Amp and preamp on same outlet?


Just how much of a no-no is this? ARC goes as far to print in their manual to say to have the amp and preamp on their own circuit. I live in an apt. and I'm forced to have both plugged into the same outlet. Cords just don't reach....How much sound quality is lost by doing this? It sounds great as is, but is there a major detriment to this? I'm curious.
audiolover718
There's no way to tell unless you try it. In your case, a good solution may be to plug the amp into the wall, and plug your preamp into a line conditioner that isolates the outlets. With power products, though, there's no telling what kind of results you get. If you call Cable Company, they can make recommendations and send you demo units to try first, before you buy. Its the best way to do it.
The first step is to be using a dedicated AC line. If not, don't plug into a line that shares use with high-draw items like appliances.
Get 2 20v dedicated lines, then you can follow ARCs advice; one line for amp and pre, next line for components.
The outlet is most likely on a 15 amp circuit that is rated for 1800 watts. If you total everything that is on that circuit it will not come close to that. If the breaker has not tripped then you should be fine. Enjoy your stuff and don't worry. Anything else is pure overkill!
Tell me you're not really plugging your power amp and preamp into the same power circuit? Do you have no shame? It's a major, no make that mega-major no-no. I'm surprised it hasn't made your system unlistenable. If you continue with this sordid behavior you will be dragged out of your apartment, taken to a public square and beaten with power cords. I harumph you!
Onhwy61 funny as hell. He actually make like it.
That punishment is not severe enough. He should be stripped naked and hung by his toes and stoned to death by the villagers with VPI magic bricks and his remains hauled off for the vultures to feed on!
Not to mention havin his 24K gold plated Audiophile card revoked!!!
it's ok as long as you want to listen to tunes.
IMO; it really depends upon which amp and preamp you are using. You never specifically mentioned that.

Many ARC products are made to be used with a 20 amp IEC power cord, is yours?

I would try plugging the amp into the wall outlet and then run a heavy duty extention cord to your preamp (using whatever connection adapters necessary) and listen for yourself.

As Yogiboy mentioned, if the breaker has not tripped then you should be fine however the system might sound better if the amp and preamp were on different circuits or dedicated circuits.
Using separate outlets, especially if they are on separate runs back to the breaker panel, will reduce the amount of amplifier-generated electrical noise that may couple back into the preamp. On the other hand, doing that may increase susceptibility to ground loop issues, including high frequency electrical noise as well as low frequency hum. If the connection between preamp and power amp is balanced, the likelihood of ground loop issues is considerably reduced.

All of this is highly dependent on the design of the particular components, and has little if any predictability. So ZD is right, "there's no way to tell unless you try it." But if, as you say, "it sounds great as is," that would seem likely to be the bottom line.

Regards,
-- Al
Audiolover718,

Depends on your circumstances.

How big is the ARC amp? What is the ARC model number?

What size is the branch that feeds the amp? 15 amp? 20 amp?

What is the length of the branch circuit wiring from the panel to the outlet receptacle the preamp and amp are plugged into?

How many other duplex receptacles and possibly ceiling light fixtures are connected to the same branch circuit your preamp and amp are plugged into? What was the wiring method used to wire the receptacles that feed onto the next receptacle of the branch circuit? Wiring daisy chained using the duplex receptacles to make the in and out wiring connections of the branch circuit wire? Corroded/loose/poor connections add resistance to the circuit. The more the load placed on the circuit the greater the VD, voltage drop. How much is the other non audio connected load connected to circuit?

All the above can affect how a piece of audio equipment will preform. Branch circuit breakers are designed to trip open in the case of a continuous overload condition, a high sustained inrush current condition well over the handle rating of the breaker, or a short circuit event.

The breaker does not respond to short bursts of current passing through it. Example, a 15 amp branch circuit, 15 amp breaker with #14 awg copper wire connected to it, will easily pass short bursts of current well over its handle rating of 15 amps all day long. The breaker could care less what is causing the short spurts of current that is passing through it over its' 15 amp handle rating. It also could care less if the voltage at the receptacle feeding the preamp and amp is fluctuating up and down due to VD, voltage drop, caused by bursts of current placed on the #14 awg wire.

The power supplies of a preamp and power amp might though. Power amp's power supplies like its' mains voltage to be steady and not fluctuating with the beat of a high dynamic music source being fed through it.
.
Jim
As usual, Almarg nails it.

