Bench testing power amps with a power supply

Foxy Love

CarAudio.com Newbie
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Hi all,

Interested in a little technical advice re testing power amps on a test bench (ie with a power supply)...

Can anyone with specific experience / specific knowledge advise what sort of idling current could be expected from a high power amp (say rated 1000 watts or so) under a no signal condition?

And also - what sort of startup / surge current might be expected?

Basically need to quickly test different amps, just to confirm they power up and play a clean signal.

In my opinion, a 30 - 40 amp benchtop PSU is more than adequate for this purpose, and should power up any car amp. Totally understand that it may not adequate to run at moderate to high volumes in some cases.

And I should also add, this isn't for the purpose of testing repairs, or auditioning etc. Just basically to sort dead ones from potentially good ones in a recycling environment.

Can anyone suggest an actual example of an amp that would not be able to simply power up to idle and run a low volume signal with such a power supply?

I maintain that no single car amp draws current beyond 30 amps at idle (ie with no signal), and I would be surprised if any amp would draw a startup surge current that would exceed what the PSU is capable of.

I have others telling me otherwise, who will point to (for example) 4 x 40A fuses on an amp (ie maximum current potentially close to 160amps) and point out that a 40 amp supply won't even switch it on. These guys know a bit about ohms law, but not much about amplifier design me thinks.

I call ******** on that theory :)   And if an amp is drawing 40+ amps at idle, then that's a hell of a lot of power being magically dispersed somewhere!! I have years of experience with domestic audio, (mains powered class A/B amps etc) but not so much with high power car gear.

For the sake of simplicity, I should add that it's not a case of looking at alternative solutions, all I am interested in confirmation that I am correct that a 30 - 40 amp bench top PSU can do this, or if I am not correct, a decent technical explanation as to why not.

Cheers!

 
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Seeing as I have a ton of experience in this department... let me be the first to say your friends are idiots lol :)  A 30-40 amp PSU will be more than enough to test functionality of any amp I have seen. 

Most I have seen a amp pull at idle was 3 amps. Most come in at about 1-2amps at idle, and that usually is dependent on if it has a internal fan or not. 

Most I have ever seen a amp pull at turn on was 17 amps, and that was a 2800W Class A/B amp. Most amps there is little to no difference between Idle current pull and turn on.

 
I bought a MeanWell knockoff switch mode power supply over five years ago and it's still going strong. I have it dialed in at 13.8v and it's good for around 50A. I have stressed it repeatedly for time periods lasting well over an hour and it delivers. Like the type below but I didn't buy from that particular seller.

https://www.ebay.com/itm/Switch-Metal-Power-Supply-Adapter-AC-To-DC-12V-10A-30A-40A-50A-60A-for-LED-Strip/382495999270?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D52885%26meid%3D04a2e12408e646b3866fafe5a36405a9%26pid%3D100005%26rk%3D3%26rkt%3D12%26sd%3D392078178398%26itm%3D382495999270&_trksid=p2047675.c100005.m1851

 
I've tested function on many amps using a RadioShack 3.0A 13.8VDC supply.  I haven't ran across an amp that won't power up and idle with it. 

I normally use an Astron-based power supply capable of 20-25A.  It is more than enough to test basic function with music and test signals. 

30A is overkill to test basic function, but never bad to have on hand.

 
Thanks all for your replies, and yes is as I expected.

Appreciate hearing it from people who have done the same plenty of times.

Cheers!

 
Thanks all for your replies, and yes is as I expected.

Appreciate hearing it from people who have done the same plenty of times.

Cheers!
I don't think any properly functioning amp will draw more than 8-10A at idle and that's pushing it.   That said, the operative word is properly functioning, so you may want to use a 3-5A fuse  when first powering up just in case there's something fishy going on inside the amp.

 
I don't think any properly functioning amp will draw more than 8-10A at idle and that's pushing it.   That said, the operative word is properly functioning, so you may want to use a 3-5A fuse  when first powering up just in case there's something fishy going on inside the amp.
Agreed.  I usually power up an unknown amp with an inline fuse, 5A-10A is usually fine. 

 
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Foxy Love

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