Hissing noise from a sub

DECKY999 · 13th February 2008, 01:16 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.

Lab_Rodent · 13th February 2008, 02:32 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, 05:11 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, 07:58 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, 10:13 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.

oshifis · 13th February 2008, 11:11 AM

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, 12:48 AM

Well lets assume that Lab_rodent is just trying to be funny

@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)?

13th February 2008, 01:16 AM	#1
DECKY999 diyAudio Member Join Date: Jul 2007	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? Thanks.

13th February 2008, 10:13 AM	#5
sfreak diyAudio Member Join Date: Apr 2006 Location: Tasmania, Australia	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. __________________ Darcher - Audio Visual - Computers

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13th February 2008, 02:32 AM	#2
Lab_Rodent diyAudio Member Join Date: Nov 2007	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.

13th February 2008, 05:11 AM	#3
DECKY999 diyAudio Member Join Date: Jul 2007	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.

13th February 2008, 07:58 AM	#4
Lab_Rodent diyAudio Member Join Date: Nov 2007	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.

13th February 2008, 11:11 AM	#6
oshifis diyAudio Member Join Date: Mar 2004 Location: Budapest, Hungary	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...

14th February 2008, 12:48 AM	#7
DECKY999 diyAudio Member Join Date: Jul 2007	Well lets assume that Lab_rodent is just trying to be funny @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)?