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Strange? class A power amplifier still consumes electricity.

vintagetree

vintagetree

Active Member
The amp is warm all the time by comparison to the surface of any other things, even after I turn it off for long time, such as one or many days. It doesn't have standby button, only power button.

Is it normal? should I unplug it from the power surge if i don't use it?

Thanks.
 
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As a rule , class A amps are drawing ( for all intents and purposes) full power all the time when they're on. It's normal for them to be hot. Also to be warm for a while after they're switched off. We don't know which amp you're referring to (as mentioned before). It's possible it has some power still flowing in off position ( what manufacturer may or may not refer to as standby) for the purpose of maintaining a certain temp for amp to be more stable at start up. If that's the case and you use it frequently, it's probably best to leave it powered. If you use infrequently, probably best to leave not powered ( in essence then , it's a 24/7 space heater. Burning electricity unnecessarily, and while probably less of a factor, the heat over a long period of time will shorten lifespan of components. )
 
other possibility is that its not actually switching off. If its one of those soft touch button deals, it likely has a relay or some solid state equivalent to actually control power flow. If that part of the circuit isn't working it will just sit there hogging power all the time. If you have something like a Kill-A-Watt or other means of watching power consumption you'd have an easy way of telling if the power use drops off when you actually shut it off.
 
It is usher 1.5 power amp. Sorry not to get it clear. Thanks.
So, it should not have warmth when turn-off..
I will check it more carefully.
Thanks again.
 
Nice amp. Looks a lot like my Threshold s/300. Are you sure that's pure class A?

Do you have an infra-red thermometer?
 
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tomlinmgt said:
Nice amp. Looks a lot like my Threshold s/300. Are you sure that's pure class A?
Click to expand...
Obviously physically cloned from later Threshold models. Internally, however, you never found op amps in the circuit path with Nelson's designs.

"Sliding bias" class A perhaps. It simply doesn't have enough heat sink for true class A operation at that power level. Nor does Usher claim it is.
 
E-Stat said:
Obviously physically cloned from later Threshold models. Internally, however, you never found op amps in the circuit path with Nelson's designs.

"Sliding bias" class A perhaps. It simply doesn't have enough heat sink for true class A operation at that power level. Nor does Usher claim it is.
Click to expand...

Yes, the size of the heat sinks are what made me wonder. They're more like what I've had on class AB amps around the same output. Seems like pure class A amps have a lot more heat sink surface area...my Aleph 5 clone certainly does and it's less than half the rated output of the Usher in question.
 
Class A to 30-40 watts is still pretty impressive.

I've not seen another amp that draws power even when turned off, even though I would guess there are indeed others.
 
yeah that looks like a clunky mechanical switch that ought to be isolating the mains feed. That should not be hot when off, or be consuming any power.
 
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