Specifications

8x8 and 16x16 VGA / HDTV Matrix Switch with Audio, RS232 & IP Control
7
2.1.1.1 Video Inputs
The video connectors on the basic unit are HD15 female. These are compatible
with PC’s VGA video signal (RGBHV). The Matrix is also compatible with
analog SD or HDTV signals (YPbPr) with resolutions from 480i to 1080p. To
connect these types of signals to the Matrix, HD15 to 3-RCA cables may be
required.
Technical Note about the Video Inputs
The HD15 inputs of the matrix handle only the color and sync signals. EDID
(extended display identification data) is absent. EDID is normally used by the
source PC to read pertinent information from the connected display. This
information includes a list of the resolutions that are supported by the LCD. If
EDID is not implemented, the source PC is unaware of the specific LCD
connected to it. Generally this is not a problem since in the absence of EDID,
most PC’s allow the user to select from a set of default resolutions for output.
Some PC’s may not output any video signal, or only allow limited resolution
settings with the absence of EDID . One way to resolve this is to change the
display settings of the PC to show all modes and not detect Plug and Play
LCD. The procedure for doing this varies depending on the operating system
and the video card in the PC. It is generally found under: Control Panel >
Display Settings > Advanced > Monitor tab.
An alternative method is a hardware solution which does not require any
changes to the PC’s display settings. Black Box manufacturers EDID emulators
that are constructed as simple HD15 pass-through adapters. Inside, they
emulate an LCD’s EDID supporting a wide range of 4x3 and 16x9 PC
resolutions. These EDID emulators are sold separately.
2.1.1.2 Audio Inputs
The audio input on the basic unit uses standard 3.5mm mini-stereo connectors. To
use these with PC audio, standard male-to-male audio extension cables would be
required. To connect from typical TV sources with separate right and left
connectors, 3.5mm male to 2 RCA cables would be needed. For mono audio, then
the tip of the 3.5mm connector (tip=left channel) should be used.
Technical Note about the Audio Inputs
Since the audio inputs are unbalanced (single ended), the ground reference of the
source has to be the same as the matrix. Of course the cable connecting the two is
tying the grounds across but if there are currents flowing in the ground it can create
potential differences that would manifest as noise. The quality of grounding at the
audio source and the matrix are important. For example if the input source is a
desktop PC, as long as the PC is properly grounded and the audio cable length is
not excessive, you can expect good results. On the other hand if the input is a
notebook PC running on battery, there is no ground reference at the source so it gets
its reference through the audio (and video) cable connection to the matrix. This
should also be okay. However if it is plugged in through its external power brick,
noise can be induced. This is because most notebook power supplies do not
properly provide an AC ground path to the system ground (some only have only 2
prong AC cords). The switching power supply circuit will inject noise into the audio
lines. In this case the solution may be to attach a low resistance ground strap to the
notebook. The other option for eliminating the noise is to use a stereo audio Balun
(or isolator). The Balun essentially couples the audio through a transformer so the
audio grounds are isolated. Baluns can also cure noise pickup in long cable runs.