[bikerhifinut]

I have to say if I was contemplating A homebrew Silicon amp I'd go straight to the "Gainclone" chip amp. Very simple as I imagine the clever electronics is in the chip but the ones I have heard sounded just like any other good decently powerful solid state amp. Which is very good.
I'm using a Mitsubishi silicon power amp that was GIVEN to me by the next door neighbour, they were going to chuck it on the recycling! It cleaned up lovely and it sounds pretty darn good to my tired old ears. I have no ideological bias towards vacuum toobs or silicon apart from I find a certain "romance" in an old school valve amp which for me is as good a reason as any.

You say you can't hear a difference between a £5 turntable and a £500 one? dare I say it thats because your £5 used deck would likely have cost the equivalent of £500 in its day and is therefore no mean machine. Also a lot of people don't take the time to set their turnatbles up in respect of a decent vibration free support, levelling and fetting arm and cartridge alignment. You can get really good results from very modest gear if a bit of time is invested getting it working right.
Not surprised your Cambrideg CD sounds better than a PC drive, it only has one job to do, probably has a decent linear power supply or if SMPS it'll have been designed to have low noise etc. I know I'll get pilloried from some sections but I do think the current crop of good well designed and made CD players squeeze a lot more off the much maligned CD than was previously thought possible. I have tried Hi res downloads and I do not feel i am missing out on anything when I listen to old fashioned (!!!) CD. Anyway thats off topic, hope you sort yer hums out, nothing more frustrating.
I'll dig out some circuit diagrams i have lying around for preamps, when you see them you'll think hmmm yep I could have designed those! Do you want tone controls? Theres an update on the baxandall circuit in the 4th ed of morgan jones book.

A.