Hello, A little while ago I built myself a passive mixer (some resistors, some switches and a bit of solder). Now I've decided to take this further and build a proper mixer using op-amps. So I have got myself some NE5532 opamps to use. I am trying to build a very simple test circuit using just one op-amp to see if I can get the gain I expect. My first problem was not realising the opamp needed ±12V, so I have now taken an old ATX power supply unit and have connected the +12V and -12V rails to the appropriate Vcc connections. Now I can turn on the power supply and can read ±12V (well, 11.6) across each rail. My problem is that when I power on the 'complete' circuit, the power immediately shorts out. I tried to lower the current by putting a resistor in series to each of the +12V and -12V op-amp supply lines, which stops the supply cutting out, but there's nothing detectable coming out of the opamp output either. My circuit is basically this: hobbyprojects(dot)com/operational_amplifier/setting_opamp_gain.html R1 = 47k R2 = 470k therefore gain should be ~10 R3 = 4.7k and I tried 10k resistors on the input rails. I've also tried a pot on the output so I can adjust the output impedence, but still get nothing. Other relevant bits: input is single channel from headphone jack on my phone, output is to an old laptop speaker - they work when connected together!