Current: Power Line and Amplifier Amp Ratings


I have little knowledge when it comes to power and alot of specifications relating to amplifiers. Hopefully some people here would be able to assist me with a few items.

My electrical sockets are currently all 15 amp.

I use a Musical Fidelity amplifier, an A300 Integrated, and the specifications mention that it can do 20 amps.

Does this essentially mean that if the amplifier was required to put out this amount of current, that it is limited by my electrical setup, or am I looking at two specifications that aren't related to each other?

If these are related, would I find a considerable improvement in being wired for 20a, with a 20a socket? When I ask this, I am not looking to find if benefit would come from a dedicated line, or changing wiring, simply from a technical perspective, if all things considered, things remaining exactly the same, but being setup for 20a instead of 15a.

Also, often I will see amplifiers that have a peak current output of say 50a, or 75a. Are these essentially meaningless high ratings if amp current is limited by your electrical setup?

Even if the above is true, is there anyway based on knowing your speakers specifications and graphs, and a certain volume level at a certain listening difference, to estimate how much current your amplifier is actually generating at typical levels, and at peak requirements?

Using my speakers as an example, they are about 87db/sensitivity, and a relatively flat 4 ohms across the frequency range.

Is it typical to find that despite the _ability_ to push our rediculous amounts of current, that most amplifiers rarely need to?

Please excuse my complete ignorance when it comes to these matters -- I have listened to many components an systems and know what sounds good to my ears, but I am still trying to understand some of the core concepts behind audio and power.

Creating short lists, and auditioning, buying value, buying quality. These are all positive things in the search for what you're looking for, but I'm sure that me understanding requirements and claims will also help me to determine exactly what and how much of certain things I need, and what is overkill.

Thanks for your help.
Hi Paris; Your 15 amp outlet has plenty of capacity for your(potential) 20 amp output amplifier. And BTW, my McCormack DNA2 Rev.A (300 wpc 8 Ohm, 600 wpc 4 Ohm, and 1200 wpc 2 Ohm) can source a theorhetical 100 amps, but under practical conditions this would never happen and I plug it into a 20 amp dedicated outlet. And I wouldn't hesitate to use a 15 amp outlet either-- if that's what I had.

I suppose if you set volume at max. your amp could possibly source 20 amps (continuous) of current but bad things would be happening to the amp and likely the speakers. For the most part, high current amps are desireable as they can be more dynamic on music as they can draw increased current for milliseconds on dynamic "peaks". This is MUCH different than sourcing 20 amps continuous.

4 Ohm Speakers with a sensitivity of 87-- 8 Ohm rating (that's 87 dB at one meter with an input of one watt) will play at 87 dB with an input of 2 watts, 90 dB with 4 watts, 93 dB with 8 watts, etc.-- power needs to double for each increase 3 dB of volume. Room size, desired listening level, and speaker sensitivity will determine max. output. In average sized home rooms, 90 dB is pretty loud (IMO) and with your set-up it only takes 4 wpc to produce that volume-- at one meter. Where the higher power becomes important is in accurately producing dynamic peaks.

And watts can be converted to amps if you want-- I just don't remember how to do it. Good Luck. Craig
Wattage equals the resistance times the square of the current. W=RxIxI. If power were 16 watts and resistance were 4 ohms, the current would be 2 amps.

By the way, the capacitors in your amp's power supply store energy like a water tank stores water. The tank is capable of delivering a high volume of water until it is depleted, even though it's refilled at a much slower rate from the pump at the well. Similarly, your power supply capacitors are filled relatively slowly from the wall current, but your amp is capable of disseminating current at a faster rate until the capacitors are depleted. Most usage requires very brief bursts of high current to support musical peaks so the capacitors almost never get fully depleted. Relative to the needs of the music, they refill quickly enough.
Paris, I'm no expert, but I'll speak from my experience and from what I've heard from those more knowledgeable than I. I have a McCormack DNA-2 LAE (Limited Anniversary Edition) and my speakers are 86db sensitivity at 4ohm.

1. I believe your MF A300 is a 300 wpc into 8ohm amplifier. If that is true, then your 4ohm load could mean amplifier power potentials up to perhaps 600 wpc. Since that potential exists, the 15 amp circuitry (wiring, outlets, and circuit breakers) could actually act as a govenor and suppress the power required by and to the amp during some to many dynamic music passages. Even at low volume levels the result can be very flat or undynamic sounding.

You could upgrade all electrical to 20 amps. But, again, if you have other components using that same 20 amp circuit as the amplifier, you will still encounter the same affects I mentioned above.

For example: I had my amplifier on a 20 amp dedicated circuit but I also had my preamp on that circuit. No big deal as the preamp only draws something like 33 watts. When I finally installed another dedicated line for the preamp, the dynamic headroom just blossomed!!! And most of my listening volume levels are at about 1/10th full volume. That's low.

2. When it comes to cleaning up the electrical, there is no such thing as overkill (within reason) so long as you aren't try to improve the sound of your am/fm clock radio.

a. You should entertain 20 amp ratings for all electrical related to the circuit for your amplifier. This would include 10 gauge Oxygen Free Copper (OFC) romex wiring, a hospital grade 20 amp wall outlet, and a 20 amp circuit breaker.

b. For your pre-amp and turntable, you should consider a second dedicated circuit at 15 amps for the electrical parts. Keep using the 10 gauge OFC romex here also.

c. For your cd player, you should consider it's own dedicated circuit since digital processing has a way of introducing digital noise back into the wall. 15 amps is good here as well. Keep using the 10 gauge OFC romex here also.

If you do these inexpensive things, you should notice some very serious improvements at the micro-dynamics level as well as a few at the macro level.

Hope this helps a bit.