I have two. One for power amp(s). The other for pre and source. The idea is to create "quiet" circuits that are receiving as little influence as possible from other power users in the house. Makes sense to me that amps may draw more power and therefore may create "noise" of their own. I suspect the preamp would be highly sensitive to noise so that's why I have 2. I further suppose one for each piece would be the ultimate but I don't have room in my panel for 6 (amps, pre, CD, phono pre, turntable) dedicate 20 amp circuits.
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Generally, you should install them on one leg. The reason is that both legs in the panel may not be the same voltage. One could be, say, 120V and the other 118V. If you put one circuit on each, then your equipment will have a 2V potential between them when plugged in. This could cause a ground loop through the interconnects, the equipment, the power cord and the wiring back to the panel. If you place the two circuits on one leg (matters not which) then the potential difference will always be zero. However, the length of both circuit wires to the breakers should be the same because a difference in resistance resulting from unequal lengths (ohms per foot) also causes a potental difference. |
I would suggest running isolated ground circuits. Each circuit has it's own ground run back to the panel to a separate ground bar. Then the Isolated ground bar has it's own ground run to it's own ground rod. If you are running two circuits, I think it would be worth the small added expense. I am not an electrician, but I play one on tv... nah, but my friend is, and we just did this, and I don't think it would matter if they are on different legs as the voltage is determined from the service wires. but if you have room on the panel, just use the same leg? If you have a meter you can check the voltage. |
if two lines are in use... or ever how many... and all are dedicated to the system... Use the same phase. Using differring phases (sides of the breaker box) intorduces possible issues, with one right off being a possible problem. Each phase in that box is going to out of phase from one another by at least 90 degrees. That's more important than a possible shortfall in voltage variances. The nearly same thing applies to running a separate ground... as the difference in potential between the two grounds being employed can be an adverse effect... if only by a few volts... and then there's the issue of creating a possible ground loop too. the issue rests with the neutral or common (white) leg of the ckt. That sole item is constant regardless what you use or how you employ dedicated lines unless you run an entirely separate service. These above listed considerations can range from insignificant to quite detrimental and most audible artifacts. The very best scenario past a new service is the above post on employing transformer isolated dedicated lines. Due to the common wire being constant throughout however, power conditioning or filtering might prove out as a more suitable solution for you... if none is/are in place presently. I have four dedicated lines. I have four power filters as well. All my ded lines are on the lighting phase, which works for me best, as I've no one here but myself. I felt it better than to place them onto the appliance side and avoid the fridge, hot water heaters, washer dryer etc. Ded lines are a plus. They may or may not be the entire answer. Good luck. |
Hanaleimike - While your idea of running separate grounds all the way to isolated/separate grounding rod sounds interesting, it is both dangerous and will likely violate your local building code. It's also not legal to work on your own electric panel without a license, although many ignore that. Wiring a home with two isolated ground rods may also void your homeowner's insurance should you have any sort of electrical problem. |
Hi Ghstudio, Sorry, I may have things a bit mixed up, but the all the ground rods are tied together. My friend Jon is a master electrician, and everything passed inspection. I had originally asked him about hospital grade receptacles and told him what I wanted to do. He suggested an Isolated ground circuit as they are what he installs for the most sensitive, both voltage and ground sensitive, computer equipment, he has done work in hospitals too but told me for what I wanted, an Isolated ground would be best. I would think that if each receptacle has it's own run via a 12/3 wire , all the way back to the panel on a separate ground bar in the panel, that there couldn't be any ground loops. I think the ground pin in the receptacle runs back to the panel, and the receptacle itself is grounded to the metal box. It sure made a difference sound wise too. |
