The Cambridge Audio A1 was a budget amp. They didn't come fitted with the phono preamp boards internally as standard. These were offered as an upgrade option. i.e. if you bought the amp to use with a turntable, then you'd pony up the extra cash to buy the boards and fit them.
Moving Magnet cartridges will put out enough power to make some sound in to a standard Line input (CD, Tuner, AUX, Tape) but the volume will be low and severely lacking in bass. The Phono input boards or an external phono pre-amp will fix both of these problems.
The weak bass is due to RIAA equalisation. The vinyl groove is cut with reduced bass to stop the needle jumping out due to excessive energy. The pre-amp restores a flat frequency response so that bass is as it should be. The low volume is because a cartridge generates a tiny fraction of the output energy compared to the 1-2 volts from a typical Line Level source.
Even with a phono pre-amp, your TV will sound louder. That's just vinyl. But the difference won't be as colossal as it is now. If your TV volume sounds good with the dial at say 10 o'clock, then depending on the cartridge in the Rega arm and the pre-amp being used, I'd expect you'll need to have the dial at 12 o'clock or 1 o'clock to get the same sound level.
Phono pre-amps can run in to the £1,000's, so what I'm about to suggest isn't high-end at all. The Project Phono MM at around £60 is thoroughly decent and a worthy companion to the Rega turntable. The Btech BT26 @ £25-£30 is best left to wannabe DJs and their home decks for scratching. Nothing wrong with Btech products in general, but this one is aimed at a different market than the Hi-Fi turntable user.
Have a look on Ebay too. There's a Project Phono Box MM currently at £23 with a day and a half left to run.
Going for a cheap pre-amp might seem like the sensible option given that you've bought a used TT. The thing to be aware of is that the real low priced jobs don't have as much gain and they're electrically noisier that the better quality branded jobs. What that means is that your amp will be working harder and the signal from the cartridge will be accompanied by more background hiss from the pre-amp. To buy the equivalent of a Planar 3 new now would set you back the thick end of £600. It deserves some decent ancillaries.
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