exaU2I - Multi-Channel Asynchronous USB to I2S Interface

[RayCtech]

Originally Posted by rsdio

I'm sure there are ways to break a USB device by messing around with power, though, which is why I pointed out that you're not going to gain any improvement to your analog sound by screwing around with the digital supply.

Is this something you have learned, been told or have you experienced it by yourself ?

[RayCtech]

I have now finished the tweaking of the exaU2I and I can now continue to make a permanent setup.

As there are some problems with attaching pictures at the moment I will make a new post later with the pictures.

First off all: There was indicated previously that it could be a problem to supply the 5 volt to the USB parts.
This caused no problems at all.
To test the robustness of the ASIO driver I pulled the USB cable when playing - cut the PCB trace for the 5 volt from the PC at the USB connector - soldered the wires from the external 5 volt supply and reconnected the USB connector.
I only needed to hit stop and then hit play again :-)

For this evaluation I have used a power supply that have 6 galvanically isolated power supplies with 30.000uF each. Each power supply have its own SiC type diode rectifier bridges.
The transformer are a custom build where I have specified a special core material and all other aspects..
In front of the transformer there are a small PCB with automatic 115 / 230 volt selection, slow start, DC trap, mains filter and option for a remote control relay / circuit with opto coupler interface.

Three of the power supplies goes to the DAC - the DAC are running from LiFEpo4 batteries and are only charged from this power supply.

The 3 remaining power supplies have either a 3.3 volt or a 5 volt two stage JFET regulator after them.

One 3.3 volt JFET regulated supply are connected to and drives the GMR isolators and LVDS transmitters and receivers (supplied through the HDMI cable).

One 3.3 volt JFET regulator supply are connected to and drives the (the exaU2I 3.3 volt regulator are bypassed) FPGA, FIFO and clocks on the exaU2I.
The 1.2 volt regulator on the exaU2I are reworked and supplied from the 3.3 volt and not the 5 volt USB power.

One 5 volt JFET regulator supply are connected to and drives the USB parts.

The 3.3 volt JFET regulators can have a LiFEpo4 battery attached to them.

I have tested with the standard USB driven supply, my own power supply, with battery only and combinations of my power supply and batteries.

I ended up with the same conclusions I got when evaluating the power supply options with the DAC and the internal SD card player:
LiFEpo4 battery with JFET charger / power supply are the best sounding solution.
LiFEpo4 battery alone as the second best.
Standard USB powered supply last..

All power rails on the exaU2I have been tweaked with OSCON 470uF/6volt and polypropylene 10nF/630volt capasitors.

All grounds from the power supplies are galvanically isolated except the 3.3 volt to the FPGA / FIFO / CLOCKS on the exaU2I and the 5 volt to the USB parts as these grounds are connected via the PCB...

Listening results:
When all of the combinations except the USB 5 volt was completed there was still a very small "greyness" to the overall audio quality and a little lack of "body" to voices and instruments, and a very little compression/masking of the transients - not much at all and whatsoever the best audio quality I had heard from a digital setup until I also connected the 5 volt to the USB parts.

The difference from the standard setup of the exaU2I in audio quality are in my setup as big as day and night, but I also know that in many so called High-End setups there may not be possible to hear any significant differences..
I tend to have some Accuphase, Electrocompaniet etc. amplifiers, preamps, CD/DVD players and several sets of branded speakers that I use for evaluation of my custom setup.

There are coming more "lyrics" / informations when I am able to post the pictures...

[AR2]

Ray Tech,

This is an outstanding report. If you would feel sharing, I would be very interested in learning more about your battery/jFet supply. Maybe you already wrote about that, but I maybe missed it, so link would be great. Not to mention schematic of the whole set up, hehe...

[qusp]

Originally Posted by rsdio

You're describing removal of USB power without replacing it, and of course that won't work. It will work if you feed the auxiliary power in on the same lines. How will the receiver know where the 5 V comes from? That's why I said that you should be careful to make sure the voltage is within USB specifications. The idea is that you have to provide the power, but not necessarily the power from the host.