Thanks for all replies. I installed the wire bought at Home Depot and it is CAROL Brand. it has four stranded 10 awg conductors, and very flexible. I used two wires for hot on each receptacle and share the ground and neutral. I then installed two breakers on each leg of the panel. There is a noise coming from the outlet (either one) when i plug Virtual Dynamic pc from the outltet to my ps audio PP. I checked the VD PC porarity and found it is correct. I even tried different VD pc and the result is the same. On the other hand the cheapy pc is ok, no noise. Another issue is that i heard hum/buz coming out of the speaker if the amp connected Directly to the outlets. Note that only amp was on at this time regarless connect or disconnect IC from pre to amp and turn off one breaker. If i connect the amp to PS Audio PP , no hum/buz come from the speakers. Any idea? |
Are they on the same leg of the main power....(i.e. did you skip a breaker when you installed your new wire? Why did you share the ground...that's something that only electricians use to save money on cable and to avoid having to pull multiple cables. Sharing the ground is OK (you want all the grounds coming to an outlet box to be grounded at the outlet box, but you should be running separate neutrals for each line back to the main power distribution box. |
01-22-09: HoustonreefYou have two separate circuits..... Not two dedicated circuits. Shared neutral for audio equipment is a bad idea.... There is a noise coming from the outlet (either one) when i plug Virtual Dynamic pc from the outltet to my ps audio PP. I checked the VD PC porarity and found it is correct. I even tried different VD pc and the result is the same. On the other hand the cheapy pc is ok, no noise. Obviously you did not hire an electrician to do the job. Outlets should not make noises.... I would turn off the two circuits at the breakers and hire an electrician. . |
01-22-09: GhstudioGhstudio, You need to reread Houstonreef's post..... Because of the wiring configuration he chose he has to have each hot wire, of the multi wire branch circuit, on opposite legs. Both hots share the same neutral, the two hots have to be fed from opposite legs. It's the nature of the beast.... 01-22-09: Houstonreef I then installed two breakers on each leg of the panel.===================== |
01-22-09: Houstonreef Houstonreef, Does the wire you bought look like this? . |
EG., see my post above for starters. Are or is this cable using twisted pairs?? In essence, did you simply run one cables then to use as a dedicated line for such a circuit? Did you keep the positive (hots) still twisted together? Same for the Neutral and ground, were they twisted together? You should have put another neutral in there as you went with using two different phases. Albeit, things should work anyhow. I’ve seen worse BTW. If so the buzzing issue you experience without the use of the conditioner is due to some ground loop issue somewhere in the house. Plain and simple. Keeping the pairs twisted together at first made me think you’ve added some inductance along the way too that would not ordinarily be there usually. But that’s not the deal. As you ran two twisted pairs of #10 AWG stranded the wire alone should stand up to 30 A. Solid #10 = 25A max. Stranded #12 = 25A., and solid #12 = 20A max. the thinking behind why use the appropriate gauge wire is this, heat as well is a factor which increases current. An appropriately sized conductor will transmit and conduct that heat energy sooner than will larger gauge conductors. …and that’s what we are trying to prevent here with proper ckt applications… fire, not necessarily saving the causer of the overload, but the rest of the array and perhaps lives. Had you ran two runs of grounds and commons, I think it would have been more to code and better overall… at least in my area, that’s code. In effect you have ONE dedicated line attached to two breakers for all intents and purposes, and again, it should work… but it’s the ‘cheapie/temp’ way to do things… and it pays to do electrical things properly. To find the issue, turn off everything BUT the breaker controlling the thing that’s buzzing. Turn on the thing. See if it still buzzes. If so it’s a ground loop… and likely comes from either your Pay TV svc. Or your phone svc. If it doesn’t buzz while it’s the only energized thing in the house, begin flipping on breakers on that phase, one at a time… continue to the opposite phase, until you find the ckt to which the ground can be attributed. Worse case scenario would be the ground issue is an accumulation of household items being used in which case l3eaving on the amp, and energizing more