Yes. Most probably the small tubes. If the hiss is annoying you will need to get 'low noise' tubes. They are usually a bit (or a lot) more expensive so be careful not to buy 'more' than you actually need. Also consider that changing tubes, unless you stick with the same brand, might well changes its sound a bit (or a lot).
More info is needed.
What make and model for the amp? How old is it? Has it been serviced lately? How many hours are on the tubes?
Does the hiss occur when only the amp is on and no sources are connected?
Same with the speakers. If the speakers are particularly efficient you may notice hiss that a less efficient set of speakers would not reveal.
In short, the more information provided, the better the answer.
I've found that Sovteks and a lot of common Russian-made tubes can be quite noisy, especially the Sovtek 12AX7LPS. It most definitely is always the preamp tubes or the smaller tube types such as 12AX7/12AU7/12AT7, 5751, etc.. Never had noise problems with Output tubes.
Welcome to the musical world of tubes. In exchange for SS nasties, there is tube hiss...our imperfect world. The EH and Tungsol tubes are known to be very quiet. Get phono grade tubes if you want really quiet. I find the tubes at RAM/Rodger Modjesky, Tube Depot, and Tubestore have good quality. There are others, but I have purchased from these. jallen
Are you referring to a 50 watt power amp or integrated? You didn't mention whether you have a tubed preamp which would be the first source I would investigate.
Newbie hit it pretty much right off.
I've had noise on SS systems, running them single ended. I've even had some noise on Ss going XLR. the former interface being the more noiseier of the two.
In combo rig, Tube + SS amp, single ended only, there was a bit more noise than all single ended Ss gear would produce.
None of the aforementioned systems did however produce enough hiss or fuzz to be noticeable at less than enormous listening levels in between the tracks.
I'd have to get up and get close to the speakers to notice it... and turn up the volume while I was very close to the speakers. XLR is/was the quietest. All SS came in second. hs + SS was third... and the noisest was all tubes runing SE.
Again, I still can't hear even the loudest (all tubes) from my listening chair. I gotta get within a couple feet of the speakers with the volume up to hear the hiss.
Two things fixed or made it better... the phono line tubes, and power conditioning. A third item helped but in a much lesser degree... tube rings... oddly enough. They helped imaging too.
As was said, it only takes one to make things irritating. give Andy at Vintage Tubes a call.
50 watt power amp and tube pre-amp. I hear the noise when source is off as well as pre-amp being off. Maybe it's just time to replace the output tubes? ... 6SN7GT x 4.
Not to be picky but I assume you mean the small tubes in the power amp? That is a logical source of hiss. And 6SN7's are not power tubes.
From what you have said yes. Now if in addition to these small tubes you meant the big power tubes as well, if you've lost some clarity as well as having hiss, after you replace the small tubes it doesn't return, then yes the power tubes as well. One way to tell is to have a spare set on hand (a good idea in any event) and substitute them in and see if you hear a change. No change - take 'em out and check again next year.
Newbee, The amp is an Audio Aero Capitole. It has four 6SN7GT tubes, four E34L tubes and four 6550C tubes. No loss in clarity just the hiss.
Now, that I think about it, have you ever heard the amp operate dead quiet? Or is it a new amp to you and you are just noticing it. If you heard it operate dead quiet, was it with the same speakers or at least speakers with a high sensitivity level.
I ask for several reasons - one is that I don't know this amp (biggie) and of your speakers are high efficiency and the amp is new to you, you might just be hearing the amp's noise floor. But since noisy 6sn7's are not hard to find, perhaps/most likely that it the problem.
BTW, How far from the speakers can you hear this hiss? Can you hear it in your listening position? Or only when you put your ear next to the tweeter. If the latter, be happy! :-)
The noise is new...same amp and same speakers. I can hear the hiss from 3-4 ft but, not really from my listening position of 9-10 ft.
I'd bet it is the 6sn7's if it annoys you get some recommendations for some good low noise tubes. The new production EH's are quiet but I don't know if you would like them in your amp. I use them in some Cary amps and compared to some NOS RCA's I have they have a tad more edge, whereas the RCA's are a tad soft/mellow - depends how you look at it, and probably how they blend with your amp and the power tubes.
One other question & suggestion. Is the noise equal between channels?
While small signal tubes are often the source of hissing (aka white noise) and can increase as tubes age, it is unlikely that all four of the 6SN7 tubes are deteriorating at exactly the same pace.
If you find the noise is louder in one channel than the other, try switching the tubes between the left and right channels. If the noise is now louder in the opposite channel you'll have confirmed that it is time to replace those tubes.
Adam, I had the same problem with one of my AA Transtracs last summer. It ended up being one of the output tubes causing the hiss. Luckily I had some extra tubes to troubleshoot and replace the faulty tube.
Adam, one other thing. The AA amps should be dead quiet. No hiss, no noise just a very slight audible hum with the volume full when your ear is about an inch away from the midwoof.
Came across thread while searching for solution to my problem of low level hiss emanating from my speakers. Have a SS amp and a tubed pre (Audible Illusions). I've cleaned all the connections in my system, made sure all connections are snug, made sure turntable ground wire was securely grounded, switched out the tubes in the preamp, rerouted cables and wiring to make sure they did not cross each other, and I still hear the hiss from my listening position 9 feet away. It's like the pea under the mattress; a minor annoyance, but an annoyance non the less. Previously, system was dead quiet between songs or during quiet interludes. Now, low level hiss is always on my mind. Only time it goes away is when I wear earplugs; but have a hard time hearing the music. So, thinking that may not be my best solution.
Rockyboy, When you changed out the tubes, did you replace the tubes with tubes tested for low noice? Lots of NOS, and new production tubes are not all that 'low noise' in demanding applications like your AA.
I went back to the tube set (E88CC/6922) that I had replaced in April. I never heard any degradation of sound while using these tubes; I replaced them only because of their age. I don't recall hearing any hiss during their use nor do I recall hearing any hiss after installing the new tube set. It's only been in the last couple months that I've noticed the hiss. I'm racking my brain trying to identify what event coincided with the onset of the hiss. For the life of me, I can't come up with one.