I have an old tube amplifier of excellent sound quality. Can I connect a preamplifier or even a modern CD player with integrated circuits at its input without danger of burning each other?
Once the two circuits are isolated from the power grid, that is, the tube amplifier uses a power transformer and the CD player also has its source isolated, just check if the signal from the CD player or another source of signal matches with the amplifier input. This means that the signal must be strong to make the excitation. If not, you may need to use a preamp. Note, however, that these amplifiers have in most cases high input impedances requiring shielded cables to prevent noise.