breakers/circuits will increase the level of the hum/buzz as you go along. The choices once the item causing the issue is found are: Call an electrician. Disconnect things from the ckt which is causing the GL until you get to the actual culprit and never use that again. Cell phone charger, UPS for the PC, rheostat (lighting dimmer) , etc. or get a better one. If the buzz is there with everything else off, it is most likely the cable TV or phone… to make sure, disconnect the coax feeding the Sat/cable box and see if you still have the buzz/hum. In that case a transformer can be put inline with the coax feeding the cable box. Sometimes right at the box, or outside the house where the coax run begins. If it’s the phone install another ground rod explicitly for the phone. I won’t guarantee this move, but I’ve seen it work. Disconnect the orig ground ckt, and drop the new rod several feet away from the orig one. 10 ft. should do. Lift the ground from the receptacle the amp is plugged into. Either by a cheater plug (both hot & common but no ground pin), or by removing it from inside the outlet itself. If you chose to put breakers one on each phase because that was the only available unused slots. There is a work around for that as well. They are called Wafer breakers. Half the size of standard breakers so that two fit into the same space as ONE regular breaker. They come in various ampere & voltage sizes too. Thus allowing you to put both ded lines onto one phase, which was recommended. I must also say here at this point, I was an electrician in my past. Mainly industrial and commercial efforts… some residential now and then on the side. I gotta say here you really should contact a card carrying sparky for this event, but if you feel compelled to proceed, it is surely at your own risk. Not trying to scare ya… I’M just CMA. Good luck. Hope that helps. |
01-23-09: HoustonreefHoustonreef, You cannot use portable Cord for fixed branch circuit wiring.... It is not approved by UL or NEC for such use. 01-23-09: Houstonreef It all depends on your circumstances as well as what your local governing authority allows. The electrician will advice you what will meet the code in your area. If allowed for your wiring situation my first choice would be NM-B cable. I would also use plastic rough-in boxes. Second choice would be MC cable with aluminum armor. At any rate tell the electrician you want 120V dedicated branch circuits. Dedicated branch circuit? A 120V branch circuit that consists of; (1) hot conductor (1) neutral conductor (1) safety equipment grounding conductor. Make sure each dedicated branch circuit has its own NM-B cable or MC cable. Do not combine dedicated circuits in the same cable or raceway, (conduit). Tell him you want solid core copper wire #12 awg minimum. If the branch circuits are long move up to #10 awg solid copper wire. And for the reasons Gs5556 pointed out in his post the length of the dedicated branch circuits should be the same. At least as close as possible in length. Terminate both dedicated branch circuits on the same leg in the electrical panel. |
The length of dedicated ckts, one to the other, is superfluous. Arbitrary. Only really extensive runs of #12 romex (which is likely what will be used, unless otherwise specified) need to be addressed by increasing the wire gauge a step up. This is not a common circumstance however. Even huge homes, or multi story homes, have additional sub fed panels these days, thus reducing the lengths of runs required. And thereby keeping the gauge of wire accordingly employed. Commercial & industrial applications can vary some here, but residential installations seldom if ever need to address voltage drop issues by up scaling the wire type being used. You can request the use of shielded cabling to further remove the ckt from ancillary or spurious artifactsÂ… adjacent EMF, IHF, IM, etc. Again, I think this is overkill. If the runs do encompass higher current carrying supply lines, like HVAC, then it would be a more valid considerationÂ… or if you simply wish to throw more $$$ at thisÂ… then by all means feel free. IÂ’d say save your money for conditioning, or other things. |
Blindjim, Just curious.... Why did you spend big bucks for Shunyata Python VX and Shunyata Research Taipan helix Alpha power cords? I believe the wire gauge in the cords is equivelent to #10 awg. For the length of the cords you could of more than likely got by with 16 or 14 ga wire. Looks like Houstonreef's branch circuit run is only 8' long. #14 awg would be plenty big.... But I would advise him to still use #12 ga. By the way the ampacity rating for #12 awg cu is 20 amps whether stranded or solid. #10 awg cu is 30 amps, stranded or solid. NEC 2008 Table 310-16, *see 240.4(D) Check out what this EE has to say about VD and power amp power supplies. |
