2. amps-preamps
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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
czbbcl's avatar
czbbcl
1,752 posts
 
Jpstereo

How do you like the Omegas. I am considering the XRS for a system up north in my cottage. I was thinking of driving them with a Cary CAD300SEI or SLI80.

Sounds like a bad tube to me I had one do a similar thing in a cj pre-amp replaced the tube and all was fine. I had a tube go microphonic in a different pre-amp which is characterized by you tapping on the or around the amp and the tapping eminates out your speakers.

Chuck
jpstereo OP
53 posts
 
The XRS are great and Louis is a wonderful person to deal with. My highest recommendation!
cyclonicman
693 posts
 
I just had a similar problem and it was not the power tubes, it was the driver tubes. It can't hurt to get a new rectifier tube(s) as you will probably need them one day anyway whether it is the problem or not. If the hiss is only coming from one channel, switch the tubes from the hissing channel one by one to the non hissing channel to find the culprit tube, process of elimination. Good Luck!
slates
35 posts
 

You know come to think of this , I have the same issue in my ARC ref 1, I just bought 4 matched sets of EH 6922 Gold pin, and it seems like one or more has gone microphonic, with my ear up close to the speaker you could hear a hiss and a bit of a hum, the hum being the lesser. Also it's seems less in the right channel than the left. I will be honest, I do not have any dampers on the tubes.
How can I rectify which tube(s) it the culprit? The tubes have less than 10 Hrs on them.

thanks in advance guys.
bless
7 posts
 
Check out the tube sockets ,sometimes they don't hold the tube pins tight. Erwin.
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