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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
15 responses Add your response
jvogt
212 posts
 
I've owned several Levinson amps (23, 27.5, 335) and none
of them thumped at power on. Sounds like something else
is going on. I'd check with the dealer and see if he can
suggest ideas. As an addendum, I think Levinson amps are
terrific.
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rauliruegas
13,052 posts
 
Dear Jim: No, it is not normal. It looks like exist a severe off-set at the Levinson amp, this means that is out of specs/design and needs to be fixed.

Regards and enjoy the music.
Raul.
porziob
316 posts
 
Sounds defective. Levinson doesn`t design in thumps. They`re frowned on in this price range.
hiend2's avatar
hiend2
418 posts
 
Sounds like a bit of DC is finding its way to the outputs on the levinson. Id Stop using it.
jim_swantko OP
301 posts
 
Thanks guys - I haven't fired it up today for fear of damage. It sucks because it does sound damn good!
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samzx12
1,220 posts
 
I have to ask. Are you turning on your CD player and preamp 1st?
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
2,016 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! :)
redwoodgarden
150 posts
 
I have two 334 Mark Levinson amps. One thumps when turned on and off, and the other one does not. Strange! I sent back the one that thumps, and they returned it saying that it meets all accepted specifications...but it still thumps!!! I guess it is something that we will have to live with.
stereoman
3 posts
 
My Levinson 332 (when it worked properly) didn't "thump" coming out of STANDBY, but it did emit small pops and clicks through both speakers. I was told this was normal.
jmrdc
4 posts
 
My 331 emits a few "cricket" like clicks and some low level thumps that the manual says are "normal and not harmful."
stereoman
3 posts
 
Follow-up to my 03-13-07 posting: My 332 went "belly-up" on me about 6 weeks ago. Although it still worked, there was a loud 60Hz hum in the right channel, and the pops and clicks evolved to really nasty transients in both channels, when going in and out of STANDBY. It's back at Levinson right now, getting completely overhauled.
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