What is the ideal order to place components on a rack?

Should the amp be far away from the pre pro or not really?

I never really thought about it that much. I usually put the amplifier on the bottom, as it's the heaviest component and I'd rather have it near the bottom for stability reasons. The pre/pro goes close to the amp to minimize the length of the cable runs (5 cables) between the two. Signal sources are further from the amp to minimize magnetic field interactions; the CD player (analog output) is near the top.

If possible, the amp should be away from other components because of the magnetic fields it can generate (power transformer, loop area of high current cabling). You must also consider the heat generated by the amplifier; if it's on the bottom of the stack that warm air will flow up through all the other components.

I follow a similar logic to mahansm: my amp(s) at the bottom, then pre-amp above that, and sources above. The source with multichannel analog output is closest to the pre-amp to help manage cable clutter. However you do it, you need to manage your cabling carefully: keep power cables as separated as possible, and I like to segregate speaker cables from analog audio cables somewhat if I can.

I have had similar thoughts with my system. My rack is pretty much fully enclosed and built into my wall, so stability is not an issue. I'm getting ready to put some exhaust fans into it to provide some air flow to keep things cool. As it stands now, the shelves are pull out shelves with 100 lbs. capacity. So when I'm using my hot running PS3, I slide that shelf out to have it in the open air. I've thought about placing my amp on the top of my rack, but I worry that it could run too hot up there even with the exhaust fans.

Any thoughts? How cool does the amp need to be?

Perhaps mahansm and tkntz could be persuaded to post pics...

If you cannot keep your hand on top of the amp without discomfort at the maximum power level you use , it is too hot.

I could be persuaded to post pics.

In regards to amp cooling; the life of electronics is cut in half for every 10 degrees C rise in temperature (rough rule of thumb). Also, the output devices (transistors of some type) will have a maximum junction temperature in their spec sheets; they are not guaranteed to survive about this temperature and may let the magic smoke out.* The designers must go through some moderately involved calculations about heat dissipation and thermal loading to ensure that these devices stay within safe limits. This also involves assumptions about ambient temperatures and restricted airflow situations. In addition, most quality manufacturers will put a thermistor (temperature sensing device) on the heat sink and use this to shut down the amplifier when it's near maximum allowable temperatures.

My 990 runs hotter than the 7500. The loudest I ever go sustained is about 95 dB average as measured on my cheapo Radio Shack meter, and that's not for more that a track or two. In a 70 degree F room, the 7500 was just warm to the touch after the aforementioned session.

* All electronic devices run on compressed magic smoke; the proof is that when you let the magic smoke out the device stops working... :-)

Thanks all for the helpful thoughts. I will try to post some pictures of my system.

Part of my dilemma rests with the PS3 and my DVR that sit on the same rack. The PS3 only runs when I use it and I have it set to turn itself off after a certain amount of inactivity. But the DVR is on 24/7 (of course) and always runs very warm. So what I keep debating in my mind is whether the DVR should be on top so that it can't warm the electronic components above it. Right now, my AVR sits on the bottom and never gets past warm. I must admit, I'm surprised that the 990 runs warmer than the 7500 in Mahansm's system. I would've thought an amp would run warmer than a pre/pro.

I think the original question of this forum relates to electrical interference between components based on Gooomz's question about distance between components, but mine is a question of heat. The question I have in my mind is whether the warmer components should go in the bottom of the rack or the top?