[Texasrocker]

You may want to try using a input line matching transformer to get the output signal from your mp3 balanced for max gain into the LPAM xmitter via its high-imp input from the old tonearm cartridge leads. Since most LPAM xmitters work better on the higher range of the band ( for more distance and better audio quality), you could also try subbing in another " fully adjustable " loop stick" type oscillator coil that would allow you to broadcast on a higher ( open in your area) frequency, but then again, other mods would be necessary as for antenna out as well since the orig design fed back into the ac line. AES has the fully adjustable BC Band loopsticks avail for cheap price. The addition of a longwire antenna will also help if you modify it. And also, the addition of a homebrew antenna-matching "pi-network" to feed the antenna output into a outdoor horizontal- "receiving type" antenna, and match the pi-network tuning cap to your broadcasting freq as set in your xmitter will get you max range and performance for LPAM broadcasting!
Unfortunately, using 530- 590 kc for LPAM transmitting is very limited at best for any distance other than across the room in my past experiences. You will need to get the input up to max (without distortion) ... you can add a 500K pot attenuator for input control if you wish for tape-deck/CD player(s) use,( or adjust your mp3 vol control high as possible without distortion) to acheive 100% full output modulation on the AM band. Still, that is a very nice vintage Philco find indeed!Have fun with your new vintage Philco LPAM transmitter!!