RE amp load With stranded wire the jacketing or insulator, can allow for an increase in current carrying, over that of solid wire of the same guage. For ex. a #14 stranded THHN will carry the same as a #12 solid romex. RE Python VX vs. Taipan helix A. Well then, i suppose wire gauge isn't the end all be all in cabling.... huh? A long time ago you could buy brand new a Camaro or a Mustang, outfitted about the same... 350cid in the Chevy and a 351 cid in the 'stang. Both are V8's.... both felt differently too. If the Taipan HA & the Python VX were the same cable they would sound the same. They don't. Elsewise only one of the cables would have been made, huh? The VX actually supplies front end & spinning gear whose current draws are far less than the draw the Taipans see routinely. One would think the larger gauge cable needed to be on the amps, not the front end. Right Well audio isn't always intuitive. Sometimes, it's all about the infulence, or what the item brings to the table in it's inherent characteristics... not it's specs. Let's not forget too, them magical beans, er, beads, in the VX. I have moved them all around in all of my systems, and they work elsewhere. I just feel they work best for me in those spots & reasons, I mentioned. Hope that makes sense. |
Blindjim, Did you read my post, (01-26-09: Jea48)? 01-25-09: Blindjim |
Jea48, At work and on the internet EE's are full of reasons why paying a premium for cables, CD players, equipment etc.is not good. EE's are non believers of anything Audio. To them all CD players are the same. A bit is a bit. They play thier Bose systems with thier lamp cord wire and brag about how much money they saved and how stupid it is to be involved in anything more. I do not even bother to listen to them anymore. Sorry, I needed to get this out. |
NEC Codes might have been updated in the past few decades, but back in the 70s and 80s, the specs i noted here were acceptable.... passing inspection everytime. I've never been red tagged following an inspection... well, when I was a practicing sparky. That career stopped in '83 adn another began thereafter. BTW... local codes can and do superceed NEC codes, routinely. |
A lot of changes since 1983. Sorry if I ruffled your feathers. Enjoy the music. Jim . |
Hanaleimike, I'm a little late to this discussion, but anyway, here is a question for you: When you said: " I would think that if each receptacle has it's own run via a 12/3 wire , all the way back to the panel on a separate ground bar in the panel, that there couldn't be any ground loops. I think the ground pin in the receptacle runs back to the panel, and the receptacle itself is grounded to the metal box. It sure made a difference sound wise too." Specifically " separate ground bar in the panel"- did you mean, that there is supposed to be a separate ground bar for each dedicated line? I understand, there is only one ground bar in the panel. Could you please explain that in more details? I always been somewhat confuzed about the term "isolated ground"- isolated exactly how? The reason I'm asking is this; I have licenced electrician to install separate panel with five dedicated lines connected to it: One for digital, one for analog, two for power mono blocks, and one for video projector He used Romex 12/3 wire, and to my understanding, at least, that's how I asked him to do it, ground wire from each receptacle (actually there are two receptacles on each run of wire) is connected to a ground bar in the panel, and the ground bar is connected to a copper ground rod right next to the panel, and to a common house ground elsewere. Still, I have a ground loop problem somewhere. Even when just a power amps connected to the speakers, and nothing else connected to the amps, and with grounds lifted on both amps with a cheater plugs, still I hear faint hum (much louder with no cheater plugs). I have tried everything: Unplugged every piece of equipment, and turned off all circuit breakers, Lifted grounds on every single piece, There is no cable, or TV on the same circuits, Disconnected copper ground rod, installed along with the new lines, from the panel- still, there is ground loop somewhere. Now, I suspect, there is something wrong with how the ground wires from the dedicated lines are connected to the panel. Unfortunately, I don't know of any audiophile electrician in my area, who could sort out the problem, and my "regular" electrician apparently has no clue. Please, could somebody explain how to correctly ground my five dedicated lines, and how exactly "isolated grounds are created?" Thanks in advance. |
