Hi Ted, thanks for clarifying. Might the phenomenon Jeff’s talking about be the (main) reason for PSA to favour I2S over USB?
Furthermore, I suppose these noise aspects have been eliminated to great extend within the Mk2. Correct? If so, are there any remaining relevant design choices we may look for in selecting the right USB IC, to keep the signal path as clean and transparent as possible?
I was only discussing the USB firmware update port not the USB DAC input. Sorry for the confusion.
Since I have no clue how PS Audio polls the USB drive and if / how many times it looks for changes, I prefer to not leave it in the DAC. I do know when the LED on the thumb drive is lit it is active.
As Jeff says the question was whether keeping the USB memory stick (used for upgrading the software) plugged in all of the time or not affects the overall sound quality. This is independent of the concerns or whether to use of USB or something else as a digital input to the DAC.
I was pointing out that the USB memory stick used for upgrades doesn’t even have to have power when you aren’t upgrading.
We don’t really favor USB over I2S (or the other way around.) We try to make each input work as well as it can. The Mk II USB solution is much quieter than the Mk I USB and much more transparent.
8 Likes
How can the LED on the thumb drive light with no power? Mine lights when I insert it. How often or when does the DAC access the drive?
Thanks!
I don’t know when the UI does what with the thumb drive. It doesn’t have to provide power, it doesn’t need to do the USB heart beat, etc. except when it’s reading/writing the USB stick. By far the majority of the noise with the USB stick is during active writing/reading to/from the stick. On the Mk I I could easily see noise from the digital USB input way down low in the output audio whether using the USB digital input or not, not so much with the Mk II or with the USB memory stick on the Mk II.
3 Likes
OK… So the question is how many times does the USB drive get read over the time it’s inserted.
Looks like I might need to do some testing.
Ether way I don’t think it’s a noise issue we would even hear. I only hear the audio mute and the 8 then 2 LED’s on the digital card light when updating.
FWIW on the MK I I could see the noise from an unused cordless phone in the room with the DAC on the scope better than the changes from using grounding plugs, etc.
Personally these issues are simply balancing convenience of one’s configuration compared to perceived audio quality or the mental stress of things not being perfect. All of us make our own choices here, just like with which IC’s, power cords, isolating footers, etc. to use.
8 Likes
Yes… We could also see noise when the WiFi was active in the MK2. I’m not a fan of radios / transmitters near audio gear.
1 Like
OK… Did some testing and discovered the USB thumb drive is active the whole time it’s plugged in.
The USB drive power LED lights the whole time indicating it is receiving power. I did not even do any firmware updates.
1 Like
That must be the reaction of the jump drive that you are using as I do not see a light on mine when it is idle.
1 Like
That good to know. I checked it with two different drives and measured the 5v pin to confirm.
Let me gather some more drives and do further research.
Thanks
OK… I found a Sansdisk Cruiser that the LED lights then goes out however there is still 5v being supplied to it until I pull it out. It seems like different USB drives use the indicator LED in different ways.
This one only indicates reads / writes and not power. My other two indicate power and also blink when it reads / writes. Ether way power is indeed powering them all when plugged in as I confirmed this with the 5v pin.
I would assume there is no real standard for USB drives and that’s also why some of them have issues when doing firmware updates as other members have reported.
1 Like
Actually, firmware updates for the PST through wi-fi or ethernet are currently active. I got the last one that way. Of course, that was over a year ago …
Yes, I updated the firmware for my PST when I first got it (last summer, I think) via Wi-Fi, which I later turned off.
1 Like
Fascinating. I’m learning more about the various ways to implement status LEDs on USB drives than I’d ever imagined one could know.
In light of what Ted said about the UI not necessarily having to provide power except during active I/O operations, does this not mean that there is always a 5V potential across the pins any time the machine is on? People on this forum have reported varying degrees of immediacy with getting the MK2 to load the images without a power cycle. I don’t know much about USB hardware, but maybe there is always power while polling only occurs occasionally?
All the thumb drives I inserted were powered on the whole time. It’s an easy test if your thumb drive has an indicator LED. Maybe all MK2 units don’t behave the same???
Get your thumb drive ready 
3 Likes
You’ve been here long enough, Jeff! There’s a better than even chance it won’t show up on the 10th. I’ll be happy to eat my words, but history is on my side. 
3 Likes
hi @jkrichards In this option when you connect by cable, why do you indicate connect, update and then disconnect? Is it bad to always leave the network cable connected to the DAC even if it is not used?