MdntTrain wrote:
*So you're suggesting to use an op-amp with about 8x amplification, and on each of its outputs have a 68ohm series resistor... and to ADD a 75ohm parallel (terminator) at monitor side _in addition_ to the monitor's 5k terminator? (On the monitor side, the signal comes in, sees a 5k terminator, then a series 4.7k before entering as the base of a simple 3 stage transistor amplifier controlling the CRT cathodes -- very direct CRT control). Alex, what about on the opamp input side? Won't I need to terminate those at 75ohms?
Not unless it is at the end of a long cable. I assume the amp is close to the source.
Michael gave you much the same answer. I'll just elaborate a bit. The purpose of the line termination is to eliminate the influence of the cable. If the cable is short and the frequency is not very high (as is the case) you can ignore the issue and likely not even notice the difference. That fact that the monitor was designed with the high impedance suggests that it should not be a problem. What I had suggested was the "right solution", not the simple one. That's how a new design for optimum performance would be done. We have both suggested video op-amps. There are even triple such beasts is a single case built for such applications. One problem is that most come in cases with a pitch much lower than the old style 0.1" DIP. If I were you I would start with trying a simple amp build out of 2 complimentary transistors (like 2N2222 and 2N3906) directly coupled and 5 resistors. Plus 2 caps - input and output.
With gratitude, JS