The "pulling high or low in a designated fashion" that you reference is also part of the USB specification, and is how the host determines the speed of the device.

no in fact i am not, i am talking about some receivers, which i quite clearly mentioned probably did not apply here due to the nature of the device, as some effort has already gone into the supplies and it is not a traditional receiver. some bus powered usb-spdif/i2s receivers do indeed use the ground and 5v power lines along with cable impedance and a resistor network to negotiate what speed is to be used and to make sure there is in fact a device there to send data to, replacing it with another 5v supply will do nothing in this circumstance, it will simply wonder where the device it is still connected to has gone. other ways around it may be found of course, but the above is not it

I'm sure there are ways to break a USB device by messing around with power, though, which is why I pointed out that you're not going to gain any improvement to your analog sound by screwing around with the digital supply. Your efforts should be focused on the DAC board analog supply, which is why Mr. exa went to such trouble to isolate the exaU2I from the DAC board.

huh..... who are you talking to?

[analog_sa]

Originally Posted by RayCtech

Standard USB powered supply last..

Many thanks for confirming this. So how does the most tweaked out version compare to the SD card player?

[RayCtech]

Originally Posted by AR2

Ray Tech,

This is an outstanding report. If you would feel sharing, I would be very interested in learning more about your battery/jFet supply. Maybe you already wrote about that, but I maybe missed it, so link would be great. Not to mention schematic of the whole set up, hehe...

When it again will be possible to attach pictures I expect you will see how simple my power supplies and JFET regulators are in construction..
Maybe a schematic are not needed..

I use the best components I can find (as I have evaluated) and even gold plated PCB´s and gold wires as I prefer the audio quality it results in..
With silver wires or copper wires it is not possible to reach the same level of coherence or the black background, but this is my personal opinion and nobody needs to get annoyed or bothered with my preferences :-D

By the way I use Lovoltech LU1014D JFET´s in my regulators even in my class A power amplifiers as they work "full function" with as little as 0.6 to 0.8 voltage drop over them...

[AR2]

Originally Posted by RayCtech

When it again will be possible to attach pictures I expect you will see how simple my power supplies and JFET regulators are in construction..
Maybe a schematic are not needed..

I use the best components I can find (as I have evaluated) and even gold plated PCB´s and gold wires as I prefer the audio quality it results in..
With silver wires or copper wires it is not possible to reach the same level of coherence or the black background, but this is my personal opinion and nobody needs to get annoyed or bothered with my preferences :-D

By the way I use Lovoltech LU1014D JFET´s in my regulators even in my class A power amplifiers as they work "full function" with as little as 0.6 to 0.8 voltage drop over them...

Awesome, I am looking forward. I have a nice stash of Lovotechs, waiting for the good opportunity...

[RayCtech]

Originally Posted by analog_sa

Many thanks for confirming this. So how does the most tweaked out version compare to the SD card player?

I have not used the SD card player after I connected the exaU2I :-)

And as I wrote the tweaked exaU2I are the best digital setup I ever have used until this day...

I am now able to hear (in melodies / records I am very familiar with) a new level of detail and separation and a fundament I until now believed was only possible with analogue recordings...

This is when playing 44.1k/16bit Flac with Foobar2000 and the advanced ASIO driver as the "music" I like best and where I have been able to experience the identical persons AND instruments are live recordings.
I do not much understand how people can evaluate their audio setup when they NOT have had the chance to experience how the records they play are supposed to sound in real life..

All records with higher bit-rates and bit-depths sounds "better" than 44.1k/16bit Flac, but to really be able to evaluate and valuate I prefer the "real thing".

[RayCtech]

Originally Posted by AR2

Awesome, I am looking forward. I have a nice stash of Lovotechs, waiting for the good opportunity...

In the evaluation setup of the exaU2I there are only used silver wires or copper wires as I needed the flexibility and thus to long and insulated wires :-D

[SunRa]

Great report RayCtech, thank you. I am curious alos about your PSU / regulator configuration as I am designing a final AK4396 board. I also own about 25 lovotech devices I bet I won't use in a pass amplifier anymore so maybe they'll find their place in the PSU.

Also I believe I am about to settle the noise problem with the DXD files. Only that I need a 384Khz digital crossover. The foo_xover plugin is not coping. I'll check if Thuneau is supporting these sample rates.