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In Reply to: RE: High Current Amps posted by itolduso1000timesb4 on April 10, 2022 at 10:34:26
I love how 'high current' means something other than the only thing it can mean, which in this case is an amp can make a certain power into a certain impedance.Current cannot exist without voltage and vice versa. Together they are called 'Watts'.
A lot of times the 'current' advertised is actually how much current is present when the power supply is shorted and nothing to do with the output section at all, other than an extra bit of capacitance in the power supply.
For example, I've seen '80 Amps' advertised. If you give the amp the benefit of the doubt, and assume that into a 1 Ohm load it can make 80 amps, that means that into 1 Ohm it can make 6500 Watts! Power = Current (squared) X Resistance (in this case 1 Ohm). If you increase the resistance you see the power going up quite a lot. I don't know of amps that powerful- for that matter I don't know of a 6400 Watt amp either!
So that means a current value like that means something else- and that 'else' is the current when the amp's power supply is shorted. Briefly.
Let's say you need 400 Watts into a set of Maggies to really make them sing.
400 Watts = Current (squared) X 4 Ohms
solving for current we get 10 Amps. That's really not that much current as these ads I've seen go, but if you want 400 Watts into 4 Ohms that's the current.
It might be that too many manufacturers have been called on making outrageous claims that can't possibly be true. Is that why we don't hear about this so much anymore?? :)
Edits: 04/11/22Follow Ups:
My old Classe DR-9 is touted to be a high current amp and it surely can handle difficult loads. The specs claim 100 watts at 8 ohms, 200 watts into 4 ohms and 400 watts at 2 ohms.
While that 400 watts may be true, I recall that a review measured it at 150 watts into 8 ohms. In theory, the DR-9 seems to have the power supply with 4 coke can sized caps to support the required 14+ amps. It strikes me that marketing department went backward from the 2 ohm spec while under rating the 8 ohm power resulting in perfect specs.
-Rod
400 Watts into 2 Ohms is about 14 Amps.
The output section has to be safe with that, the heatsinks have to be adequate for that, and finally the power supply has to be able to provide the current without collapsing the voltage.
The point here is that as long as the amp can make the current into the load such that the power is made, you're 'golden'.
This was what the term "high-current amp" was supposed to signify back in the day. The term was not necessarily meaningless but it may have been somewhat ill-defined.
which had nothing to do with the actual power the amp made. I gave an example earlier.
As usual so clearly stated. Thanks Ralph ; UT
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