# Amps start-up causes a speaker thump



## scoobyman (Jun 25, 2011)

Hi guys, slight problem....again 

After my amps have powered up, and just as the music is about to start, i get a thumping sound from all my speakers.

I've done some tracing ( magnum P.I. style ) and figured out that it's my dls amp that's causing this when daisy-chained or Y-cabled to another amp, so if any other amp has any connection to DLS's RCA input or output, my speakers get a thump right before any music starts to play..

Will do my best to explain what i have figured out..

Basically, if i have front and rear RCA's from my HU going to my DLS amp or any other amp working alone, there is no start-up thump. However, if i then connect my other amp ( amp A ) to my DLS's RCA output and i connect my speakers to amp A, then i get a thump. The thump also happens if i use a Y-splitter to split my DLS's input signal to go to DLS and to amp A.

If i connect my front HU output to DLS amp, and rear HU output to amp A, then i get no thump..

If i connect amp B instead of DLS and then daisy chain it to amp A and run speakers off amp A, there is no thumping sound..

I figure my dls amp sends out some voltage through all it's channels as soon as it starts receiving sound from HU and then my other amps that are somehow connected to it's chanells amplify and pass that signal on to the speakers, anyone ever heard of anything like that ?


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## Danometal (Nov 16, 2009)

I may be reading this wrong, but if using more RCAs from the HU (vs. daisy-chaining) eliminates the thump, I would do that.


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## scoobyman (Jun 25, 2011)

Danometal said:


> I may be reading this wrong, but if using more RCAs from the HU (vs. daisy-chaining) eliminates the thump, I would do that.


Yes, you have understood everything correctly, however - i have 2x4 channel amps + 1 mono amp for sub. I already have 4 pairs of rca cables in there ( 1 for front, 2 for rear, 1 for sub + i had 1 daisy chained channel for the front, which now makes my front speakers thump ) and my sides are completely full, they simply wont take the fifth pair


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## ecbmxer (Dec 1, 2010)

It's probably an issue of turn on delay. Do you have remote turn on wires running to all the amps or to the amps have auto turn-on sensing from the RCAs?


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## scoobyman (Jun 25, 2011)

I have 1 remote wire split into 3 wires going to all amps


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## hottcakes (Jul 14, 2010)

your results may vary, but, i had a minor turn on thump before and went to a slightly bigger remote wire and that seemed to solve my issue. my wire is daisy-chained however and not split off into three.


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## scoobyman (Jun 25, 2011)

hottcakes said:


> your results may vary, but, i had a minor turn on thump before and went to a slightly bigger remote wire and that seemed to solve my issue. my wire is daisy-chained however and not split off into three.


Thanks, i will try that!


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## jason19 (Jan 21, 2011)

might wanna try using a rely too


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## jomin1016 (Jul 20, 2011)

Yeah - I'd have to go with Hotcakes....what size wire is your remote turn on? - Might need a little larger gauge. I had a system with 3 amps with one remote wire like that - split into three and I had a little turn on thump. Never did fix it - traded the car in...workin on another system.


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## scoobyman (Jun 25, 2011)

Done some reading, it seems that HU remote turn on only provides 5v output, which isnt enough for 3 amps as each amp requires at least 2 volts of remote input. - it wont matter which gauge wire i use. 

Seems like the only way to go is a relay, thanks jason19


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## 96jimmyslt (Jan 31, 2011)

Try grounding the RCA's, specifically, from the amp that is causing the thump


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## Vital (Feb 23, 2010)

Do you have any crossovers, eqs, processors?
Either way this article is probably the best one i've seen explaining turn-on and turn-off pop. Very easy, simple english so you can understasnd it AND i've actually tested it with turn-on/off delay relays as i has these issues and they do work. I had turn-off thump at one point and just recently turn-on with a different equipment - now i'm thump free lol.

And also please do install power relay as well as mentioned in this thread already so juice will be taken from your battery, not headunit. Any headunit manufacturer you will call (i did) will tell you the same thing - h/u's remote wire is only meant to power up 1 amp. Are they simply being on the safe side by telling you this? I'm sure they are, i had multiple amps running of that wire without any issues but i also know a person who's h/u fried due to multiple amps hooked up to that wire. I kid you not. 
It's really up to you i quess but do you really wanna risk it over $10 relay?



> What causes TURN ON/OFF POP and how to cure it:
> 
> When a car audio system utilizes additional components such as amplifiers and processors, those devices are turned on and off automatically with a signal from the source unit (known as remote turn-on).
> 
> ...


