Mod Dwarf USB Host Power

I have my Dwarf hosting two MIDI devices that require power over USB. The Duo’s host amperage is higher so I was able to host and power these with an unpowered hub. However, I need to power the hub when using these with the Dwarf. But the super weird thing I’ve noticed when doing so is that if I need to restart the Dwarf and I unplug its power connector, it doesn’t fully power off but rather sound stops being processed and the screen, LEDS, buttons and knobs continue to work until I disconnect power from the USB hub. That seems wrong and somewhat scary. I don’t want to damage my Dwarf with a brownout! Is this OK?

Also it seems to confuse the Dwarf as to which MIDI devices are connected and they become unresponsive until I do some combination of restarting the Dwarf/hub and using the WebUI to get everything back up (haven’t figured out a combo that works every time, which I’ll need if I’m on stage and things start acting up). And is there another way to restart the Dwarf without unplugging it or using the WebUI?

UPDATE: It’s this hub that uses a USB A to USB A cable. Tried a different powered hub with a USB A to USB B cable and the Dwarf powers off when I pull its power cable. Seems like I have to use a different hub!

What sucks is that I have this hub that works flawlessly with my Duo but its USB A connector is loose in the Dwarf and therefore only works intermittently (and same problem when I plug it into my laptop). Why can’t these things be standardized for real???


Are you using the original power supply on the Dwarf?
For only two MIDI controllers I wouldn’t say that you need more power than the Dwarf can supply.


Indeed I am using the original Dwarf power supply (with a 2-prong adapter due to loud ground loop noise). But I also tried my Duo adapter with the Dwarf and with either adapter, one or both MIDI controllers intermittently wouldn’t power up. But they’re absolutely fine with an unpowered hub connected to the Duo.


Which MIDI controllers are we talking about? Maybe we need to do some research

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You know, I think the current draw issue might be my Dirtywave M8. It has an internal battery that also charges via USB so I suspect when it’s fully charged, there’s almost no current draw but if the battery starts changing, problems.

I guess at this point my only real concern is that I fry the Dwarf by unplugging its main power while it remains partially powered on via the host connection to the powered hub. If you pros think this isn’t an issue, I’m cool.

And I guess related, it would be very handy to be able to reboot the Dwarf via some system menu option and not have to unplug the power and USB host cable! I mean, I feel like that would be handy for anyone, not just those using a powered hub. Sometimes it’s tricky to reach back there and unplug/replug with all the other cables going in/out!


I would say that yes. I didn’t know the Dirtywave M8 - checked it really quickly and it seems interesting. That screen really looks like it could be the source of the issue.

On this, I would ping @Jan and his expertise :slight_smile:

This one I mapped out :wink: