I tried feeding relay with batterypower, there's no sq improvement in comparrison with feeding relay with usb power, at least, with my usb cable.
 
 
Cheers 

 
Alex

 
Step 2) alone is not dangerous. Regular usb cable will not do any damage at this point. You can still hear relay clicking on with usb power connected and off when disconnected. 
 
But Step 2) is pointless without going further for Step 3), which is dangerous.
 
But we can do a Step 4) to make U12 totally safe with regular USB cables again. I didn't mention Step 4) because so far all steps can be easily reversed and I can return U12 to its original factory condition simply by removing the three connections in steps 1- 3. Step 4 will be a little beyond the point of return.
 
This is what we need to do for Step 4): remove USB socket Vcc connection to the PCB.
 
It can be achieved by simply pulling out the USB positive leg in the socket or by cutting the USB Vcc pinout before it connects to pcb. We will need a hot air rework station or Chipquik pack for desoldering the USB socket so that we can cut the Vcc and negative pinout before we put the socket back in. I don't have a hot air station or a Chipquik pack so I can't do it now.
 
Cheers

 
pakultra

 

[Walderstorn]

Thanks m8. it doesnt pay off to return it right now, so we'll wait and hope for a firmware upgrade.

 

[korn-fi]

   
Step 2) alone is not dangerous. Regular usb cable will not do any damage at this point. You can still hear relay clicking on with usb power connected and off when disconnected. 
 
But Step 2) is pointless without going further for Step 3), which is dangerous.
 
But we can do a Step 4) to make U12 totally safe with regular USB cables again. I didn't mention Step 4) because so far all steps can be easily reversed and I can return U12 to its original factory condition simply by removing the three connections in steps 1- 3. Step 4 will be a little beyond the point of return.
 
This is what we need to do for Step 4): remove USB socket Vcc connection to the PCB.
 
It can be achieved by simply pulling out the USB positive leg in the socket or by cutting the USB Vcc pinout before it connects to pcb. We will need a hot air rework station or Chipquik pack for desoldering the USB socket so that we can cut the Vcc and negative pinout before we put the socket back in. I don't have a hot air station or a Chipquik pack so I can't do it now.
 
Cheers

 
pakultra

I wanna ask  a question :why should do the step 1 ?

 

[b0bb]

  Hi !  what about this USD isolator between the pc and the Gustard ? 
 
http://www.ebay.com/itm/111648127278
 

 
I bought one to try out. 
It has a power plug receptacle marked 6V-24V.  
Any decent PS would be better than the dirty pc usb lines i guess. 
What you think ?
Thanks,  gino 

From the Ebay description : "This module is designed based on ADUM4160, a Full/Low speed 5kV USB isolator."
 
This is USB marketing speak for the low speed stuff so it will not work with 480Mbps USB2.0, if this isolator is used the interface is limited to USB1.1 which limits the audio to a max sample rate of 96kHz.

 

[b0bb]

  @Alex thank you for your advice. I will put bigger values back in and let them burn in. I was aware of this burn-in effect but I was just too impatient to wait for a whole week before U12 could sound good again. The effect of replacing original caps with 2200uf Nichicon 14 mohm was instant and immediate. Without a single minute of burn-in, I heard breathtaking imaging. I was expecting the same level of performance from the Pana's... I will order some 4700 uf Nichicon 11 mohm to see if there is a difference between the Nichicon and Pana's.
 
Cheers

 
pakultra

The Panasonic FCs are an old design and quite laid back. They were quite popular in taming the sound of the delta-sigma DACs in CD Players 10-15 years ago.
 
The present day equivalent to the low impedance Nichicons are the Panasonic FMs. The Panasonic FRs are even lower impedance. They are the equivalents of the Nichicon HE and HW respectively.
 
Agree with abartels, on digital stuff, new caps in my mods take 24-48 hours of continuous operation to settle down.

 

[ginetto61]

  From the Ebay description : "This module is designed based on ADUM4160, a Full/Low speed 5kV USB isolator."
This is USB marketing speak for the low speed stuff so it will not work with 480Mbps USB2.0, if this isolator is used the interface is limited to USB1.1 which limits the audio to a max sample rate of 96kHz.

 
HI thanks a lot for the very helpful advice.
I have to say that 95% of my music collection is on cds ... so it could be still useful for me despite of this important limitation
In the meantime i took out a usb power supply i have at hand, the Teradak U9, and indeed i hear a better sound. 
The sound of instruments stands out more from the background with the Teradak in. I will leave it. 
So it seems that the noise from my pc affects the performance of the Gustard.
I agree with who say that a very good interface should provide also isolation from the pc power lines. 
Unfortunately i do not have the skills to perform the mods proposed here.
Thanks a lot again,  gino 

 

[MINORISUKE]

U12 & MX-U8 on the same PC?
 
Has anybody here tried to install both U12 and MX-U8 on a single PC?
Both should work with the same XMOS driver theoretically.

 

[pakultra]

 

  @Alex thank you for your advice. I will put bigger values back in and let them burn in. I was aware of this burn-in effect but I was just too impatient to wait for a whole week before U12 could sound good again. The effect of replacing original caps with 2200uf Nichicon 14 mohm was instant and immediate. Without a single minute of burn-in, I heard breathtaking imaging. I was expecting the same level of performance from the Pana's... I will order some 4700 uf Nichicon 11 mohm to see if there is a difference between the Nichicon and Pana's.
 
Cheers

 
pakultra

The Panasonic FCs are an old design and quite laid back. They were quite popular in taming the sound of the delta-sigma DACs in CD Players 10-15 years ago.
 
The present day equivalent to the low impedance Nichicons are the Panasonic FMs. The Panasonic FRs are even lower impedance. They are the equivalents of the Nichicon HE and HW respectively.
 
Agree with abartels, on digital stuff, new caps in my mods take 24-48 hours of continuous operation to settle down.

 
@b0bb Thanks. That cleared things up. My 2200 uf caps are Nichicon HW. I will order more Nichicon HW to try.