I recently bought this amp. It was made by the "International Projector Corporation" Model NP-20 and is built into an old school wooden suitcase with leather corners and metal clasps with a 12" magnavox speaker complete with transformer bolted to the speaker chassis and weird copper mesh speaker grill.
Now, according to the owner from whom I bought the amp, there were a pair of these amps at a local cinema for many years. One day, one of them was stolen and the cinema owner decided to upgrade the sound system altogether and sell the remaining amp. It was then shuffled around/used as a P.A./stored/used by muso's and finally traded to a music and english teacher who sold it to me, as well as two nylon guitars to Keira.
It sounds fantastic: surprisingly loud and articulate, yielding huge tonal changes with small adjustments of any of the knobs. It just oozes character. Strangely, the bass knob controls bass, but the treble knob seems to control the treble and midrange at the same time. The more you crank the volume, the more bass you get, until the whole room vibrates. Really amazing considering it is such an old speaker.
First question: What the hell is this thing?
Second question: What should I look at replacing/checking? Apparently it dates to the 40's. It looks like the tubes are the only things that have ever been replaced. Everything is full of gunk and dust. Reason I ask - the pots crackle like Guy Fawkes day and when I switched it on after leaving it plugged in overnight (but turned off) it made some really loud and strange unstable squeaking feedback type sounds when turned on that only went away after I unplugged the amp. Also, it sounds like a fridge (hummmmm) and I hear something like cracking glass when I switch it off ??? However, I like the unique sound - will the amp's tone change if I change caps?
Help ?
P.S. - what is that ugly little transformer on the right and what on earth is the black stuff that seems to be growing on it? ??? ?
