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.
I would like share some info in regards to the Krell references made on this thread. I also believe the info would be of interest to the OP Audiolover.
If I can ask Audiolabyrinth a couple questions first.
@Audiolabyrinth
Am I reading your posts here right that you are using a 30 amp circuit breaker, but not 30 amp rated line or a 30 amp outlet; and therefore a 30 amp terminated male end on your Krell power cord ?
Has your 20 amp line been checked ?
So I have a friend considering a Krell amp. He has a shared 15 amp line for his present set up. To offer him more insight I reached out to Patrick at Krell about a dedicated 15, 20 and even 30 amp service (in a second email) - this due to what I read in this thread. I would like to share this info from Patrick.
Patrick's answer.
The answer to this is somewhat dependent on the speakers being used, as well as the length of the speaker cables. We recommend 20 amp service because with rare exception it almost always works best in terms of the amplifier always having continuous current available to be able to instantly respond to whatever type of listening style a customer may have.
The above now said, in some homes installing a 20 amp line is either not possible, and or its install cost can be prohibitive, depending on the age of the house. I know for a fact that there are many customers out there who are successfully running systems with large Krell amplifiers using a 15 amp line. Would there be a dramatic sonic difference between using a 15 amp line and a 20 amp line? Maybe and maybe not. A good stiff 15 amp line verses a weak 20 amp line, in my opinion you would probably not hear the difference between these two.
As the expression goes, the proof is in the end result. If when using a 15 amp line, the amp sounds open and fast and detailed with good bass and sound staging, and it does not pull the 15 amp line breaker down during loud playback or loud musical transients, he should be good to go as is. However if he is tripping the 15 amp AC line breaker occasionally during playback, he should go up to a 20 amp line if possible.
The Key words that stood out to me in the above.
Speakers used Length of Speaker Cables The proof is the end result (the amp sounds open and fast and detailed with good bass and sound staging) A good stiff 15 amp line versus a weak 20 amp line.
And from some of the discussions on this thread about 30 amp service I asked.
Whats the deal with 30 amp service. Is it ever needed or warranted. FWIW I take his response as normal for someone representing a company that makes high power amplifiers.
Patrick's response
As they say, the more the better and giving a powerful amp like the FPB-600/600c/700cx a dedicated 30 amp line will make a serious difference from a performance perspective that would be obvious straight across the audio frequency spectrum. Under these circumstances however you would need to re-terminate the male end of the amps AC cord with a 30 amp twist lock type male connector. Is this really needed? Not really. But you asked . . .
I interpret Patrick's comments that for 30 amp service, a 30 amp breaker, 30 amp line, 30 amp outlet and a 30 amp male connector is required to go this route.
Ralph- The guy just does not get it. He's talking how he think it sounds, you and Jim are talking electrical safety codes and specifications.
Audiolabryinth- Even if were true that the larger breaker is somehow making your system sound better (I'm betting the recommendation from Krell came about like Jim theorizes, but let's put that aside. What do you think might happen if there is a short or other failure downstream of the 30 amp breaker, such that there is a long term "demand" for more than 20 amps but less than 30 amps? I'm no ee, but my guess is that there is a reasonable possibility that the house wiring, or receptacle, or power cord downstream of the breaker, will overheat, unless they are ALL also rated for 30 amps. What happens after that? I'll give you a hint, you can't shout it in a crowded theater. If your insurance co. is diligent, they'll hire a forensic ee like Jim, who will tell them that you modified your electrical system in a manner that is unsafe and does not meet code. Then your insurance company will say, "thank you" to Mr. EE and "go pound sand" to Mr. Audiolabyrinth. CLAIM DENIED. Of course, there's also the possibility that the insurance co wont' be talking to you, they'll be talking to your heirs. It's your call, dude. They are looking out for you. Do you think Krell gives a rats a$$ about you?
^^ If you are going to operate a 30 amp breaker, make sure the line it controls is also rated for 30 amps.
Otherwise you risk a fire. I bet you will find though that the 20amp wiring is also 'limiting' the amp; at any rate you will do well for yourself to follow my advice in the above paragraph.
Jea48, also, this captive cord is a 10/3 copper power cord,when I get the money, I will be changeing the wall plug to a furutech or oyaide for performance, It seems I really don't need it, but I can always return it if something like this wrecks my sound, I am a skeptic by nature, so we will see Jim, cheers.
