2. amps-preamps
  3. 1157900563

Levinson turn-on thump... normal??

My dealer let me borrow one of his Levinson 431's (I am ampless at the momeny - looong story) to play with for the weekend.

I noticed that when I take it out of stand-by there is a horrible turn-on thump that comes through the aerials. This happens even when there are no single ended connectors attached (ie no input thumps which could be coming from my Unidisk pre-amp). It's really unpleasant and I'm afraid it's going to damage the 10T's. Is this normal with Levinson gear? I certainly didn't expect it.

I am using a single pair of speaker terminals which are firmly snugged down under the binding posts.

Another thing I noticed was that after the thump the woofer stayed in the "out" position. Not completely pushed out - but further out than it's typical "resting" position (amp off). It seems to only happen on one of the Aerials. I switched to the other channel of the Levinson and it still did it. Any ideas? Is it possible that the resting state is not the "neutral" position of the voice-coil?

Other than those two oddities I am in love with this thing. It really creates a 3 dimensional sound and everything just sounds "right". Bass response is absolutely stunning.

Thanks in advance.
jim_swantko
jim_swantko OP
301 posts
 
Yes I am. I thought that may be the issue - so I tried the amp completely disconnected from ANY interconnects...just the amp connected to the speakers. Still get the same result.

It HAS to be an issue with the amp.
aball
2,018 posts
 
There is DC on the output. Something is definately wrong in the amp.
misterdoggy
11 posts
 
I have 433 and 436's and no thump at turn-on. I do have a thump when the 433 fires up using a jack to start from the processor.

Note: I had a thump using a jack at startup with one of the 436's as I didn't have the rj45 plug but after using the rj12 to rj45 plug between amps for link the thump stopped.
helios1033
9 posts
 
No, he is not normal, this happened with my old Audio Research 100.2 built in 1996 without delay protection to the start button. Mine 431, instead, release when it switch power off a small noise of current from the tweeter, like a “tzzz tzzz”, but much light one. I have tried to detach all cables but it does not change null. Also this for me is not normal. Ciao Alessandro from Roma
jim_swantko OP
301 posts
 
I determined that using the shorting pin for the balanced inputs will eliminate the thump. I tested my 336 and sure enough with the pins removed I would get the thump... with them in it was quiet.

That's what I get for using single-ended inputs I guess! :)
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