tube amp hiss

[jay43]

reading alot on here and the web about tube amp people sometimes mention that with tube amps there may be an audible hiss. is this always the case w tube amps. How about with hybeid amps?

 

[Mr. Foxen]

Some tube amps are silent. Bunches of old ones used carbon composite resistors which degrade and hiss, can be fixed by replacing them. Really well made ones tend to be quiet, but you nee good valves and maintenance to keep it like that. Messier the wiring inside, the noisier they tend to be.

 

[Rockmusician]

I have always had some hiss with my tube Ampegs. I can't hear it when I play so I don't let it bother me.

 

[B-string]

Some tube amps are silent. Bunches of old ones used carbon composite resistors which degrade and hiss, can be fixed by replacing them. Really well made ones tend to be quiet, but you nee good valves and maintenance to keep it like that. Messier the wiring inside, the noisier they tend to be.

All of mine were quiet, but I repair amps

 

[rodl2005]

Never had a problem with any meself. Sometimes a SLIGHT hiss, but I think apart apart from not being an issue when playing, I reckon if the cab had a tweeter, turn that off & the hiss goes totally

 

[NecroticImbecil]

I have owned tube and solid state ("hybrid" included) heads. My experience is that both types include some examples that hiss, and some that have no detectable background noise. I have never had a hybeid amp so I cannot comment on those.

 

[JimmyM]

There are a lot of tube amp myths that get spread by people who never touched tube amps. This would be one of them. There is nothing about tube amps that's any noisier than any other kind of amp. My tube amps are extremely quiet. So are my SS amps.

 

[csm672]

I can't speak for pure tube amps, but I do have a hybrid Ampeg and it is very quiet. The only hiss I ever get is when the tube starts going out (unfortunately that is happening again now!) Otherwise it just sounds great.

 

[jmpiwonka]

Have an svt2 that is completely silent.
Had both tube, hybrid and solidvstatevamps that had a little noise too.

 

[okcrum]

There are a lot of tube amp myths that get spread by people who never touched tube amps. This would be one of them. There is nothing about tube amps that's any noisier than any other kind of amp. My tube amps are extremely quiet. So are my SS amps.

Well, yes and no. A well designed tube amp is very quiet, but remember that the noise floor in any signal chain is essentially set by the first preamp stage. All electronic parts, including resistors, produce noise called thermal (or shot) noise. This increases with temperature, and is why systems with very low noise preamps (like radiotelescopes) are often cooled with liquid nitrogen or even liquid helium.

Tubes, because of how they work, have additional sources of noise unique to them, like flicker noise and partition noise. Triodes are quieter in preamps than pentodes or tetrodes because triodes do not have partition noise - it's a product of the geometry of the more complex tube types, specifically, having a screen grid.

The high gain triodes commonly used in preamps get noisier as they age, because of the additional source of flicker noise. I think that's where the old wives' tales are rooted.

Transistors also have this aging behavior for different physical reasons. If it gets too noisy, then it's bad, no matter whether tube or SS.

You'll hear some hiss from amps, even very good ones, if you boost the high end enough, and your speakers and ears will reproduce it.

Prolly (apologies to speling purists ) more than you wanted to know, but there ya go.

 

[seamonkey]

Some tube amps are silent. Bunches of old ones used carbon composite resistors which degrade and hiss, can be fixed by replacing them. Really well made ones tend to be quiet, but you nee good valves and maintenance to keep it like that. Messier the wiring inside, the noisier they tend to be.

Or the carbon composites with high voltage running through them are the magic mojo:
http://www.geofex.com/article_folders/carbon_comp/carboncomp.htm

It can be measured.