Jea48, one of these audiogon members that has e-mailed me for months about the 30 amp breaker is MRvordo, you can consult with him, maybe bring him to this thread, he uses the 30 amp breaker on his krell 750mcx mono amps, I believe a 30 amp breaker for each?, any way, every aspect of what he said this will do for my amp was spot on correct, he is one among many others that have done this with no issues.
Hi Jim, sorry, I just got back to this thread, yes, I have been listening, I do have a 10/3 romex connected to a furutech GTX-D Rhodium for my amp, yes, The Krell 700cx amp comes with a captive power cord that says 600 volts rating on it, Jim, I have said over and over, my amp is NOT useing all 30 amps, it simply spikes over 20 amps, all I am saying Jim-Jea48, My krell 700cx runs cooler, more dynamic, bigger sound stage, more or less, effortless useing a 30 amp single pole breaker versus a single pole 20 amp breaker, I was shocked after 20hrs of burn-in of the breaker at the difference this made, Damn Jim, this is the best cheap tweak ever I have done, more than cost effective, I do not know why or how Jim, But I assure you, the 20 amp breaker in my opinon, was chocking my amp!, Thankyou jim for all the post you have done, I really don't have an explaination, I am just telling you that this works, no problems, and was worth doing, and that I know many members of audiogon that did the same here with their Krell amps, I was afraid to do it Jim, Chris Vanhas of vh-audio sold me the furutech GTX-D R with the understanding that it would not heat up or damge the outlet with a 30 amp breaker because of how well it is built, as it turns out, he was correct, not even warm!, I have checked this outlet over and over, the wires going to it, if any smell was coming from it, for heat, nothing, the wpo-wall power outlet is cold all the time with NO issues, thanks jim.
Jim (Jea48), it seems that John (Jmcgrogan2) was right. Fool Hardy has no interest in learning to sing and you are getting frustrated trying to make it happen. I remember you trying to tell him the same thing in another thread a while back. Hopefully, others reading this thread will follow your advice, which as usual, is excellent. It would be a shame for anyone to burn their house down for the sake of trying to make their system sound better. One of the things I remember from the other thread is that after all of those "upgrades", he was still tripping breakers and wasn't sure why. YIKES!
Jea48- Save the bandwidth. He's not listening. Or he can't read. Or he believes that the building and electrical code writing authorities are conspiring w Bose to make us listen to inferior sound ;-)
Edit for previous first post dated 03-03-15: Jea48
NEC Code 210.21 (B)(3) Receptacle Rating. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacles ratings shall conform to the values listed in table 210.21(B)(3), ...........
NEC Table 210.21(B)(3) Receptacle Ratings for Various Size Circuits.
The branch circuit breaker size determines the size of the branch circuit.
If the branch circuit breaker is 30 amp then the minimum wire size must be #10 AWG. It can be bigger but it cannot not smaller. The receptacle must be a NEMA 125V 30 amp rated receptacle. It cannot be bigger, it cannot be smaller, it can only be a NEMA 30 amp rated receptacle. .
AC POWER GUIDELINES The Full Power Balanced 300cx and 350Mcx amplifiers need to be operated from a dedicated AC power line rated at a minimum of 15 amps. The Full Power Balanced 700cx, 750Mcx, 400cx, and 450Mcx amplifiers need to be operated from a dedicated AC power line rated at a minimum of 20 amps. Please contact your authorized Krell dealer, distributor, or Krell before using any devices designed to alter or stabilize the AC power for Full Power Balanced amplifiers.
Note the word [minimum] used for the "750Mcx, 400cx, and 450Mcx amplifiers need to be operated from a dedicated AC power line rated at a minimum of 20 amps."
If the equipment is manufactured for use in the USA with the intent of using a power cord with a NEMA 5-20P 125V 20 amp plug then the max branch circuit ampacity rating is 20 amps. Period! The minimum branch circuit ampacity rating because of the NEMA 5-20P plug is 20 amps. Period!
Minimum wire size #12AWG copper. Branch circuit breaker size, 20 amp. Period! Receptacle, if the Krell power cord plug is a NEMA 5-20P plug then a NEMA 5-20R 125V 20 amp receptacle for the plug to fit it is required.
All the above are NEC Code minimum electrical safety standard requirements.
