I have a Sunfire sub that sounds great when the volume doesn’t go up too much, but as soon as the sub gets moving a good bit (and I mean a decent amount of output) it starts making a popping noise from the driver every time it “hits” the bass note. The amplifier was recapped about 2 years ago, I used it for about a year and it was then given to a friend who used it for about a year when he complained of the popping.
A little reading led me to a couple of answers, one being that the nuts around the controls needing tightening. Sure enough the nuts were loose along with most of the screws holding the plate amp and the driver/passive. After tightening everything it didn’t seem to help.
The other answer I found was that these amps have problematic ground planes and the recommendation was to solder a wire from the grounds of the rca inputs and control potentiometers directly to the ground of the power cord input which has a 2” wire that is bolted directly to the plate amp face.
Using my meter I measured the resistance between the power cord ground to the control pot grounds and its a dead short, 0.1-0.2 ohms. On the other hand the ground to the input rcas to the input power ground is measuring a little over 550 Kohm. The inputs are on their own tiny board and of course there is a dead short between the rca ground and the speaker level input/output ground and the scope ground attachment.
I look a little close at the input board and see there are two “grounds”, one labeled WP2 and the other WP3. WP3 is wired directly to the chassis/faceplate, so it has a dead short to the power cord ground. WP2 is wired to the ground of the RCA inputs, speaker in and out grounds, and scope ground. The only thing between WP2 and WP3 is C46 which is a 33nF film and R91 which is a 560 Kohm resistor (hmmm, explains my resistance reading).
So to perform this persons fix I would just need to remove R91 or C46 and put a jumper in and that would be equal to soldering a wire from the RCA input ground to the power cord ground.
Does this seem right to anyone? Could that be the cause of the popping noise? Anyone with the popping noise figure it out? I just don’t want to wire a wire in between the grounds before hearing from others on the subject.
Thank you,
Dan
A little reading led me to a couple of answers, one being that the nuts around the controls needing tightening. Sure enough the nuts were loose along with most of the screws holding the plate amp and the driver/passive. After tightening everything it didn’t seem to help.
The other answer I found was that these amps have problematic ground planes and the recommendation was to solder a wire from the grounds of the rca inputs and control potentiometers directly to the ground of the power cord input which has a 2” wire that is bolted directly to the plate amp face.
Using my meter I measured the resistance between the power cord ground to the control pot grounds and its a dead short, 0.1-0.2 ohms. On the other hand the ground to the input rcas to the input power ground is measuring a little over 550 Kohm. The inputs are on their own tiny board and of course there is a dead short between the rca ground and the speaker level input/output ground and the scope ground attachment.
I look a little close at the input board and see there are two “grounds”, one labeled WP2 and the other WP3. WP3 is wired directly to the chassis/faceplate, so it has a dead short to the power cord ground. WP2 is wired to the ground of the RCA inputs, speaker in and out grounds, and scope ground. The only thing between WP2 and WP3 is C46 which is a 33nF film and R91 which is a 560 Kohm resistor (hmmm, explains my resistance reading).
So to perform this persons fix I would just need to remove R91 or C46 and put a jumper in and that would be equal to soldering a wire from the RCA input ground to the power cord ground.
Does this seem right to anyone? Could that be the cause of the popping noise? Anyone with the popping noise figure it out? I just don’t want to wire a wire in between the grounds before hearing from others on the subject.
Thank you,
Dan
Attachments
It's a ground loop breaker for taming Hum. Try shorting and check if there isn't hum without them.
Check if the woofer actually moves freely, since the popping noise could be it bottoming out on the pole piece. Could also be insufficient rail Voltage due bad filter capacitors. Are You overloading / clipping the input ?
On the picture the black ones seem glued. Where they replaced also when You performed the recapping ? What are those red flimsy wires ? They should be about the same size as the woofer's connecting wire.
If the capacitor that charges for standby mode is bad the sub may be going into standby to quickly and the bass note hitting is sharply waking the sub and causing the popping sound.