I had an old 15 volt power supply to my computer speakers getting pretty crispy. So I bought a new one. Unfortunately it is a switcher and very noisy to these old speakers.I was thinking about installing a filter along these lines.

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I remember reading on these kinds of chokes that polarity matters. Before I build it I was just wanting to get a second opinion.
Parts Capacitor, Choke coil.

 

How much current does the amplifier draw? The filter chokes need to handle that much current.
Do you have large caps that you are not using. You could try just adding more caps and see what happens. It will not be as good but might work.

 

The old power supply was rated for fifteen volts at one amp.

 

What's the new one rated for?

 

The choke/transformer is rated at 1A.
The inductance is listed at 40mH in one place and 40uH in another.
I tried to find the part somewhere different so I can get more information but cannot find it easy.

 

I measured it at forty-four mH each.

 

what is the switcher PSU that you plan on using? all supplies have limit for how much capacitive load they can handle. 20000uF sounds extremely excessive.
old rule of thumb is to use up to 2000uF per amp when filtering rectified mains frequency. switchers operate at much higher frequency (80kHz - 1Mhz). so filtering any remaining ripple should be fine with few smaller caps (meant to handle the frequencies you are trying to filter out).

 

I had an old 15 volt power supply to my computer speakers getting pretty crispy. So I bought a new one. Unfortunately it is a switcher and very noisy to these old speakers.I was thinking about installing a filter along these lines.

View attachment 373075​

I remember reading on these kinds of chokes that polarity matters. Before I build it I was just wanting to get a second opinion.
Parts Capacitor, Choke coil.

Of course, you can use such a filter. But the capacitance is way too high, about 1000uF would be enough. And you should connect ceramic capacitors, around 0.1uF to each of the two electrolytics.
Whether such a filter will be useful, nobody can say for sure.
It could be that the adapter itself isn’t well designed and it might need to be modified. First, you should make sure if the adapter has a mains filter like the one in this post. Secondly, are the HF rectifier diodes shunted with small capacitors (100-1000pF). Third, is there a small capacity (500-2000pF, Y-class) capacitor between the primary and secondary windings of the transformer. But you can only see that by taking the adapter apart, and that's not always that easy

 

What does the noise sound like? Is it whine or buzz?