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Mark Levinson Amplifier Hiss

I am auditioning a Levinson ML-9. I do not have a low noise floor by any means. I am using the ML-9 pre with the amp. When I have the amp idling and no source either playing or even on, I have a hiss coming from the speakers.

As I go through the volume range, the hiss disappears greatly around 2 and to a great, but lesser extent, around 5 (12 o'clock) on the volume knob. I have tried using a 2 prong plug on the pre and the amp, but no change in the hiss. I have also shut down the sub, but have not removed it from the audio chain.

I have hooked up my CDP with variable out to the amp and the noise floor has lowered, but is still noticable.

So, as it stands, I am out of ideas on how to remove the hiss. As you close in on the speakers, the hiss is noticeable. Even as you listen to quiet passages, you can hear it.

What can I do, or is the amp just noisy?

Teanks,
eragot
5 responses Add your response
aball
2,018 posts
 
The ML-9 is at least 20 years old and, particularly early Levinsons who ran wide open, the caps may be cooked by now. A dirty volume pot will make scratching noise only when turned. I think the amp probably needs an overhaul which will cost a fortune for Harman to do it.

Shorting plugs on the unused inputs of the preamp are a must so be sure to do that first - it may cure all your hissing problems. I bought a few on ebay from Singapore and they look and work great.
nsgarch's avatar
nsgarch
2,524 posts
 
Well, another likely thing it could be (due to age) is one of the pots might be dirty (volume or balance) Is the hiss (level and tone) always identical on both channels?
eragot OP
13 posts
 
Also to add... Regardless of the input selected on the pre amp (only one has a source hooked up) the hiss remains.
eragot OP
13 posts
 
The amp is the ML-9. I'll make some shorting plugs as I wanted to try this out anyway. But, the hiss goes up then away, then comes back, steadily gets louder, then dies a bit at 1/2 volume and will then come back.

You definitely get to know where the tweeters are on the Ohms when you go close to them.
nsgarch's avatar
nsgarch
2,524 posts
 
You didn't say what amp, the ML9?

Anyway, with preamps, especially older designs, you might want to put shorting plugs in the unused inputs. The fact that the hiss goes down as the volume goes up leads me to this conclusion.
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