Are they all on the same leg in the circuit breaker box? They are probably on both legs. Try plugging everything into one outlet and see if the hum goes away... I have learned alot from this thread. I found that my 3 dedicated circuits were not only on the 2 legs, but one of the grounds, neutrals were put on opposite sides of thier hot wire. So, I moved everything to the same side in the breaker panel, including grounds and neutrals. |
I have licenced electrician to install separate panel with five dedicated lines connected to it:A sub panel fed from the main electrical panel. By chance do you know what size wire he used to feed the sub panel? I assume the electrician fed the sub panel from a 2 pole breaker in the main panel. Look on the breaker handle of the breaker what is the number? 40, 50,60, ect? Because you have a sub panel the panel will have a separate ground bar. The equipment grounding conductors that are part of the dedicated branch circuits that feed the receptacles will terminate on this bar. The ground bar will have an equipment grounding conductor, wire, that goes backs and connects to the main electrical panel ground bar. No exception....per NEC. He used Romex 12/3 wire, and to my understanding, at least, that's how I asked him to do it, ground wire from each receptacle (actually there are two receptacles on each run of wire)......A dedicated circuit feeds two duplex receptacles? Is that correct? Why did you use 12/3 with ground? Is the ground bar in the sub panel an isolated ground bar? There by isolated from the panel's metal enclosure? ...... is connected to a ground bar in the panel, and the ground bar is connected to a copper ground rod right next to the panel, and to a common house ground elsewere. More than likely here is your problem. Just bet you have a difference of potential, voltage, between the equipment ground at the receptacles and the neutral, the grounded conductor. Per NEC the feeder equipment grounding conductor shall be installed in the same cable, or raceway, as the feeder current carrying conductors. And the equipment grounding conductor shall terminate in the same panel the feeder is fed from. http://www.aes.org/sections/pnw/pnwrecaps/2005/whitlock/whitlock_pnw05.pdf |
Jea 48, Sub panel is connected to the main one with 4 AWG wire, with Black, White, Red and naked copper ground conductors. Breaker in the main panel, feeding the sub panel is 60. The wire he used for dedicated circuits has Black, White and naked copper ground conductors, so I guess, I mistakingly called it 12/3. All five dedicated circuits feed 5 duplex receptacles, that is correct. I don't think, that the ground bar in the sub panel is isolated from the panel metal enclosure. Yes, sub panel ground bar IS connected to the main panel ground bar. Also main panel ground bar is connected to an additional copper rod, installed at the same time, as the sub panel. And one more thing: I noticed, that a small connector box with TV and Internet cables, has a ground wire, connected to the main panel ground bar. I have two questions: 1. When evrybody says "isolated ground" does it mean ground bar in the panel isolated from the metal enclosure? And, if it's not isolated from the panel (like in my case, it seems), would that be a problem causing ground loop? 2. You'd have to forgive me, but I'm not entirely clear about the last part of your post; "More than likely here is your problem. Just bet you have a difference of potential, voltage, between the equipment ground at the receptacles and the neutral, the grounded conductor. Per NEC the feeder equipment grounding conductor shall be installed in the same cable, or raceway, as the feeder current carrying conductors. And the equipment grounding conductor shall terminate in the same panel the feeder is fed from". And how exactly should I correct this problem? Thanks a lot for taking your time- it's really priceless. |
1. When everybody says "isolated ground" does it mean ground bar in the panel isolated from the metal enclosure?I don't know about everyone else.... But that meets the definition as far as NEC. Then from the isolated ground bar an insulated equipment ground wire would run back to the main panel and connect there. And, if it's not isolated from the panel (like in my case, it seems), would that be a problem causing ground loop?No. 2. You'd have to forgive me, but I'm not entirely clear about the last part of your post; I was going by your statement: ...... is connected to a ground bar in the panel, and the ground bar is connected to a copper ground rod right next to the panel, and to a common house ground elsewere.