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Bad tube?

I just bought my first piece of tube audio equipment, an all original HH Scott 299. I'm a bit green when it comes to tubes so I'm asking for a bit of help. When I'm using the turntable I get this noise out of one channel that's almost like pink noise, but at a very very low level. It doesn't appear when I listen to the two line level inputs. Could it be a bad tube in the phono section? Or could it possibly be a result of the way the Regas ground their cable in the plug? It should probably not go without mention that since the Scott is original it has an original, un-grounded power cord.
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rodman99999
6,171 posts
 
Hopefully you can perfrom the test suggested by Mr M, and the problem will simply be a noisy tube. If it were a grounding issue, the sound would be a hum rather than a hiss. For future reference: First rule of purchasing tubes for a phono stage or pre-amp is be certain the tube has been graded and is certified "low noise, pre-amp grade" or better. Any reputable tube seller will provide that service/quality control. For instance: (http://www.upscaleaudio.com/product.asp?itemid=42&catid=40)
hyperreal's avatar
hyperreal OP
14 posts
 
Thanks for all the info guys. I called my resident tube guru here in town and he stocks JJ tubes. Unfortunately, he does not have the time to check the tubes, but it's still incredible that someone stocks tubes in Des Moines, IA of all places. I ended up swapping in and out to find a combo that resulted in the lowest noise. The JJ's weren't a good match as a pair, however, when I paired one of the JJ's with an Amperex (Holland) from the good channel I was totally blown away with how quiet it was. My next question is this: is this a good thing to do or not, mixing different brands of tube in the phono stage? I can say from a tube life standpoint that I know the Amperex will give out long before the brand new JJ, so I'll be going back to square one after a while.
rodman99999
6,171 posts
 
Some NOS tubes are rated for 10kHrs of life, and just as many newly manufactured tubes fail as those that were made back in the 40's through 70's. The Amperex may last as long as you own the piece of gear. It can't hurt anything to mix tube brands, but the chances of your having a balanced soundstage are slim, IF they are at the same gainstage, one in each channel. Then again- If they are dual triode tubes, and used(one each)in different gainstages: You've solved your problem and can just go on enjoying your music. If the Amperex tube was installed when you got the gear: Do you know how many hours were on it? It may have been the original tube. You would do yourself a huge sonic favor by shopping NOS tubes for the unit, and retubing the whole thing. Of course if you're happy with the sound now: Why bother? Happy listening!
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