2 LM3886 BTL advice

[Mark Whitney]

This is an inverting amp configuration. Changing the output by 180 degrees. This could be good or bad depending on the filters and the other amps in your system. To reverse the output you would need to reverse the driver/speaker connections.

 

[Philfr]

Hi Mark,
Thank you for this great comment !
I had not seen it.
So PA100 is an inverting amp too ?
PA100 DIY 2x LM3886 in parallel gainclone audio amplifier
Phil.

 

[AndrewT]

Hi all,...................

Do you see something wrong ?.........

4k5 input impedance !!!
Is the 47k required?
Omitting that would raise the input impedance to 5k, but still very low !

Signal Grounds/Returns mixed up with the Power Grounds.

Is the 220pF and/or the 47pF hanging off the -IN pin a problem?

VA = VC,
when hot or warm or cold?
Or does temperature for the measurement and equality not matter?

No grounding resistor before the input cap.

The input is AC coupled, the NFB route is DC coupled. This gives a mixed AC & DC coupling. Leads to bigger output offsets and bigger drift in output offsets. It also increases the risk of speaker damage.

One commoned Output Zobel may not work.
The Zobel would work better if it is attached to the Output Pin and the Decoupling Ground. This requires an Output Zobel for each chipamp.
Is there a Decoupling Ground?

The next link posted is a non-inverting topology.
If you can't understand that you should NOT be considering a parallel build.

 

[Philfr]

Hi,
Indeed, this schematic has a lot of problems, thank's Andrew..
What do you think about PA100 :

Phil.