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In Reply to: RE: Why do subwoofers thump when turning on power amp? posted by tketcham on April 11, 2017 at 09:17:51
Well plate amps are made about as cheaply as possible. Some that thump on turn on or turn off are just either draining or rushing in a bit of DC current. In a stereo you would not get that thump because there is cap across the power button terminals, with speaker relay or blocking cap and large filter caps to block this DC. But in a cheap amp no relays, no large filter caps and no blocking cap = thump.
It's a miracle that plate amps last as long as they do. And they are getting even cheaper.
An example is I tried finding a new plate amp last month. The only "reasonable" plate amp I found uses jFET output transistors mounted on a grossly underrated cooling fin. After an hour it heats up and begins to hum. If you turn the plate amp over and "blow" on the fin the humming goes away. I mean what the f@#k. And people are buying these things for a grand or two. Subs are the biggest rip off in audio today.
Thanks for the reply. Based on your answer I'm still not sure whether it's the power amp at fault or the subwoofer plate amps. See my response to BigguyinATL.
Thumps are the signature of Poorly designed gear.. period.
Start unplugging / substituting components to try and isolate the culprit?
Subs that thump during turn-on are not necessarily "the signature of Poorly designed gear .. period."
That statement is painting all subs with a very broad brush.
Servo subs thump on turn-on. That's just the servo engaging ...... it's the nature of the beast.
My Velodyne ULD-15 Series II has been happily thumping every time I fire up my HT system for about 20 years. Perfectly normal ......... I'd worry if it didn't thump when I turned it on. It even says so in the owners manual :-)
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