Krell can spec #10 AWG copper wire, which I would recommend. For long branch circuit runs maybe even #8 AWG Cu. They can spec an HM, High Magnetic, 20 amp breaker must be used to help prevent nuisance breaker tripping. They should spec that only power cords that has a NEMA 5-20P plug can be used with a minimum cord conductor wire size of #10AWG. They can spec only a NEMA 5-20R 125V 20 amp heavy duty commercial/industrial rated receptacle be used. The bigger wire and heavy duty receptacle will help reduce voltage sag on the branch circuit wiring, receptacle contacts to plug blades, and power cord wire right up to that 20 amp IEC inlet connector mounted on the back of the unit caused by the Krell amp's dynamic power connected load.
They cannot spec a 30 amp circuit breaker be used on a 20 amp branch though. You will notice in the owner manual a 30 amp branch circuit was not mentioned. Everybody reading this thread by now should know the reason why.
Jim, you do not understand, Krell runs 30 amp braker on every krell 700cx, 750mcx amp there at the factory, BTW, I have 4 fuses, well with-in the current capability useing a 30 amp breaker, as I said befor, I am not useing all the 30 amps!,however, This amp in particular spikes well above 20 amps while in use, maybe you should call krell, then you will get all the theory as to why this works properly you want, remeber, this amp at full power is 6,000 watts!
Audiolabyrinth,
IF, Krell is indeed telling customers the amp was designed to be connected to a 120V 30 amp branch circuit for use in the USA or Canada. Again IF!!!
You are the one that that does not understand what Krell is actually up to. If Krell is having to connect the amp to a 120V 30 amp circuit for the amp to operate properly as designed as well as to achive the amps reported specs then Krell should be using a captive power cord and a NEMA 125V 30 amp plug on the end of the cord. The user, customer, would then be required, per NEC Code, to install a 120V 30 amp branch circuit with the correct NEMA 125V 30 amp receptacle for the Krell amp plug. Per NEC Code a 30 amp branch circuit requires #10AWG minimum wire and shall be connected to a 30 amp branch circuit breaker, period. The receptacle must be a NEMA rated 125V 30 amp receptacle, period. No exceptions.
Instead Krell is apparently more interested in building a product that violates NEC code safety standards for the USA by using a 20 amp max rated IEC inlet connector on the amp where by the user can use a power cord that has a NEMA 5-15P or a NEMA 5-20P plug. Then Krell has the gull to tell a customer that bought the amp to change out the breaker at the electrical panel from a 20 amp to a 30 amp, which I believe the real reason is, because the Krell amp is nuisance tripping the 20 amp breaker on startup in rush current.
So because Krell was too tight to design/incorporate a soft start circuit to limit inrush current to solve the customer's problem of the 20 amp breaker nuisance tripping they tell the customer to change out the 20 amp breaker to a 30 amp breaker. What they should be telling the customer is to change out the 20 amp breaker to a 20 amp HM, High Magnetic, breaker that has a longer delay time for startup inrush current. Problem solved.
I wonder how many Krell users have followed the advice of krell? How many users who changed out the 20 amp breaker to a 30 amp on a 20 amp dedicated branch circuit that has #12AWG 20 amp rated wire?
As I have pointed out earlier in this thread the current carrying contacts as well as the other current carrying metal parts of a 20 amp breaker are identical to that of a 30 amp breaker. Had an EE at Krell done his/her homework he/she would know this as well. They would also know as well a typical TM, thermal magnetic, breaker will easily pass short bursts of current of 120 amps all day long. More than enough for their amp but not enough apparently for startup inrush current. A 30 amp TM breaker will pass short bursts of 300 amps. Hell you can arc weld with 120V at 30 amps. And if the branch circuit wire is of any length and #12AWG copper once I get the #12 branch circuit wire cooking I won't have to worry about tripping the 30 amp breaker.
I have looked at every article in NEC Code that pertains to the code violations and nowhere in the NEC Code book is an exception given for Krell inc.
Audiolabyrinth , did you know?
NEWS from CPSC
U.S. Consumer Product Safety Commission
Office of Information and Public Affairs Washington, DC 20207
Amplifiers Recalled by Krell Industries Recalled Due to Fire Hazard WASHINGTON, D.C. - The U.S. Consumer Product Safety Commission, in cooperation with the firm named below, today announced a voluntary recall of the following consumer product. Consumers should stop using recalled products immediately unless otherwise instructed. Units: Distributor: Krell Industries LLC, of Orange, Conn.
