I'm currently working on developing a very specialised piece of professional audio equipment.
While thinking about the circuits some questions did arise that I have not been able to answer for myself yet.
Basically the device will have several balanced inputs and several balanced outputs. Internally all connections will be
unbalanced - because the device will also have to interface to unbal. equipment - , so I need a BALUN / UNBAL circuit.
For the balanced inputs I chose TI's INA217, because it is easy to use and the datasheet promises excellent properties.
Here's the basic circuit I came up with, basically just what TI say in the datasheet. Pin 1 & 8 are unconnected to give
a gain of 1.
When I apply 1,55V (+6dBu) at the bal. input I suppose I'll also get 1,55V at the unbal. output.
But what would happen if I were to connect the - bal. and the GND line at the input to connect an unbalanced device to it, as is common practice? Would that mean I'd loose 6dB?
I haven't tested any of this yet, it's early days and this just popped into my head.
Also, a very basic question: How do I measure across a balanced line using a mV meter that only has a negative and a positive terminal, e.g. your run-off-the-mill multimeter? I suppose across the hot/cold leg, right?
Same problem, just the other way round: How do I get a signal from my signal generator in? Will I have to make up a circuit to balance the sig. gen's output, or is there an easier way?
Maybe I'm just thinking to complex, that is often my problem
Thanks in advance