So, you are trying to get your preamp to tell your amp to turn on using an RC-5 jack on the preamp?
I'm gonna need manufacturer names and model numbers.
BUT, if the preamp has an RC-5 in and an RC-5 out jack, those are only passing the IR remote control codes. The preamp's RC-5 jack is not going to send out a control code at power on other than the preamp's power on that you are sending it via remote control. So, you COULD use a device that recognizes that RC-5 preamp on code, then outputs a 5-12 VDC constant to trigger your amp (all amps I've seen with 12 VDC triggers will acccept 5-12 VDC because it's just a relay, but that's why you should supply model #, or better yet, check with the manufacturer direct) Such a device would be expensive.
What I would suggest instead is one of three status indicator devices:
1) A 12 VDC wall wart power supply plugged into the switched outlet on your preamp if there is one. if not, 2
2) A current sensing power strip (Niles makes one) plug your preamp into this, when you turn it on, the strip detects the current draw, outputs 12VDC for you to send to your amp, if you don't like this, or your power conditioner configuration won't allow it, then 3
3) A light sensor (again, Niles makes one) that would stick to the front of your preamp, when the display lights up, it tells its brain "the preamp's on" and the brain sends 12 VDC to your amp.
You might have other options depending upon the preamp model number.