============ Sub panel is connected to the main one with 4 AWG wire, with Black, White, Red and naked copper ground conductors.Well the #4 awg copper wire is good.... Actually good for 70 amps.... Not sure what all the bare, you call naked, copper ground wire is all about. I assume the insulated #4 awg wire is installed in a conduit back to the main panel. Are the bare ground wires in the conduit? I have a feeling the answer is no. Per NEC the feeder equipment grounding conductor shall be installed in the same cable, or raceway, as the feeder current carrying conductors. And the equipment grounding conductor shall terminate in the same panel the feeder is fed from".Call the electrician and have him redo the job per NEC at no charge to you. >>>>>>>>>>>>>>>>>>>> How big is the conduit for the sub panel feed? 1", or 1 1/4"? Approximately how long is the run? Because of the 60 amp breaker used that feeds the sub panel the equipment grounding conductor would only have to be a #10 awg copper wire. (NEC 2005 Table 250.122) If it were me I would have the electrician install an insulated #6 copper wire. Minimum, a #8...... =========== Ozzy asked the question, are the branch circuits hots connected to the same leg in the panel? Post from a member on AA Also check the receptacles for the proper AC polarity. |
I made pictures of the both main and sub panels. You can see it in my system or try the link below. http://cgim.audiogon.com/i/vs/i/f/1233285302.jpg http://cgim.audiogon.com/i/vs/i/f/1233285348.jpg |
Jea48, As I posted above, there a pictures of the panel, that should answer some of your questions. 4 AWG wire is not in a conduit, it's the thick white one in the picture, and the bare copper ground is inside of the white insulation, with the black, white and red ones. The run for the 4 awg is just about 3-4 ft. 3 of the hots appear to be connected to the L leg, and the other two to the R leg (see pictures). Polarity in the receptacles is fine. What do you think about ground from the cable connector box?, it's the green insulated wire going into the main panel from the left. (see pictures). |
Maril555, Looks ok to me..... I see the feeder equipment grounding conductor is part of the feeder cable. I assume it connects to the ground bar in the main electrical panel. Sub panel looks fine. Branch circuits are fed from L1, leg, of the panel. Branch circuit equipment ground wires are connected to the ground bar. I see nothing wrong with the installation. I see you used #10 NM-B, (romex example of), for 4 of the branch circuits. Orange cable sheath signifies #10.... What does the #14 NM-B feed? (white sheathed cable) Approximately how long are the branch circuit runs? |
The white one #14 NM-B feeds front projector. Breakers are 30 amp., I don't know, why he used them. The cable runs are approx. 50-60 ft. ? I also see one orange 12 awg. cable entering the sub panel- the black (hot ?) wire is not connected to the breaker, terminated with the cap, the white and bare ground are connected to corresponding bars. What's that about, I don't know. Could that cause a problem? In any case, I'm back to square one. What else can I do??? |
I also see one orange 12 awg. cable entering the sub panel- the black (hot ?) wire is not connected to the breaker, terminated with the cap, the white and bare ground are connected to corresponding bars. What's that about, I don't know.It appears to be a spare future branch circuit run. Could that cause a problem?No ======= Looking at your picture of the sub panel, the neutral bar on the left side of the panel appears to have a machine screw with a round or pan head on it. The machine screw is near the top part of the bar. Is that the case? If that is the case, is the screw head green in color? Does the screw look like it might be go all the way through the bar and screw, fasten, to the panel enclosure? ============================== In any case, I'm back to square one. What else can I do??? There is no cable, or TV on the same circuits,But do you have CATV connected to the audio system? Did you try disconnecting the CATV company's coax cable totally from the audio/video system? |
Jea48, I will have to look at that screw when I get home, but what are you thinking about? There is no CATV cables connected to my audio system. The only video cable, is DVI, connecting DVD player to the front projector, and disconnecting it doesn't change anything. As you probably noticed, the amps and preamp are balanced design, could that be a culprit? I have a computer in the same room, but it's not connected to audio in any way, and is on a different circuit electrically. |
I will have to look at that screw when I get home, but what are you thinking about?Looking again closely to the picture it looks like the screw is used to connect the left side neutral bar to the cross tie bus to the right side neutral bar..... I thought at first glance the screw was a bonding screw to bond the neutral to the enclosure. That would have been a no no for a sub panel.... ================= |
