USB DAC isolation ?

[maxlorenz]

Oops! I forgot to post here my findings and posted on -ECdesign's- "Ultimate NOS DAC" thread only...

I have built three units based on Oleg's PCB's from circuitsathome.com and I am using them for USB audio and it works great. Sound is better than ever, more detailed, more dynamic and extended, with better timbre of instruments...real bargain at US$14

I use them with its own power supply which allows to be used as a cable extender.
I used an "audiophile" discrete Vreg but I had some troubles since it wasn't very good regulating when the USB receiver was bus powered due to current demand: to weak.
I suppose part of the good effect comes from isolation itself and part from the better power supply of the isolator compared to that of the source (PC or whatever), because at first, with a wallwart Tx and weak supply capacitance it sounded detailed but thin and when I added a monster supply, the bass, punch and overall fullness of the sound became awesome. Try for yourselves and tell me...

For the bus powered DAC I will try today a plain L7808 supply and then swap it forp a TeddyReg supply and see if the sound changes.

Hi 2A3SET,
Wow, congratulations, though I have to say it looks a little scary from here
I had to use a TVC to get rid of the hum on the main system number 1, due to the multiple sources, TV Cable, DVD, TV set, DAC etc...

Guys, try the chips, it is worth.

Regards,
M

[2A3SET]

I did all the modification designed by ECdesign posted on TDA1541 forum.

48M clock, feed async shift-register reclocker, 1/4 to feed PCM2706.
I2S attenuator and dynamic attenuator for BCK, LED regulator at 5.2V for 1543, LED shunt regulator for 1543 bias at 3.8V as I am using 910R I/V.

Originally Posted by jkeny

Sorry guys, I've nothing to report on the ADUM board as I haven't built it yet - it won't work with high-speed USB so I had no need!

2A3SET, what modification did you apply?

[maxlorenz]

Hi 2A3SET,

I did all the modification designed by ECdesign posted on TDA1541 forum.
48M clock, feed async shift-register reclocker, 1/4 to feed PCM2706.
I2S attenuator and dynamic attenuator for BCK, LED regulator at 5.2V for 1543, LED shunt regulator for 1543 bias at 3.8V as I am using 910R I/V.

Today I bought my Red LEDs for the bias of my many DIDACs.

Cheers,
M

[felis]

Originally Posted by maxlorenz

I suppose part of the good effect comes from isolation itself and part from the better power supply of the isolator compared to that of the source (PC or whatever)

I think there is one other factor - among other things, ADuM4160 performs USB clock recovery for the peripheral side so DAC works off of cleaner clock.

Oleg.

[simmconn]

Originally Posted by felis

I think there is one other factor - among other things, ADuM4160 performs USB clock recovery for the peripheral side so DAC works off of cleaner clock.

Oleg.

You should know that the audio clock has little to do with the USB clock, except in synchronous mode, which is rarely used.

[sk1]

Hi all,

We have an off the shelf USB isolator in a nice little USB stick box, with built in isolated power transfer also. Selling it cheap at USB 2.0 Isolator - Isolated USB

There is no clock recovery in the adum4160 - which is also used in the USB2ISO stick. There will be no extra jitter - the transfer of data is done via magnetic coupling - just introducing a constant delay as 1 hub/wire.

The ground loop noise is removed but the sound quality is the one of the USB DAC. Normal USB sound cards uses a 16bit AC97 compliant sound chip with integrated dacs.

When the USB2ISO module is put between, there is no galvanically connection from PC to amplifier. This also removes the risc of damaging the PC and Amp.

Hope this solves your problems, as it solved mine with 5.1 HD-DTS audio from PC to Surround system.

[jkeny]

Two points:
- ADUM will NOT work with the Hiface USB 2.0 asynch transport but it seems some have reported that it works with the Musiland USB 2.0 asynch transport. Why?
- How much of the reported benefits are due to the external 5V supply that you provide with ADUM, rather than the galvanic isolation? Maxlorenz has hinted at this!

[sk1]

Originally Posted by jkeny

Two points:
- ADUM will NOT work with the Hiface USB 2.0 asynch transport but it seems some have reported that it works with the Musiland USB 2.0 asynch transport. Why?
- How much of the reported benefits are due to the external 5V supply that you provide with ADUM, rather than the galvanic isolation? Maxlorenz has hinted at this!

Hi Jkeny,

Thanx for the info, I will add the results to our support page. The reason is the BUS speed - please note that USB 2.0 does not imply USB bus speed - read more USB2ISO support page.
The Adum4160 is a fullspeed isolator running at 12Mbps=1.5MBps-protocol=1.1MBps. Both USB SPDIF modules run 192KHz*24bit*stereo (1MBps) so they are probably both hispeed 480Mbit. The one using the cypress chip (Musiland) also claims that they do not use the USB clock, which might indicate that the Musiland does? - so both a bandwidth issue and clock issue can be why the Hiface does not work and the Musiland does work with USB2ISO.

[sunil]

Hi,

I was wondering if the USB2ISO can help a situation I'm having, since nobody else has. I have a thread on diy, but heres a summary of the problem.


I have a PC based audio setup (Ubuntu /USB). The USB output feeds a Firestone DAC that goes to an Audiolab preamp. The preamp feeds a Behringer 2310 and from there to the power amps. A subwoofer (Dayton 315 with Oaudio 500) is connected to the pre-out on the preamp.

PC (USB) --> DAC --> Preamp --> Behringer active X/O --> Power-amps

Preamp --> Subwoofer

Pulseaudio is used in Ubuntu and the volume is disabled. The DAC volume is set to ‘shunt’ mode and the pot fixed at 12’o clock.

Most program material plays fine. If there is deep bass and/or the volume is turned up the USB stream gets cut-off and replaced with very loud white noise from the main speakers. Turning the volume on the preamp down stops this. Restarting the audio player in Ubuntu (Audacious) does not bring the music back completely. There’s noise riding on the signal & the audio bit is very feeble.

Switching the amps and DAC off brings it back online, till the next ‘white noise’ break. So far, I’ve been able to play the system without problems if the SUB is switched off completely.

Weird – I don’t know, why – I have no clue. Has anybody seen this before ?
Can somebody please help me understand how to fix it.

Thanks,
Sunil

[Telstar]

This thread needs a bump.

Anyone found 480mbit USB isolators, besides the boxes from Ircon (which costs 800$/€)?