2. amps-preamps
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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

Showing 5 responses by jea48

jea48
4,733 posts
 
Just grabbing at straws here, but is there a chance you may have a cold solder joint on one of the tube socket terminals caused when changing out the tubes? If you put back in the three tubes you had pulled before the hiss, and you still have it, then I think that eliminates the tubes from the equations.
Jim
jea48
4,733 posts
 
>>"Jea48: You wrote: "If you put back in the three tubes you had pulled before the hiss, and you still have it, then I think that eliminates the tubes from the equations." I'm not following you. If I put the same tubes back in and the hiss is still there I don't see how I ruled out the tubes. If it is a bad tube, then wouldn't putting it back in cause the hiss to continue?"<<
[Snipes]
>>>>>>>>>>>>
I misunderstood the start of your thread. I thought you had reinstalled the original tubes, the tubes that were in the Line One before the hiss problem.

If the preamp did not hiss before you pulled the original tubes, but did after installing the NOS tubes, then I suggest you start from ground zero. Pull all of the 6 nos tubes and reinstall the original 6 tubes. Make sure you keep the right channel tubes separated from the left channel tubes when you pull them. If the hiss is not there, then that's great news.... That means that one, or more, of the nos tubes you pulled from the right channel is either shorted or has excessive grid emissions.

Post back after you install the original tubes.......good luck.
==================

Phd, the Sonic Frontiers Line one, two , and three, are not hybrids as far as I know. The SFL-1 is a hybrid.
===================
Jim

jea48
4,733 posts
 
Snipes, curiosity killed the cat!!
How about an update.....
Jim
jea48
4,733 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
jea48
4,733 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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