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Yeah, I swapped my JBL monoblock for a Zapco ST 850 monoblock thinking I was upgrading and I had all kinds of noise issues including what sounded like the mosfets buzzing when cold. I also wasn’t impressed with the sound so after fucking with that POS for a few months I ripped it out and put the cheaper JBL club 5501 back in and no more noise of any kind and noticeably better sounding bass.

This is my second experience with budget Zapco amplifiers and I’m not impressed, especially with all the hype they get.
 

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Yes, same power and ground... I'd hate to think it's power or ground related. Those connections are solid. :eek:
Just pull its fuse... and then see what happens?
 

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Discussion Starter #23
Yeah, I swapped my JBL monoblock for a Zapco ST 850 monoblock thinking I was upgrading and I had all kinds of noise issues including what sounded like the mosfets buzzing when cold. I also wasn’t impressed with the sound so after fucking with that POS for a few months I ripped it out and put the cheaper JBL club 5501 back in and no more noise of any kind and noticeably better sounding bass.

This is my second experience with budget Zapco amplifiers and I’m not impressed, especially with all the hype they get.
I have had great luck and great sound with them so far, but I am accepting that they are budget amps.
 

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I have had great luck and great sound with them so far, but I am accepting that they are budget amps.
Sorry David I’m just pissed about the whole ordeal I’ve personally had with that amp and I tried everything and couldn’t figure it out either.
 

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Discussion Starter #25
Sorry David I’m just pissed about the whole ordeal I’ve personally had with that amp and I tried everything and couldn’t figure it out either.
No apologies necessary... As I think/plan (dream) of what I will do in my next build, I definitely will replace the amps and I'll most likely go with Mmatts. Lots of power, small footprint and made in America.
 

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I never had any issues with my budget Zapco amps either and still have the ST-4X SQ installed and bridged to midbass playing 90-300. Not surprised about some reliability issues though because of the corners that probably had to be cut to hit the price point they're at. I got my ST-4X SQ and ST-5X ii for less than $300 for the pair brand new from a hookup I had a couple years ago.
 

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Has anyone mentioned vibration as a potential culprit? If the bass is at a specific level and there is crackling in the mids and highs and you turn the bass down -3db and it stops but then you increase the volume +3db and it's back because you just increased the overall volume which includes the bass then my guess is vibration. The bass is vibrating something.

I would look at the RCA's coming OUT of the DSP that go to the amplifier that goes to the highs. I would look at the connections on the amp going to the highs and make double sure they are tight (RCA's, power, ground, remote and speaker connections). I would look for stray strands of copper. If it turns out to be the RCA cables vibrating then you can use dielectric grease on the RCA's before they are connected to the amps and DSP. It will cut way down on corrosion AND vibration.
 

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Has anyone mentioned vibration as a potential culprit? If the bass is at a specific level and there is crackling in the mids and highs and you turn the bass down -3db and it stops but then you increase the volume +3db and it's back because you just increased the overall volume which includes the bass then my guess is vibration. The bass is vibrating something.
....
No sir, I do not believe it has been mentioned.
Ideally that causal mechanism would go on a fishbone diagram.
Then a test concocted to prove or exonerate that mechanism.
Pulling a fuse or RCA to the sub amp would be possible approaches.


...
I would look at the RCA's coming OUT of the DSP that go to the amplifier that goes to the highs. I would look at the connections on the amp going to the highs and make double sure they are tight (RCA's, power, ground, remote and speaker connections). I would look for stray strands of copper. If it turns out to be the RCA cables vibrating then you can use dielectric grease on the RCA's before they are connected to the amps and DSP. It will cut way down on corrosion AND vibration.
This is probably worthwhile even if it is not vibration related.

One could even listen in with headphones if there are RCAs being presented to the amps, and not a digital source goin to the amps.

If the amplifiers are faithfully reproducing what they are presented, then changing them out may not result in successful resolution to the observed problem.
 

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Discussion Starter #30
Has anyone mentioned vibration as a potential culprit? If the bass is at a specific level and there is crackling in the mids and highs and you turn the bass down -3db and it stops but then you increase the volume +3db and it's back because you just increased the overall volume which includes the bass then my guess is vibration. The bass is vibrating something.

I would look at the RCA's coming OUT of the DSP that go to the amplifier that goes to the highs. I would look at the connections on the amp going to the highs and make double sure they are tight (RCA's, power, ground, remote and speaker connections). I would look for stray strands of copper. If it turns out to be the RCA cables vibrating then you can use dielectric grease on the RCA's before they are connected to the amps and DSP. It will cut way down on corrosion AND vibration.
Thanks. For sure a good thought, and it was one of the first things I checked because the noise would happen with the bass line, which made me think the same as you... I have not been able to find anything loose, yet.

