If your HT receiver has no phono pre amp, you'll need to buy one. Otherwise, you'll not get much sound from the B&O. It's about time to upgrade your table though. When was the last time you bought a new B&O cartridge?

B&O stopped "making" cartridges not long after they stopped building turntables in the late 1980's. I would hestitate to buy a twenty plus year old cartridge since the rubber suspension that holds the cantilever in place is likely to have dried out. Not to knock your table but there are far better tables and cartridges around than B&O ever constructed so I wouldn't take the chance on a cantilever problem. Tables have changed over the last thirty years and they have generally improved. Even the tables that are still around from when you bought yours are better than they were back then.

As I remember the 4002 table requires the older style round bodied cartridge which would be even more of a chance on eBay. Whether you require the round or square bodied cartridges, the B&O tables only accept B&O cartridges. If you haven't changed you cartridge recently, which is unlikely or you would have known the situation with B&O cartridges, you shouldn't be playing your LP's with a worn out stylus. In this case, if the stylus is shot, so is the table. Invest in a new table and cartridge. You'll hear much more music from your discs than you have for the last 30 years. I promise.

Hi
I used to have one of those -- Tis a bit beyond its "Use by" date... I was never happy with the slight lack of acoustic isolation. Even though it is a good sounding deck and very pretty to look at, I think it is one to consign to the museum, with all respect.

Could I recommend - LINN LP12 - Ittok - Troika?

To answer your question if I understand it correctly.
You need to purchase a phono pre amp.
You have more than just a gain issue.
A phono cartridge does not have a flat frequency response and needs a gain stage with a response that is the inverse of the cartridge to provide a flat response.

The cartridge has a "relatively" flat response. It's the original RIAA EQ applied to the cutter head that isn't flat.