lm3875 mono blocks design

[BionicSniper]

Ok so I have all the parts picked out. I have the toroids coming and i got the lm3875's for free as I'm a electrical engineering student. I'm getting the boards fabed by advanced circuits for free but I want to make sure theres is nothing i need to change at the last second.

So here is the schmatic for the amp its self



Here is the board for the psu



and here is the board for the cap bank (caps are 100nf poly film, then 1000uf, 2200uf, 3300uf, 2200uf, 1000uf, 100nf poly film)

[pacificblue]

On the cap's PCB there is a small trace missing in the lower left corner.

Do you expect anything in particular from the first increasing and then decreasing capacity values?

[mjf]

hello.
r2=1k and c5=22uf give you a high pass filter around 7hz.
with a 47uf (non polarised) elcap you can get around 4hz......
greetings............

[BionicSniper]

What is a good value for the high pass filter to be? Just that 4k

[mjf]

i think so:
the -3db cutoff frequency should be far away (5times......10times)
from the lowest (bass )frequency you want to hear without attenuation........so 30hz gives you 6hz.........to 3hz and so on.
at least that all depends on your imagination of sounds......
greetings....

[star882]

Putting all the parts on one board will make for easy assembly, but is not always the most optimum for reducing size. Start with approximately what size of enclosure you want and use that to optimize layout of parts. It is often optimum to split the circuit into two boards, with one mounted on top of the other.

[BionicSniper]

I'm custom making all of the cases. The actual amp is very small. The power supply is going to be much larger. I'm waiting to get the toroids to start drawing up the cases. I may split the cap bank in half to reduce size but i still need to get the toroids in hand first. I'm just worried about the amp's schematic

[star882]

I think the DC block capacitor should go on the input instead of the feedback.

[AndrewT]

Originally posted by star882
I think the DC block capacitor should go on the input instead of the feedback.

I think an AC coupled amplifier needs DC blocking caps on both the NFB lower leg and on the input.

A DC coupled amplifier should have neither, but needs other systems to protect the output load from damage.

[AndrewT]

does the chipamp manufacturer have any recommendations for additional circuits to ensure stability and minimising noise and interference?

Do you recognise the difference between signal ground and decoupling ground and power ground and speaker ground and mains ground?