I am trying to not have to pull the amp rack out, but it looks like I might have too... It's a pain in the ass! :p


 

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Since we're shooting out random ideas now: With music playing, you could also try simply touching or slightly wiggling each of the RCA connections to see if that induces the crackling. I once had a DSP that the RCA output became faulty and very flaky. Result is that the speaker would crackle or cut out entirely.
 

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Thanks. For sure a good thought, and it was one of the first things I checked because the noise would happen with the bass line, which made me think the same as you... I have not been able to find anything loose, yet.

I am trying to not have to pull the amp rack out, but it looks like I might have too... It's a pain in the ass! :p


Damn Germans and their over-engineering:p
 

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Discussion Starter #33
Since we're shooting out random ideas now: With music playing, you could also try simply touching or slightly wiggling each of the RCA connections to see if that induces the crackling. I once had a DSP that the RCA output became faulty and very flaky. Result is that the speaker would crackle or cut out entirely.
Yep. Though I have already checked to the degree that I can with reaching through the holes in my amp rack, I will need to check them again...

I do have the Stinger 9000 locking rcas and they were tightened pretty good when I put them in... Nonetheless, it's a good idea to go through and double check em.

The RCAs and DSP are brand new, I hope there are no defectives already.

Damn Germans and their over-engineering:p
I know, it's a sickness with no cure or treatment. :p :blush: My entire trunk has a sequence to take things out and put things in...

1st - remove aluminum strips on the sub box
2nd - remove foam inserts on sides
3rd - remove huge bolt through small hole in amp rack
4th - fold down back seats
5th - lift and pull sub box onto back seats
6th - pull amp rack out

All that just to verify RCAs are tight... etc, etc, etc :cool:
 

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I talked to a guy once that had a weird noise issue that got traced to that particular amp being mounted to mental. The amp was trying to use that as a ground, he said. Don't know if that is an issue here or not....it shouldn't be....but it is car audio.
 

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Discussion Starter #35
I talked to a guy once that had a weird noise issue that got traced to that particular amp being mounted to mental. The amp was trying to use that as a ground, he said. Don't know if that is an issue here or not....it shouldn't be....but it is car audio.
The amps are completely decoupled from the aluminum rack - plastic spacers and nylon hardware. No metal on metal touching anywhere... ;)
 

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Also... on long circuit boards in some amps, there is no support in the middle of the board and they can vibrate and short... even if intermittent. Chokes and coils in amps that have not been secured well with silicone can also wiggle and cause issues. Your subs are beating the crap out of that amp rack I am sure. Try test tones that make the mids and highs crackle that way you can sustain the issue while you track the culprit down.
 

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Have you tried testing the optical or rca input of the processor? I couldn't imagine it being related to the install or connections. It looks like you have troubleshooted just about everything else. I feel like the quickest work around is just swapping that amp out with another one. Then at least you know the amp is not the culprit. Sometimes processors can be bad and make noise out of the box well.
 

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Discussion Starter #38
Have you tried testing the optical or rca input of the processor? I couldn't imagine it being related to the install or connections. It looks like you have troubleshooted just about everything else. I feel like the quickest work around is just swapping that amp out with another one. Then at least you know the amp is not the culprit. Sometimes processors can be bad and make noise out of the box well.
Well, there is that buzzing in the mono amp that is concerning... Maybe it's an indication of a bigger problem, and maybe the crackling issue is related?? The buzz is sometimes so loud, I can hear if with the deck lid covering the audio in the trunk and driving at 35mph... The buzzing started well after the crackling issue, though, but it does go away within a couple minutes of it warming up.

I have not checked the input on the dsp, yet. That is on the to-do list, along with check all rcas...

I am really focusing on the bass amp and it's connection to the dsp, as the system works perfectly in the absence of bass. The other thing would be settings in the dsp, but that seems to be unlikely as, again, everything works fine until I push the bass in loud recordings...
 

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Well, there is that buzzing in the mono amp that is concerning... Maybe it's an indication of a bigger problem, and maybe the crackling issue is related?? The buzz is sometimes so loud, I can hear if with the deck lid covering the audio in the trunk and driving at 35mph... The buzzing started well after the crackling issue, though, but it does go away within a couple minutes of it warming up.

I have not checked the input on the dsp, yet. That is on the to-do list, along with check all rcas...

I am really focusing on the bass amp and it's connection to the dsp, as the system works perfectly in the absence of bass. The other thing would be settings in the dsp, but that seems to be unlikely as, again, everything works fine until I push the bass in loud recordings...
My bet is the the actual amplifier. I dont think a buzzing sound coming from any electronics is a good sign. I hope you figure it out soon. I know the feeling of putting a lot of work into a system and then something super small is creating the issue.
 

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...
I am really focusing on the bass amp and it's connection to the dsp, as the system works perfectly in the absence of bass. The other thing would be settings in the dsp, but that seems to be unlikely as, again, everything works fine until I push the bass in loud recordings...
So with the bass amp off works?
Or
With the bass line of the music attenuated in the DSP it works?

When did it get confirmed it as not gain structure related?
(I missed that one)
 
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