2. amps-preamps
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Amplifier current draw/wattage

Hello All,
Trying to figure my system's total power requirement.
I'll have 12 devices plugged into the wall, or some kind
of power supply. By reading fuse sizes and/or power
consumption, I come up with about 24.75 amps (120-VAC).
This is only steady-state operation and I don't think
includes startup surges. The power amps take most of this
draw.
I feel fairly comfortable with the accuracy of this figure.
Here's my point of uncertainty: I do not know if the
amplifiers draw more current as I increase the volume.
I have 4 amps (powering 4-way speakers):
Bryston 3B-ST..............5-A fuse
Linn 5105 - 2 of these....."6.3-A MAX"
NAD 2600a..................5-A fuse
So at peak current draw the 4 amplifiers would supposedly
draw about 22.6 amps.
Can anyone tell me what class each of these amplifiers
belongs to, I know only that none are class A.
********
I can certainly supply more info if anyone asks.
Does my reasoning seem sound ?
The whole result is that it appears I need to add
a new 30-A circuit from my breaker panel, probably
with 8-ga wire. This will be a fair amount of work.
noslepums
magfan
1,583 posts
 
Another, more obtuse path to the same data would use an SPL meter, test tone disk and a good DVM or scope....scope preff'd. The voltage at the speaker is related to *power* to the speaker.
OR
You could also measure watts used...of the amp, and calculate backwards using probable efficiency of amp. Hi/Lo estimates will yield a range of powers.

Al's method relys on knowing the sensitivty of the speaker. Not always reliable or even measured the same way.

BTW, Charles, amps need a load to generate power. So, in that sense they are entwined. Don't run any tube gear without a load or you'll get another lesson in electronics....and the bill to prove it.
noslepums OP
22 posts
 
Hi Everyone,
For me, this thread has been quite helpful, thank you !
Elizabeth, I believe I could have described my problem
with better wording, but I do understand and agree with
your explanation.
Ngjockey, you raise a good point about impedance matching;
another variable I should examine closer.
Koestner, I don't know why I didn't think of getting
a wattmeter myself.
So, hopefully I'll be fine with a normal 20-A supply,
and listening to the music at semi-sane levels.
charles1dad's avatar
charles1dad
10,249 posts
 
Hello AL,
Thanks for your response. Al I already knew the calculation and realized that at my listening distance= 9feet and usual sound levels=70-85db(depends on recording) I`m only using small fractions of a watt! I was just curious to know if the inexpensive device could measure and confirm with an actual meter readout.
Best Regards,
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