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.