A lot of changes since 1983. Sorry if I ruffled your feathers. Enjoy the music. Jim . |
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. |
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? . |
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? |
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. |
Blindjim, Did you read my post, (01-26-09: Jea48)? 01-25-09: Blindjim |
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 |
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. |
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? |
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? |
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..... |
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 . |
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?No, you will not be checking if the receptacle polarity is correct. You will be checking if the 120V AC polarity orientation of the primary of the power transformer of the power amps is correct. If you do not have a multimeter you might just try a simple listening test. Same set up with the ground cheater just listen for any difference..... The meter is the best sure way though. You can pick up a decent one at Rat Shack for around 50 bucks.... ====================== http://www.audioasylum.com/audio/general/messages/449743.html http://forum.audiogon.com/cgi-bin/fr.pl?htech&1014011751&openusid&zzSean |
new measurements:Wow, I could see where the reading might be high in one direction, but not high in both directions. I just checked my little ARC VT 50 power amp. Correct plug orientation with the ground lifted was 3.6Vac When I reversed the cheater in the receptacle outlet the voltage jumped up to 93.5Vac...... ================================= Would you do me a favor and conduct another small test for me? Set you meter on the 250Vac scale. Use the receptacle you were using for your test. Insert one probe in the T slot, (neutral), of the recept and the other probe in the equipment ground making sure of a good mechanical contact. Any voltage reading? It should be zero. If no voltage, set the meter on the 50Vac scale and repeat the same test. Any voltage reading? Again it should be zero. Move the meter selector down to the next lower scale and repeat. The meter should still measure zero Vac. One final test. Set the meter on the 250Vac scale. Measure the voltage between the Hot contact, small slot, and the neutral, T slot. Make note of the reading. Next measure the voltage from the Hot contact to the equipment hole contact. Both voltage readings should be the same. . |
I would take the noisier of the two amps back to your friends house and have him connect it to one of his speakers...... Take along the power cord and the speaker cable. Take along your multimeter too. If it does not hum/buzz there, &^#@$%#@, Check the voltage at the wall outlet he plugged the amp into. See if the voltage is lower than yours. Are these amps self biasing? |
Maril555, You misunderstood what I wanted you to do. All the test measurements are taken at the wall receptacle outlet only. No audio equipment is involved with the test. In simple terms the test will tell if there is a good electrical continuity between the main incoming service neutral conductor, of your electrical service, and the equipment ground. At some point the electrical service entrance neutral conductor is connected to earth and is also bonded, connected, to the main equipment enclosure as well as equipment grounding bus bar/s. In most cases this is done at the main service electrical panel. Not sure in your case though. I noticed from your pictures the main breaker is not in the main panel so it is more than likely out side by the electric meter. Connection to earth and equipment bonding may have been done there. So the test is a simple way to look at the thing just from one branch circuit and receptacle. I tried to explain best I can in layman terms. So at the wall receptacle outlet only. Measure from the neutral to the equipment ground, (U shape hole).... Should show 0 volts Measure from the hot to the neutral.... Should be around 120V to 123V Measure from the hot to the equipment ground, (U shape hole)... Should be the same as the voltage measurement from Hot to neutral. And one more measurement if you would. Plug in and turn on one of the power amps and using the other receptacle of the duplex receptacle measure the voltage from the hot to the neutral. This will give a somewhat load condition on the branch circuit for any voltage drop. The voltage should be within about one volt of the reading with the power amp not connected and turned on. A true test would be to play some music at a moderate level and take the measurement. |
The measurements are good...... The bad news is it does not help the hum problem. From the pictures you supplied of the sub panel what I could see the electrician you hired did a good job. The only code violation I could see was the (4) 30 amp breakers he installed for branch circuit protection instead of 20 amp breakers..... Just guessing he did what you probably requested. At any rate that would not be causing your hum problem. You seem to have isolated your hum problem.... The problem exists between the power amps and the speakers. Could your problem be RFI/EMI on the AC mains of your home's electrical system? Well if you live in an area that is warm at the present time you could shut off every breaker in the main panel except the 2 pole breaker that feeds the sub panel. Then check the amps for the hum. LOL, take a flashlight with you.... If the hum is gone then start turning back on the breakers one at a time until you find the source of the problem. Still hum? Then, jmho, I would think that would rule out RFI/EMI noise, interference, on the mains. That is, at least from a source within your home. That does not mean EMI/RFI noise is not coming in from outside your home on the utility power. ========================== Maybe the problem is the power amps and the sensitivity of the speakers?? By chance do you have another pair of speakers you could try? Less efficient? You might try a different pair of speaker cables. For a test just some cheapo Home Depot rip cord would do. Sorry, I am out of ideas...... I did send an email to an EE who posts here on Agon. I asked him to read the thread and post a response if he has any ideas. Jim |
BTW, what's your take on the high chassis voltage, higher with the correct polarity?Well the lower chassis to equipment ground voltage is the correct orientation polarity for the amps. Seems odd to me both amps would have the primary of their power transformers wire incorrectly. By chance are you using aftermarket or home brew power cords on the amps? If so it could be the cords are wired wrong. The wiring on the 3 wire NEMA plug could be right but the hot and neutral on the IEC are reversed. Easy to check with your multimeter. Just pull each cord from the amps and check the continuity from end to end on the pcs. |
Hevac1, The two pole 60 amp breaker will trip just fine if there is an overload or short circuit on just the one pole of the breaker. It is designed to do so. I assume the reason Maril555 paid to have the sub panel installed was to keep his audio branch circuits somewhat isolated from the loads in the main panel. If you look at the pictures, Maril555 supplied, you will see he had plenty of room in the main panel for the 5 branch circuits. Your post got me to look at the picture of the main panel again and that reminded me I was going to ask Maril555 why he didn't have the electrician move the two GFI breakers, across from the 2 pole 60 breaker, to another location in the panel. |
A bad tube can definitely cause a buzz and a bad electrolytic in the power supply can cause a hum. I would also think a leaky cap in the signal path could cause a hum. You might want to send an email to BAT customer support and ask them. You never answered my question. Do the amps have auto biasing? If you do not know for sure I would not just switch the tubes around. |
