popping/ crackling noise from speakers

[pyonc]

Hi I need your advice and insight on this issue.
I've recently had my vintage JBL SA640 amplifier serviced by a technician. He replaced some bad parts on the left channel of the amp.
Strange enough, when I turn it on, I hear noticeable popping and cracking noise from the right speaker for several seconds on two or three times. The initial light pop-up comes on from both speakers, and then the right one produces rather big crackling noise for several seconds.
As I listen in a bi-amp mode, the noise comes from mid-range driver (2121) of my speakers (4343).
So, I took it to the technician and had him check it, and he told me I don't have to worry, adding it will not cause any damage to the speakers.
Well, it is really annoying as I keep hearing that kind of popping/crackling whenever I turn on the amplifier,
which I have never had from other amplifiers at home I have tested with.
What might be the cause of the noise? Is it real concern? Continued popping/crackling might damage the driver?
Thanks a lot for any feedback, trouble-shooting or insight in advance.

[SEAWOLF97]

so ...this wasn't happening "before fix" , but does happen
"post fix" ??? And then the tech says "don't worry 'bout it" ?

Don't trust tech's word with your expensive gear , doubt he'll cover any damages.

Hope you paid by credit card. I'd dispute payment until it's fixed correctly.

[DavidF]

Hi I need your advice and insight on this issue.
I've recently had my vintage JBL SA640 amplifier serviced by a technician. He replaced some bad parts on the left channel of the amp.
Strange enough, when I turn it on, I hear noticeable popping and cracking noise from the right speaker for several seconds on two or three times. The initial light pop-up comes on from both speakers, and then the right one produces rather big crackling noise for several seconds.
As I listen in a bi-amp mode, the noise comes from mid-range driver (2121) of my speakers (4343).
So, I took it to the technician and had him check it, and he told me I don't have to worry, adding it will not cause any damage to the speakers.
Well, it is really annoying as I keep hearing that kind of popping/crackling whenever I turn on the amplifier,
which I have never had from other amplifiers at home I have tested with.
What might be the cause of the noise? Is it real concern? Continued popping/crackling might damage the driver?
Thanks a lot for any feedback, trouble-shooting or insight in advance.

I don't possess extensive knowledge of electrical circuits. I know enough to presume the tech is correct in stating that the source of the noise itself won't cause damage to the drivers. I am not so comfortable with the notion that there is nothing to worry about with the general condition of the amp. Since you are using the amp on the high range drivers there is at least a capacitor in line with the drivers. This will block damaging DC from the driver in the worst case.

It is definitely not unusual for a solid state amp to have some mild pop or thump at turn on. Depending upon the design. The popping/crackling described in one channel is not so common for an amp within spec. With vintage gear and their very old components you can hear intermittent cracking and popping as components warm up. I was never certain that this does not portend some future total failure, however.

How about a second opinion?

[pyonc]

so ...this wasn't happening "before fix" , but does happen
"post fix" ??? And then the tech says "don't worry 'bout it" ?

Don't trust tech's word with your expensive gear , doubt he'll cover any damages.

Hope you paid by credit card. I'd dispute payment until it's fixed correctly.

Yes, this did happen after fix. I've taken it to the tech again for re-examination.
So, what might be the cause? Any idea?
I can say with 100% certainty my speakers have no problem.

[pyonc]

With vintage gear and their very old components you can hear intermittent cracking and popping as components warm up.


Thanks for your feedback. Looks like the tech said something similar to what you just said. Actually, he checked into the circuits, capacitors, and other components of this vintage amp, but found nothing wrong with them, except some bad transistors and resistors that he replaced. What I hear is tiny audible pop from both speakers when I turn on the amp, and then audible crackling/cracking noise from the right speaker for several seconds before it disappears.

[hjames]

Thanks for your feedback. Looks like the tech said something similar to what you just said. Actually, he checked into the circuits, capacitors, and other components of this vintage amp, but found nothing wrong with them, except some bad transistors and resistors that he replaced. What I hear is tiny audible pop from both speakers when I turn on the amp, and then audible crackling/cracking noise from the right speaker for several seconds before it disappears.

Sounds like a dirty contact in a potentiometer, trim pot, or something similar somewhere ...

[martin2395]

I don't think it's a potentiometer if it occurs while no music is plaiying. :dont-know: To me it sounds like a bad capacitor, maybe in the PSU or a cold solder joiint somewhere.
Also, with gear that old you might want to replace parts on both channels and do a full adjustment. You could also check all the connectors inside the amp!

I wonder if the SA640 is entirely built and designed by JBL or could it be made by Adcom or Hafler?
http://www.hifido.co.jp/KW/G0104/J/490-10/C12-64946-35512-00/

[Mr. Widget]

I don't think it's a potentiometer if it occurs while no music is plaiying. :dont-know: To me it sounds like a bad capacitor, maybe in the PSU or a cold solder joiint somewhere.
Also, with gear that old you might want to replace parts on both channels and do a full adjustment. You could also check all the connectors inside the amp!
I agree on both counts.


I wonder if the SA640 is entirely built and designed by JBL or could it be made by Adcom or Hafler?
http://www.hifido.co.jp/KW/G0104/J/490-10/C12-64946-35512-00/Neither Adcom nor Hafler existed when this amp was made… I suppose it could've been designed or built by someone other than JBL but I think they were doing everything in house at that time.


Widget

[Mike Caldwell]

Short of maybe a little "thump" as you turn on the amp no amp should make a snapping/cracking sound for several seconds until it settles down after power up.

My gut feeling is there's a bad capacitor or capacitors that are leaking DC voltage till they form up/stabilize after power up.

I would say it needs looked at again by another tech.

[pyonc]

Thanks a lot for your feedback and diagnosis.:applaud:
I had it checked again by the same tech, and he said he heard no such noise from the speakers at the shop.
I was there with him to check this, and I heard no noise, even no pop-up when turned on. However, when he wiggled the RCA jack about half, not fully, into the inputs on purpose, he and I heard some scratching noise, which he blamed on GND issue. He explained this kind of "old school" amp like JBL SA 640 has that, compared with noise-free modern amps. When I brought the amp back home and tested it, I still heard an instant gentle pop-up from the mid-range drivers of JBL 4343 when the amp was plugged in (I'm listening in bi-amp, and this amp is for the mid-range), but not the kind of rather annoying noise I used to hear. According to the tech, all the internal parts including capacitors are fine...