^ This topic has been discussed
many times here over the years. It is all a little murky, but I have never seen a definitive answer. Like thomasdk7, I have powered mine with an off-the-shelf 9V battery box from Sound Professionals. I have also used an MPS6030 and an MMA6000, both of which also use 9V batteries.
At some point, Jon from Naiant posted (now gone or, at least, not easily findable) that the DPA phantom adaptors had an 8.2V zener in them, which suggests that 8.2V is no problem. Additionally, the MPS6030 manual states, "The DPA MPS series is designed to work as battery power supplies for the entire range of DPA Miniature Microphones. Furthermore, the MPS6001 and MPS6010 will work as 48 V phantom power adapters. The MPS6001 delivers 5 Volts to the microphone voltage supply while the 2-channel power supplies deliver 9 Volts."
I have also asked DPA directly; the service manager in Longmont at the time (2013), said:
These are very good questions, the mic ideally like 8-12V to run. I have seen people use as high as 18V with no problems and as low as 5V. If you get lower than that the mic gets really noisy. Most of our little power supplies put out around 7-8V. Hopes this helps.
On the other hand, Len from Core Sound (I think) said 9V will fry the capsules.
So, in my opinion, 5 - 8.2V sounds like it should be OK. Maybe higher, maybe not...