I’ve just assembled this amp as illustrated in the manual using components bought from Maplin:-

2x30v toroidal transformer
4k7 potentiometer with switch for input control

I’m using the subwoofer input from my AV amp, but even turned up to the max my subwoofer remains very quiet, accurate but quiet.

Previously, I was driving the sub with one channel of a NAD C350 amp (60 watts per channel), this has been powerful enough to give me ample bass, so I expected this 100w rms unit to perform just as well.

Should I use a preamp for the input or something? I’ve loosely connected wires so far, rather than soldered to test run it, will the soldering make all the difference? Is there something basic I am doing wrong?

Your advice would be greatly appreciated.

4K7 is a very low value for a volume pot. Furthermore, I’m not sure it is connected as it should be.
A switch in an audio line is hmmm, well, not-done.

Thanks for this.

The manual says 47k pot, I thought this was a mistake and meant 4k7. Do I actually need to find a 47k pot?

I’ll at least get something without the switch.

Your advice is greatly appreciated

I’ve tried with a new pot, and even with no pot, it doesn’t seem to make any difference.

Any ideas?

Apparantly, the sub output of your AV is not delivering sufficient output signal to fully drive the VM100.
(VM100 needs 600mV for full output). Check manual of AV amp if this is the case.