Topic: powering the USBPre 2 with Eneloop cells (for iPad usage)

[todoke]

Hey Guys!

First: I'm now succesfully using 8 Eneloop cells to power the USBPre 2.
That's quite easy, I connect 4 in series (there are battery holders for exactly that), do that twice and then connect the two packs of four in parallel.
They're rated at 1.2V and what I'm measuring at the end of the whole package is 5.03V, which is great, since it's within the 5.0 +- 0.25 V that are specified by the USB standard.
I haven't done much testing yet, but since their voltage almost doesn't decrease until they're close to be empty and only then rapidly falls, they should be fine for a lot of applications. Remark: I couldn't test it with phantom power on, yet. (because I don't have any condensor mics here at the moment).


Second: Now I'd like to connect the USBPre 2 to the iPad through the "Camera Connector".
With an USB hub this works; without a hub it (of course) doesn't work.
Unfortunately it also doesn't work with my DIY battery pack.
The iPad complains that the device draws to much power when I'm attaching it.
I went further and cut the two power wires going to the iPad, so only the two data lines were connected, but still, it kept complaining.
This, while the USBPre is up and running nicely on battery power.

So what's the problem?
How to make the iPad accept the autonomously powered USBPre 2?

I'd greatly appreciate some help to get this fine combo working!

[kirk97132]

Hey Guys!

First: I'm now succesfully using 8 Eneloop cells to power the USBPre 2.
That's quite easy, I connect 4 in series (there are battery holders for exactly that), do that twice and then connect the two packs of four in parallel.
They're rated at 1.2V and what I'm measuring at the end of the whole package is 5.03V, which is great, since it's within the 5.0 +- 0.25 V that are specified by the USB standard.
I haven't done much testing yet, but since their voltage almost doesn't decrease until they're close to be empty and only then rapidly falls, they should be fine for a lot of applications. Remark: I couldn't test it with phantom power on, yet. (because I don't have any condensor mics here at the moment).


Second: Now I'd like to connect the USBPre 2 to the iPad through the "Camera Connector".
With an USB hub this works; without a hub it (of course) doesn't work.
Unfortunately it also doesn't work with my DIY battery pack.
The iPad complains that the device draws to much power when I'm attaching it.
I went further and cut the two power wires going to the iPad, so only the two data lines were connected, but still, it kept complaining.
This, while the USBPre is up and running nicely on battery power.

So what's the problem?
How to make the iPad accept the autonomously powered USBPre 2?

I'd greatly appreciate some help to get this fine combo working!

Could you explain what you are trying to do with the iPAD?  Are you just trying to power both?  OR are you trying to send signal to the iPAD?

[todoke]

Could you explain what you are trying to do with the iPAD?  Are you just trying to power both?  OR are you trying to send signal to the iPAD?

I'm trying to send signal to the iPad (and from the iPad to the USBPre 2). I'm not trying to power the iPad. Its battery is large enough.

[todoke]

With further googling it seems that independently of the actual power drawn, each connected device declares it's power draw upon connecting and that's what prevents the iPad from accepting the connection, since it declares to use more then 20mA that the iPad allows to provide.
The only solution seems to be to put a hub in between. Interestingly even unpowered hubs seem to work.
I ordered a small, unpowered hub and I'll let you know if it works when I get it.

[todoke]

It's working!
iPad -> Camera Connection Kit -> a small passive "Dr. Bott T3Hub" -> an opened USB cable with the battery pack attached -> USBPre 2

The cable with the battery pack is on the (+) and (-) wires of the USBPre 2 side only, I didn't reconnect the (+) wire going to the iPad.
But I doesn't seem to make a difference, I just wanted to be sure the USBPre 2 can't drain the iPad's battery.
Without a battery it doesn't work. So the hub alone can't fool the iPad into delivering a lot of current,
but at least it can trick the iPad into not refusing service to a device that doesn't draw any current.

I'm quite happy with this setup! Much better playback quality and great recording capabilities.

[cd2go]

I'm quite happy with this setup! Much better playback quality and great recording capabilities.

What software do you use to record to the ipad?

[Popmarter]

Hmmm... interesting. Do you have some pics? Do you think this works with mixpre-d?

[todoke]

What software do you use to record to the ipad?

Currently "Pocket Wavepad HD", but I haven't done any recording, besides testing, yet.
Can't recommend it yet, but it's free, so you can try and see.
If you know other programs, please let me know.


@popmarter:
I don't know the mixpre-d, I thought it has internal batteries. But this cabling should work with other USB devices that work with the iPad.
Basically I expect it to work with devices that would also work with a powered hub.