2. amps-preamps
  3. 1142033337

preamp tube hiss from my SF Line 1

I'm trying to diagnose a very audible hissing sound that recently showed up. The symptoms are, hissing sound coming from the right speaker. Its very noticable from my chair. It does not get louder as I turn up the volume. The sound is there regardless of which input I select. It does go away when I switch on the HT Passthrough. I thought I had a bad tube and have tried swapping out each of the three tubes ont the right channel and it makes no difference. All the tubes are NOS Amperex and I've been using them for a while now without any issue. This all started when I swapped out the bottom pair of tubes with some better ones that I had. All my tubes were recently tested so I know they still have plenty of life in them. Any ideas? I find it unlikely that I have multiple noisy tubes, but of course I could try putting the stock ones in all three right positions. Any insight would be appriciated.
snipes
snipes OP
119 posts
 
I finally got around to working out the problem today. SUCCESS!! The problem was due to noisy tubes. I had one very noisy tube and one of my spare tubes of the same type, Amperex Jan Green, was also very noisy. Luckily I had a few more good spares and was eventually able to find 6 tubes that were dead quite. Funny thing is I ended up with the same setup I was running before all of this business started up. Amperex Jan Greens up top, Amperex USA Whites in the middle and a pair of Russian Rockets (not sure what they are) in the bottom pair. It was the bottom pair I tried swapping out when all of this started up. I put my Herbie tube dampers back on and I'm back in business.
Thanks to everyone for their interest and help.
phd
1,008 posts
 
Snipes that's excellent! Keep playing them tunes!
jea48
2,944 posts
 
Snipes, sounds great. Glad to hear you are back in business.

Just to clarify your tube placement in order of importance.

(1) Middle row, LV2 -- V2
(2) Back row, LV1 -- V1
(3) Front row, LV3 -- V3

Where do you have the Herbies HAL O dampers positioned?
I run mine near the top of the tubes.
Jim
snipes OP
119 posts
 
Jea48: I remember one of your previous threads concerning the order of importance and yes, that's how I have them. I run the tube dampers about 25% the way down from the top. I didn't play around with placement much as the concensus seems to be towards the top like you mention. Any experience or have you heard comments concerning some of the new EH gold pin tubes in the SF line? I'm curious about how they might sound. At $15 a pop for brand new tubes, it's tempting. I've read that their production quality has really been improving, whatever that means.

Brad
jea48
2,944 posts
 
Snipes, just buy two matched pairs of the EH tubes and try them. Be careful who you buy them from. Quality control in Russia ain't the best. A good dealer will throw away tubes that don't meet their specs. Some will pass marginal tubes and sell them to customers anyway.

If you do not like the sound you can move one pair to the front row LV3 -- V3. Put the other pair back in the boxes for backup and future.

http://www.upscaleaudio.com/product.asp?

http://pages.prodigy.net/jimmcshane/

If you do go for it post back and lets us know how they sound.
Jim
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