critterkllr
Well-known member
I'm trying to wrap my brain around input and output impedance of studio gear. I believe I'm understanding most of it. Where I'm confused is on what the best practice is for connecting legacy and modern gear together in a signal chain. As I'm understanding it, some legacy gear expects to see a certain input impedance in order for the transformers to give the most accurate frequency response. I have also read that some gear expects to see a certain load on the output to give the sound that it was designed for. For example, a preamp connected inside a console would sound different if the next stage had an input impedance of 600 ohms, vs connecting straight to a modern interface at 10k. I don't know if this is accurate or not.
I am under the impression that if I want to increase the impedance that I should put two matched resistors in series on the positive and negative signals. If I want to decrease the impedance, I should add a resistor as a shunt between the positive and negative signals, thus having the effect of adding resistance in parallel to the original output impedance.
In order for me to understand this better, here are a few components in my signal chain, some different ways they might be connected and the specs that I could find on them. I have more 600 ohm gear, but am just using the 1176 as a placeholder for all of them. Please correct me if I'm wrong.
Interface (input: 10K ; output: 100 ohm)
EZ1290 preamp (I don't know the output impedance, but have seen that some Neve pre's are about 75 ohm output?)
Hairball 1176 (input: 600ohm ; output 600 ohm)
Passive HPF/LPF combo (requires 600ohm to be connected at input and output)
EZ1290 > Interface - I shouldn't need to change the impedance.
EZ1290 > 1176 > Interface - I should increase the EZ1290's output impedance from 75 ohms to 600 ohms by connecting two 525 ohm resistors in series.
Interface > 1176 > Interface - I should increase the interface's output impedance from 100 ohms to 600 ohms by connecting two 500 ohm resistors in series.
EZ1290 > Filter > 1176 > Interface - I should increase EZ1290's output from 75 to 600 ohms. Since the 1176's input impedance is already 600, I do not need to change it for the filter.
Am I close here?
I am under the impression that if I want to increase the impedance that I should put two matched resistors in series on the positive and negative signals. If I want to decrease the impedance, I should add a resistor as a shunt between the positive and negative signals, thus having the effect of adding resistance in parallel to the original output impedance.
In order for me to understand this better, here are a few components in my signal chain, some different ways they might be connected and the specs that I could find on them. I have more 600 ohm gear, but am just using the 1176 as a placeholder for all of them. Please correct me if I'm wrong.
Interface (input: 10K ; output: 100 ohm)
EZ1290 preamp (I don't know the output impedance, but have seen that some Neve pre's are about 75 ohm output?)
Hairball 1176 (input: 600ohm ; output 600 ohm)
Passive HPF/LPF combo (requires 600ohm to be connected at input and output)
EZ1290 > Interface - I shouldn't need to change the impedance.
EZ1290 > 1176 > Interface - I should increase the EZ1290's output impedance from 75 ohms to 600 ohms by connecting two 525 ohm resistors in series.
Interface > 1176 > Interface - I should increase the interface's output impedance from 100 ohms to 600 ohms by connecting two 500 ohm resistors in series.
EZ1290 > Filter > 1176 > Interface - I should increase EZ1290's output from 75 to 600 ohms. Since the 1176's input impedance is already 600, I do not need to change it for the filter.
Am I close here?