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What is an acceptable level of transformer hum on a Krell S300i?

Greetings from a newbie. Just a quick intro:
  
Not rich, but I've been into hi-fi since college (Dual CS506 era). 20 years ago, I had progressed to Michell Gyrodec/Rega, Roksan Caspian CD/bi-amp, Sonus Faber Concertos.

The speakers never sounded as good as when the dealer had demo'd them hooked up to a Krell KAV 400i. But this was not a pressing issue as everything went into storage while I went travelling/working overseas.

Fast forward to present day. My brother has just got into vinyl (having discovered a killer high end McIntosh set up while staying at an Air B'n'B), so I unboxed my kit and set it up to show him what he should be listening to.

We both felt the sound was disappointing and my thoughts returned to that Krell demonstation 20 years earlier. My focus then wandered to eBay and I found myself winning the bidding on a S300i amp.

It is in excellent condition but it hums, even when in standby and without speakers or sources connected. I have tried different locations around the house, different houses, cheap mains cleaners and 3 into 2 mains plugs to eliminate the earth. Nothing makes any difference. When I press the mains switch on the back, the amp starts with a 'cough' which settles down to a constant hum after 2 seconds. I think it is higher than 50/60hz. Possibly closer to 200 hz. It does not vary at all after that. I convinced that this is the transformer because it also occurs in standby without any connections.

If the amp is on the floor and I stand next to it, I can hear the hum.   At 15 feet away, I can't really hear it, but with it in the rack and in my seating position, my ear is only 5-6 ft away and it is clearly audible when the room is quiet. It is annoying when reading in silence to the point that I need to disconnect the power.

My question to you... is this an acceptable level of hum? I would have expected that unless I put my ear next to the casing, I would not be able to hear anything. I have hunted the forums and web but can't find an answer for this specific issue. I use Transparent cables but these aren't relevant because it hums without any cables connected.

Your comments/thoughts will be greatly appreciated. I have already raised this issue with the seller who claims that it did not hum when he sold it. If the hum was really loud, there would obviously be a problem with amp. It is at a level that I can't be sure about without anything to compare it to.

Kind regards. 

rickx

Showing 4 responses by uberwaltz

uberwaltz's avatar
uberwaltz
13,381 posts
 
OP
Not quite sure why you decided lajollaplanars was the response you were looking for when quite a number here have already told you it should be dead quiet and is faulty and you should return it.
A number of responces indicated past ownership of Krell amps unless you were waiting for that ONE person who had the exact same model?

If you had bought from a garage sale or similar and had no recourse to return yes I can understand trying to fix it but with ebay returns it should be gone and you on the hunt for something better.... and quitter.
Personally it would have been back at the ebay sellers door long ago by now.....
uberwaltz's avatar
uberwaltz
13,381 posts
 
I still say don't even mess with it, demand a return from the eBay seller. Not sure how much you paid or what the description was but it is obviously far from functioning correctly.

Does not matter if his ad even states no returns, eBay will make them take it back if you state it is not as described.
Good luck
uberwaltz's avatar
uberwaltz
13,381 posts
 
You could well be correct on the xlr shorting pins, in fact if I remember right Krell suggests to not even use single ended if the shorting pins are not in,place. This was true on,older amps, not sure if the newer stuff is up to the same requirements.

And I am afraid I must respectfully disagree on eBay. Only way you would really lose money is if you were not in the right or did not read the description correctly.
After 19 years of eBay and multi 1000 feedback I might just know a thing or two there.......
uberwaltz's avatar
uberwaltz
13,381 posts
 
In today's age with all the choices we have and the fact that eBay nearly always stand behind the buyer I would be demanding a return. If seller will not work with you just open an eBay case, they will be left with little choice.
Both of the Krell amps I have owned for absolutely silent and I am pernickity about that sort of thing.

Something is not right with it and unless it was sold under "for parts or repair" back it should go.I would not even,open it up as may give seller a possible out.

Good luck
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