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Tube hiss - any idea what's causing it?

I own an Eastern Electric M520 integrated amp that I am very fond of. However, recently I have noticed that there is a great deal of rather disturbing hiss eminating from my Omega XRS speakers once I power the unit up. The hiss does not increase when the volume is turned up. It's always there and very noticable during quiet passages. It's definitely a hiss and not a hum.

I checked the tubes and noticed that when I touch or slightly jiggle the front EF86 tubes, the hiss gets louder/softer when they are moved. Could it be that these tubes are going already? I do not have many hours on them. Maybe 100 at best. Should I consider replacing them or perhaps checking the other tubes too - perhaps the 5 AR4 rectifier tubes? I doubt it's the power tubes.

Do you have any thoughts/recommendations for me at this point. I am not sure how to proceed. As always, thanks for your time.
jpstereo
dweller's avatar
dweller
3,781 posts
 
Purchased a BAT 300X-SE and out-of-the-box it was hissing like a can of spray paint.
This was a constant hiss (both channels) and not volume dependant.
I didn't pee myself or throw a hissy-fit toward the seller but instead agreed to ship the unit to BAT for repair.
In a week or so, BAT shipped a fully repaired 300X to me and I've lived happily-ever-after. The repair cost me nothing.
BAT said the problem was a "voltage regulator".
jpstereo OP
53 posts
 
I replaced the 12au7s and I still have hiss in both channels. The EF86s are coming next week. If that doesn't clear things up then it's back to the manufacturer for a check up. Perhaps it is the voltage regulator.

Many thanks to all for chiming in on this issue!
herman
2,253 posts
 
Well that is something that I overlooked. A solid state component common to both channels could cause the hiss. A rectifier or regulator perhaps.
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