new amp

[Jack Bruce]

I am planning to make a new amp and I need feedback on my design.
my amp is intended for a small sub-woofer.
I have attached a schematic below.

[AndrewT]

Hi,
the 26r (or 27r?) on the output seems a little high.
And you should add the other half of the Thiele network to the the output so that the amp sees a high frequency load.

The passive single pole low pass filter seems a bit unusual.

It will let through much of the audio signal.
In fact the signal out of the sub will be quite intelligible the way you have shown it.

[Jack Bruce]

thanks for the reply. I am new at this.

do you have a link to a good crossover?

[Jack Bruce]

I am not sure what wattage the second output resistor needs.
here is an updated diagram.

[davidlzimmer]

I have to agree with AndrewT about the passive crossover. I messed with them for quite awhile and never got rid of the spikes they allowed to pass.

Also, I just built a sub amp using an LM3886 and with the below active crossover, the thing peforms way past my expectations.

Edit: Your schematic does not show the mute resistor.

Concider this.

[Jack Bruce]

I do not plan to use the mute .

thanks for the active x-over diagram though.

[Greg Erskine]

Originally posted by Jack Bruce
I do not plan to use the mute.

You don't have an option, it has to be connected. Leave the switch out.

[Jack Bruce]

ok thanks.

[Jack Bruce]

would this work for a low frequency output?

the capacitor is a .1 uf

[Jack Bruce]

my new sub-woofer amp works.

8 inch sub
50 watt trafo
adjustable gain
8200 uF filter capacitors