Why do I need power management if I have a great power cord?

I just installed a dedicated circuit for my system.  I installed 10 awg solid copper.  Although 10 awg supports up to 30amp, I used a 20amp breaker.  More than I need.  I also installed a 240V circuit.  I needed it since I bought a European amp that only uses 240V.  But I'm glad to have it for any future amps as doubling the voltage cuts the current in half for the same power.  This makes your amp feel like it is just sitting next to the power plant with a huge cord.  I too highly recommend running your amp at 240volts instead of 120 if possible.

To install 240V circuit the marginal cost increase compared to the 120V circuit is not much.  An extra breaker (perhaps $10) and 3 conductor vs 2 conductor wire, and then a slightly more expensive outlet.  the main cost of the circuit is all the labor and work inside the wall and cutting wallboard and replacing it.  All of that doesn't change when you install the 240V circuit with your 120V circuit.

Doubling the diameter of a wire increases cross sectional area, and approximate power carrying capability, 4 times, not 2.

The power delivered to the speaker is almost irrelevant to the power the amp needs, especially for class A.  Not sure why that discussion broke out.  My class A 35 WPC amp, that I run at about 1 wpc 99% of the time, uses 400 wpc, either at idle or at max volume.

I reference people back to page one to the post I made with a quote from the AR user manual where Audio Research requires a 20 amp, 12 awg circuit for a 75 wpc class AB tube amp.  I know many of you don't believe it can be true unless you hear it from an OEM so it is there in black and white.  I copied and pasted it.

Jerry

The bottom line is you need to deliver plenty of power reserves to your amp to allow it to make good bass response.  It isn't as simple as supplying the nameplate current to the amp.  

The second half of the question, which is often debated, is, do you need to "clean up the power" to be 120V with "no noise" in it.  Many think that isn't necessary since the power is promptly rectified in the amplifier.  Others think it makes a huge difference.  

The problem I have is when the second effort affects the first.  If a power conditioner restricts current availability to address spikes needed to make good bass, it affects the sound. 

Everybody wants to sell more stuff.  But if a power conditioner comes with a 14 gauge cord on it, then I would suggest passing, it isn't designed to provide power for the spikes.  The exception would be if a power conditioner has provisions to store power internally to address the spikes.  Need to makes sure impedance doesn't limit the ability to address fast spikes.   

Bottom line is, putting anything upstream of an amp except a heaver (10 awg) power cord has a lot pitfalls that for sure some manufacturers don't address.  Do your research.  If possible, demonstrate the conditioner in home and have someone help you with a blind test vs plugged directly into the wall.

Jerry

From Audio Research VT80SE manual. This manufacturer gets it:

"A.C. Power Connection It is important that the VT80 SE 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 VT80 SE for On/Off control of the amplifier, or the 12V start-up trigger for remote installations. The AC power source for the VT80 SE 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 100 or 120 volt circuits, the VT80 SE 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. "

Note that it requires 10 amps at 120V.  That is 1200 Watts.  Nameplate wattage for this amp is 200 watts at low power.  This is the concept that many "audiophiles" reject.

@raysmtb1 Pretty sure guys paying $37k for a cable are not going to drive a $37k car.  

@atmasphere great discussion of these two power conditioners.  I wonder 2 things: 

1.  How much load do they add?  To supply a 400W amp does the load (and heat in the room) go up to 800 watts?

2.  Are these expensive high end units able to totally eliminate transformer hum?

thanks, 
Jerry