ADSL modem DC adapter

The other day, when fiddling around trying to connect our new VOIP voice box, my dad fried the power adapter for our ADSL modem. No big deal, turns out the voice box adapter fits it and works – but it’s the wrong voltage and ampage. Either way we needed to replace it, so I went out and bought a new adapter for the electronics shop.
The modem requires a 9v, 1A DC adapter. I got a 9V 1.6A adapter (under the advice that it will regulate the amps) But when I plug it in, the modem turns on, (power, and status) but doesn’t connect (ethernet or phone)
However, the other adapter (we were using temporarily from the voice box) is 12v, 0.5A – and it works perfectly. Both have exactly the same plugs to them, I just can’t figure it out.
Any ideas as to why this is happening?
Answer #1
Go to Dicksmith or something and show them the device.