Hevac1, It couldn't hurt if Maril555 moved the projector branch circuit over on the other leg, L2, of the sub panel. Might even help in balancing out his main electrical panel. Will that solve his hum problem? No, jmho. As for the total load that is connected to L1 leg of the sub panel, I would just about bet the total combined FLA of all the associated audio equipment is 20 amps or less..... |
Even when just a power amps connected to the speakers, and nothing else connected to the amps, and with grounds lifted on both amps with a cheater plugs, still I hear faint hum (much louder with no cheater plugs).Maril555, If your hum problem exists with nothing connected to the inputs of the power amps to the extent you even used ground cheaters on the plugs of the power cords maybe the problem is the power amps and the The Bolero's sensitivity of 92dB/W/m. (much louder with no cheater plugs).Again with no ics connected to the amps inputs? Just the amps connected to the speakers? Totally isolated from one another? |
OK....before you kill yourself and us....pull out your amp and take it to an audio store...or high end used equipment seller....or just a friends house who has some halfway decent speaker (almost anything costing over $100 will do). Connect the amp with no input to their speaker(s). See if there is a hum and if it changes when you touch the amp case. If it does....fix your home electrical so it's up to code and get your amp fixed. If there is no hum...come back and we'll work on the problem. |
Jea 48, Just last night I did another experiment- connected both power amps and preamp to a single outlet with a power strip, no cheater plugs- faint hum in the R channel and louder hum in the left. Funny thing is, that I have the same model power amp before, just in stereo configuration (BAT-75 SE), and had the SAME problem, hum louder in the L channel. I am absolutely sure the amps are fine, they are on loan from my friend, and are absolutely quiet in his system. I didn't take them to my living room system to try, just because they are so heavy. I will try again with no ICs connected, but then I'd have to use plugs in the inputs, otherwise they pick- up noise as antennas. Ghstudio, I'm pretty sure my electrical is up to code, as Jea48 seems to agree with. |
Just did it again- no ICs connected, plugs in the inputs- same hum.Maril555, By chance do you have a multimeter? If so why not try a plug polarity orientation test for each power amp. To do the test you will need to trim the polarized plug blade on one of the ground cheaters. A pair of tin snips will do the job. Trim it down to match the non- polarized blade. The idea is so you will be able to plug the cheater either way into the wall receptacle. For the test, no ics, just the plugs on the inputs of the amps. Plug the modified ground cheater in the 120v recept the normal way and plug the amp into the cheater. Turn on the amp. Set the multimeter to AC volts. Insert one test probe of the meter into the U shaped ground hole of the recept making good contact with the metal ground contact. Touch the other probe of the meter to the chassis of the power amp. If you have to, remove a screw on the back somewhere to make a good contact to bare metal. Note the AC reading..... write it down. Now turn off the amp..... You will need to wait awhile before you can turn the amp back on for the rest of the test, so just preform the same test on the other amp next. Just follow the same procedure for the second amp. Again make note of the voltage measurement. Now go back to the first power amp. This time you want to flip the cheater plug 180* in the recept. Turn on the power amp. Again measure the AC voltage from the ground of the recept and the chassis of the amp. Note the voltage. The lower of the two voltage measurements is the correct plug orientation polarity. Repeat the test for the other amp. Big question now is the hum less for each amp? If the preamp has a 3 wire plug you might want to check it as well. Make sure all ics are disconnected from the inputs as well as the outputs. ================ http://www.soundstage.com/weaver01.htm . |
Jea48, First to answer your question- If I understood you correctly, you are asking if the hum is less with ICs disconnected?- No, it is not. Can I use a polarity checker, kind they sell in Home Depot, to accomplish the same, unless you meant to do this test for a purpose, other, than to check polarity of each receptacle? I cannot understand one thing, though- how come the hum is louder in one channel??? |
