Crackly sounding amp in powered sub, any thouhts?

flyingtele · 30th November 2010, 10:52 AM

Hello all,
My mate has a Cerwin Vega VE-28S powered sub, its 125W and has two 8" drivers.
For a while now it has had a low level crackle to it whenever its plugged in, sounds similar to vinyl crackle. Would still play music fine, but whenever it was idling you could hear it.
Just recently it blew its input opamp, its got a TL084CN for the left and right input, and a TL802CP for the LFE input. First the L&R inputs stopped working and sounded all distorted, but the LFE input continued to work before doing the same thing.
I am currently waiting on the new IC's to arrive, but was wondering if the blown opamp could cause that soft crackling noise? Or is it likely to be something else like maybe a dried cap?

If anyone has any ideas they would be most appreciated.

jaycee · 30th November 2010, 11:31 AM

Quite likely. The question is what blew the opamps.

flyingtele · 1st December 2010, 11:29 AM

Thats what I was wondering. The sub has been crackling away for a long time, and the owner reckons it would go away if he nudged the power plug or turned it off and back on. Also said it would get worse with volume, so I suspect its a broken connection somewhere after hearing that.
The sub has had a pretty hard life and has been run pretty hard for a long time, and when I received the sub the lfe input was still working as normal, only the L+R line ins weren't going. But while testing the sub at reasonably high volume with a tone generator (trying to find what frequency and volume etc the crackling noise got worse) it suddenly fizzled out and then went all distorted and sounded just like the normal line inputs.
I'll chuck some new opamps in tomorrow and see how it goes, they are only about $1.5 each so if they blow again I'll look further into it.

jaycee · 1st December 2010, 02:47 PM

Check the power supply voltages to the opamps first, pins 4 and 8. If you've got a scope and can check for ripple or noise on them, even better.

30th November 2010, 10:52 AM	#1
flyingtele diyAudio Member Join Date: Jun 2009	Crackly sounding amp in powered sub, any thouhts? Hello all, My mate has a Cerwin Vega VE-28S powered sub, its 125W and has two 8" drivers. For a while now it has had a low level crackle to it whenever its plugged in, sounds similar to vinyl crackle. Would still play music fine, but whenever it was idling you could hear it. Just recently it blew its input opamp, its got a TL084CN for the left and right input, and a TL802CP for the LFE input. First the L&R inputs stopped working and sounded all distorted, but the LFE input continued to work before doing the same thing. I am currently waiting on the new IC's to arrive, but was wondering if the blown opamp could cause that soft crackling noise? Or is it likely to be something else like maybe a dried cap? If anyone has any ideas they would be most appreciated.

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30th November 2010, 11:31 AM	#2
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Quite likely. The question is what blew the opamps.

1st December 2010, 11:29 AM	#3
flyingtele diyAudio Member Join Date: Jun 2009	Thats what I was wondering. The sub has been crackling away for a long time, and the owner reckons it would go away if he nudged the power plug or turned it off and back on. Also said it would get worse with volume, so I suspect its a broken connection somewhere after hearing that. The sub has had a pretty hard life and has been run pretty hard for a long time, and when I received the sub the lfe input was still working as normal, only the L+R line ins weren't going. But while testing the sub at reasonably high volume with a tone generator (trying to find what frequency and volume etc the crackling noise got worse) it suddenly fizzled out and then went all distorted and sounded just like the normal line inputs. I'll chuck some new opamps in tomorrow and see how it goes, they are only about $1.5 each so if they blow again I'll look further into it.

1st December 2010, 02:47 PM	#4
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Check the power supply voltages to the opamps first, pins 4 and 8. If you've got a scope and can check for ripple or noise on them, even better.

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