preamp tube hiss from my SF Line 1

Brf: I swapped out one tube at a time using an extra tube I had. I've actually tried a few "extra" tubes, swapping out only one a time and get the same result. My next step is to put all six stock tubes in it and see what happens.

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? The hissing didn't start until after I swapped out a pair of tubes. Maybe I did in fact break a solder joint. There aren't any error lights on though..

Phd: Did you happen to get an estimate on the repair work? The hiss is very audible and I won't be able to live w/it. Thanks for the info.

Thanks for all the suggestions. I'll update the thread after I swap out all six. I've had good luck with SF / Anthem tech support so I think it's time to shoot them an email as well.

One more piece of information. The hissing doesn't start until about 1 minute after the input is anything other than SSP. Assuming the starting point was the SSP or coming out of standby. This happened every time after I swapped out a tube trying to diagnose the issue earlier in the week. The previous instances were after powering the pre, this time the same thing happened after switching the source from SSP(HT passthrough) to the CD player. The pre has been running for a few hours so it's nice a warmed up. It seems more and more relevant considering it's a consistant issue after about a minute.

Snipes, I did get an estimate from SF but that was last year & can't remember the exact dollar figure but it wasn't alot. In my case as well, sometimes the hiss was not there when it was initially turned on but became evident as the unit was left powered up.

With hybrids tube rolling can be fun but you always have to make sure the unit has been powered off at least two minutes before swapping tubes, (100% tube designs being the exception). My belief that this is the leading cause of failure to the solid state followers. Some mfgs will stress this in the manual. Unfortunately not all of us are aware of this problem as some units are purchased without the manual or the manual is not read thoroughly.

Jea48 mentioned another good point with cold solder joints & could be looked into as well.

Unfortunately, a lot of parts in SFequipment went bad. I don't know why, since they used lots of quality components. Perhaps it was the circuit design. As much as I loved the SF stuff, so gorgeous and heavy, this is the reason I don't and won't own any of their gear, especially since they are out of business. I find it amazing how many people buy the used preamps and amps. This is what you have to look forward to.

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