cmichnovicz
New member
- Joined
- Aug 5, 2018
- Messages
- 3
Hi all,
I am trying to diagnose some issues with a few channels on an X32 producer and have been really studying the schematic for the X32 preamps as a result. I think I understand what's happening from IC17-B onwards to the right, i.e. a balanced to unbalanced differential amplifier, then a voltage divider (with a switch to lower gain further), and an additional gain stage (with a switch to increase gain via a change in feedback). I am confused about the middle block (the two transistors and IC45A&B). How are these working and how is the gain setting being accomplished? I have some funny feeling that this is a beefed up long-tail pair where the op-amps are supplying current or something, but I can't really wrap my head around it. It seems like there is some fixed gain in this section that is then compensated for by the feedback network of DG411 switches, and by removing sections of the feedback network, the gain can be increased? I just don't really see what the feedback network is actually working on and where that gain is coming from.
Thank you!
I am trying to diagnose some issues with a few channels on an X32 producer and have been really studying the schematic for the X32 preamps as a result. I think I understand what's happening from IC17-B onwards to the right, i.e. a balanced to unbalanced differential amplifier, then a voltage divider (with a switch to lower gain further), and an additional gain stage (with a switch to increase gain via a change in feedback). I am confused about the middle block (the two transistors and IC45A&B). How are these working and how is the gain setting being accomplished? I have some funny feeling that this is a beefed up long-tail pair where the op-amps are supplying current or something, but I can't really wrap my head around it. It seems like there is some fixed gain in this section that is then compensated for by the feedback network of DG411 switches, and by removing sections of the feedback network, the gain can be increased? I just don't really see what the feedback network is actually working on and where that gain is coming from.
Thank you!