Amp and preamp on same outlet?

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

Jea,

I will agree that sound quality usually benefits from proper power conditioning. There are many ways to achieve that effectively. Best approach will vary case by case. A dedicated circuit can introduce its own problems associated with grounding as pointed out so it is not a panacea in of itself. Alone, even if doe right, it might not make any difference in any particular case just is it may in others.

I'd think about applying a power conditioner and perhaps noise limiting power cords to line level devices first in most cases. Of course one can take things as far as they want if they deem it worth it.

Tim (Mitch2), this post by Atmasphere dated 6-3-14 is one of those in which he has explained the brief high current spikes which characterize the majority of the current draw of most power amplifiers, as Jim (Jea48) indicated above.

To put things in perspective, a 50 foot run of 12 gauge Romex will have a total resistance for both conductors (100 feet total) of around 0.16 ohms. A spike of say 30 amps (just my not particularly well informed guess as to a representative number) would result for a brief instant in a voltage drop of 30 x 0.16 = 4.8 volts across that resistance. There would be additional effects on the high frequency components of the spike due to the inductance of the wiring.

I wouldn't expect that voltage drop **in itself** to have a major effect on a preamp that may be powered via the same run as the amp, in part because (in contrast to most power amps) most preamps have regulated power supplies. But note that Ralph (Atmasphere) refers to the spike having frequency components in the 30 to 100 kHz area, and perhaps even at higher frequencies. That is what I had in mind in my initial post in this thread when I referred to putting the two components on separate lines as having the upside of "reducing the amount of amplifier-generated electrical noise that may couple back into the preamp."

Regarding Audiolabyrinth's Krell 700CX specifically, I would be hesitant to extrapolate what is likely to happen with most amps from experiences with that amp. It is an understatement to characterize it as a monster compared to most other amps, as some of its specs will make clear:

Maximum rated power per channel into 8 ohms, apparently with both channels driven: 700 watts
Into 4 ohms: 1400 watts
Into 2 ohms: 2800 watts

Power consumption at idle: 430 watts
Maximum power consumption: 6000 watts

Weight: 180 pounds

It is not a Class A amp, btw, as is made clear by the difference between its idle and max power consumption numbers, and as might be expected based on its huge output power capability.

I'm perhaps exaggerating only somewhat in saying that I would sooner expect that amp, when playing highly dynamic music at high volume through low efficiency low impedance speakers, to be more likely to cause a neighborhood-wide brown-out than to NOT have an effect on a preamp powered from the same outlet :-)

Best regards,
-- Al