Hissing noise from a sub

DECKY999

Member
2007-07-18 7:06 am
I have this anoying problem - a 10" sub (el cheapo made in ebay/PRC) has a hissing noise. It is not too loud but still audiable. Initially a thought that I managed to damage the driver but after replacing it the problem is still there. I replaced power caps and output transisitors (Tip 35/36) in the amp but no change.

The hiss is constant and not function of gain. Does anyone have any idea?

Thanks.
 

DECKY999

Member
2007-07-18 7:06 am
Lets define "hissing" - I think a better word to describe it is "white noise". It is audiable regardless of gain setting. The amp is not maiking any hum-like noises - in other words it is not the transformer noise. The amp is a plate sub amp with active crossover - can there be something wrong with it maybe.

Regarding the driver - I would agree with you in you comment if I don't hear what I hear. There is definetelly a low level hiss - just enough to be anoying on quiet songs.
 

Lab_Rodent

Member
2007-11-27 9:00 am
To be more specific and defined. A speaker can not make any noise with out an electrical current flowing through it. So the only way for a speaker to make any noise is if the amp is giving it power. If no audio signal is going through the amp, and you should not hear audio from the speakers, yet you do. Your amp is sending the white noise current to the speaker.
 
DECKY999 said it was a white noise, not hum. I think the culprit is the amplifier or the crossover. I would have a look at the internals and check the types of ICs or transistors in the crossover. If they are not low-noise types, replace them. Being produced in PRC, there is a good chance you'll find some 741s or 1458s inside...
 

DECKY999

Member
2007-07-18 7:06 am
Well lets assume that Lab_rodent is just trying to be funny :rolleyes:

@oshifis

Well, the crossover is my assumption as well. So you think that transistors should be the first to be replaced. What about passive components. Resistors are harmless but what about caps, are they worth wile replacing (electrolitics that is)?