wwenze, I thought you were saying in this quote that your DAC had it's own power anyway (not powered from USB) & later on you said you just cut the USB power & gnd wires to reduce noise?
Anyway, the link above seems to say gnd is needed - it's a pity as I would have liked to isolate the PC completely.
I still ask how is the opticics done - it's galvanically isolated, I believe - does anybody know?
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USB 2.0 spec section 6.4.2: The GND lead provides a common ground reference between the upstream and downstream ports. The maximum cable length is limited by the voltage drop across the GND lead. Refer to Section 7.2.2 for details. The minimum acceptable wire gauge is calculated assuming the attached device is high power.
According to this article you can also use a chip to isolate usb signals: http://www.analog.com/library/analogDialogue/archives/43-06/USB_isolator.html
According to this article you can also use a chip to isolate usb signals: http://www.analog.com/library/analogDialogue/archives/43-06/USB_isolator.html
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The article points out the AD 'ADuM' isolator chips. These are quite nice. These would be my first guess at something that would work well for USB isolation. They have bidirectional models that provide for a couple of serial data lines. I think they have some that can handle USB edge rates.
Hi.
Here is an interesting article.
http://www.edn.com/article/CA6347257.html
12MBit is pretty much the maximum optical USB can do. This is also what TI told me a while ago.
There is one solution: ICRON Ranger 442 http://www.icron.com/products/usb/usb20_ranger_442_444.php
This one is the only device I am aware of which will handle 480MBit/s. It is USB over IP.
Here is an interesting article.
http://www.edn.com/article/CA6347257.html
12MBit is pretty much the maximum optical USB can do. This is also what TI told me a while ago.
There is one solution: ICRON Ranger 442 http://www.icron.com/products/usb/usb20_ranger_442_444.php
This one is the only device I am aware of which will handle 480MBit/s. It is USB over IP.
If you want to isolate galvanically, use a good transformer, with a proper circuit. What makes you think that an opto circuit sounds better? They usually sound worse.
this isn't digital audio stream in the same sense as s/pdif. It's basically packet data. The OP trying to isolate a USB serial communication stream. Normal transformers won't work for this purpose, as they need to be very high speed to not mess up the digital signals. (which regardless of data rate tend to have fairly fast edges)
The ADuM parts aren't opto-isolators. They are actually very much like tiny little transformers on a chip. (or they actually *are* little transformers) Also with bidirectional buffers built in to each side of the IC. I think they tend to be faster that opto's...
In addition to AD, Silicon Labs (silabs.com) also make some of these style digital isolator. I really think these are the best bet. And since you're isolating the USB stream, they shouldn't crap up the sound any more than uSB already has. -- that is, in the USB path, they should have zero effect on the resulting audio signal - other than that you've now isolated yourself from the computer, which should be a very good thing.
I only skimmed the article. Did give me a thought though. As they are saying with SPI in their example, yuo could isolate the resulting I2S signal before it goes to the DAC chip. (but again there are ADuM parts I think that can do 150Mbit so either way should work)
1. First of all: Nothing "made me think"! --- I am running an Opticis and won't do anything without it. (AFAIK even Wavelength is using it. Ayre runs also optical isolation)
2. See eclectic2k answer. It will still depend on the jitter tolerance of the receiver chip if
the optical transmission and conversion makes things worse.
3. If you run asynchronous (M-Audio Transit) the data/timing quality on the USB link doesn't matter anyhow as long as it stays within the jitter tolerance of the receiver.
4. Ground-loop usually still exists due to shielding if you not go for optical.
5. Through a battery powered receiver (modded Opticis PS ) I can feed BUS powered devices very well -- e.g. my M-Audio Transit is working much better afterwards.
6. I guess you are well aware of the USB-cable discussions at AA, where people spent a couple of hundreds bugs on USB cables to reduce the transmission losses. I don't have that issue at all.
Let us know if you found or if you know or if you've tested by yourself a plug'n play device or a DIY solution based on transformers.
THX
I guess I run a different strategy to what you appear to be doing. I prefer excellent jitter suppression and excellent dacs through spdif, I2S or sdif2 and have equipped myself to do so. I also try to run these into as good a system as possible.
Franky, the discussion about the superiority of I2S is a diversion. It is just as sensitive to cabling and socketry as anything else.
If you go from usb to spdif to an external dac, opto isolation of the 'packets' should not be a factor, when the data is assynchronously transferred and reclocked. Or have I missed something?
Interesting. Now you're switching subjects.
What happened to your idea of isolating USB with transformers?
I had no such idea. I thought you were going from usb to spdif, in which case galvanic isolation can come thru a transformer.
Whay have you been talking about?
Guys, don't kick-off on one
I wanted to see if USB isolation could be achieved with great expense & high speed. fmak, as you know, I'm using one of those Musiland DAC so will be looking at going I2S into a DAC.
In the end you've got the same issues.
1. You don't want to have a ground loop or any other capacitive coupling in place
2. You need to get rid of the buspower
3. You need a high speed link, which manages 24/192
4. You don't want another SPDIF with reclocker and masterclock and ASRC and god-knows-what-else solution. -- "Keep it simple" ( Therefore the ecd SD-card player seems to be the kind of equipment which is IMO going into the right direction )
I know we're cross-posting between the two threads but ec-designs is not for me in a main system (too expensive, too rudimentary, too restrictive) and it doesn't address galvanically isolated USB connection to PC? Peufeu's, ethernet DAC would be more in keeping with what I am about but this is besides the point (and it's dead anyway, by the looks)
Has nobody on DIYA opened up their Opticis & looked inside or sucessfully DIYed a USB galvanic isolation?
Opticis is USB 1.1. This won't work.
Afaik Peufeu gave up on his project. Correct me if I'am wrong.
We can discuss ec-designs SD-card solution over there.
I just brought it up here because it delivers best isolation or better "decoupling" of all ( if battery driven). .
Oh yea, forgot that but how did it work anyway - using optosisolators, transformers, other?
Nobody knows - no communication from him for most of the year then some on Aug 1, then nothing??
the answer:
http://www.circuitsathome.com/mcu/usb/usb-isolator
from a posting by cuibono, here:
http://www.diyaudio.com/forums/showthread.php?p=1927483
http://www.circuitsathome.com/mcu/usb/usb-isolator
from a posting by cuibono, here:
http://www.diyaudio.com/forums/showthread.php?p=1927483
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