Hello, I'm currently building a chip amp based amplifier and want to try measuring distortion with my Scarlett 2i2 gen 4 sound card. I've seen some protection circuits and posts about earlier generation 2i2 but there are still some things I do not fully understand, and I'd hate to blow up my sound card.
First I want to ask about protection. I guess there are 3 things I need to consider:
Another thing I wonder about is the balanced inputs and outputs. The user guide says:
Does this mean that I can choose whatever and it detects what I'm using? If I use a TRS jack, should I if so ground the right channel so the sound card thinks I'm using mono? I'd prefer using mono for simplicity. In this thread https://www.diyaudio.com/community/...r-measurements-whats-next.301166/post-4963930 @wintermute says that it's important for 2i2 gen 1 to atleast output balanced audio, but I'm not sure if it's the same with gen 4.
So, for my protection circuit, Could I simply add another pair of 3v3 zener + 1kR to the inverted output as well going into the linked bal->SE converter, and output that into my amplifier and keep the rest of the protection circuit same if using balanced output?
Last thing, why shouldn't I use speaker out - for line in ground? I know for certain amplifiers the speaker - is not ground, but if it's not ground how do I get accurate/any measurements by putting line in ground on line out ground instead? Since speaker + is referenced to speaker - and not line out gnd? This does not make any sense to me.
First I want to ask about protection. I guess there are 3 things I need to consider:
- Amplifier power rails touching line in or line out.
- I use 60V center tapped to power my chips. From what I understand I can use 2x 3.3v zener diodes to protect from this. Could someone elaborate on this? Why does the 1k resistor take up the load?
- Level too high on line in
- I'll use a simple voltage divider for this so it becomes <1Vrms for my measurement.
- DC on line in.
- First off, isn't line in already AC coupled? and if not, what capacitor should I choose so it doesn't affect my measurements? Should I also put one on line out?
Another thing I wonder about is the balanced inputs and outputs. The user guide says:
Does this mean that I can choose whatever and it detects what I'm using? If I use a TRS jack, should I if so ground the right channel so the sound card thinks I'm using mono? I'd prefer using mono for simplicity. In this thread https://www.diyaudio.com/community/...r-measurements-whats-next.301166/post-4963930 @wintermute says that it's important for 2i2 gen 1 to atleast output balanced audio, but I'm not sure if it's the same with gen 4.
So, for my protection circuit, Could I simply add another pair of 3v3 zener + 1kR to the inverted output as well going into the linked bal->SE converter, and output that into my amplifier and keep the rest of the protection circuit same if using balanced output?
Last thing, why shouldn't I use speaker out - for line in ground? I know for certain amplifiers the speaker - is not ground, but if it's not ground how do I get accurate/any measurements by putting line in ground on line out ground instead? Since speaker + is referenced to speaker - and not line out gnd? This does not make any sense to me.