Hopefully this is a quick and easy question, instead of using a relay for line level signal switching (on or off) , what would be an appropriate transistor?
Would a general purpose one be good enough?
If you are referring to audio line level, a standard bipolar transistor does not work well for that. You need to use a CMOS transmission gate which will also require a dual plus and minus power supply.
Alternately you can use a transmission gate with a single supply if you capacitively couple the signal and dc offset the signal to 1/2 the supply voltage (5V supply would be more than adequate for this).
in audio signals as curtchow rightly said, it is advicable not to use a relay because it wont last and very slow.even the click sound of the relay makes it useless.
If ur talking about 220 - 240v ac, u can only use a triac only for low current consuming equipments