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## scoobyman (Jun 25, 2011)

Ok, im seriously pissed. Installed a relay for remote amp turn-on and re-wired my headunit to have a proper 12 gauge wire connection to the battery. Everything was working great, relay was working as intended...12.5volts at HU wiring..consuming about 2 amperes..so i'm listening to music and decided to start the car up and see if i'll have any problems and BAM, as soon as i start the car, VERY loud THUMP as my stereo turns off and on again on car start-up...the result of this ? Another blown midbass..wow..


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## Vital (Feb 23, 2010)

Can you post your full set-up? From headunit to x-overs to eqs to amps to speakers and everything else in between?


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## scoobyman (Jun 25, 2011)

Ok, but It is most likely my amp..

Headunit=Kenwood DNX 8220

amp= DLS CA40 4 channel( running only 1 atm for testing )

2 passive crossovers ( 1 pair ) for front channel, 2 passive crossovers for rear channel ( 1 pair )

1 farad capacitor.

Wiring:

Battery = 4 gauge = > Capacitor ( 0 gauge ground cable ) = > 4 gauge power cable to amp AND 11 gauge power cable to headunit. 
Headunit is grounded by an 11 gauge wire at the same spot as capacitor and amp.
Remote wire is going from headunit to 5-point relay ( relay takes power from capacitor via 11 gauge cable ), then to amp.


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## 96jimmyslt (Jan 31, 2011)

Try removing the capacitor.


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## Vital (Feb 23, 2010)

96jimmyslt said:


> Try removing the capacitor.


^^^ +1 and replace your mibass while u're at it :laugh: 
sorry, couldn't help it lol


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## scoobyman (Jun 25, 2011)

I'm pretty sure my amp is letting some DC through, there's no way it would ruin 2 speakers otherwise, grrr. I'm getting another amp by the end of this week, will test it out then.


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## hottcakes (Jul 14, 2010)

how's aboot the gain settings? i know when i was setting things up and before i went to a larger wire, i had the gain too high and this greatly exaggerated the minor thump i initially had. lowered the gain, made the thump almost nonexistent. to the point where i could only make it out if my head was near the speaker.


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## scoobyman (Jun 25, 2011)

Will wire in a switch today so i can turn amps on/off when i please as a temporary measure to prevent car start-up thumping


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

scoobyman said:


> Will wire in a switch today so i can turn amps on/off when i please as a temporary measure to prevent car start-up thumping


Don't do this, or at least only do this to the RTO wire... otherwise you WILL leave your amps on... 

Your thump is likely just dues to timing of the turn on... I can't remember right now if you want the amp on or off when signal is applied, but I do know there are small timer circuit you can get just for this.. 

They get placed on the RTO line and just time the turn on in/out a few seconds is all...


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## scoobyman (Jun 25, 2011)

The problem that i noticed is that when i turn my ignition key from on position to start, there is a circuit-break ? and my HU and amps turn off for half a second and then turn on again as the car starts, which cused that previous thump that destroyed my second speaker. 
What i want to do is have a switch that will interrupt remote wire when i want to turn the amps off before i start the car and then turn them on again, will see if that makes a difference.

Or maybe i will just run uninterrupted 12V from battery to HU so i can turn it on and off manually, instead of relying on my key position which seems to have a problem with it ( but i remember on my previous cars that used to be happening too, HU doesnt constantly stay on in transtion from on position to start )


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Sounds like the amp isn't "draining down" fast enough, or the turn on circuit (sometimes a delayed mute circuit built in) isn't reacting fast enough... 

If the amp is ON and the input from the HU is interrupted whatever comes down that line is going to get amplified... So.. I donno..


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## ecbmxer (Dec 1, 2010)

One other thing, are your crossovers all set at the HU or is anything set at the amp as well? Maybe try to turn on a high pass on the amp (even if it's redundant) to protect things (if your amp has acceptable crossover points available).


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## jester (Jun 1, 2011)

Sounds like your amp is turning on slower than your HU. Try putting in a noise gate in if your amp doesn't have one.


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## scoobyman (Jun 25, 2011)

Made a switch to manually turn off the amps, now i just turn the amps off before starting the car and then turn the amps on after the car has started = no thumps and no problems whatsoever.

Also rerouted my 12 volts ignition to have a constant 12v so i can turn the stereo on whenever i want with a push of a button even if my key isnt in the barrel, will wire it in after a capacitor next, so that my stereo's 12v wont get interrupted as i start the car.


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## scoobyman (Jun 25, 2011)

Thanks everyone for the help!


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## Erlewine (May 30, 2011)

I always had that problem when I used a 12v for remote rather than the hu remote but mine always bumped when they were shut off also.


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## jester (Jun 1, 2011)

Try a noise gate. Your amp may have one...


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