Using separate outlets, especially if they are on separate runs back to the breaker panel, will reduce the amount of amplifier-generated electrical noise that may couple back into the preamp. On the other hand, doing that may increase susceptibility to ground loop issues, including high frequency electrical noise as well as low frequency hum. If the connection between preamp and power amp is balanced, the likelihood of ground loop issues is considerably reduced.
02-09-15: Almarg

Hi Al,

The late Al Sekela, an EE, used to post on the AA Forum why decoupling the power supplies of audio equipment by using separate dedicated circuits benefited the SQ of audio equipment. Especially decoupling digital equipment from analog equipment.

As for ground loop problems I would say most ground loop problems caused from the use of multiple dedicated branch circuits is due to the choice of the materials and wiring methods used.

Worst wiring method is a single conduit run with multiple single current carrying conductors with insulated safety equipment grounding conductors pulled in the same conduit.

Dedicated branch circuits should never occupy the same conduit, or cable.

Best branch circuit wiring practices for dedicated branch circuits is the use of 2 wire with ground NM-B cable, (Romex is a Trade Name for NM-B cable), or 2 wire with ground MC Cable with an aluminum outer armor. The construction of the two cables cancels the EMF effect from inducing a voltage onto the safety equipment grounding conducting by the magnetic fields of the hot and neutral current carrying conductor caused by the connected load.

When Romex is used for moderate to long parallel runs of the cable they should be separated by at least 6 or 8 inches to prevent voltages from being induced from the hot and neutral current carrying conductors of one dedicated circuit onto others plus the safety equipment grounding conductors. Keeping them separated also, imo, helps prevent EMI/RFI noise transfer from one Romex cable to the other. Especially when one of the Romex cables will be used to power digital equipment.
Jim
I have always had my amp plugged straight into the wall and use a power conditioner to isolate the rest of my gear. I currently use a Furman Elite 15 PFI and it works well with my Audio Research equipment. It also protects my gear from spikes and noise while not having a negative effect on the sound. I don't know what ARC models you have. My Ref 110 has a max of 800 watts and the rest of my gear maybe 400 watts at most. There should be no problem with everything plugged into a 15 amp outlet. An extension cord can effect the sound. The only way to find out for sure is to try it and see.
I will not even read the other post!, NO!, do not ever do that.
Thanks, Jim (Jea48). Excellent points, some of which are further emphasized and explained on pages 31 to 35 of this excellent paper, which you had called attention to a while back.

Wrm, thanks also. Best regards,
-- Al
Plug your amp straight into the wall and the preamp into a power conditioner of your choice along with the rest of your non-amplification components. Then enjoy your system, and consider the many excellent high-end tweaks which do so much more to improve your system than continuing to worry about the item in question here.
Unless you are set to add additional lines, which the apartment owner will probably allow as long as it is done to code, I would do as Brauser suggested. You should not have any problems with noise or ground loops if you plug your low level components into a decent conditioner and the amp directly into the wall outlet.

enjoy
Audiolover, don't worry too much about it. If your ARC were to be plug in to its own circuit , you would hear a slight increase in bass definition and weight overall. But, I would not let it keep me from enjoying the music, if it sounds good, it is good!!
Utter nonsense, all of it. Plug those components and listen to music already!
Thanks guys- I have an LS-17 and HD220 plugged into a 20 amp line, unfortunately, this line is shared with my kitchen. This line also has the high hat lighting on it. The source equipment, is plugged into the conditioner, which is on different 15 amp circuit, around the corner on another wall. I wasn't happy with what the conditioner did to the sound of the LS 17. I tightened up the sound but made it too analytical, and lost tonal bloom.

I might try the extension cord and see what happens. But then the extension Cod may foul up the sound.
"If it sounds good, it is good" - Duke Ellington
;-) sounds good to me!
This line also has the high hat lighting on it
02-09-15: Audiolover718

What type of bulb/lamp?
Incandscent?
CFL?
LED?
.
Incandescent. Usually off when I listen.
Stevecham

You're right. I did plug the preamp into the other circuit and had no improvement, albeit, I did use an extension cord, which did muddy the sound. But the experiment did prove that it's nothing to be worried about. My system sounds terrific.
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.
I have been following this post, avoiding comment due to agreement with the early posts suggesting that Audiolover not worry about the situation as “It sounds great as it is”.

