Some help with my Tekefunken radio

[radix39]

I'm trying to get some help in fixing a few small issues with my Opus 7 (I think?). Pretty much everything works great, AM, FM, SW, the eye, all dials, switches, etc. The case is in excellent condition. I've only noticed a few small things:

1.) The bass sounds kind of "farty". Thats the best way I can describe it. Instead of a THUMP for a beat, you'll hear more of a fart sound. Its not too bad, but i'm sure it can be fixed. Only problem is, i'm not sure how. Do I need to replace the tubes? Something else? What kind do I need, and where can I get them? More importantly, how much would they cost?

2.) The unit gets next to no reception unless I short (ie. tie together) these two extenal plugs that come out the back of the unit. I assume these are supposed to plug into an external antenna, but since I don't have that antenna, it gets no reception until I artifically create one by shorting those 2 wires. Am I correct in assuming this? Is this how its supposed to work, or is there something wrong here?

I would like to fix these problems myself, if possible, since I have a lot of fun doing this kind of stuff, and I always love learning new things. But if you guys think its beyond me, maybe you can recommend a good place to get it fixed somewhere here in NYC.

Oh, here's a picture so you can see it too.