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DECKY999 13th February 2008 02:16 AM

Hissing noise from a sub
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?


Lab_Rodent 13th February 2008 03:32 AM

subs are usually not capable of producing hiss, seeing they are too large... Is it a full range 10"? If so, then I would ask if your hiss is coming from the amp.

DECKY999 13th February 2008 06:11 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 13th February 2008 08:58 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.

sfreak 13th February 2008 11:13 AM

Might be something as simple as moving the sub input cable away from the AC cable. Had a few people with similar problems and that was the cause, and the cure as simple as moving a few cables.

lcsaszar 13th February 2008 12:11 PM

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 14th February 2008 01:48 AM

Well lets assume that Lab_rodent is just trying to be funny :rolleyes:


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)?

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