monoblocks: one dedicated line or two?

For most amps one 20/30 amp line is generally ample (keep in mind that a 30 amp outlet requires a different plug and outlet rated for 30 amps to meet code), two dedicated lines on separate breakers will be even better. You will have twice the breaker contact area on the service panel's bus bar, and effectively isolate the electrical demand and ground for each channel. Whether they should be from the same phase or one from each phase is something you will have to experiment with. This can sometimes introduce hum. I have two dedicated 20 amp lines for my amp(s) using 10 ga. Romex, and run a line from each leg/phase by using a 2 pole breaker at the service panel. This set up has worked very well with a pair of Bryston 7B STs, and now with a Classe Omicron. For what it is worth, I find the two phase aproach to sound more dynamic, although a smidge leaner then using a single phase.

If I may offer: Any common line-born noise will emerge from monoblock "A" with "+" polarity and any from monoblock "B" will be "-". The noises (is that a word?) will come out your speakers, "meet in the middle" and cancel each other! Result is lower noise floor which is a good thing. GBA

i disagree with jnovak. i just installed 4-20 amp dedicated lines in my audio room. all the lines are equal length, 10 guage "home runs", from the top of my panel, and on the same phase. my electrician used top level circut breakers. i am using jena labs cryo'd duplex outlets. i am using one outlet each for digital and analog and one each for my monoblocks.

my opinion is that it is ideal to use 2-20 amp circuts for monoblocks as long as they are on the same phase. 2-20 amp circuts will be like giving your monoblock power supply a little more headroom on peaks....it might help but it will never hurt.

after much reasearch i have learned that the potential noise cancelation of opposite phases is far outweighed by the "ground loop" problems caused by trying to use opposite phases.

the electrician that installed my lines is a kind of "electrican to the stars" here in the seattle area. he has done hundreds of high end theatre and audio rooms and has to fix many problems caused by trying to use opposite phases. i recommend talking to a local electrician with experience in this issue for the practical side. doing the basic things right is most important in good power.

i have heard the "opposite phase" viewpoint promoted but feel that hum or noise caused by grounding problems are much more difficult to deal with than actual noise from your local neighborhood transformer.

of course, YMMV.

Just built a new home using 4 dedicated 20 amp lines. 2 lines ( 1 each) for monos. and 2 other for components. Cost about $300. Works fine Using Thor Audio 30 watt tube monos'
Hope that helps.

jnovak, I didn't quite understand that. If the power to one amp is in phase and power to the other amp is opposed in phase how does that affect each amp separately? i.e. how do they cancel out?

If you decide to run two lines to your amps, make sure that they are out of phase. That is, one line from each side of your service. The idea is that noise from one leg will cancel or equal 0 on the other. All components in a system are supposed to be in phase with the exception of monoblock amps.

I recently istalled 5 dedicated lines; 3 20amp and 2 30amp lines. One line for the digital front end; one for the turntable and phono preamp; one for tape deck. One 30amp line for each of my Krell 650MC's.

A dedicated line for each amp will improve dynamics and costs virtually nothing extra to install. If they have to run two lines, why not throw in a couple extra for good measure. Be certain to install hospital grade or audiophile grade sockets in the wall. They have a tighter connection. I used Romex, 10 gauge wire from the wall to my box,but some other audiophiles have mentioned a better stranded wire for audio. I can't remember the name.

when the job is complete, allow at least two days of having your equipment on for the new lines to break-in. My were harsh sounding at first, then glorious when burned in.

Best tweek there is in my mind. Much better than swapping for new equipment.

The answer to this question depends upon where the lines are comming from, and the 'quality' back at the service connection. If you have clean power to the hi-fi,(from the service connection) separating out the feeds to the amps won't necessarily improve the situation. If your existing lines are a source of noise, from RFI and grounding problems, then new feeds will help, though the front end will benifit more than the amps.
Good luck