Amp and preamp on same outlet?

A well regarded equipment manufacturer told me having everything on the same line is optimum. I suspect this is related to the ground loop considerations Al posted. Also, this is based on the assumption the one line is a dedicated circuit, as posted by Lowrider57. I have two 20-amp dedicated lines but currently use only one of them into an Isoclean filter, and the system sounds great.
If I add the fuse values of my two amps, preamp, DAC, and linear supply for my computer, together, my system can only draw a total of 15 amps so, from a power supply standpoint, I do not need the second line. Although, I have considered upgrading the breaker to 30 amps.
I have read about some new grounding devices coming to market that are said to make significant improvements in some systems.

Unless you have issues with too much current draw, just plug 'em in together enjoy and don't worry about it.

If it were a problem for me with my gear, I'd probably just buy different gear that works better together and be done.

If you have noise issues doing it the simple way, then you have a problem somewhere else and better to address that appropriately.

Or if you have a second outlet on a different circuit try that as an option. If it sounds better to you then keep it there otherwise it doesn't really matter.

Audiolover718,I can tell you if I plug anything into the same outlet-dedicated circuit as my Krell 700cx, I can hear a difference of poor quality, the amp litterally suck's the required power-current for a pre-amp,cd-player, etc... right out of the componet's requirement needs to operate the way it was designed, then when I use a pre-amp, cd-player etc.. on it's own dedicated circuit, wala!, the dynamic's and transparency, sound quality in general is back with a vengence!, to conclude what I have said here, The only way this scenerio will not happen to you is if you have a very low current draw amplifier that does not require 20amp single pole breaker to a 30 amp single pole breaker dedicated circuit line, also, the last time I lived in an apartment, LOL!, I had a krell fpb-200 and the amp literally dimed the light bulb's and blew the bulb's untill I installed a dedicated line for the amplifier, just my exsperience's here that has happened many time's over, what do I know, ha, he,ha, hope this help's you.

if I plug anything into the same outlet-dedicated circuit as my Krell 700cx, I can hear a difference of poor quality, the amp literally suck's the required power-current for a pre-amp, cd-player, etc... right out of the component's requirement needs to operate the way it was designed

I have a hard time believing you are drawing a full 20 amps, even with a large Class A Krell. Therefore, I do not understand how your amplifier can draw enough current to affect your other components on a dedicated 20 amp line, assuming the total current draw is not more than 20 amps. I am not arguing with you, but rather just trying to learn something here. Is there some other reason the sonics could be affected, like voltage fluctuations when the circuit approaches its maximum amperage? Any electricians or EEs here?

LOL, I get a kick out of some of you guys that say a dedicated circuit is not needed to improve the sound of an audio system. It will sound its' best just plugged into a regular convenience outlet branch circuit. I guess the same could be said for OEM power cords vrs good quality after market power cords. Don't waste your money.

Mitch2,
It is not the continuous current draw of the power amp that is the problem. It is short spurts of higher than the average current pulled from the mains that can cause VD, voltage drop, on the mains that causes problems with the power supply of the amp.

A few years ago I remember reading a post by, I believe it was from Atmasphere, where he spoke on the subject. I'll look and see if I can find the post.
Jim