Dual LM3886TF – 2 x LM3886TF on one board

2-Channel LM3886TF

This pcb consists of two LM3886TF amplifiers. With it, you can easily construct a high quality stereo amplifier. Only quality components are used. No ceramics in the signal path. In fact, the input which is often an electrolytic capacitor is a 2.2uF film cap. Feedback cap is a silvered-mica. All resistors are 1% metal film. A bit of a luxury for a chip amp.

The board is fairly compact, measuring only 4.3″ x 1.6″. To keep to this size, the power supply filter caps are not on board. Users have the choice of the PSU20K or their own power supply.

The LM3886TF high input impedance is wonderful but can present issues at times. It can pick up unwanted radio waves. I can attest to this myself because there’s a radio station down my road and I pick up their broadcast. To avoid this problem, I used RF chokes. They are in the feedback path and will not affect the sound. If you live in an area and you are not picking up stray FM broadcast, you can replace the RF chokes with jumper wires. The LM3886TF will function as normal.

One of the benefits of having two chips on one pcb is the ease of bridging. The output of Ch-1 can be directed to the inverting input of Ch-2 via a resistor. For the bridging to work, the non-inverting input of Ch-2 must be grounded. It is a very simple modification. Bear in mind that the speaker must be 8 ohms when in bridge mode and the ground is floating.

Another option is to use two LM3886TF in parallel. The outputs of two LM3886TF are tied together to provide double the power to the speaker. However, a small value resistor must be at the output first.

Lastly, having two LM3886TF is ideal for BI-amping. With one of my crossover boards, one LM3886TF can be assigned for the tweeter while the other for the woofer. This is often done in commercial active speakers.

The Gerber files will be with my board maker soon. Stay tuned.