However I do not agree that the generated discussion was “Utter nonsense, all of it.” Simply not true.
ARC goes as far to print in their manual to say to have the amp and preamp on their own circuit.
Audiolover718

Oh well, so much for ARC's credibility.

Though in their defense it still would be nice to know from what ARC model owners manual the statement is from.
If you wanted to set up the preamp and amp in an optimal manner you would have them on separate circuits. You would also have your digital on a separate circuit. The OP is not in a situation where he can do that.

Audiolover718, glad it has worked out well for you. Your punishment has been reduced to publicly wearing a sign stating "I have my amp and preamp on the same circuit."
Your punishment has been reduced to publicly wearing a sign stating "I have my amp and preamp on the same circuit."
Onhwy61

I have my preamp and amp plugged into the same 20 amp dedicated branch circuit and the digital on another. Works great for me. To maintain a constant voltage at the receptacle feeding the amp and preamp I chose to use 10-2 W/Grd NM-B cable branch circuit wiring.

As for my responses to this thread, I was trying to justify the reasoning behind the supposedly statement made by ARC in the owner’s manual the OP referred to.

In the case of the OP all that matters is his system sounds good to his ears plugged into a 120V 20 amp convenience outlet branch circuit. He does not have the luxury of finding out if just a new single 20 amp dedicated branch circuit would make a difference in the SQ sound of his system, let alone two.
Jim
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.
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
Thanks Al for the link. Interesting comments by Ralph and some reasons why power cords can sound different from each other. I had not seen that post before. Not sure if the voltage drop part is as applicable to my current Class D amps, which don't draw as much as my former Class A Claytons, or other big amps I have owned, but I went ahead and plugged the amps back into the second 20A circuit just in case I feel the need to rock out :~)
Al,

Thanks for finding that particular post by Atmasphere. I believe he has at least one more out there he either posted here on Agon or AA where he goes into more detail the effect a voltage sag can have on the filter caps of a power supply. The part that is the same is this statement of Ralph's,

The more insidious problem is high frequency bandwidth. The power supplies of most amplifiers have a power transformer, a set of rectifiers, and a set of filter capacitors. The rectifiers only conduct when the power transformer output is higher than that of the filter caps. So:

When the caps are fully charged the amp is able to play. As it does so, the caps are discharged until the AC line voltage waveform gets high enough again that the rectifiers in the power supply are able to conduct. Depending on the state of charge of the filter capacitors, this might only be for a few microseconds or it might be a few milliseconds. Either way, the charge is a spike which has very steep sides- and requires some bandwidth to make it happen.

Thanks Al for your example of VD, voltage drop, due to a sudden demand draw of current placed on the branch circuit wiring. Your example should be plain enough for anyone reading it. I would like you to also give an example where the branch circuit wiring is #14 gauge wire which would be a more real world example for the majority of homes in the US where guys are plugging their audio systems into a 15 amp convenience outlet circuit in the living room or a den.

As for the length of the branch circuit I would be willing to bet the length of the 15 amp branch circuit wiring feeding a living room is longer than 50' on average. Of course with that said we have no way of knowing where in the entire length of the branch circuit the audio equipment is plugged into a receptacle. It could be close to the electrical panel or it could at the farthest end or somewhere in the middle.

Something else, though it is impossible to calculate, is the wiring method used by the residential electrician when he made up the joints, wiring connections, feeding in and out of each convenience electrical duplex receptacle outlet wall box. Did the electrician directly connect the in and out branch circuit hot and neutral wires together respectively and extend out pigtails to feed the duplex receptacle? Or did he use the terminal side screws on the cheapo residential grade device to make the in and out connections, daisy chain, of the branch circuit? Or worse yet did he stab the wires in the back of the cheapo residential grade receptacles relying on the spring tension clip inside the receptacle to make a good electrical connection?

All the above can throw a monkey wrench into the equation, especially when corrosion or an ever so slightly loose connection in the branch wiring is thrown into the mix. In this instance VD could/will be greater because the resistance through a corroded connection can change due to the load placed on it.
Jim
Thanks, Jim. All good points.
I would like you to also give an example where the branch circuit wiring is #14 gauge wire which would be a more real world example for the majority of homes in the US where guys are plugging their audio systems into a 15 amp convenience outlet circuit in the living room or a den.
The resistance of 100 feet of 14 gauge wire, corresponding to a 50 foot run, is about 0.25 ohms. For the 30 amp current spike I hypothesized, that would result in a voltage drop of 0.25 x 30 = 7.5 volts. A 75 foot run would increase that by 50%, to 11.25 volts.