Hazard: The amplifiers were designed to operate at a temperature warm to the touch. However, a component input device can fail and cause the amplifiers to overheat, posing burn and fire hazards to consumers.
Incidents/Injuries: Krell has received 50 reports of the amplifiers overheating including reports of smoke and electrical fire. No injuries have been reported.
Description: This recall involves Krell power amplifiers with model numbers KAV-250a, KAV-250a/3, KAV-500i and KAV-1500. The amplifiers are used to provide power to a loudspeaker in a home audio playback system. The Krell logo is printed on the front of the amplifier.
Sold by: Authorized dealers and distributors of audio equipment nationwide from January 1997 through February 2001 for between $3,000 and $8,000.
Manufactured in: USA
Remedy: Consumers should immediately stop using the amplifiers, and contact Krell to schedule the free installation of replacement fuses.
Consumer Contact: For additional information contact Krell at (888) 436-6055 between 9 a.m. and 4:30 p.m. ET Monday through Friday, or visit the firm's Web site at www.krellonline.com. Consumers can also email the firm at service@krellonline.com
I would bet that no owner of the Krell amp mentioned in this thread has anything in writing from a representative of Krell inc. stating Krell recommends changing the breaker on a 20 amp branch circuit from a 20 amp to a 30 amp breaker. All a user/customer has is a verbal conversation that is worthless in a court of law.
So who is in violation of State, and local governing body safety electrical codes and electrical safety standards when a 20 amp breaker is changed out to a 30 amp breaker on a 20 amp branch circuit? . The person/home owner that changes it out of course.
I suggest you call you insurance agent and ask him/her if you are covered by your home owners insurance policy in the event of an electrical fire if it is found a 30 amp breaker is installed on a 20 amp branch circuit.
Then call the governing electrical inspection department in your city and ask them about changing the 20 amp breaker to a 30 amp breaker on a 20 amp branch circuit.
NEC Code 210.21 (B)(3) Receptacle Rating. Where connected to a branch circuit supplying two or more receptacles or outlets, receptacles ratings shall conform to the values listed in table 210.21(B)(3), ...........
NEC Table 210.21(B)(3) Receptacle Ratings for Various Size Circuits.
But we should keep in mind that the amp is likely never going to produce such power, as it would only be possible if the load were one ohm. I remember the Apogee Full-Range speaker approached that value, but the speaker cables used in such an installation would add to the load impedance and limit the possibility of such power.
On most 4 ohm loads the output power is about 1500 watts.
In addition if I recall correctly, its the power transformer in that amp that has that rating, not the amp itself. The transformer would current-limit the amp even if the output section was capable of delivering such power.
Line voltage sag can cause some amps to heat up as the bias point can shift somewhat depending on the design so I can see that reducing the sag with a higher current breaker might have an effect. But installing such a breaker without upgrading the associated wiring would be foolhardy and would not meet code in any state in the country.
John, yes your math is of course correct. And the 700cx does indeed have a max power consumption spec of 6000 watts, which if anything seems a bit low in relation to its specified output power rating of 2800 watts/channel into a 2 ohm load (the 8 ohm and 4 ohm ratings being 700 and 1400 watts respectively).
But it seems safe to assume that it would be an unusual occurrence for the amp to be used in a manner that would require it to draw more than 20 amps x 120 volts = 2400 watts for a long enough time to cause a 20 amp breaker to trip.
Jim, you do not understand, Krell runs 30 amp braker on every krell 700cx, 750mcx amp there at the factory, BTW, I have 4 fuses, well with-in the current capability useing a 30 amp breaker, as I said befor, I am not useing all the 30 amps!,however, This amp in particular spikes well above 20 amps while in use, maybe you should call krell, then you will get all the theory as to why this works properly you want, remeber, this amp at full power is 6,000 watts!
Jea48, I do not understand why you would make humor of the truth, I had numerous others with the Krell 750MCX mono block's and the stereo Krell 700cx say the same thing, they encouraged me to use the 30 amp breaker as did krell them selfs,no one knows it all, we all learn from each other, I did not believe that the 30 amp breaker would do any thing either, but when I got 20hrs of break-in on the breaker, it turned out to be the best cheap tweak ever I have done in my life time, the benefit's was worth thousand's of dollar's to me!
