Do you just have three wires? +, - and ground? Used an XLR imo, they even make 5 pin XLRs now if you were to have more voltages. For my tube preamp, I am moving the iron to a seperate box and using a 6 pin Amphenol connector but that is because some are high voltage and quite a few secondaries. Amphenol connector that I have is a bit spendy ($25 & $8, m/f). There is also neutrik Powercon which are killer power connectors and made for such a job.