The Apple-firmware AMD/ATI 5000 series and above feature Mini DisplayPort. These ports are capable of producing DVI signal timing instead of Mini DisplayPort timing just by asserting a signal input to the port. Unfortunately, the DVI signal levels produced are marginal for one Single-Link DVI adapter, and dysfunctional for Dual-Link DVI adapters or two adapters. You need signal boosters with ACTIVE signal Re-Driver circuits in them, and they can be costly.
Third-party Single-Link DVI ACTIVE adapters are available for about US$35. Dual-Link DVI ACTIVE adapters (required for displays over 1920 wide) often use a USB lead to pick up even more power from a USB port, and sell for about US$100, the price of the Apple adapter.
thankBut it is strange that it worked a week
I used this
I have two possibilities on the monitor:
vga or hdmi
which is the most economical system?
I just need 2 monitors for pro tools, I do not care about resolution ...
That adapter should be working. It is sold as an ACTIVE adapter, and if it is still working, you should still have a picture... unless something else has gone wrong.
Be skeptical when you seen the "no input signal" message. It should say no useable signal (because the resolution is set too low or too high).
HDMI is a re-wire of DVI, no adaptation required. You can even get a DVI-to-HDMI cable.
VGA is an Analog signal, and will not give you results that are as good as any of the others, which are all Digital.
Sometimes Users display get set to Mirror by accident. This can force the resolution to change on one or more displays, and can sometimes cause the "no input signal" message to pop up.