Buying a Pro-Ject Debut Carbon Phono USB means that you don't need a phono pre-amp. It is already built in to the turntable. The turntable can connect directly to any amplifier with a line level input. These are the sockets on an amp marked as AUX, CD, Tuner, DVD, Line etc. The only socket not suitable on an amp for this turntable is the Phono input.
A conventional Hi-Fi system would comprise of:
1x Project Debut Carbon USB
1x Hi-Fi stereo amplifiers (for source selection, volume control and to power the speakers)
1xpair Hi-Fi speakers
plus interconnect cables and speaker wire.
This type of set-up would potentially be the best quality from that particular turntable.
The signal direct from a turntable cartridge (A.K.A. "the needle") is very low power. It needs boosting and also correcting for bass/treble balance. A Phono Pre-Amp does this. Without a phono preamp you would have to turn the volume up all the way to max just to hear a signal, and the sound would have no bass.
Buying a turntable with a phono preamp built in means you get up and running at minimal cost.
The alternative is to buy a turntable where the phono preamp is either an extra outboard box sitting between the TT and the Hi-Fi amp, or buying a Hi-Fi amp with the phono preamp built in to that. Hi-Fi amps with a pair of sockets marked as the Phono Input are the ones with the phono preamp built in.
Phono preamps range in quality quite widely. Any budget Hi-Fi amp with one built-in will use quite basic circuitry. It will work and it won't sound totally awful. But it will always be a bottleneck on quality. The same is true but to a lesser extent with the built-in phono preamp on the Debut Carbon USB.
Where you'd notice this limit is when it's time to replace or upgrade the cartridge. The one supplied is a £35/$60 Ortofon OM10. It's a decent basic cartridge but you can do better. The nice thing about the Ortofons is the ability to replace just the stylus (the needle bit) rather than the entire cartridge body. You get slightly better bang for your $ buck this way, but the OM20 and OM30 stylii are a massive jump up in price even for the stylus alone. I'd be temped to go for the Ortofon 2M Red at around £80/$130. Anything much better and I think you'd hit the ceiling of what the built-in preamp can handle.
The flip side is convenience. Having a USB output means the ability to hook up to a PC or Mac and archive your vinyl. So in the end it's a choice between ultimate quality with a Debut Carbon + external phono preamp, or good quality + convenience with the Carbon Debut USB with its built-in preamp.
Whichever way you go on the turntable, you'll need an amplifier somewhere in the chain to drive the speakers.
The best music quality without blowing thousands will come from Hi-Fi speakers driven by an external Hi-Fi amplifier. The alternatives are some active monitor speakers where the amp is built in to one speaker. These type are often used for in-studio monitoring but there's a lot of cheap stuff kicking around designed for PC use. They're not in the same league as the studio stuff, so it's definitely true that you get what you pay for.
At the bottom of the quality list are PC speakers. Those sub $100 stereo speaker kits with an "subwoofer" and a pair of desktop cubes really aren't up to it for Hi-Fi. Even the more accomplished Logitech z906 kit (£240/$330) isn't Hi-Fi grade. It's just more boom and tizz for gaming or playing Dubstep really loud.
If this was me putting together a first time system then I'd go with a pair of Dali Zensor 1 speakers, some budget speaker stands, and a Yamaha AS500 amp. Round it off with some reasonable quality speaker cable an interconnects and enjoy.
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