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
elizabeth
6,726 posts
 
No no no.
The total peak draw would only occur at max output.
An amp like the Bryston 3B-ST will only be drawing a fraction of that power.
What you want to do is find the idle wattage. Then the maximum wattage actually used.
The fuses are not an indicator of amperage used.
I would say your three amps if used to play music at Rock Concert levels.. might start needing a lot of power.
As they are normally used. 15 amp circuit would be fine.

So if you plan on having endless 120dB concerts.. you do not need 30amps service.
A 20 amp would be fine for all your stuff.
ahendler
416 posts
 
Elizabeth is correct. The fuses are there for protection in case something goes wrong with the amp and it suddenly draws excessive current. you will be ok with a standard 15 or 20 amp circuit
koestner
293 posts
 
You can get a watt meter at Home Depot for about $20 that will give you a digital readout. It also reports current drawn, voltage, freq. and other cool stuff. I use mine to very accurately read idle watts being used on various equipment. If you plug all your stuff into a nice power strip, then into the meter then the wall you will get your answer.
ngjockey
1,042 posts
 
Bryston 3B SST: 668W @ 150W (8 ohm), 1096W @ 250W (4 ohm)

Linn 5105: 25-850W. 4700 ohm input impedance might be interesting for your setup.

Divide by 115 to get amps.

Didn't find particular specs on NAD.
magfan
1,583 posts
 
Spend the 20$ or so on a 'Kill-A-Watt' meter. This will allow you to MEASURE what you are curious about.
If you are plugged into a 20 amp circuit, you must derate by 20% for a continuous load....something like 3 hours is the time limit.

The meter will also allow you to check out 'power factor' which is an indicator of how reactive the load is. Watch your power line voltage sag as the load increases. Fun stuff.
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