Jim, science is not all!, I am telling you, please listen, My amp does not get hot any more, got a bigger sound stage, runs smoother, hugely more dynamic, Jim, how do you explain why a single pole 30 amp breaker did all this when a 20 amp breaker choked the crap put of my amp in every way?, also Jim, this is very incredibly noticeable of the difference between the 20 amp and 30 amp breaker on my amp,I also have a $240.00 top of the line furutech GTX-D Rhodium for an outlet with the breaker, works safly, the outlet is cold all the time, period.
Jea48, Asit turns out, my krell manual for my amp says to use 20 amp single pole breaker min, they put it in their manual, that means 20am will work, really terrible, but you can get by, the 30 amp single pole allows my amp to get the correct current, does it use all 30 amps, of course not!, however, it spikes well above 20 amps, the amp never runs hot like with the 20 amp breaker, way more dynamic, bigger sound stage, it's a fit! 02-26-15: Audiolabyrinth
Audiolabyrinth,
I am sure the Krell user manual says the amp should be connected to a 20 amp circuit. They did not a have a choice if they wanted to use a NEMA 5-15P or a NEMA 5-20P plug and cord to feed the amp.
Just going from memory in another thread here on Agon you and I have discussed the code violation of using a 30 amp breaker on a 20 amp branch circuit that uses NEMA 5-15R, (two or more), or NEMA 5-20R receptacles connected to the branch circuit wiring.
If I remember correctly you used #10awg for your branch circuit wiring instead of #12. I believe in that thread as well as this thread #10 wire I said why #10AWG wire does a better job of controlling VD, voltage drop, placed on the circuit caused by the Krell amp. As I said in the other thread the current carrying contacts as well as the other current carrying conductors in a 20 amp breaker are exactly the same as 30 amp breaker. Only the magnetic and thermal trip units settings are different.
I may not be able to convince you otherwise but it is my hope that others reading this thread or other threads like it will not think it is ok to use a 30 amp breaker in place of a 20 amp breaker.
If the current carrying components inside of a 30 amp breaker are larger than a 15 or 20 amp breaker then why would they sale for the same price?
If the 20 amp breaker felt warmer to the touch with the #10AWG wire connected to it the reason could be the breaker was defective. Again it had nothing to do with the differences in the size of current carrying metal components in the 20 amp verses the 30 amp breaker because there is no difference. . Jim
Jea48, Asit turns out, my krell manual for my amp says to use 20 amp single pole breaker min, they put it in their manual, that means 20am will work, really terrible, but you can get by, the 30 amp single pole allows my amp to get the correct current, does it use all 30 amps, of course not!, however, it spikes well above 20 amps, the amp never runs hot like with the 20 amp breaker, way more dynamic, bigger sound stage, it's a fit!
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.
This has nothing to do with ground loops which are an entirely separate matter (FWIW, if your equipment is properly designed, ground loops should never be a problem).
The concern with different lines is that one might be on one side of the incoming AC power into the house, the other might be on the other. Sometimes you can have leakage problems caused by the two lines being of slightly different phase (or a lot different phase if taken off of a 3-phase circuit). Sometimes this can result in hum. If the equipment is properly designed though this should be a minor concern.
IOW two different lines off of the same side of the incoming AC line (which is 240 Volts in the US and then gets split into 2 halves each 120Volts...) eliminates that concern. If your equipment is prone to ground loops that can still happen though...
Move to a more efficient amp like Class D and no problem ever. I have both my 500w/ch monoblocks on the same outlet and dynamics match teh best I hear anywhere and are teh best I have ever had myself.
Efficiency done well is always a good thing.
My circuit breaker used to go frequently with modestly high power power sucking Class a/b amps.
Now the only time it might go is if I power up both 500w/ch Class D monoblocks at the same time. They never show any signs of strain or break a sweat running. Plus I can leave them on most of the time and teh impact to my power bill is negligible as quality power amps tend to go, so overall cost of ownership is lower as well.
How much/many dynamics will be lost in the same outlet? How much/many of thom will be gained via dedicated linez? Will there be anything more lost or found in the same outlet?
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.
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.
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. .
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.
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.
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!
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.
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 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 :~)
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 :-)
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.
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
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?
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.
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.
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 owners 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
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."
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.
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.
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.
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