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Loud thump when I power on or off

I have some NHT VT3's hooked up to a fairly nice system. The amp is the Mc6850. These speakers have the built in power amps and come with a preamp of they're own. The thumping noise never happened on my last several pairs of speakers with my current Amp. It also seems to of gotten quite a bit worse since I hooked up a turntable a few weeks ago. It is worse when the volume is turned up more.
I don't mean to sound like an idiot but my first few ideas are as follows: Buy a line conditioner, hmm, not sure what else. Do I have a ground issue? Does anyone have any ideas. Thanks,
128x128rilands
jafox
1,447 posts
 
"It is worse when the volume is turned up more."

A good practice is to always turn the volume control all the way down when powering up/down components as well as changing sources, dropping the arm down on an LP, etc. It is also good practice to power up the system from the front end to the amps....and power it down in reverse order.....always with the volume down. Following these practices might be the end of your thumping sounds.
reubent
6,939 posts
 
Rilands,

Sounds like the typical thump when using a subwoofer amplifier that has an auto-on circuit. When the amp senses a signal, it turns the amp on. I've heard this thump in many setups that have an amp that uses an auto-on circuit.

I would guess that the built-in amp in your NHTs has an auto-on circuit and you are hearing the amp turn on and "thump" the woofer.

TIC
hiend2's avatar
hiend2
376 posts
 
Another way of thinking about it is , try Floating a ground or 2. A turn off thump can be leaking caps on the amplifiers also
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