Finally the amp arrived.
(Attachment Link)
Everything connected fine, plugged together well, and powered up as expected.
The amp has a light around the main dial on the front, which is the volume, and this light gradually changes colour.
The speakers both work!
Although due to lack of space they are a metre and a half behind me. Listening to some familiar music it seems that I have cotton wool in my ears as the sound seems muffled.
The volume goes up reasonably well, but not as high as I'd expect, probably due to the amp.
So at least they work, which was the biggest question. Now to decide whether I want to spend more money to get them to work better, if they even can.
I'm wondering whether the muffledness is because the speakers are behind me on the floor, rather than sitting on the desk in front of me. Or because they are 1.5m behind me instead of 30cm in front of me. Or because they have huge woofers whereas the little Logitech speakers don't. Or because they are aged and inform, whereas the Logitech speakers are only a couple of years old (and the power button is already broken).
Any thoughts
Thanks for all the help so far
I will give you my thoughts.
First, check the connections inside the speaker itself. Be sure all the speakers are properly connected and listen to each speaker in the cabinets and check if they are making sound at all.
I am guessing your midrange/tweeters are not functioning properly and if you play some music, double-check to see if there is any sound coming from them at all. If there is little or no sound, they may need to be repaired because the surrounds are deteriorating. That's normal.
It may even be happening with your woofers too. Check and see if the edges of the speakers are solid. They may be very worn out, and may need to be reconed or replaced.
Since they are not pushing/pulling properly, you will not get good sound at all.
The good news is you don't need to spend an arm and a leg to restore them.
A poor man's solution is using silicone on the surrounds. You need a paintbrush and silicone. It's not a great fix, but it may be something you can try. You apply a thin layer and let it dry.
Hopefully, you will have speakers that work once again, but depending on the damage, they may not work at all. The voice coils may be burned out. If this is the case, you will need to replace the speaker components themselves.
If you find that to be too costly, you might want to look into a new pair of speakers.
Edit: Here is a good example of a midrange and tweeter that could be repaired using the silicone method. I really should just replace them on both speakers. We will see how they turn out.