Tube newbie needs some help!!

eteller

eteller

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I received a Yaqin MS-12B tube pre-amp this week to use with my TT, going to my Onkyo M501 amp. The first night of use (5hrs.@ 1/4 volume) I was blown away with excellent sound. Last night I powered it up and found there to be MUCH less gain and what sound their was, was very flat. I assume a 12ax7 tube has failed, am I correct in this assumption? Is this a typical symptom of a failed pre-amp tube?
 
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ya you might have a look in the top link for local tube testers.
Could be a bad tube or sumthin is out of tolerance. You sure you let it all warm up before use ? Maybe check cable connections and that stuff.
 
All connections checked, tried a different TT/cartridge, amp warmed up about 30min playing MP3's through the CD input.
 
I have done alil more research on the Yaqin MS-12B they have a 220/110 version and a 240/120 version. If you have the 220/110 operation version this could over voltage the tubes here in the us.
I have only found a few articles about this and I don't know how credible it is. But its worth looking into.
 
Hmm, came with a IEC US plug, and there is no voltage switch on it. I'm thinking it's the 12ax7 tubes. A failing tube will still light, right?
 
yes it will still light up if the filament isn't borked. Only way to find out its a bad tube is to have them checked. Seems the problem is common to both channels so it may or may not be the tubes. If it came with a manual I would find out if its the 110/220 model or the 120/240.
 
So it's one tube for each channel huh? That makes some sense. I was thinking they were in stages for some reason. I'll look in the manual, although it's one of those poorly translated chinese types.
 
I understand that as tubes burn in, they go through sonic changes until they have 'settled'. Give the tube a few more days of play to see if sound improves. If not, get a replacement on eBay or elsewhere, try it out and you will know the answer.

I had a 12AU7 go bad the other day and completely lost a channel. No sparks, showers or prior indication of the failure.
 
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