As you indicated, less than optimal connections could worsen that significantly.

Best regards,
-- Al
Mitch2,That is funny!, my amp got way to hot on just a single pole 20 amp breaker, krell told me that my amp was designed to run on single pole 30 amp breaker, guess what, I did what krell told me to do, my amp has incredible dynamic's, bigger sound stage and transparency, and now for the kicker, the amp never run's hot and operates smoother, my krell kick's a 20 amp in the Axx!
Thankyou Almarg for clearing thing's up for me, A very good job indeed, yes, I have to go about thing's different with my amp, also, a couple of good friend's here on audiogon confirmed what krell told me, why?, they own the Krell 750mcx mono block's, these guy's talk to me often to help me, they have even bigger than my amp, the 750mcx has the exact power supply as my amp, however, the mcx amps have two!, oem to oem, the 750mcx has a bigger sound stage, but with my modds,up-graded none oem caps through out, tweaked power supply, up-graded most transistor's to higher grade,etc... it should be awful close, cheers.
Al,

Thanks for your response to my previous post.
Jim
hello,

As per my manual:

A.C. POWER CONNECTIONS: It is important that the HD220 be connected via its supplied 20 amp IEC 12-gauge power cord to a secure, dedicated A.C. power receptacle. Never connect to convenience power receptacles on other equipment. Only use the power switch on the front of the HD220 for On/Off control of the amplifier, or the 12V start- up trigger for remote installations.
The AC power source for the HD220 amplifier should be capable of supplying 10 amperes for 100 or 120 volt units, or 5 amperes for 220 or 240 volt units.
For the very best performance on domestic 100 or 120 volt circuits, the HD220 should be connected to its own AC power circuit branch, protected by a 15 amp breaker. The preamplifier and other audio equipment should be connected to a different power circuit and breaker.

I have been not been up to date on this thread, because I've been enjoying the music too much! This statement is found in other models in the ARC range.

Cheers
Audiolover718, This support's what i have said, why not do what ARC has said?
Krell should be ashamed of themselves "IF" they are telling someone to install a 30 amp breaker when their equipment is designed and manufactured using a 15 or 20 IEC inlet connector connected to a NEMA rated 125V 15 or 20 amp plug by a cord that is designed to plug into a 15 or 20 amp NEMA rated 15 or 20 amp receptacle. Per code two or more 15 amp receptacles can be connected to a 20 amp branch circuit. To be a 20 amp branch circuit the breaker handle rating is 20 amps. Minimum wire size, #12 AWG. If a NEMA 20 amp receptacle is used the branch circuit must be a 20 amp, period. 20 amp breaker....

IF the Krell amp's FLA is 12 amps or less per UL,NEC,CSA, a NEMA rated 125V 5-15P amp plug can be used to power the amp. If over 12 amps but less than 16 amps a 20 amp NEMA rated 5-20P plug must be used.

If Krell equipment is UL listed I suggest they ask UL if it is ok to tell their consumers that for their amp to operated at its' best, as designed, the customer needs to change out the 20 amp branch circuit breaker in the electrical panel to a 30 amp. Doesn't matter if it is in violation of the local governing body electrical safety codes, UL, or NEC code.

Also it should be said in some states a company can be held libel in a court of law for injury or loss of life or property damage if it is proven they knowingly knew information they were giving to the buying consumer of their product violated electrical safety codes and or accepted electrical safety standards.

Disclaimer. I do not know if Krell is indeed telling customers to use a 30 amp breaker to feed the amp mentioned in this thread. If they are, they are grossly ignorant of accepted safety electrical standards.
.
Interestingly (only to me perhaps), after switching to a moderately powered tube power amp (60 to 85 watts or so per side) I found that the lights no longer dimmed at loud passages like they did with my previous 100 watt pc high current SS amp. Also, all my stuff is in the same wall plug (power conditioned with a PS Audio Humbuster II for the amp) except the sub which required activating the little ground lift switch. Works.
If you have modern, reasonably decent gauge copper electrical wiring and a quality outlet, invest in a great noise reducing PC and conditioner. I use Transparent and MIT PC's and Transparent power conditioning with great success.
Loss of dynamics will happen.
I agree with Ebm, +1