Matching parts for the bridge connection feature
Matching parts for the bridge connection feature. Click on the pictures to get a larger view.
If you are really sure that you want the bridge connection feature add, R19-R22, C24-C26 and IC6 or IC7, J1-J3. You can skip this and solder those parts when you really need bridge connection. It's very easy to do this afterwards but you should match some resistors first. See below.
If you are planning to use the amp in bridge mode, read this, important:
In order to get maximum performance you should match the resistors so they are alike across the channels. Strive for 0.05-0.2% tolerance. The goal is to get identical gain, the whole idea of bridge connection.
R19, R20
Non-inverting LM3886
R8, R30
R9, R31
R17, R39
R14, R36
Inverting LM3886
R7, R29
R9, R31
This matching procedure is only necessary if you are planning to use the bridge connection feature. It's possible that it's not necessary to match but experience will tell. I will report later.